Posterior-chamber phakic implantable collamer lenses with a central port: a review

Refractive outcomes after V4c Toric collamer lens implantation over 1y of follow-up

AIM

To evaluate refractive outcomes and corneal astigmatism changes after Toric implantable collamer lens with a central port (V4c T-ICL) implantation over 1y of follow-up.

METHODS

A retrospective study was performed including 50 eyes of 50 patients that underwent V4c T-ICL implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, refractive and corneal astigmatism changes and corneal coupling correction were evaluated preoperatively, 1 and 12mo postoperatively. Vector analysis was used for astigmatism changes. Coefficient of adjustment (CAdj) was calculated for corneal coupling analysis.

RESULTS

The mean UDVA achieved was 0.03 logMAR at 1mo and remained unchanged throughout the whole follow-up (P=0.193). At the last visit, 84% of the eyes achieved a CDVA of 0.00 logMAR or better. Regarding spherical equivalent refraction (SEQ), 96% of eyes were ranges of ±1.00 D and 84% of them within ±0.50 D. Also, 94% of eyes had a remaining refractive cylinder within ±1.00 D and 78% of them within ±0.50 D. Both, SEQ and refractive cylinder, remain stable over the postoperative follow-up (P=1.000 and P=0.660, respectively). In terms of surgically induced astigmatism (SIA), no statistically significant differences were found over the follow-up (P=0.102) and under correction was found with a correction index lower than the unit at each visit. A keratometric astigmatism induced of 0.59±0.53 (vector mean: 0.26×73°) D was reached at the last visit. No significant changes in terms of corneal astigmatism orientation were reported over post-surgery visits (P=0.129 and P=0.097 at 1 and 12mo respectively). No clinical significance was found for CAdj on with-the-rule astigmatism. No postoperative complications resulting from the surgery were found.

CONCLUSION

Refractive outcomes suggest that the V4c T-ICL implantation for correction of myopic astigmatism was satisfactory in terms of effectiveness, safety, and stability during 1y of follow-up. Corneal astigmatism induced by the incision around 0.5 D is achieved according to the remaining refractive cylinder found at one-year post-surgery. Corneal coupling analysis results in no unexpected spherical change.

Long-term observation of V4c implantable collamer lenses implantation for moderate to extreme high myopia correction: five years follow-up

BACKGROUND

This study aims to assess the long term effectiveness, safety, predictability and stability of V4c implantable collamer lenses (ICL) for correction of moderate to extreme high myopia.

METHODS

We reviewed 125 eyes from 64 patients who implanted V4c ICL at the Refractive Surgery Center of West China Hospital in Chengdu, China, between May 2015 and January 2017. The median spherical equivalent was -11.50 D (interquartile range [IQR]: -13.00 to -9.00 D). We followed up with the patients over five years and evaluated several parameters, including uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), axial length, refractive error, endothelial cell density (ECD), intraocular pressure (IOP), white-to-white distance (WTW), and vault. We performed a correlation analysis to explore the potential impacts on vault following implantation.

RESULTS

The median safety index (postoperative CDVA/preoperative CDVA) during the last follow-up was 1.00 (interquartile range [IQR]: 1.00-1.20), and the efficacy indices (postoperative UDVA/preoperative CDVA) were 1.20 (IQR: 1.00-1.25), 1.20 (IQR: 1.00-1.33), and 0.8 (IQR: 0.65-1.00) at postoperative 1 week, 1 month, and 5 years, respectively. At the five-year mark, 16% of the eyes were within ±0.50 D of expected correction, and 73% were within ±2.00 D. No significant difference in ECD was observed between pre-operative and post-operative measurements. Compared to baseline, we observed a significant increase in IOP at the one-week follow-up, which decreased significantly at the one-month visit. Furthermore, we identified ICL size and spherical equivalent (SE) as independent variables in a multiple linear regression model that accurately predicted the five-year vault after surgery.

CONCLUSION

In conclusion, V4c ICL implantation is an effective and safe treatment for moderate to extreme high myopia with good predictability and stability over the long-term.

Repeatability and Agreement of Central Vault for Implantable Collamer Lens Obtained by the Tomey OA-2000 Biometer and Spectralis OCT

Objective

To assess repeatability and agreement of central vault for implantable collamer lens (ICL) measured by the Tomey OA-2000 biometry and Spectralis optical coherence tomography (OCT).

Methods

In this prospective study, the central vault was measured by the Tomey OA-2000 biometer and Spectralis OCT in 84 eyes (43 patients) after ICL implantation at six month follow-up. Three consecutive scans were obtained by one experienced technician using Tomey OA-2000 and the Spectralis OCT in the same day. The coefficient of variation (CoV), intraclass correlation coefficient (ICC), within-subject standard deviation (Sw), and 2.77 Sw were calculated to assess the repeatability and reproducibility. The paired t-test and Bland-Altman plots were used to analyze the differences and agreements of central vault measured by two devices.

Results

Repeatability of the central vault measured by Tomey OA-2000 biometer and Spectralis OCT showed that the CoV was 2.71% and 1.66%, respectively. The ICC for both devices was 0.996 and 0.999, respectively. The paired t-test showed that central vault measured by Tomey OA-2000 biometer was -7.25 ± 23.57 microns lower than that measured by Spectralis OCT (P = 0.006). The mean difference between measurements for Tomey OA-2000 and ASM-OCT with 95% limits of agreement (LoAs) was -38.94 to 53.44 μm.

Conclusion

Both Tomey OA-2000 biometer and Spectralis OCT displayed good repeatability for the measurement of central vault of ICL. Good reliability and agreement were observed between Tomey OA-2000 biometer and Spectralis OCT. Both instruments are useful but not replaced each other for central vault measurements.

Clinical Observation of Posterior-Chamber Phakic Implantable Collamer Lens V4c Implantation in Myopic Patients with Shallow Anterior Chamber Depth: A Retrospective, Consecutive Observational Study

Purpose

The reference range for the preoperative anterior chamber angle width for ICL surgery is unclear. Our objective was to assess the clinical effect and the range of anterior chamber angle width of posterior-chamber implantable collamer lens V4c (ICL V4c) implantation in patients with anterior chamber depth (ACD) < 2.8 mm.

Methods

Patients who underwent ICL V4c implantation with shallow ACD were included in this retrospective study. The patients' uncorrected and corrected distance visual acuity, angle of trabecular-iris (TIA), angle-opening distance (AOD500), trabecular-iris space area (TISA500), corneal endothelial cell density, vault, retinal nerve fiber layer thickness, intraocular pressure, visual field, and complications were analyzed.

Results

Forty-one patients (68 eyes) completed at least 12 months of follow-up (median follow-up, 30 months). The effectiveness and safety indices were 1.09 ± 0.13 and 1.04 ± 0.21, respectively. The preoperative TIA values on the nasal and temporal sides were 39.78 ± 7.68 degree (range, 25.8-65.1 degree) and 41.54 ± 8.03 degree (range, 28.5-63.00 degree). Forty-seven eyes had uncorrected distance visual acuity ≥1.0, and 55 had corrected distance visual acuity ≥1.0 at the last follow-up visit. The TIA, AOD500, and TISA500 on the nasal and temporal sides were significantly reduced compared to those before surgery (all P < 0.01); no eye had an angle closure or elevated intraocular pressure. The ICL V4c vault was 290.88 ± 153.36 μm (range, 60.0-880.0 μm). No severe complications occurred in any patient.

Conclusions

In patients with myopia with shallow ACD (2.55-2.79 mm), a preoperative TIA >25.8° is safe and effective for a relatively long time after surgery; however, an extended long-term close follow-up is needed.

Precision of a new SS-OCT biometer to measure anterior segment parameters and agreement with 3 instruments with different measurement principles

PURPOSE

To evaluate the repeatability of a new swept source optical coherence tomography (SS-OCT)-based biometer to measure anterior segment parameters and to assess the agreement with 3 other imaging devices based on different measurement principles.

SETTING

Unit of Eye and Vision, Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.

DESIGN

Prospective, comparative case series.

METHODS

3 consecutive measurements were obtained in unoperated eyes with the Eyestar900 (SS-OCT), Lenstar 900, MS-39, and Sirius. The following anterior segment parameters were evaluated: central corneal thickness (CCT), corneal diameter (CD), aqueous depth (AQD), and corneal power metrics. The repeatability limit (Rlim), coefficient of variation (CoV), and a repeated measures Bland-Altman analysis were performed.

RESULTS

74 eyes of 74 participants were measured. The Rlims for CCT, CD, and AQD were lower than 10 μm, 0.3 mm, and 0.10 mm for all devices, respectively. The corresponding CoVs for these parameters never exceeded 1.2%. The Rlim for the corneal power metrics never exceeded 0.60 diopter (D) for any of the instruments. Lenstar showed the best agreement with the MS-39 to measure CCT, CD, and AQD (limit of agreement interval, LoA: 15.54 μm, 0.55 mm, and 0.16 mm, respectively). The mean difference for keratometry parameters was lower than 0.3 D for all device comparisons, and the LoA interval ranged between 0.52 D and 1.21 D.

CONCLUSIONS

The repeatability for measuring anterior segment parameters was good, and the agreement among all the instruments was good for CD and AQD measurements. However, for CCT and keratometer parameters, the instruments cannot be used interchangeably due to large LoA interval.

Ten-year follow-up of posterior chamber phakic intraocular lens with central port design in patients with low and normal vault

PURPOSE

To assess the clinical outcomes and postoperative complications of the implantable collamer lens (ICL) with a central port throughout 10 years of follow-up in patients with low and normal vault.

SETTING

Fernández-Vega Ophthalmological Institute, Oviedo, Spain.

DESIGN

Retrospective and comparative case series.

METHODS

This study included eyes that underwent a V4c ICL implantation with 10 years of follow-up. The eyes were divided into 2 groups according to the vault at 1 year postoperatively: vault <250 μm and between 250 μm and 800 μm. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), intraocular pressure (IOP), endothelial cell density (ECD), vault, complications, and secondary surgeries were analyzed.

RESULTS

37 and 90 eyes were enrolled in the low and normal-vault groups, respectively. No differences in UDVA, CDVA, and refraction were found between the groups over 10 years of follow-up. No cases developed ICL-induced anterior subcapsular opacity over the follow-up period. 2 (5.4%) and 8 (8.9%) eyes in the low and normal-vault groups, respectively, required ICL exchange. 1 (2.8%) and 2 (2.2%) eyes in the low and normal-vault groups, respectively, required excimer laser to correct residual refractive error. The IOP remained stable throughout the 10-year follow-up. The loss in ECD from that preoperatively to 10 years postoperatively was 3.8% and 4.5% in the low and normal-vault groups, respectively ( P = .4). No pigment dispersion glaucoma or other vision-threatening complications were reported.

CONCLUSIONS

This study shows good long-term outcomes of the V4c ICL, supporting that the central hole provides safety to the procedure and prevents the potential risk associated with low vault.

The Influence of Lens Position, Vault Prediction, and Posterior Cornea on Phakic Posterior Chamber Intraocular Lens Power

BACKGROUND

Achieving precise refractive outcomes in phakic posterior chamber intraocular lens (pIOL) implantation is crucial for patient satisfaction. This study investigates factors affecting pIOL power calculations, focusing on myopic eyes, and evaluates the potential benefits of advanced predictive models.

DESIGN

Retrospective, single-center, algorithm improvement study.

METHODS

Various variations with different effective lens position (ELP) algorithms were analyzed. The algorithms included a fixed constant model, and a multiple linear regression model and were tested with and without incorporation of the posterior corneal curvature (Rcp). Furthermore, the impact of inserting the postoperative vault, the space between the pIOL and the crystalline lens, into the ELP algorithm was examined, and a simple vault prediction model was assessed.

RESULTS

Integrating Rcp and the measured vault into pIOL calculations did not significantly improve accuracy. Transitioning from constant model approaches to ELP concepts based on linear regression models significantly improved pIOL power calculations. Linear regression models outperformed constant models, enhancing refractive outcomes for both ICL and IPCL pIOL platforms.

CONCLUSIONS

This study underscores the utility of implementing ELP concepts based on linear regression models into pIOL power calculation. Linear regression based ELP models offered substantial advantages for achieving desired refractive outcomes, especially in lower to medium power pIOL models. For pIOL power calculations in both pIOL platforms we tested with preoperative measurements from a Scheimpflug device, we found improved results with the LION 1ICL formula and LION 1IPCL formula. Further research is needed to explore the applicability of these findings to a broader range of pIOL designs and measurement devices.

Implantable Collamer Lens Procedure Planning: A Review of Global Approaches

More than 2 million implantable collamer lenses (ICLs) have been implanted worldwide. With a central port to improve aqueous flow through the ICL, the latest iteration of this phakic intraocular lens (pIOL) has been shown to have stable outcomes with very low rates of adverse events. However, correct planning and ICL size selection continue to be important to achieve an optimal vault. Shallow or excessive vaults are not complications in and of themselves but may increase the risk of complications. Historically, surgeons have relied on measurements of anterior chamber depth (ACD) and manual, caliper-measured white-to-white (WTW) distance to select the ICL size. New diagnostic and imaging technologies such as optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM) provide additional opportunities for visualization and measurement of the intraocular dimensions involved in phakic intraocular lens implantation, including sulcus-to-sulcus (STS) and angle-to-angle (ATA) diameters. This paper reviews various approaches to ICL planning and sizing that have been published in the peer-reviewed literature, all of which produce acceptable results for predicting vault and size selection. Surgeons may also want to identify a methodology for patient evaluation and ICL size selection that best aligns with their personal preferences, diagnostic technology, and familiarity with analytical optimization tools.

Effect of vault on predicting postoperative refractive error for posterior chamber phakic intraocular lens based on a machine learning model

PURPOSE

To investigate how vault and other biometric variations affect postoperative refractive error of implantable collamer lenses (ICLs) by integrating artificial intelligence and modified vergence formula.

SETTING

Eye and ENT Hospital of Fudan University, Shanghai, China.

DESIGN

Artificial intelligence and big data-based prediction model.

METHODS

2845 eyes that underwent uneventful spherical ICL or toric ICL implantation and with manifest refraction results 1 month postoperatively were included. 1 eye of each patient was randomly included. Random forest was used to calculate the postoperative sphere, cylinder, and spherical equivalent by inputting variable ocular parameters. The influence of predicted vault and modified Holladay formula on predicting postoperative refractive error was analyzed. Subgroup analysis of ideal vault (0.25 to 0.75 mm) and extreme vault (<0.25 mm or >0.75 mm) was performed.

RESULTS

In the test set of both ICLs, all the random forest-based models significantly improved the accuracy of predicting postoperative sphere compared with the Online Calculation & Ordering System calculator ( P < .001). For ideal vault, the combination of modified Holladay formula in spherical ICL exhibited highest accuracy ( R = 0.606). For extreme vault, the combination of predicted vault in spherical ICL enhanced R values ( R = 0.864). The combination of predicted vault and modified Holladay formula was most optimal for toric ICL in all ranges of vault (ideal vault: R = 0.516, extreme vault: R = 0.334).

CONCLUSIONS

The random forest-based calculator, considering vault and variable ocular parameters, illustrated superiority over the existing calculator on the study datasets. Choosing an appropriate lens size to control the vault within the ideal range was helpful to avoid refractive surprises.

Endothelial cell loss post-implantable collamer lens V4c: meta-analysis

Endothelial cell density (ECD) loss is a noted effect of implantable collamer lens (ICL) V4c surgery. Current literature provides a wide range of values for ECD loss postsurgery, which may not be helpful in advising patients and clinicians. A meta-analysis exploring ECD loss in ICL V4c for myopia correction was undertaken. 18 studies were included in this meta-analysis with 2 subgroup analyses to account for the variability in follow-up lengths. The average ECD loss 3 months, 12 months, and 21.25 (mean) months postsurgery were 1.32% ± 1.28% ( P < .001, 95% CI, -75.158 to -1.19), 1.75% ± 2.17% ( P < .001, 95% CI, -134.09 to 14.52), and 3.84% ± 1.78% ( P < .001, 95% CI, -156.04 to -54.26), respectively. ECD loss is most pronounced 3 months postsurgery, suggesting that acute surgical trauma was the primary contributor rather than long-term lens implantation. Overall, ICL V4c is for myopia correction exhibits similar ECD loss as seen in other ICL models, thereby affirming its safety.

Effects of crystalline lens rise and anterior chamber parameters on vault after implantable collamer lens placement

BACKGROUND

To analyze vault effects of crystalline lens rise (CLR) and anterior chamber parameters (recorded by Pentacam) in highly myopic patients receiving implantable collamer lenses (ICLs), which may avoid subsequent complications such as glaucoma and cataract caused by the abnormal vault.

METHODS

We collected clinical data of 137 patients with highly myopic vision, who were all subsequent recipients of V4c ICLs between June 2020 and January 2021. Horizontal ciliary sulcus-to-sulcus diameter (hSTS) and CLR were measured by ultrasonic biomicroscopy (UBM), and a Pentacam anterior segment analyzer was used to measure horizontal white-to-white diameter (hWTW), anterior chamber depth (ACD), anterior chamber angle (ACA), anterior chamber volume (ACV), CLR, and postoperative vault (Year 1 and Month 1). The lens thickness (LT) was determined by optical biometry (IOL Master instrument). The predictive model was generated through multiple linear regression analyses of influential factors, such as hSTS, CLR, hWTW, ACD, ACA, ACV, ICL size, and LT. The predictive performance of the multivariate model on vault after ICL was assessed using the receiver operating characteristic (ROC) curve with area under the curve (AUC) as well as the point of tangency.

RESULTS

Average CLR assessed by UBM was lower than the average value obtained by Pentacam (0.561 vs. 0.683). Bland-Altman analysis showed a good consistency in the two measurement methods and substantial correlation (r = 0.316; P = 0.000). The ROC curve of Model 1 (postoperative Year 1) displayed an AUC of 0.847 (95% confidence interval [CI]: 74.19-95.27), with optimal threshold of 0.581 (sensitivity, 0.857; specificity, 0.724). In addition, respective values for Model 2 (postoperative Month 1) were 0.783 (95% CI: 64.94-91.64) and 0.522 (sensitivity, 0.917; specificity, 0.605).

CONCLUSION

CLR and anterior chamber parameters are important determinants of postoperative vault after ICL placement. The multivariate regression model we constructed may serve in large part as a predictive gauge, effectively avoid postoperative complication.

One-stage versus two-stage bilateral implantable collamer lens implantation: a comparison of efficacy and safety

Implantable collamer lens implantation (ICL) represents a safe and effective treatment for myopia and myopic astigmatism. To compare the outcomes of a bilateral one-stage same day approach to a two-stage approach, the databases of the University Eye Hospital Munich, Ludwig Maximilians-University and Smile Eyes Linz, Austria were screened for eyes that had undergone ICL implantation. Two-stage surgery was performed at an interval of 1 day (17 patients), 2 days (19 patients) and 1 week (2 patients). Variables analyzed were preoperative, 1-day and last follow-up uncorrected distance (UDVA) and corrected distance visual acuity (CDVA), manifest refraction, refractive spherical equivalent (SEQ), astigmatism, age, endothelial cell count (ECD), intraocular pressure (IOP) and ICL vaulting. In total, 178 eyes (100 eyes one-stage, 78 eyes two-stage) of 89 patients were included in this study. Mean follow-up was 1.1 ± 0.8 and 1.3 ± 0.5 years. Mean preoperative SEQ was - 7.9 ± 2.6 diopters (D) in the one-stage and - 8.0 ± 1.7 D in the two-stage group (p = 0.63) and improved to 0.00 ± 0.40 and - 0.20 ± 0.40 D at end of follow-up, showing slightly better stability in the one-stage group (p = 0.004). There was no difference in the efficacy (1.1 vs. 1.2, p = 0.06) and the safety index (1.2 vs. 1.2, p = 0.60) between the two groups. No eye (0%) in either group lost 2 lines or more of UDVA (p > 0.99). Refraction within ± 0.50 D and ± 1.00 D around target was achieved comparably often (89 vs. 86%, p = 0.65; 99 vs. 99%, p > 0.99). Endothelial cell loss was slightly higher in the two-stage group (1.3 vs. 4.3%). Vaulting at the final follow up was higher in the one-stage group (373.8 ± 205.4 µm vs. 260.3 ± 153.5 µm, p = 0.00007). There were no serious intraoperative complications in either group. In conclusion, this study demonstrates that both the one- and two-stage approaches are equally effective, predictable and safe. Regarding endothelial cell loss, vaulting and SEQ stability, the one-stage group showed slightly better outcomes, but these results are clinically questionable because they are so small. Larger studies are needed to quantitatively evaluate a potential benefit.

A review of posterior chamber phakic intraocular lenses

PURPOSE OF REVIEW

Posterior chamber phakic intraocular lenses (pIOLs) are increasing in popularity as a viable alternative to laser refractive surgery. The purpose of this review is to evaluate the recent updates to pIOLs and to assess the advancements and safety of the procedure.

RECENT FINDINGS

Accurate lens sizing is the key determinant to suitable vault prediction, advancements to sizing formulae including the use of very high frequency (VHF) digital ultrasound and the application of artificial intelligence and machine learning has led to improved vault prediction and safety. The introduction of the central aquaport has been shown to reduce the formation of cataract and is now adopted in most myopic pIOLs. Recently published studies have demonstrated that pIOLs have an excellent safety profile with no increased risk of retinal detachment or endothelial cell loss. Advancements have led to the introduction of extended depth of focus pIOLs for the correction of presbyopia, further research is required to evaluate the efficacy of new lens designs.

SUMMARY

pIOL surgery is experiencing traction with improved lens design and increased lenses choices such as larger optical zone and presbyopic options. Accuracy of implantable collamer lens sizing is paramount to the safety and clinical outcomes, greater predictability is likely to encourage more posterior chamber pIOL users due to fewer sizing related complications.

Effects of Decentration of Implantable Collamer Lens V4c on Visual Quality With the OPD-Scan III Aberrometer

PURPOSE

This study aimed to analyze the relationship between visual quality and implantable collamer lenses (ICL) decentration.

DESIGN

Prospective treatment evaluation clinical study METHODS: This prospective study included 119 eyes with ICL implantation. Refractive parameters and ocular aberrations were examined pre- and postoperatively. ICL decentration and higher-order aberrations (HOAs) were evaluated using the OPD-Scan III aberrometer.

RESULTS

At the 1-month follow-up, the mean values for decentration were 0.38 ± 0.19 mm (0.02-0.78). Regarding the position of decentration in right and left eyes, 22.8% and 17.7% were located in the superior nasal section, 0% and 6.5% in the inferior nasal section, 50.9% and 53.2% in the superior temporal section, and 26.3% and 22.6% in the inferior temporal section, respectively. The root mean square values of whole-eye total HOAs, coma, and trefoil had significantly increased. Decentration had a significant negative correlation with variation in the pre- and postoperative trefoils of the whole eye.

CONCLUSIONS

ICL decentration had a slightly negative correlation with trefoil and slightly affected visual quality.

Influencing factors comparing different vault groups after phakic implantable collamer lens implantation: review and meta-analysis

BACKGROUND

Studies on the factors affecting vault after posterior chamber phakic Implantable Collamer Lens (ICL) have been carried out, but most of them are single-centered and subjective selections of parameters. The present study aimed to systematically analyze the factors for vault.

METHODS

A systematic review of case series, case-control, and cohort studies derived from the articles published in PubMed, the Cochrane Library, Embase, Web of Science, CNKI, CBM, Wanfang and VIP, as well as ClinicalTrials, which were conducted to search for studies on factors of vault using four core terms: phakic intraocular lenses, vault, risk factor and observational study, from January 01, 1997, to February 20, 2023. The included studies were meta-analyzed quantitatively and described qualitatively. Subsequently, meta-regression and subgroup analysis were used.

RESULTS

We identified 13 studies (1,607 subjects), and 14 factors were considered. Meta-analysis showed that anterior chamber depth (ACD), horizontal corneal white-to-white (hWTW), ICL-size, and age are dual effects of the abnormal vaults; anterior chamber volume (ACV) and lens thickness (LT) are a one-way effect; while axial length (AL), ICL- spherical equivalent (ICL-SE) and Km are insignificant. In addition, descriptive analysis of anterior chamber angle (ACA), horizontal sulcus to sulcus (hSTS), ciliary processes height (T value), crystalline lens rise (CLR), and gender showed that all factors except gender tend to have significant effects on vault. Sensitivity analysis showed stable combined results. Country and design respectively affect the heterogeneity in ACD and ICL-size at low vault, while design affects the heterogeneity in ACD at high vault. No publication bias exists.

CONCLUSIONS

Vault after ICL is related to multiple factors, especially anterior segmental biologic parameters, and they are weighted differently. We hope to provide a reference for the selection and adjustment of ICL.

Causes and management strategies for elevated intraocular pressure after implantable collamer lens implantation

With the widespread application of Implantable Collamer Lens (ICL) implantation surgery in the field of myopia correction, a comprehensive understanding of its potential complications, especially those related to intraocular pressure (IOP), becomes crucial. This article systematically reviews various complications that may lead to IOP elevation after ICL surgery. Firstly, common complications after ICL surgery, including residual viscoelastic, steroid response, and excessive vault of the ICL, are detailed, emphasizing their potential impact on intraocular pressure. Regarding residual viscoelastic, we delve into its direct relationship with postoperative elevated IOP and possible preventive measures. For steroid response, we stress the importance of timely adjustment of steroid therapy and monitoring intraocular pressure. Additionally, excessive vault of the ICL is considered a significant potential issue, and we elaborate on its mechanism and possible management methods. In further discussion, we focus on relatively rare complications such as Toxic Anterior Segment Syndrome (TASS), Urrets-Zavalia Syndrome (UZS), Pigment Dispersion Syndrome (PDS), and malignant glaucoma. For these relatively rare complications, this review thoroughly explores their potential mechanisms, emphasizes the importance of prevention, and provides guidance for early diagnosis and treatment. This is a comprehensible review that aims to offer eye care professionals a comprehensive understanding and effective management guidance for complications of elevated IOP after ICL surgery, ultimately providing optimal care for patients' visual health.

Comparison of the Accuracy of Seven Vault Prediction Formulae for Implantable Collamer Lens Implantation

INTRODUCTION

This study aimed to compare the accuracy of seven implantable collamer lens (ICL) implantation vault prediction formulae.

METHODS

We retrospectively analyzed 328 patients (328 eyes) who underwent ICL implantation and the prediction accuracy of seven formulae: NK, KS, WH, Luo, Zhu, Hun, and ZZ were compared. Moreover, the accuracy of the seven formulae for different ICL sizes was compared. The formulae were tested using mean absolute prediction error (MAE), median absolute prediction error (MedAE), prediction error (PE) percentages at ± 50 µm, ± 100 µm, ± 200 µm, and ± 300 µm, and Bland-Altman analysis.

RESULTS

The PE of the seven formulae were statistically significant (P < 0.001). The KS (101.00 µm) and WH formulae (116.65 µm) had the smallest MedAE, followed by the Luo (123.62 µm), NK (141.50 µm), Hun (152.68 µm), ZZ (196.00 µm) and Zhu formula (225.98 µm). The highest percentage of PE in the range of ± 300µm was 94.3% and 93% for the KS and WH formulae, respectively. Among the different ICL size groupings, the KS formula predicted the smallest MedAE for 12.1 mm and 12.6 mm, whereas the Luo and WH formulae predicted the smallest MedAE for 13.2 mm and 13.7 mm, respectively.

CONCLUSIONS

The KS and WH formulae provided better outcomes by predicting the vault with higher accuracy than of the NK, Hun, Luo, ZZ, and Zhu formulae.

TRIAL REGISTRATION

ChiCTR2200065501.

Assessment of the iridocorneal angle pigmentation and structures after the implantation of EVO+ Visian Implantable Collamer Lens

PURPOSE

To evaluate the effect of EVO+ Visian Implantable Collamer Lens (ICL) implantation on the iridocorneal angle pigmentation and structures.

METHODS

Myopic refractive surgery candidates who underwent posterior chamber EVO+ ICL implantation were evaluated preoperatively and 3 and 6 months postoperatively. High-resolution images of the iridocorneal angle (nasal, superior, temporal and inferior quadrants) were acquired during gonioscopy. A masked observer, blinded to study visits and patients' information, evaluated the angle width, apparent iris root insertion, iris configuration, and trabecular meshwork pigmentation according to the Spaeth scale in two different occasions. The intra-rater reliability was estimated using the weighted Gwet's Agreement Coefficient (AC2). Differences between visits were analyzed using the Cochran Q test or the Friedman test.

RESULTS

Twenty-one patients (13 females and 8 males) aging 31.3 ± 6.3 years old were recruited. The intra-rater reliability of gonioscopy assessment was excellent for every parameter assessed (AC2 ≥ 0.97). No significant differences were found among the study visits for any quadrant in the angle width (p ≥ 0.74), apparent iris root insertion (p ≥ 0.22), iris configuration (p ≥ 0.21) and trabecular meshwork pigmentation (p ≥ 0.24). Mean pigmentation of trabecular meshwork for the four quadrants did not vary either among visits (p = 0.25).

CONCLUSIONS

The EVO+ ICL implantation after uneventful procedures appears not to clinically affect the iridocorneal angle pigmentation and/or structures during a short-medium follow-up using gonioscopy assessment. The intra-rater reliability of glaucoma specialists assessing iridocorneal angle structures using gonioscopy images is very high.

Changes of dysfunctional lens index before and after implantable collamer lens V4c implantation in patients with moderate-to-high myopia

BACKGROUND

Dysfunctional lens index (DLI) changing is rarely reported after implantable collamer lens (ICL) implantation. In the current research, we hope to investigate the changes of DLI by ray-tracing aberrometry before and after implantation of the posterior chamber phakic implantable collamer lens with a central artificial hole for patients with moderate-to-high myopia.

METHODS

This retrospective, observational case series included 206 eyes of 104 patients with moderate-to-high myopia who underwent ICL V4c implantation. Data were collected on ocular indicators preoperatively and at 1 day, 1, 3, and 6 months postoperatively. The i-Trace Visual Functional Analyzer was used to assess the DLI measurement.

RESULTS

The overall values of safety index and efficacy index were both more than 1. Preoperatively, the mean spherical equivalent (SE) of included 206 eyes was - 10.77 ± 3.46 diopter (D). Then at 1-day postoperation, the mean SE was - 0.22 ± 0.55 D, and barely changed from 1 day to 6 months postoperatively. Although the endothelial parameters had no significant differences between preoperation and postoperation, the mean loss of endothelial cells was 0.74 ± 0.98% at 6 months. Regarding the vault, there was a significant difference between each time of follow-up (P < 0.001). The mean of the vault decreased 109.6 ± 13.5 µm from 1-day post-op to 6 months post-op. The DLI values were 3.70, 9.26, 10.00, and 9.68 at baseline, 1, 3, and 6 months, respectively (P < 0.001), but no significant differences were found between 1, 3, and 6 months postoperatively (P > 0.05). The preoperative lnDLI showed a significant positive linear correlation (r = 0.621, P < 0.001) with the preoperative spherical equivalent (SE). The lnDLI was negatively correlated with the axial length (r = - 0.462, P < 0.001), corneal thickness (r = - 0.207, P = 0.003), preoperative LogMAR UDVA (r = - 0.189, P = 0.006), and preoperative LogMAR CDVA (r = - 0.306, P < 0.001).

CONCLUSIONS

The postoperative refractive parameters were confirmed excellent in efficacy, predictability, and stability in half a year. The DLI was significantly improved after the ICL V4c implantation in patients with moderate-to-high myopia and showed good stability during the follow-up periods. The DLI deserves a more comprehensive understanding and application in clinical services.

Predicting Vault and Size of Posterior Chamber Phakic Intraocular Lens Using Sulcus to Sulcus-Optimized Artificial Intelligence Technology

PURPOSE

To investigate the accuracy of posterior chamber phakic intraocular lens (PIOL) vault and size prediction models based on sulcus to sulcus (STS) optimized artificial intelligence and big data analysis technology.

DESIGN

Big data and artificial intelligence prediction model.

METHODS

We included 5873 eyes with posterior chamber PIOL implantation, and the postoperative vault was measured using an anterior segment analyzer (Pentacam AXL) 1 month postoperatively. A random forest regression model and classification model were used to predict the postoperative vault and PIOL size. The postoperative vault and PIOL size were set as output features; other vault-related eye parameters were set as input features. The influence of white to white (WTW), horizontal sulcus to sulcus (STS), and vertical STS on predicting postoperative vault and PIOL size was analyzed and compared.

RESULTS

The mean preoperative WTW diameter was 11.64 ± 0.37 mm, the mean horizontal STS diameter was 11.85 ± 0.47 mm, and the mean vertical STS diameter was 12.39 ± 0.52 mm. In the regression model for numerical prediction of the vault, the combination of WTW, horizontal STS, and vertical STS was the most optimal for vault prediction (R2 = 0.3091, root mean square error [RMSE] = 0.1705); solely relying on WTW was the least optimal (R2 = 0.2849, RMSE = 0.1735). Among the models for classification prediction of the vault, the combination of WTW, horizontal STS, and vertical STS was the most accurate (accuracy, 0.6302; mean area under the curve, 0.8008; and mean precision recall rate, 0.6940). Moreover, the combination of WTW, horizontal STS, and vertical STS exhibited the highest accuracy for classification prediction of PIOL size (accuracy, 0.8170; mean area under the curve, 0.9540; and mean precision recall rate, 0.8864). Whether in the regression prediction models of vault values or in the classification prediction models of vault and PIOL size, the accuracy of STS optimized model was significantly improved compared with the traditional WTW model (P < .001).

CONCLUSION

Artificial intelligence combined with STS optimization contributes to the accuracy of PIOL size and vault prediction models. The random forest machine-learning model optimized by STS is superior to the traditional WTW model.

Vault predicting after implantable collamer lens implantation using random forest network based on different features in ultrasound biomicroscopy images

AIM

To analyze ultrasound biomicroscopy (UBM) images using random forest network to find new features to make predictions about vault after implantable collamer lens (ICL) implantation.

METHODS

A total of 450 UBM images were collected from the Lixiang Eye Hospital to provide the patient's preoperative parameters as well as the vault of the ICL after implantation. The vault was set as the prediction target, and the input elements were mainly ciliary sulcus shape parameters, which included 6 angular parameters, 2 area parameters, and 2 parameters, distance between ciliary sulci, and anterior chamber height. A random forest regression model was applied to predict the vault, with the number of base estimators (n_estimators) of 2000, the maximum tree depth (max_depth) of 17, the number of tree features (max_features) of Auto, and the random state (random_state) of 40.0.

RESULTS

Among the parameters selected in this study, the distance between ciliary sulci had a greater importance proportion, reaching 52% before parameter optimization is performed, and other features had less influence, with an importance proportion of about 5%. The importance of the distance between the ciliary sulci increased to 53% after parameter optimization, and the importance of angle 3 and area 1 increased to 5% and 8% respectively, while the importance of the other parameters remained unchanged, and the distance between the ciliary sulci was considered the most important feature. Other features, although they accounted for a relatively small proportion, also had an impact on the vault prediction. After parameter optimization, the best prediction results were obtained, with a predicted mean value of 763.688 µm and an actual mean value of 776.9304 µm. The R2 was 0.4456 and the root mean square error was 201.5166.

CONCLUSION

A study based on UBM images using random forest network can be performed for prediction of the vault after ICL implantation and can provide some reference for ICL size selection.

Clinical and Aberrometric Outcomes of a New Implantable Collamer Lens for Myopia and Presbyopia Correction in Phakic Patients

PURPOSE

To assess the clinical and aberrometric outcomes of a new Implantable Collamer Lens (EVO Viva ICL; STAAR Surgical) to correct moderate to high myopia and presbyopia.

METHODS

The study included 80 eyes of 40 patients who had bilateral EVO Viva ICL implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, presbyopic add power, binocular through-focus visual acuity, total ocular spherical aberration (SA), coma aberration, and root mean square of ocular higher order aberrations (RMS HOAs) (i-Trace Aberrometer; Tracey Technologies) for a 4.5-mm pupil size were evaluated.

RESULTS

The mean binocular postoperative UDVA and CDVA were 0.09 ± 0.19 and 0.02 ± 0.03 logMAR, respectively. The postoperative spherical equivalent was -0.61 ± 0.54 diopters (D). The presbyopic add power reduced from +1.31 ± 0.74 D preoperatively to +0.44 ± 0.58 D after surgery (P < .0001). The mean visual acuity was 0.1 logMAR or better (20/25 or better) across the vergence range from +0.50 to -1.50 D, better than 0.2 logMAR (20/32 or better) up to the vergence of -2.00 D, and remained better than 0.3 logMAR (20/40 or better) up to the vergence of -2.50 D. The total ocular aberrations induced by EVO Viva ICL were -0.34 ± 0.09 µm of SA, 0.24 ± 0.18 µm of coma, and 0.26 ± 0.12 µm of RMS HOAs.

CONCLUSIONS

The outcomes support that the new ICL might be a good alternative for myopia and presbyopia correction in patients aged between 45 and 55 years. Further studies are needed to evaluate the threshold lens misalignment from which the patient´s visual quality would be affected. [J Refract Surg. 2023;39(9):589-596.].

Effect of phakic collamer intraocular lens with a central hole on structural tests measurements of retinal nerve fiber layer and macula

AIM

To evaluate whether the Visian Implantable Collamer Lens with a central port (V4c ICL®; STAAR Surgical, Switzerland) affects the retinal nerve fibre layer (RNFL), macula and optic nerve head (ONH) measurements obtained by optical coherence tomography (OCT), and Heidelberg Retina Tomography (HRT).

METHODS

This prospective study included myopic patients undergoing V4c ICL® implantation. RNFL thickness, macular thickness, ganglion cell analysis (GCA) and ONH main parameters were evaluated with RTVue OCT (Optovue Inc., USA) and Cirrus-HD OCT (Carl Zeiss Meditec, USA). ONH variables were also analysed with HRT-3 (Heidelberg Engineering, Germany). All measurements were performed before and 1 week and 12 months after the surgery.

RESULTS

31 eyes of 31 patients (mean age 30.1 ± 5.5 years) were included. Comparing with preoperative values, no significant differences in average RNFL thickness were found with RTVue, while a slight increase (4.3 µm) was detected with Cirrus-HD (85.2 ± 10.3 µm, preoperatively) at 1-week postoperatively (89.5 ± 8.3 µm; p < 0.05). Those changes were not observed at the last follow-up visit (86.6 ± 8.6 µm; p = 0.41). Cirrus-HD detected that macular thickness was slightly higher 1 week after surgery, compared with the preoperative examination (3.4% increase; p = 0.04). That difference remained stable at the 12-month postoperative visit (p = 0.01). GCA showed no changes. The ONH analysis with Cirrus-HD determined that rim area (p = 0.03) as well as disc area (p = 0.04) significantly increased. HRT-3 found no significant changes affecting those variables.

CONCLUSIONS

The implantation of V4c ICL® did not induce a clinically significant impact on the results of the RNFL/ONH analysis with OCT and HRT.

Analysis of vault prediction in phakic implantable phakic collamer lenses: manufacturer's calculator vs theoretical formulae vs clinical practice

BACKGROUND

Implantable collamer phakic (ICL) intraocular lens sizing calculations are necessary to avoid complications associated to inadequate sizing. Historically, Holladay R, Dougherty, Hernández-Matamoros, and other authors have tried to create new formulas that solve calculation problems and provide higher reliability. In addition, in recent years, the appearance of new equipment, parameters, and formulas have led to significant progress. This paper compares the sizing according to manufacturer's method and other methods.

METHODS

Forty-three eyes of 24 patients with EVO ICL implanted, with at least 1 year of follow-up, were analysed. The analysed variables were white to white (WTW), anterior chamber depth (ACD), ACW (angle-to-angle), crystalline lens rise (CLR), ICL size, vault measured at 1 week and 1 year after surgery, ICL size, and vault predicted by Nakamura-2 as well as vault size predicted by Igarashi.

RESULTS

Sizing calculation with Online Calculation and Ordering System according to WTW and ACD is a good indicator with 86% success rate. The calculation with Nakamura 2 suggests larger ICL sizes in 32.5% of cases and smaller in 18.6% of cases, while the resulting Vault according to Igarashi obtains better results without significant differences.

CONCLUSIONS

ICL sizing according WTW and ACD, using the manufacturer's algorithm, seems to be the most predictable method compared to other algorithms using other variables. The surgeon's expertise also has a high importance in the final ICL size election.

Rotational Stability After Implantation of Two Different Phakic Toric Intraocular Lenses

PURPOSE

To compare clinical outcomes and rotational stability of the toric implantable Collamer lens (TICL) and toric implantable phakic contact lens (TIPCL).

METHODS

Charts were reviewed from January 2011 to January 2023 to identify all TICLs and TIPCLs implanted by a single surgeon. Implant size was generally chosen according to the manufacturer's recommendation, but 15 TIPCLs 0.25 mm larger than recommended to increase vaulting were included.

RESULTS

Eighty-four TICLs and 98 TIPCLs were identified and yielded excellent refractive and visual results in eyes with high myopic astigmatism at the last follow-up visit. No case of acute glaucoma or cataract induction was observed. In total, 15 (8.2%) rotated lenses were recorded; 2 (2.4%) TICLs and 13 (13.3%) TIPCLs (P = .013). Eyes in both groups were similar in preoperative spherical equivalent, cylinder, white-to-white distance, anterior chamber depth (ACD), anterior chamber angle, and mean follow-up times (P = .925, .673, .822, .794, .358, and .873, respectively). Average TICL size was larger than TIPCL size (P < .001). Rotation of the lenses was positively correlated with cylinder and negatively correlated with ACD but not with vaulting (P = .001, r = 0.253; P = .011, r = -0.193; P = .488, r = -0.057; respectively). Vaulting was positively correlated with preoperative ACD (P ≤ .001, r = .329). In eyes with a rotated TIPCL, preoperative cylinder was higher and ACD was shallower than in eyes with a stable TIPCL (P = .001 and .007, respectively). Increasing the implant size had no significant effect on rotation rate (P = .685).

CONCLUSIONS

Although both implants were safe and effective in highly myopic eyes, TICL rotated less frequently than TIPCL and required fewer secondary interventions. Rotation was correlated with preoperative cylinder and ACD but not lens vaulting. [J Refract Surg. 2023;39(7):463-472.].

Evaluation of the Performance of Two Nomograms and Four Vault Prediction Formulas for Implantable Collamer Lens Size Selection

PURPOSE

To evaluate the performance of different nomograms and vault prediction formulas in predicting the optimal Implantable Collamer Lens (ICL; STAAR Surgical) size and vault.

METHODS

This retrospective study included 108 participants (214 eyes) who underwent ICL implantation. The efficacy of the manufacturer's nomogram, Parkhurst nomogram, NK formula, KS formula, Zhu formula, and ZZ formula was assessed by comparing the indicated ICL sizes to the postoperative vault measurements. Additionally, Bland-Altman plots and the Friedman test were used to assess the agreement and absolute error between the actual vault and predicted vault.

RESULTS

The proportions of the ideal ICL category recommended by the manufacturer's nomogram, Parkhurst nomogram, NK formula, KS formula, Zhu formula, and ZZ formula were 50.5%, 45.3%, 46.7%, 42.5%, 50.0%, and 28.5%, respectively. The mean differences between the actual vault and the predicted vault using the NK, KS, Zhu, and ZZ formulas were 144.1 ± 261.1, -19.3 ± 179.6, 70.8 ± 284.2, and 182.6 ± 361.5 μm, respectively. The predicted ICL vault tended to overestimate the actual ICL vault, particularly when choosing a larger ICL size. The KS formula shows the smallest deviation in prediction error and is least affected by variation in ICL size.

CONCLUSIONS

White-to-white distance from the Pentacam (Oculus Optikgeräte GmbH) coupled with the manufacturer's nomogram performed well for ICL size selection. Four vault prediction formulas tended to overestimate the actual ICL vault, particularly when selecting a larger ICL size. The KS formula appeared to have the least bias of the formulas. Simultaneously, vault prediction formulas need to be modified according to the ICL size. [J Refract Surg. 2023;39(7):456-461.].

Analysis of Inter-Eye Vault Differences After Implantable Collamer Lens (V4c) Implantation

Purpose

The safety and stability of implantable collamer lens (ICL) implantation are closely related to the vault. We aimed to assess clinical data from patients with similar anterior segment anatomy who received ICL of the same model placed in the same position and analyze common range and factors affecting the vault inter-eye difference.

Patients and Methods

A prospective study was performed, including 162 eyes of 81 patients with a bilateral ICL (V4c) implantation. Subjects were evaluated before the surgery and 1 day, 1 week, and 1 month postoperatively, and they were divided into 4 groups based on the ICL size. Bivariate correlation and multiple linear regression (stepwise) analyzed associations between vault inter-eye differences and horizontal sulcus-to-sulcus diameter, anterior chamber depth, lens thickness, ICL size, spherical equivalent, and vault.

Results

One month after surgery, mean vault inter-eye differences were 74.59 ± 55.59 µm. Nearly 70% of patients presented with vault inter-eye differences lower than 100 µm. The second eye vault variance of 69% was attributed to the first eye vault. Vault inter-eye differences were positively correlated with ICL spherical equivalent (regression equation: vault inter-eye differences (μm) = 139.415 + 6.295 × ICL spherical equivalent). Vaults after ICL implantation were similar in fellow eyes, with some considerable differences. The 95% confidence interval of the vault inter-eye difference was -34.4 ~ 183.6 μm.

Conclusion

In eyes with similar anterior segment anatomy, there is a 95% probability that the vault will vary from -34.4 μm to -183.6 μm when a similar ICL is implanted. These results can help surgeons to select an appropriate ICL size to achieve an ideal vault. The smaller the spherical equivalent, the larger the difference between the two vaults, which provides a reference for size in moderate myopia. ICL spherical equivalent affects and predicts vault inter-eye differences after ICL implantation.

Effects of brimonidine tartrate 0.2 and 0.15% ophthalmic solution on the static and dynamic pupil characteristics

Aims

To investigate the differences between 0.2 and 0.15% brimonidine tartrate eye drops for anti-mydriatic effects and the optical quality under different light conditions.

Methods

This prospective study involved 80 consecutive high myopia patients undergoing implantation of a V4c ICL. The patients were randomly instilled with brimonidine 0.2 and 0.15% 2 weeks postoperatively. Visual quality, pupil center, pupil size, and refraction under different light conditions were measured before and 0.5 h after brimonidine administration. A symptom questionnaire was also evaluated.

Results

There was no statistical difference in the static and dynamic pupil diameters and velocity after LS between the two groups (p > 0.05). The 0.2% group had significant changes in pupil center before and after treatment, while there was no obvious movement of the 0.15% group under all illumination condition (p > 0.05). The OSI after treatment of the 0.15% group was lower than that of 0.2% group (p = 0.012). The PVA9% and PVA100% of the 0.15% group was higher than that of 0.2% group in the dark (p = 0.009, p = 0.012). The HOA RMS of the 0.15% group was lower than that of 0.2% group (p = 0.016). The QIRC score in the 0.15% group was significantly higher than that in the 0.2% group (p = 0.043).

Conclusion

0.15 and 0.2% brimonidine tartrate eye drops had similar anti-mydriatic ability, while 0.15% group had better visual quality than 0.2% concentration, and hardly introduced pupil shift. 0.15% brimonidine tartrate eye drops may be more suitable for patients with nocturnal glare symptoms in the early postoperative period after ICL implantation.

Development and validation of a new multivariable prediction model to estimate risk of abnormal vault

PURPOSE

To develop and validate a new multivariable prediction model to estimate risk of abnormal vault after EVO Implantable Collamer Lens (EVO-ICL) implantation using the preoperative parameters.

METHODS

This retrospective study comprised 282 eyes of 143patients who underwent EVO-ICL surgery between May 2021 and April 2022. We measured preoperative parameters before surgery and vaults in 1 week after the operation using swept-source optical coherence tomography (SS-OCT). Risk factors for abnormal vault were determined by univariate and multivariate logistic regression analyses, and a nomogram was developed to forecast the risk of abnormal vault after EVO-ICL implantation. We assessed the performance of nomogram in terms of discrimination and calibration, including concordance index (C-index), receiver operating characteristic curve (ROC), area under the ROC curve (AUC), and decision curve analysis (DCA). Bootstrap resampling was used as an internal verification method.

RESULTS

The logistic regression analysis revealed the independent risk factors for abnormal vault were white-to-white(WTW), anterior chamber angle(ACA), pupil size, and ICL-size, all of them were used to establish a nomogram based on multivariate logistic regression to predict the risk of abnormal vault. The C-indexes and AUC were 0.669 (95%CI, 0.605, 0.733). The calibration curves of the nomogram showed relatively small bias from the reference line, implicating an acceptable degree of confidence. The DCA indicates the potential clinical significance of the nomogram.

CONCLUSIONS

We developed a new multivariable prediction model to estimate risk of abnormal vault. The model shows good prediction effect and can provide assistance for clinical decision of ICL size.

Comparison of higher-order aberrations between implantable collamer lens V4c implantation and simulated spectacle correction in patients with high myopia

PURPOSE

To investigate the differences in higher-order aberrations between non-toric or toric implantable collamer lens (ICL or TICL) V4c implantation and simulated spectacle correction.

METHODS

Patients with high myopia who underwent ICL/TICL V4c implantation were enrolled. The "total no defocus" pattern of iTrace aberrometry to simulate the condition of spectacle correction was measured before ICL/TICL implantation, and higher-order aberrations in this condition were compared to those 3 months after surgery. Related factors with changes in coma were comprehensively analyzed.

RESULTS

A total of 89 right eyes of 89 patients were included. Compared to simulated spectacle correction, total-eye coma (P<0.0001 ICL, P<0.0001 TICL) and internal coma (P<0.0001 ICL, P<0.001 TICL) decreased in the ICL- and TICL-treated groups after surgery. Total-eye secondary astigmatism (P<0.0001 ICL, P=0.007 TICL) and internal secondary astigmatism (P<0.0001 ICL, P=0.009 TICL) were also decreased in both groups postoperatively. Spherical error showed positive correlations with variation in total-eye coma (r=0.37, P=0.004 ICL; r=0.56, P=0.001 TICL) and internal coma (r=0.30, P=0.02 ICL and r=0.45, P=0.01 TICL). Axial length revealed negative correlations with changes in total-eye coma (r=-0.45, P<0.001 ICL; r=-0.39, P=0.03 TICL) and internal coma (r=-0.28, P=0.03 ICL and r=-0.42, P=0.02 TICL).

CONCLUSIONS

Both ICL- and TICL-treated groups demonstrated a decrease in coma and secondary astigmatism after 3 months, postoperatively. ICL/TICL may confer a compensatory effect on coma aberration and secondary astigmatism. Patients with a higher myopia achieved a greater improvement in coma and may benefit more from ICL/TICL implantation than from spectacle correction implantation than from spectacle correction.

The Non-uniform Distribution of Horizontal and Vertical Crystalline Lens Rise Using Optical Coherence Tomography

PURPOSE

To observe the crystalline lens rise (CLR) in horizontal and vertical orientations using anterior segment optical coherence tomography (AS-OCT).

METHODS

Non-invasive swept-source AS-OCT was used to measure the lens thickness, CLR, and angle-to-angle distance (ATA) in both the horizontal and vertical orientations. Anterior chamber depth (ACD) and horizontal white-to-white corneal diameter were obtained using the Pentacam HR (Oculus Optikgeräte GmbH). Axial length was obtained using the IOLMaster 700 (Carl Zeiss Meditec AG). The paired t test was used to analyze the difference in CLR between the two orientations. Pearson correlation analysis was performed to investigate the correlations between CLR and other ocular variables.

RESULTS

This prospective observational study comprised 99 eyes (99 patients) that underwent Visian Implantable Collamer Lens (STAAR Surgical) implantation for myopic correction. The mean CLR was 64.29 ± 168.04 and 208.09 ± 173.12 µm in the horizontal and vertical orientations, respectively. The vertical CLR (VCLR) was significantly greater than the horizontal CLR (HCLR) (P < .05). Both the HCLR and VCLR were positively correlated with lens thickness and negatively correlated with ACD (all P < .05). The difference in CLR (VCLR-HCLR) was positively correlated with the axial length and the difference in ATA between the two orientations (P < .05).

CONCLUSIONS

VCLR was greater than HCLR in most patients with myopia, especially in the longer eyes. This nonuniform distribution in CLR implied different placements of the iridocorneal angles in the horizontal and vertical orientations and should be considered for the selection of ICL size and placement position. [J Refract Surg. 2023;39(5):354-359.].

Prediction of Implantable Collamer Lens Vault Based on Preoperative Biometric Factors and Lens Parameters

PURPOSE

To establish and validate the accuracy of implantable collamer lens (ICL) vault size prediction formula based on preoperative biometric factors and lens parameters.

METHODS

This study included 300 patients (300 eyes) with Visian ICL V4c (STAAR Surgical) implantation. They were randomly divided into the formula establishment group and formula validation group. Anterior segment measurements, ICL V4c size and power, and vault 1 week postoperatively were collected from all patients. Multiple linear regression analysis was performed to establish the prediction formula. Mean absolute error (MAE), median absolute error (MedAE), root mean square error (RMSE), and Bland-Altman diagrams were used to evaluate the prediction formula.

RESULTS

Anterior chamber depth (ACD) had the greatest influence on vault 1 week after ICL V4c implantation, followed by ICL V4c size and angle-to-angle distance (ATA). The prediction formula was obtained according to the partial regression coefficient, which was vault (mm) = -1.279 + 0.291 × ACD (mm) + 0.210 × ICL V4c size (mm) - 0.144 × ATA (mm) (R² = 0.661). In the formula validation group, the mean predictive vault, MAE, MedAE, and RMSE were 628.10, 135.09, 130.42, and 150.46 µm, respectively. The Bland-Altman diagram showed the predictive vault was in good agreement with the actual vault.

CONCLUSIONS

A novel ICL V4c vault prediction formula was developed and shown to be an effective method for predicting the vault to reduce surgical complications. [J Refract Surg. 2023;39(5):332-339.].

Artificial intelligence-based refractive error prediction and EVO-implantable collamer lens power calculation for myopia correction

BACKGROUND

Implantable collamer lens (ICL) has been widely accepted for its excellent visual outcomes for myopia correction. It is a new challenge in phakic IOL power calculation, especially for those with low and moderate myopia. This study aimed to establish a novel stacking machine learning (ML) model for predicting postoperative refraction errors and calculating EVO-ICL lens power.

METHODS

We enrolled 2767 eyes of 1678 patients (age: 27.5 ± 6.33 years, 18-54 years) who underwent non-toric (NT)-ICL or toric-ICL (TICL) implantation during 2014 to 2021. The postoperative spherical equivalent (SE) and sphere were predicted using stacking ML models [support vector regression (SVR), LASSO, random forest, and XGBoost] and training based on ocular dimensional parameters from NT-ICL and TICL cases, respectively. The accuracy of the stacking ML models was compared with that of the modified vergence formula (MVF) based on the mean absolute error (MAE), median absolute error (MedAE), and percentages of eyes within ± 0.25, ± 0.50, and ± 0.75 diopters (D) and Bland-Altman analyses. In addition, the recommended spheric lens power was calculated with 0.25 D intervals and targeting emmetropia.

RESULTS

After NT-ICL implantation, the random forest model demonstrated the lowest MAE (0.339 D) for predicting SE. Contrarily, the SVR model showed the lowest MAE (0.386 D) for predicting the sphere. After TICL implantation, the XGBoost model showed the lowest MAE for predicting both SE (0.325 D) and sphere (0.308 D). Compared with MVF, ML models had numerically lower values of standard deviation, MAE, and MedAE and comparable percentages of eyes within ± 0.25 D, ± 0.50 D, and ± 0.75 D prediction errors. The difference between MVF and ML models was larger in eyes with low-to-moderate myopia (preoperative SE >  - 6.00 D). Our final optimal stacking ML models showed strong agreement between the predictive values of MVF by Bland-Altman plots.

CONCLUSION

With various ocular dimensional parameters, ML models demonstrate comparable accuracy than existing MVF models and potential advantages in low-to-moderate myopia, and thus provide a novel nomogram for postoperative refractive error prediction and lens power calculation.

Characteristics and factors associated with the position of the haptic after ICL V4C implantation

PURPOSE

To assess the position of implantable collamer lens (ICL) haptic after ICL V4C implantation using standardized panoramic ultrasound bimicroscopy (UBM), to analyze its characteristics, associated factors, and the relationship with the clinical vault quantitatively.

SETTING

Hankou Aier Eye Hospital, Wuhan, Hubei, China.

DESIGN

Cross-sectional study.

METHODS

167 subjects (323 eyes) implanted with ICL V4C who had a 3-month follow-up with UBM examination were included in this study. The relative position of ICL to the adjacent structure and ICL haptic-related parameters (the final tip point of ICL haptic [ftICL haptic], measured from the scleral spur to the final tip of the ICL haptic, the posterior of the ICL to ICL haptic [ICL arc], measured from the posterior surface of the ICL to the ICL haptic plane, and the height of the crystalline lens from the ICL haptic (lens arc), measured from the anterior surface of the crystalline lens to the ICL haptic plane and other parameters), were estimated on the UBM image. Eyes were divided into 3 subgroups according to the ftICL haptic (Group 1: ≤0.5 mm; Group 2: 0.5 to 1.0 mm; and Group 3:≥1.0 mm, respectively), and the factors associated with the ICL haptic-related parameters and their impact on the clinical vault were evaluated.

RESULTS

The haptics could be imaged in the ciliary sulcus, on the ciliary body, and under the ciliary body in 629 (48.7%), 525 (40.6%), and 138 (10.7%) eyes, respectively. The ftICL haptic and the summation of ICL arc and lens arc showed a correlation with the clinical vault ( r = -0.34, P = .00; r = 0.87, P = .00). When the ftICL haptic results were divided into 3 groups, the percentage of eyes that exhibited clinical vault >750 μm were lowest in Group 3. Multivariate regression analysis showed spherical equivalent, white-to-white (WTW), anterior chamber volume (ACV) and iris-ciliary angle (ICA); the difference between the implanted ICL size and horizontal sulcus-to-sulcus (ICL size-STS) were associated with the ftICL haptic. The IOP, WTW, ACV, and the ICL size-STS were significantly associated with ICL arc, while the ICA and lens rise were associated with lens arc.

CONCLUSIONS

The position of ICL haptic was associated with the clinical vault. Its quantitative evaluation may provide valuable information to help clinicians to select the best ICL size before surgery and understand the formation of clinical vault after surgery.

Postoperative vault prediction for phakic implantable collamer lens surgery: LASSO formulas

PURPOSE

To develop and evaluate reliable formulas for predicting postoperative vault more accurately after implantable collamer lens (ICL) surgery in a White patient population with varying degrees of ametropia.

SETTING

Private clinical practice.

DESIGN

Retrospective analysis on dataset split into a separate training and test set.

METHODS

115 eyes of 59 patients were used to train regression models predicting postoperative vault based on anterior segment optical coherence tomography (OCT) parameters (Least Absolute Shrinkage and Selection Operator [LASSO]-OCT formula), ocular biometry data (LASSO-Biometry formula), or data from both devices (LASSO-Full formula). The performance of these models was evaluated against the manufacturer's nomogram (Online Calculation and Ordering System [OCOS]) and Nakamura 1 (NK1) and 2 (NK2) formulas on a matched separate test set of 37 eyes of 19 patients.

RESULTS

The mean preoperative spherical equivalent was -5.32 ± 3.37 (range: +3.75 to -17.375 diopters). The mean absolute errors of the estimated vs achieved postoperative vault for the LASSO-Biometry, LASSO-OCT, and LASSO-Full formulas were 144.1 ± 107.9 μm, 145.6 ± 100.6 μm, and 132.0 ± 86.6 μm, respectively. These results were significantly lower compared with the OCOS, NK1, and NK2 formulas ( P < .006). Postoperative vault could be estimated within 500 μm in 97.3% (LASSO-Biometry) to 100% of cases (LASSO-OCT and LASSO-Full).

CONCLUSIONS

The LASSO suite provided a set of powerful, reproducible yet convenient ICL sizing formulas with state-of-the-art performance in White patients, including those with low to moderate degrees of myopia. The calculator can be accessed at http://icl.emmetropia.be .

ICL Postimplantation Decentration and Tilt in Myopic Patients with Primary Iridociliary Cysts

Purpose

To observe the decentration and tilt of implantable collamer lens (ICL) as well as possible visual effects postimplantation in primary iridociliary cysts.

Methods

The present investigation was a retrospective cohort study. All 48 patients (91 eyes) who underwent ICL surgery at the Center of Refraction Surgery of Tianjin Medical University Eye Hospital between July 2018 and May 2020 were split into two groups based on the absence or presence of primary iridociliary cysts established by ultrasonic biological microscopy (UBM) examination. Intraocular pressure (IOP), corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), anterior chamber angle (ACA), anterior chamber volume (ACV), and anterior chamber depth (ACD) were recorded preoperatively and postoperatively at 1, 6, and 12 months. Additionally, we performed an analysis of the ICL vault, decentration, and tilt using a rotating Scheimpflug Oculus Pentacam camera system at 1, 6, and 12 months after surgery.

Results

No serious complications were observed. Significant postoperative improvement (P < 0.05) of UDVA was established in the two studied groups; however, we did not observe statistically significant intergroup differences (P > 0.05) throughout the entire research period. In each group, the preoperative ACA, ACV, and ACD were statistically significantly reduced (P < 0.05), but no such decrease was established between their postoperative values (P > 0.05). We observed no statistical differences between both groups with regard to their values of IOP, ACA, ACV, ACD, ICL vault, ICL decentration, and tilt at 1, 6, and 12 months after surgery. Similarly, no statistically significant within-group correlation (P > 0.05) of the decentration of ICL and the tilt and the CDVA values was established.

Conclusion

No postimplantation effect of ICL with a central hole on vision was established in myopia patients with primary iridociliary cysts, within certain limits of ICL decentration and tilt values.

A quantitative study of the effect of ICL orientation selection on post-operative vault and model-assisted vault prediction

Background

Appropriate vault height of implantable collamer lens (ICL) implantation matters for it has risks of corneal endothelial cell loss, cataract formation and intraocular pressure elevation, which could lead to irreversible damage to optic nerve. Therefore, pre-operative prediction for an ideal vault height is a hotspot. However, few data exist regarding quantitative effect of ICL orientation on vault height. This study is aimed to quantitatively investigate the effect of ICL implantation orientation on vault height, and built a machine-learning (ML)-based vault prediction model taking implantation orientation into account.

Methods

473 consecutive case series treated with ICL implantation were retrospectively analyzed (408 were horizontally implanted, and 65 were vertically implanted). Multivariable logistic regression analysis was performed to determine the association between ICL orientation and achieved vault. ML was performed to develop a new vault height prediction model taking ICL orientation into account. Receiver operating characteristic curve (ROC) and net reclassification index (NRI) were obtained to assess the prediction ability.

Results

95% of all the patients achieved 20/20 uncorrected distance visual acuity (UDVA) or better. No complications including cataract formation, dispersion or optic nerve injury were observed in any cases. Sex, sphere power, cylinder power, axis, ICL size and ICL orientation were all significant risk factors associated to vault height, and age was positively co-related. Of note, ICL size and ICL orientation were the top-ranking risk factors. Comparing to conventional horizontal implantation, vertical implantation could reduce the achieved vault by 81.187 μm (p < 0.001). In regarding to different ICL sizes, vertical implantation had no good to vault reduction when using ICL of 12.1 mm. However, it could reduce the vault by 59.351 μm and 160.992 μm respectively when ICL of 12.6mm and 13.2 mm were implanted (p = 0.0097 and p = 0.0124). For prediction of vault height, ML based model significantly outperformed traditional multivariable regression model.

Conclusion

We provide quantitative evidence that vertical implantation of ICL could effectively reduce the achieved vault height, especially when large size ICL was implanted, comparing to traditional horizontal implantation. ML is extremely applicable in development of vault prediction model.

Posterior-Chamber Phakic Implantable Collamer Lenses with and without a Central Hole: A Comparative Study

Purpose

 This study aimed to compare the short-term outcome of implanting the Visian implantable collamer lens V4 ICL versus the Visian V4c ICL in patients with moderate and high myopia.

Patients and Methods

 This is a retrospective that was conducted on patients with moderate or high myopia who were scheduled for ICL implantation at our institution, Patients who underwent V4 ICL implantation with peripheral iridectomy were assigned to group A, and those who underwent V4c ICL implantation without peripheral iridectomy were assigned to group B. In group A, a preoperative peripheral iridectomy was performed. In group B, the patients received cycloplegic and dilating agents. The patients underwent a complete ocular examination preoperatively and during the follow-up visits that were conducted at 3, 6, and 12 months postoperatively.

Results

This study included 214 eyes from 107 patients; group A included 110 eyes, and group B included 104 eyes. Postoperatively, the UCVA and BCVA showed statistically significant improvement across the follow-up time points (p<0.001), with no significant difference between the two groups. No statistically significant difference was found between the two groups in the mean achieved correction or the residual refraction. Both groups showed a strong correlation between the target and the achieved correction, with R2 = 0.99 in the two groups. No significant difference was found between the two groups in the IOP across all time measures. However, the intraocular pressure showed a statistically significant postoperative increase in group A (p=0.004), and no significant change in group B (p=0.817). There was a downward slope in the vaults of both groups across time, with significant variation in the last follow-up measure compared to the 3-month measure in the two groups (p<0.001). No significant difference was found between the two groups across all time measures.

Conclusion

The current study adds new evidence concerning the feasibility, safety, and efficacy of ICL V4c implantation for the treatment of moderate and high myopia, with safer postoperative IOP.

The EVO ICL for Moderate Myopia: Results from the US FDA Clinical Trial

Purpose

To evaluate the safety and effectiveness of collamer posterior chamber phakic refractive lenses with a central port design (EVO and EVO+ Sphere and Toric implantable collamer lenses [ICLs]) for correction of moderate myopia with or without astigmatism.

Patients and Methods

Six-month results of a multicenter clinical trial were performed under United States FDA Investigational Device Exemption. Subjects 21 through 45 years of age with manifest refraction spherical equivalent ranging from -3.00 D to -6.00 D and astigmatism up to 4.00 D underwent implantation of EVO or EVO+ Sphere or Toric ICLs. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, intraocular pressure (IOP), endothelial cell density, and adverse events were evaluated over 6 months.

Results

This report includes a retrospective review of 200 eyes of 114 subjects with mean age 35.1 ± 5.1 years that completed the 6-month visit. Mean preoperative spherical equivalent (SE) measured -4.61 ± 0.87 D (range: -3.00 to -6.00 D). At 6 months, mean SE was -0.085 ± 0.26 D, with 91.5% within ± 0.50 D of target and 100.0% within ±1.00 D of target. Mean postoperative UDVA and CDVA were -0.065 ± 0.08 logMAR and -0.14 ± 0.07 logMAR, respectively. About 98.0% of eyes maintained or gained lines of CDVA, and no eye lost more than 1 line CDVA. Efficacy and safety indices were 1.03 and 1.21, respectively. No eye experienced pupillary block, required preoperative or postoperative peripheral iridotomy or iridectomy, developed anterior subcapsular cataract or had elevated IOP due to angle narrowing or pigment dispersion. Mean endothelial cell density declined by 2.2%.

Conclusion

EVO ICL lenses demonstrated accuracy, predictability and stability of refractive correction with achievement of high levels of UDVA and an excellent safety profile for patients with moderate myopia with or without astigmatism.

Descriptive Analysis of Footplate Position After Myopic Implantable Collamer Lens Implantation Using a Very High-Frequency Ultrasound Robotic Scanner

Purpose

To assess the position of the haptics of the implantable collamer lens (ICL) in myopic eyes using a high-frequency ultrasound robotic scanner.

Methods

This was a prospective, single-arm, observational study carried out at the Instituto Zaldivar SA (Mendoza, Argentina) in a sample of 52 eyes who have been submitted to successful ICL implantation prior to enrollment. Images of the eyes were obtained using a very-high frequency digital ultrasound robotic scanner (VHFDU) to establish the position of the ICL in the posterior chamber and its relation to the ciliary sulcus. New parameters for lens position analysis were also described.

Results

In 81% of cases (42 eyes), the ICL rests on the ciliary body (CB) in both temporal and nasal sides, being slightly lower than 6% (3 eyes) those that rest on the sulcus in both sides, with significant correlations between ICL position and vault values (p<0.05). Cases in which the ICL position was CB-CB yielded central vault values across the whole range determined within the sample, but most of the eyes where the ICL rests on both the sulcus in one side and the CB in the other yield greater central vault values. Correlation was significant between ICL position and retroposition distance on the temporal side (Spearman's rho -0.487, p<0.001). A significant but weaker correlation was also found between ICL position and retroiridian space (p<0.05).

Conclusion

ICL for myopia footplates tend to locate outside of the sulcus in a significant percentage of patients after successful implantation. VHFDU assessment in eyes implanted with an ICL to properly study the lens footplate position and posterior anatomical relations provides important additional information besides post-surgery vault.

Validation of the vault prediction model based on the sulcus-to-sulcus diameter and lens thickness: a 925-eye prospective study

BACKGROUND

To verify the accuracy and stability of the prediction formula based on the ciliary sulcus diameter and lens thickness and to analyse factors influencing the prediction results.

METHODS

In total, 925 eyes from 506 subjects were enrolled in this prospective study between July 1, 2020, and June 30, 2021. Subjects were divided into four seasons, each spanning three months. The target vault was set to be between 300 μm and 700 μm according the prediction formula. The actual vault was measured one month postoperatively. The Bland-Altman test, 95% confidence intervals (95% CI) and 95% limits of agreement (95% LoA) were used to evaluate the agreement between the predicted vault and the actual vault. Eyes with absolute prediction errors greater than 300 μm were further analysed.

RESULTS

The mean predicted vaults for the four seasons were 503 ± 99, 494 ± 96, 481 ± 92 and 502 ± 93 μm, while the mean actual vaults were 531 ± 189, 491 ± 179, 464 ± 179 and 529 ± 162 μm, respectively. The predicted and actual vaults of the overall subjects were 493 ± 95 and 500 ± 180 μm, respectively. Of the 925 eyes, 861 eyes (93.08%), 42 eyes (4.54%), and 22 eyes (2.38%) showed a normal vault, high vault, and low vault, respectively. Bland-Altman plots showed that the mean difference between the actual vault and predicted vault overall (± 95% LoA) was 6.43 ± 176.2 μm (-339 to 352 μm). Three UBM features may lead to large prediction errors (more than 300 μm): wide iris-ciliary angle (ICA), iris concavity and anteriorly positioned ciliary body.

CONCLUSIONS

This study demonstrated the accuracy and stability of the prediction formula through the validation of a large sample size and a long time span. Wide ICA, iris concavity and anteriorly positioned ciliary body may have an effect on vault.

Early outcomes of anterior segment parameters after implantable collamer lens V4c implantation

Background

This study investigated the early outcomes of anterior segment parameters after implanting an implantable collamer lens with a central hole (ICL V4c) in patients with myopia and determined the earliest follow-up time for detecting potential complications.

Methods

Sixty-two patients were included, and the following parameters were measured at baseline (preoperative), 1 day, 1 week, and 1, 3, and 6 months after the operation: intraocular pressure (IOP), endothelial cell density (ECD), central anterior chamber depth (CACD), anterior chamber volume (ACV), nasal and temporal anterior chamber angle (n-ACA and t-ACA), horizontal corneal diameter (white-to-white, WTW), and axial length (AL). The vault was measured at each post-operative timepoint.

Results

The postoperative IOP and ECD at the 6 months were both statistically similar to the baseline. The post-operative CACD and ACV were significantly less at all timepoints compared with the baseline (P < 0.001) and stayed stable from 1 day and 1 month after the operation, respectively. Postoperative n-ACA and t-ACA decreased significantly at 1 day and 1 week compared with the baseline (P < 0.001), while tended to stabilization at 1, 3, and 6 months. The vault kept decreasing significantly at 1 day, 1 week, and 1 month, but stayed stable at 3 and 6 months. The postoperative n-ACA and t-ACA positively correlated with the baseline ACA, CACD, and ACV.

Conclusions

The anterior chamber parameters tended to stabilization early after the operation. Thus, it is essential to evaluate patients’ anterior segment status at earlier timepoints and prevent complications with prompt and non-invasive intervention.

The effect of implantable collamer Lens V4c on ocular biometric measurements and intraocular lens power calculation based on Pentacam-AXL and IOLMaster 500

Background

To investigate the possible effect of implantable collamer lens (ICL) V4c on ocular biometric measurements by a new biometer Pentacam-AXL and partial coherence interferometry (PCI)-based IOLMaster 500 and intraocular lens power calculation using fourth-generation formula.

Methods

We retrospectively enrolled patients who underwent ICL (EVO-V4c, STAAR Surgical Co. Nidau, Switzerland) implantation surgery from September 2020 to November 2021. The Pentacam-AXL and IOLMaster 500 biometers were used to measure axial length (AL), anterior chamber depth (ACD), keratometry (K), white to white (WTW), and central corneal thickness (CCT) values before and at least 2 months after ICL V4c implantation. The IOL power was calculated using the Barrett Universal II formula.

Results

The study included 45 eyes in 28 patients. There was a significant increase in ALs (average 0.03 ± 0.07 mm, p = 0.01) and a significant decrease of ACDs (average 0.19 ± 0.17 mm, p < 0.001) based on Pentacam-AXL. Similar changes in ALs and ACDs were also found in IOLMaster 500. In addition, the difference in WTWs in the two devices and that of CCTs in Pentacam-AXL were statistically significant. However, the preoperative and postoperative K1 and K2 were separately comparable using either device. The IOL power calculated by the Barrett Universal II formula did not change significantly either by the software built in Pentacam-AXL or by manually putting the parameters of the IOLMaster 500 into the formula manually (p = 0.058, p = 0.675, respectively).

Conclusions

Ocular parameters including ALs, ACDs, WTWs, and CCTs using a new Pentacam-AXL and standard PCI-based IOLMaster 500 changed significantly before and after the ICL V4c implantation, while IOL power prediction using the Barrett Universal II formula was little affected.

Clinical observations of EVO-ICL implantation and changes in corneal astigmatism using a modified technique

Background

Implantable collamer lens (ICL) surgery techniques are constantly progressing. The purpose of this study was to investigate the application effect of the modified technique and its impact on the change in corneal astigmatism in EVO-ICL surgery.

Methods

The analysis of retrospective cohort data included 153 eyes of 81 patients with myopia from July 2018 to May 2020. An EVO-ICL was inserted by modified surgical skills, including a single 3.0 mm corneal incision and no ophthalmic viscosurgical device (OVD) before the insertion of the ICL (modified technique group: 41 cases, 80 eyes) and standard procedure (standard technique group: 40 cases, 73 eyes). Early postoperative intraocular pressure (IOP) was monitored at 2 and 24 h. IOP, corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), vault, and anterior chamber depth (ACD) were measured 1, 6, and 12 months following the initial examination. The corneal endothelial cell density (ECD) was monitored at 6 and 12 months after the operation. Surgically induced astigmatism (SIA) in the total, anterior, and posterior corneal surfaces was analysed 1 month after the operation.

Results

No serious complications were detected. The two groups had no difference in visual outcomes, ICL vaults, or ACD at any time point (P > 0.05). Two hours postoperatively, IOP was significantly lower in the modified technique group (16.22 ± 2.22 vs. 18.37 ± 1.92 mmHg, P < 0.05) than in the standard technique group. IOP decreased gradually after 24 h to preoperative levels. The postoperative IOP remained stable over a 12-month period. The ECD at 6 and 12 months was not significantly different between the groups (P > 0.05). SIA in the total, anterior, and posterior corneal surfaces were assumed to have no clinically meaningful differences between groups at one month after operation (P > 0.05).

Conclusions

The modified technique is efficient and safe, producing comparable visual and structural outcomes without adversely affecting ECD, and reduces fluctuations in IOP at the early postoperative stages. The auxiliary incision in the standard technique does not increase corneal SIA, which is also a factor to consider for inexperienced surgeons.

Three-year follow-up of posterior chamber phakic intraocular lens with a central port design after deep anterior lamellar keratoplasty

Background

To evaluate clinical outcomes of the Visian implantable collamer lens (ICL) with a central port to correct myopia and astigmatism after deep anterior lamellar keratoplasty (DALK) for keratoconus throughout 3 years of follow-up.

Methods

This study included 20 eyes of 20 patients that underwent V4c ICL (13 eyes with a spherical ICL and 7 eyes with a toric ICL) implantation after DALK. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, intraocular pressure (IOP), endothelial cell density (ECD), and vault were analyzed.

Results

The mean UDVA improved from the preoperative 1.18 ± 0.33 logMAR to 0.25 ± 0.14 logMAR at 6 months after surgery (P < 0.0001) and remained unchanged throughout the whole follow-up (P = 0.4). All eyes gained lines of CDVA compared to preoperative values. At the last follow-up visit, all eyes achieved CDVA of 0.2 logMAR or better and 13 eyes (65%) 0.1 logMAR or better. At 6 months post-surgery, all eyes (100%) had a spherical equivalent within ± 1.50 D, and 19 (95%) within ± 1.00 D. The mean manifest spherical equivalent was stable over the postoperative follow-up (P = 0.25). No significant increase in IOP occurred in any case throughout the 3 years of follow-up. The loss in ECD from the preoperative baseline at the last follow-up visit was 2.27%.

Conclusions

The clinical outcomes suggest that the V4c ICL implantation for correction of myopia and regular astigmatism in post-DALK eyes was satisfactory in terms of effectiveness, safety, and stability during 3 years of follow-up.

Refractive outcomes of implantable collamer lens implantation in 1212 eyes with suboptimal corrected distance vision acuity

Purpose: To analyze the factors related to corrected distance vision acuity (CDVA) after implantable collamer lens (ICL) implantation in patients with preoperative suboptimal CDVA.Methods: This retrospective study included patients with suboptimal preoperative CDVA (CDVA ≤20/25) who underwent ICL implantation (V4 or V4c). Preoperative and postoperative clinical evaluations included CDVA, uncorrected distance visual acuity (UDVA), and refraction.Results: A total of 1,212 eyes from 731 patients were identified. CDVA increased in 90.8% of the eyes after surgery. Among them, 57.5% of the eyes (697 eyes) gained more than one line. The preoperative LogMAR CDVA was 0.32 ± 0.23, which significantly improved to 0.13 ± 0.17 postoperatively (p < 0.001). There was no significant difference between ICL V4c and ICL V4 in the LogMAR UDVA, sphere, cylinder, SE, LogMAR CDVA, efficacy index, and safety index after surgery (p > 0.05). For eyes with full correction, the postoperative LogMAR CDVA =0.575 * preoperative LogMAR CDVA -0.061 (p < 0.001, R² = 0.53). For eyes with partial correction, the postoperative LogMAR CDVA =0.536 * preoperative LogMAR CDVA - 0.007 * SE - 0.196 (P < 0.001, R² = 0.55).Conclusion: ICL implantation can improve CDVA in eyes with suboptimal CDVA. This study provides the postoperative outcomes of eyes with different preoperative CDVA, which makes it convenient for surgeons to communicate with such patients before surgery.

Changes in Accommodative and Binocular Function following Phakic Intraocular Lens for High and Low-to-Moderate Myopia

The aim was to evaluate accommodative and binocular function of phakic intraocular lens implantable collamer lens (ICL) in high and low-to-moderate myopia. Prospective comparative cohort study with 38 myopic patients who underwent ICL implantation were divided into two groups of 19 patients, each one based on the spherical equivalent (SE): high-power (SE ≤ −6 D) and low-to-moderate (SE > −6 D). The push-up amplitude of accommodation (AA), monocular accommodative facility (MAF), distance and near ocular deviation, near convergence amplitude, near point convergence (NPC), stereopsis, and accommodative convergence/accommodation (AC/A) ratio were assessed before surgery and 1 week and 1 month postoperatively. The mean residual refractive error at 1 month after surgery improved in both groups, 0.18 ± 0.34 D and 0.09 ± 0.26 D, respectively (p < 0.001). There was a significant decrease in AA in both groups between preoperatively and at 1-week (p = 0.001; p = 0.008, respectively) and 1-month follow-up (p = 0.001; p = 0.008). For the rest of the binocular measurements, no statistically significant postoperative changes were found in any group. This finding suggests follow-up studies on amplitude of accommodation in phakic intraocular lens ICL implantation.

Assessment of biosafety and implantation feasibility of novel phakic refractive lens

Purpose

We investigated the biosafety and implantation feasibility of a new phakic refractive lens (PRL) in rabbit eyes.

Methods

Short PRLs (S-PRLs), large PRLs (L-PRLs), and large-grooved PRLs (LG-PRLs), were prepared by molding medical-grade liquid silicon. The cytotoxicity and cellular adhesion of the PRLs was assessed in vitro. To assess implantation feasibility, the S-PRL, L-PRL, and LG-PRL were implanted in the posterior chamber of rabbit eyes and the relative position was assessed by optical coherence tomography. The intraocular pressures (IOP) were compared between the S-PRL, L-PRL, LG-PRL, and control groups to evaluate the PRL biosafety after implantation.

Results

The in vitro assays showed that cell viability and cellular adhesion in the S-PRL, L-PRL and LG-PRL groups was not significantly different to those in the control group throughout the study. After implantation into the posterior chamber of rabbit eyes, there were no obvious signs of inflammation or increases in IOP at each time point relative to the control group, demonstrating good biosafety of the PRL. The relative positions of the L-PRLs and LG-PRLs in the posterior chamber were appropriate and the retention frequencies were high.

Conclusions

The newly developed LG-PRL showed good biosafety with negligible in vitro cytotoxicity, ocular inflammation, or fluctuations in IOP. The LG-PRL provided the best implantation feasibility. The grooves on the LG-PRL provided channels for aqueous humor circulation. The LG-PRL is a promising type of PRL with an appropriate size and surface structure for effective correction of refractive errors in rabbit eyes.

Predictive factors for postoperative visual acuity improvement with ICL-V4c for ultrahigh myopia above - 10 D

PURPOSE

The purpose of this study is to evaluate the predictive factors for postoperative visual acuity improvement (PVAI) in subjects who underwent phakic intraocular lens implantation with a central hole (ICL-V4c) for ultrahigh myopia above - 10 D.

METHODS

This was a retrospective study. Eyes with ultrahigh myopia above - 10 D undergoing ICL-V4c implantation were studied. Univariable linear regression models were used to assess the association between PVAI and preoperative parameters. Myopic maculopathy was classified into 5 categories by fundus photography. After the 1-month follow-up, the PVAI was compared within different age and preoperative spherical degree groups.

RESULTS

This study included 726 eyes from 419 patients (111 men and 308 women), and the mean age, spherical refraction, and axial length were 28.67 ± 7.93 years, - 13.61 ± 3.44 D, and 28.59 ± 1.50 mm, respectively. At baseline, myopic maculopathy was classified (grades C0-C4) as follows: C0 was observed in 200 eyes (27.5%), C1 in 297 eyes (40.9%), C2 in 147 eyes (20.2%), C3 in 22 eyes (3.0%), and C4 in 60 eyes (8.3%). The PVAI was significantly negatively associated with age and positively associated with SD-pre(-Sph), but no significant association between myopic maculopathy classification and axial length was found. After 1 month, 417 eyes (57.4%) gained more than 1 line at BCVA, 250 eyes (34.4%) remained the same, and 59 eyes (8.13%) lost 1 line. The postoperative visual acuity of 52 eyes was improved by more than 3 lines, and 42.3% were grade C4.

CONCLUSIONS

The ICL performed well for the correction of ultrahigh myopia above - 10 D. Younger patients and those with a higher preoperative spherical degree had greater postoperative satisfaction.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2000036335). Date of registration: 2020/8/22.