Anterior Chamber Changes After Implantable Collamer Lens Implantation in High Myopia Using Pentacam: A Prospective Study

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.

Differences in anterior chamber depth in keratoconus patients with binocular very asymmetry ectasia

BACKGROUND

To evaluate the difference in anterior chamber depth (ACD) between two eyes among keratoconus patients with binocular very asymmetric ectasia (VAE) and to explore the influencing factors.

METHODS

The corneal curvature and ACD in both eyes of patients with VAE were measured by Sirius (version 3.2, CSO, Italy) at the following points: corneal vertex, maximum curvature (apex), and the 1.5 mm, 2.5 mm, and 3.5 mm superior-, inferior-, nasal-, temporal-paracentral from center. The mean pupil power (MPP) and corneal morphology parameters were also measured. Correlations between ACD and curvature and morphology parameters were analyzed by linear regression.

RESULTS

172 eyes of 86 patients (9 to 45 years) were classified into the VAE-N (n = 86) group and the VAE-E group (n = 86) based on the corneal morphology. The central (3.32 ± 0.27 mm versus 3.43 ± 0.29 mm, P < 0.001) and paracentral ACDs increased significantly in the VAE-E group, and the corneal morphology parameters were also significantly higher. The central ACD was significantly correlated with the MPP (r = 0.465), KVf/b (Keratoconus Vertex front/back) (r = 0.306, r = 0.327), and BCVf/b (Baiocchi Calossi Versaci front/back) (r = 0.356, r = 0.416). Linear regression showed good relationships between △ACD and △MPP (R2 = 0.429) and △KVf/b (R2 = 0.504, R2 = 0.536).

CONCLUSIONS

The ACD was larger in the VAE-E group. The difference in ACD between the VAE-E and VAE-N groups was significantly correlated with corneal curvature and the extent of corneal elevation, indicating the influences of both the corneal magnification effect and corneal ectasia on ACD.

Comparison of a new implantable collamer lens formula to standards formulas using spectral domain optical coherence tomography

PURPOSE

To use spectral-domain optical coherence tomography (SD-OCT) data to develop a new implantable collamer lens (ICL) sizing formula and compare vault outcomes with the Online Calculation and Ordering System™ (OCOS) and the NK2 formula.

METHODS

Consecutive eyes (n = 237) were evaluated that had undergone ICL/toric ICL implantation. Actual ICL vaults were measured, and a what-if analysis was performed to predict vault values with the NK2 formula using SD-OCT data. To develop a new formula (EPB), multiple regression analysis was performed with different parameters than the NK2 formula. Predicted vaults with NK2 and EPB formulas were compared to the actual vaults.

RESULTS

Parameters that were correlated with optimal ICL size were white-to-white, anterior chamber width, lens rise and desired refractive correction. The mean postoperative vault was 489 ± 258 μm. At last visit, 94.5% of eyes were within the manufacturer's acceptable vault range. Predicted vaults in the acceptable range were 74 and 87% with the NK2 and EPB formulas, respectively. Six percent had a predicted vault less than 100 μm with the EPB formula compared to 1% for actual outcomes. The NK2 formula resulted in a shift toward higher predicted vaults while the EPB formula was similar to the actual postoperative vaults but with slightly more cases with extremely low and high vaults.

CONCLUSION

SD-OCT data with OCOS result in good postoperative vaults. Further refinement is required to the NK2 for use with SD-OCT data. Although the EPB formula provides acceptable predicted vaults, further refinement with a larger sample size is needed.

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.

The best choice for low and moderate myopia patients incapable for corneal refractive surgery: implantation of a posterior chamber phakic intraocular lens

PURPOSE

This study aims to evaluate the early clinical outcomes of central hole phakic posterior chamber intraocular lens(ICLV4c) implantation for low and moderate myopia correction.

METHODS

This retrospective clinical study included 27 patients(47 eyes)who underwent ICLV4c implantation to correct myopia with spherical equivalent (SE) between - 1.75D and -6.0D. The uncorrected visual acuity (UCVA), intraocular pressure(IOP), central anterior chamber depth (ACD), vault, and endothelial cell density (ECD) were evaluated after surgery.

RESULTS

At one year follow-up, the postoperative UCVA of patients was higher than the preoperative CDVA and showed a stable trend. There was no significant difference in ECD (p > 0.05) one month after the surgery, the vault was 0.77 ± 0.32 mm, which decreased to 0.63 ± 0.26 mm after one year of surgery. Similarly, ACD was 3.24 ± 0.25 mm in the preoperative, which decreased significantly to 2.05 ± 0.39 mm at one month, while rose to 2.2 ± 0.39 mm at one year after surgery. There was no significant correlation between IOP and ACD and vault at one month and one year after surgery. The correlation coefficient between ACD and vault was found to be - 0.72 at one month after surgery, while the same -0.71 after one year. One patient developed visual fatigue, one with glare, and while no other complications were observed with the rest of the patients.

CONCLUSION

The ICL implantation is a safe, effective and stable method to correct low and moderate myopia, and may be a good alternative for patients with low and moderate myopia who cannot undergo corneal refractive surgery.

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.

Evaluation of impact of posterior phakic IOL implantation on biometry and effectiveness of concomitant use of anterior segment OCT on IOL power calculation for cataract surgery

PURPOSE

To evaluate the effects of phakic intraocular lens (pIOL) implantation on the intraocular lens (IOL) power calculation and subsequently to evaluate the effectiveness of concomitant use of anterior segment optical coherence tomography (AS-OCT) against biometric changes.

SETTING

Masayuki Ouchi Eye Clinic, Kyoto, Japan.

DESIGN

Prospective consecutive case series.

METHODS

100 patients (100 eyes) who underwent pIOL implantation were enrolled. In each eye, biometry was performed using partial coherence interferometry (PCI) and AS-OCT. Pre-pIOL and post-pIOL implantation IOL power calculation using SRK/T (S), Haigis (H), and Barret Universal II (B) formulas was compared.

RESULTS

100 patients (100 eyes) were included. Anterior chamber depth (ACD) was significantly shorter at post-pIOL implantation for both PCI (P < .001) and AS-OCT (P = .05). When using PCI, the crystalline lens surface was misidentified in 75% of eyes, and in these eyes, the ACD difference between pre-pIOL and post-pIOL implantation exceeded that with both PCI and AS-OCT. The estimated IOL power was significantly lower at post-pIOL implantation according to the H and B formulas (both P < .001) but remained unchanged by the S formula. However, no difference was observed when AS-OCT-derived ACD and lens thickness (LT) values were introduced in the H (P = .16) and B (P = .55) formulas.

CONCLUSIONS

Misidentification of the lens surface occurs in many pIOL-implanted eyes with PCI measurements and could influence the power calculation with H and B formulas while leaving the S formula unaffected. AS-OCT-derived ACD and LT value substitution is recommended for H and B formulas.

A Prospective Comparative Study between Implantable Phakic Intraocular Contact Lens and Implantable Collamer Lens in Treatment of Myopia in Adults

Purpose

To compare implantable collamer lenses (ICLs) and acrylic implantable phakic contact lenses (IPCLs) in the treatment of myopia in adults, as regards refractive outcome and adverse effects.

Methods

Prospective, randomized comparative study with phakic intraocular lenses (IOLs) was carried out for treatment of myopia. Patients were randomized into two groups: one for ICL and the other for IPCL. Preoperative assessments included a full examination, pentacam, endothelial cell count, and biometry. We compared the adverse effects and refractive outcomes between both groups. The study was registered in clinical trials and the registration number is NCT04624035.

Results

Sixty eyes of sixty patients (28 in the ICL group and 32 in the IPCL group) with a follow-up period of 12 months. The mean preoperative spherical equivalent was −12.7 ± 3.4 D and −13.6 ± 4.4 D in the ICL and IPCL groups, respectively (P=0.37). The mean postoperative spherical equivalent value was ±0.4 ± 0.2 D and ±0.6 ± 0.1 D in the ICL and IPCL groups, respectively. Uncorrected visual acuity (UCVA) has improved from 1.3 ± 0.06 to 0.15 ± 0.02 Log MAR in the ICL group (P < 0.001) and from 1.3 ± 0.02 to 0.15 ± 0.01 Log MAR in the IPCL group (P < 0.001). The mean endothelial cell count was reduced by 3.3% in the IPCL group and by 3.2% in the IPCL group.

Conclusion

Both ICL and IPCL are effective methods to correct high myopia in adults with no statistically significant differences between the two lenses as regarding adverse effects.

Changes of ocular biometry in eyes with posterior chamber phakic intraocular lens implantation

OBJECTIVE

To evaluate changes in biometric variables and intraocular lens (IOL) calculation results after posterior chamber phakic IOL (PCPIOL) implantation.

METHODS

This retrospective, observational study included 65 eyes of 38 patients who underwent PCPIOL (EVO Visian ICL) implantation for correction of myopia. Prior to and a minimum of one year (mean 14.9 months) after EVO Visian ICL implantation, biometric variables and IOL calculation results were compared. Optical biometry, including anterior chamber depth, axial length, flat, steep, and mean keratometry values and IOL calculation results for the Holladay 2, Hoffer Q, Haigis, and SRK/T formulas were measured using the IOLMaster 700 SWEPT Source OCT biometer.

MAIN RESULTS

The mean anterior chamber depth decreased from 3.70±0.22mm to 3.34±0.39mm, the mean axial length increased from 26.61±1.61mm to 26.71±1.66mm, and the mean flat keratometry changed from 42.82±1.86 D to 42.73±1.83 D. These changes were statistically significant. The mean IOL power calculation also revealed a statistically significant decrease with all four formulas (ranging from 0.19 D to 0.30 D) after PCPIOL implantation.

CONCLUSIONS

Biometric variables and IOL calculation results showed statistically significant changes one year after EVO Visian ICL implantations. However, IOL power calculations yielded a decrease of less than 0.50 D, inducing much less refractive deviation in the spectacle plane; and the change was primarily related to an increase in AL measurements. IOL power calculations in eyes with EVO Visian ICL in situ provided satisfactory and reliable results.

Effect of Implantable Collamer Lens on Anterior Segment Measurement and Intraocular Lens Power Calculation Based on IOLMaster 700 and Sirius

Purpose

To investigate the possible effect of an implantable collamer lens (ICL) on ocular biometrics and intraocular lens (IOL) power calculation.

Methods

Ocular measurements were taken preoperatively and at the two-month follow-up using IOLMaster 700 and Sirius in 85 eyes (43 patients) who had previously undergone ICL surgery. IOL power was calculated using either IOLMaster 700 (Barrett Universal II formula) or Sirius (ray-tracing). All data were compared using the paired t-test.

Results

The difference between preoperative and postoperative anterior chamber depth (ACD), lens thickness (LT), and keratometry on the steep axis (K2) measured by IOLMaster 700 was statistically significant (p < 0.001). In 11 of 85 eyes, IOLMaster misjudged the anterior surface of the ICL as that of the lens, leading to an error in ACD and LT. There were no significant differences between preoperative and postoperative axial length (AL) (p = 0.223), white to white (WTW) (p = 0.100), keratometry on flat axis (K1) (p = 0.117), or central corneal thickness (CCT) (p = 0.648), measured using IOLMaster. The difference in IOL power calculated using the Barrett II formula was significant (p = 0.013). Regression analysis showed that AL and K had the greatest influence on IOL calculation (p < 0.001), and ACD and LT had less influence (p = 0.002, p = 0.218, respectively). K1 and K2 were modified to exclude the influence of K2, and modified IOLs showed no difference between pre and postoperation (p = 0.372). Preoperative and postoperative ACD measured using Sirius were significantly different (p < 0.001); however, the IOL power calculated using ray-tracing technology showed no significant differences (p > 0.05).

Conclusions

The ocular biometric apparatus may misjudge the anterior surface of the lens, resulting in measurement errors of ACD and LT, which has little effect on the calculation of IOL power when using IOLMaster 700 (Barrett Universal II formula) and Sirius (ray-tracing).

Toric Implantable Collamer Lens for the Treatment of Myopic Astigmatism

Purpose

To report visual outcomes following surgical correction of myopic astigmatism with Visian Toric implantable collamer lens (ICL) (STAAR Surgical, Monrovia, CA, USA) at a single tertiary refractive center in the United States.

Patients and Methods

Toric ICL was implanted in 96 eyes (55 patients) with mean preoperative sphere of −8.98 ± 3.04 diopters (D) and cylinder of −2.67 ± 1.02 D from December 2018 to February 2021. Primary visual outcomes of efficacy, safety, stability, predictability of refractive correction, and astigmatic analysis were reported at three and twelve months postoperatively. Secondary subjective outcomes included patient-reported dry eye symptoms and glare/halos at postoperative visits. Other secondary outcomes were biometric data and postoperative vault over time.

Results

At three and twelve months, 75 and 46 eyes were evaluated, respectively. At twelve months, the mean manifest refraction spherical equivalent (MRSE) was −0.23 ± 0.47 D with 93% achieving within ±1.00 D of target refraction. The manifest refractive cylinder (MRC) at twelve months was −0.73 ± 0.51 D, with 86% within ±1.00 D of target. Uncorrected distance visual acuity (UDVA) was 20/20 or better in 74% of eyes at twelve months. No patients lost ≥2 lines of corrected distance visual acuity (CDVA) at twelve months. The mean angle of error was −0.9 ± 10.2° at three months and −1.6 ± 12.8° at twelve months. One patient required bilateral lens rotation, four patients underwent secondary enhancement with LASIK/PRK, and seven patients underwent postoperative limbal relaxing incisions.

Conclusion

This initial single-site experience finds Toric ICL implantation for myopic astigmatism to be safe and effective. Patients can achieve markedly improved UDVA in a single surgery with stable vision over time and minimal adverse subjective symptoms.

An anterior segment optical coherence tomography study of the anterior chamber angle after implantable collamer lens-V4c implantation in Asian Indian Eyes

Purpose:

To quantitatively assess anterior chamber and angle parameters by anterior segment optical coherence tomography (AS-OCT) in myopic eyes undergoing Implantable Collamer Lens (ICL V4c) implantation.

Methods:

Prospective noncomparative observational case series. Pre and postoperative (1^st and 3^rd month) AS-OCT angle parameters (anterior chamber depth [ACD], anterior chamber angle [ACA], Angle opening distance [AOD], trabecular iris space area [TISA], scleral spur angle [SSA]) were evaluated in 32 eyes (16 patients). SPSS version 20 with paired t-test for intragroup and Mann-Whitney U value test for intergroup comparisons.

Results:

It included 6 (37.5%) males and 10 (62.5%) females. Preoperative ACA of 34.6 ± 2.3° reduced to 32.2 ± 2.4°, 31.9 ± 2.5° at 1 and 3 months postoperatively (P = 0.001). Preoperative mean AOD500, AOD750, TISA500, TISA750, SSA of 0.34 ± 0.06 mm, 0.52 ± 0.15 mm, 0.09 ± 0.02 mm², 0.20 ± 0.04 mm², 34.27 ± 4.6° decreased to 0.32 ± 0.06 mm, 0.48 ± 0.15 mm, 0.08 ± 0.02 mm², 0.17 ± 0.05 mm², 32.5 ± 4.3° at 1-month (P = 0.001); 0.32 ± 0.06 mm, 0.47 ± 0.13 mm, 0.08 ± 0.02 mm², 0.17 ± 0.05 mm² and 32.4 ± 4.6° (P = 0.001) at 3-months, respectively. Correlation analysis between preoperative ACD/intraocular pressure (IOP) was − 0.62 (P = 0.0002) [1^st month], −0.40 (0.024) [third month]; between IOP/postoperative ACA, AOD500, AOD750, TISA500, TISA750, SSA was − 0.04 (0.81), −0.03 (0.85), −0.08 (0.64), −0.12 (0.48), −0.10 (0.57), −0.06 (0.73) at 1 month; −0.09 (0.58), 0.04 (0.78), 0.12 (0.48), −0.02 (0.9), −0.04 (0.79), 0.02 (0.88) at 3 months; between ICL vault/ACA, AOD500, AOD750, TISA500, TISA750, SSA was 0.38 (0.02), 0.24 (0.17), 0.21 (0.25), 0.05 (0.75), 0.15 (0.41), 0.27 (0.13) at 1^st month; 0.19 (0.28), 0.06 (0.71), −0.03 (0.85), 0.005 (0.97), 0.05 (0.78), 0.07 (0.68) at 3^rd month.

Conclusion:

Postoperatively significant angle narrowing was noted. There was a negative correlation between IOP and preoperative ACD. There was no significant correlation between IOP and ICL vault with postoperative AS-OCT angle parameters.

Changes in anterior lens density after Implantable Collamer Lens V4c implantation: a 4-year prospective observational study

PURPOSE

To investigate the changes in anterior lens density with a Pentacam after Implantable Collamer Lens (ICL) V4c implantation in patients with myopia.

METHODS

This prospective case series examined 62 eyes of 32 patients (mean age, 28.5 ± 5.73 years) with myopia or myopic astigmatism after ICL V4c implantation. Uncorrected distance vision acuity, corrected distance vision acuity (CDVA), manifest refraction, intraocular pressure, anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), endothelial cell density and Pentacam images of lens density were obtained pre- and postoperatively. The vault was obtained during the follow-ups.

RESULTS

Patients were followed up for an average of 51 ± 2.7 months (range, 48-57 months). All surgeries were uneventful, without any complication. The efficacy and safety indices at the last follow-up were 1.03 ± 0.2 and 1.22 ± 0.22, respectively. No eye had decreased CDVA, and 66% eyes gained ≥1 line. Furthermore, refractive error in 90% eyes was within ±0.50 D and that of 100% was within ±1.0 D of the attempted refraction. Anterior average lens density (a-ALD) in the 0.5-, 1.0- and 1.5-mm depth zones increased by 10.41 ± 11.51%, 17.1 ± 11.09% and 16.76 ± 10.4%, respectively, compared to preoperative values (all p < 0.05). The change in a-ALD between two different age groups was not significant. Moreover, there were no significant correlations between the change in a-ALD and age, preoperative spherical equivalent, ACD, ACA, ACV or vault.

CONCLUSIONS

Implantable Collamer Lens (ICL) V4c implantation demonstrates safety and efficacy for myopia correction. Although a-ALD increased slightly at 4 years postoperatively, no cataract developed during the follow-up. Further studies should investigate the reason for the postoperative increase in a-ALD.

Peripheral Anterior Chamber Depth and Angle Measurements Using Pentacam After Implantation of Toric and Non-toric Implantable Collamer Lenses

Purpose: To evaluate the characteristics of peripheral anterior chamber measurements by Pentacam after posterior implantable collamer lenses (ICL) and toric ICL (TICL) with central hole (V4c) implantation.

Methods: Prospective, non-randomized consecutive case series. Forty-six patients undergoing ICL implantation in one eye (Group A) and identically sized TICL in the contralateral eye (Group B) in the Refractive Surgery Center of Eye and ENT Hospital of Fudan University were prospectively included. According to ICL/TICL size, these eyes were further divided into four subgroups. Peripheral anterior chamber depth (PACD) and angle (ACA) in nasal and temporal sides were measured using Pentacam pre-operatively and 12-month post-operatively.

Results: The safety indices were 1.34 ± 0.32 and 1.25 ± 0.16 and the efficacy indices were 1.20 ± 0.24 and 1.19 ± 0.19 for ICL and TICL groups, respectively. There was no significant difference in pre-operative PACD or ACA between the two groups. Post-operative PACD and ACA were significantly lower than pre-operative values. Variations of PACD and ACA of TICL group were significantly larger than those of ICL group. The change of ACA for 13.2 mm lenses was significantly larger than that of 12.6 mm lenses. Pre-operative CACD and vault were significantly associated with post-operative PACD, while pre-operative ACA and vault were significantly associated with post-operative ACA.

Conclusions: Variations of PACD and ACA were greater in eyes after TICL (V4c) implantation compared with identically sized ICL (V4c) implantation and with larger size than smaller size lens implantation. Pre-operative anterior chamber structure and vault affect post-operative PACD and ACA.

Prediction of anterior chamber volume after implantation of posterior chamber phakic intraocular lens

PURPOSE

To predict the anterior chamber volume (ACV) after implantable collamer lens (ICL) implantation based on ICL size and parameters of anterior segment optical coherence tomography (AS-OCT).

DESIGN

Retrospective study.

METHODS

This study included 222 eyes of 222 patients who underwent ICL implantation at Nagoya Eye Clinic. The patients were divided into two groups: prediction group, for creating the prediction equation (148 eyes, mean age: 32.11 ± 8.04 years), and verification group, for verifying the equation (74 eyes, mean age: 33.03 ± 6.74 years). The angle opening distance (AOD), anterior chamber width (ACW), ACV, anterior chamber depth, lens vault, angle-to-angle distance, angle recess area, and trabecular iris space area were calculated using AS-OCT. A stepwise multiple regression analysis was performed. After the creation of the prediction equation, its accuracy was verified in the verification group.

RESULTS

The ACV, AOD750, ACW, and ICL size were selected as explanatory variables to predict postoperative ACV. Mean predicted (114.2 ± 21.83 mm3) and actual postoperative ACVs (116.1 ± 25.41 mm3) were not significantly different (P = 0.269); absolute error was 10.59 ± 9.13 mm3. In addition, there was high correlation between actual and predictive ACV (adjusted R2 = 0.6996, p < 0.0001). Bland-Altman plot revealed that there was no addition or proportional error between predicted and actual postoperative ACV.

CONCLUSION

Postoperative ACV was accurately predicted using AS-OCT parameters and ICL size. This prediction equation may be useful for making decisions regarding ICL size.

Application of a Partial Least Squares Regression Algorithm for Posterior Chamber Phakic Intraocular Lens Sizing and Postoperative Vault Prediction

PURPOSE

To develop and validate a new algorithm for predicting the postoperative vault of the myopic EVO Visian Implantable Collamer Lens (ICL) V4c (STAAR Surgical AG).

METHODS

This study included 81 eyes of 43 patients who had undergone ICL implantation. Preoperative data obtained by swept-source optical coherence tomography, Scheimpflug camera, and anterior segment optical coherence tomography were applied to develop a new partial least squares (PLS) regression algorithm. ICL sizing was performed using the standard white-to-white method with the online calculation and ordering system. The postoperative vault was assessed based on anterior segment optical coherence tomography. The PLS approach was applied to create the calibration model for predicting the postoperative vault. The new PLS model was cross-validated using the leave-one-out method and compared to a recently published linear regression model. Agreement between the actual and predicted vault values for the two methods was assessed by the Bland-Altman method.

RESULTS

There was a statistically significant correlation (P < .001, r = 0.73) between the postoperative vault values and those predicted by the PLS algorithm. Validation of the PLS model yielded lower mean differences and limits of agreement (0 and 410 µm, respectively) than the linear regression method (400 and 750 µm, respectively).

CONCLUSIONS

The PLS algorithm increases the precision of ICL vault prediction. However, it shows a tendency to overestimate small vault values and underestimate high vaults. [J Refract Surg. 2020;36(9):606-612.].