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.].

Agreement Between Angle-to-Angle Distance and Aqueous Depth Obtained With Two Different Optical Coherence Tomographers and a Scheimpflug Camera

PURPOSE

To compare angle-to-angle (ATA) distance and aqueous depth (AQD) readings produced by two different optical coherence tomography (OCT) devices and a Scheimpflug camera.

METHODS

ATA distance and AQD were measured in 60 eyes using the Visante time-domain OCT (TD-OCT) (Carl Zeiss Meditec AG), the Anterion swept-source OCT (SS-OCT) (Heidelberg Engineering GmbH), and the Pentacam HR Scheimpflug camera (Oculus Optikgeräte GmbH). Moreover, ATA distance was measured along the horizontal and vertical meridians. Bland-Altman analysis was used to assess the agreement between devices.

RESULTS

All three devices did not yield similar horizontal ATA distance: 11.96 ± 0.47 mm (TD-OCT), 11.96 ± 0.42 mm (SS-OCT), and 11.05 ± 0.52 mm (Pentacam). More specifically, the Pentacam yielded significantly smaller values (approximately 0.9 mm, P < .001). Mean vertical ATA distance was 12.61 ± 0.65 and 12 ± 0.65 mm for the TD-OCT and SS-OCT, respectively (P = .983). Vertical ATA distance was significantly larger than horizontal ATA distance for both OCT devices (approximately 0.6 mm, P < .001). The lowest mean difference was found between both OCT devices (0.0068 and -0.0415 mm, for horizontal and vertical meridians, respectively) and the highest between the Pentacam and the two OCT devices (approximately 0.9 mm). As for AQD, inter-device mean values were also statistically significant: 2.89 ± 0.48, 2.82 ± 0.49, and 2.79 ± 0.50 mm, for the TD-OCT, SS-OCT, and Pentacam, respectively (P < .001). Mean differences were similar for the TD-OCT versus SS-OCT and SS-OCT versus Pentacam (approximately 0.02 mm), and larger between the TD-OCT and Pentacam (approximately 0.05 mm).

CONCLUSIONS

The results show that the TD-OCT and SS-OCT are interchangeable instruments for ATA distance measurement but the Pentacam is not with either of the two OCT devices. A clinical criterion should assess whether these three devices could be used interchangeably for AQD measurement. [J Refract Surg. 2021;37(2):133-140.].

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.].

Angle-to-angle and spur-to-spur distance analysis with high-resolution optical coherence tomography

Background

To measure angle-to-angle (ATA) and spur-to-spur (STS) distances along six meridians using high-resolution swept-source optical coherence tomography (SS-OCT) and to compare those values with horizontal white-to-white (WTW) distance.

Methods

68 eyes from 68 patients were quantitatively assessed with the Anterion SS-OCT (Heidelberg Engineering, Heidelberg, Germany). ATA and STS distances were measured with the SS-OCT’s B-Scan in six cross-sectional images corresponding to the vertical (6–12 o’clock), 1–7 o’clock, 2–8 o’clock, horizontal (3–9 o’clock), 4–10 o’clock and 5–11 o’clock meridians. WTW was measured horizontally with the device’s infrared camera. A Pearson correlation analysis was carried out to compare ATA and STS distances with WTW.

Results

The largest values were found for the vertical meridian and the shortest for the 2–8 o’clock meridian, both for ATA and STS distances. No statistically significant differences were found between WTW, ATA and STS along the horizontal meridian (p > 0.1). However, ATA and STS showed statistically significant differences elsewhere, except for the horizontal and the 2–8 o’clock meridians (p > 0.05). Moreover, we found that ATA and STS varied significantly depending on the meridian being assessed, except for ATA at 4–10 versus 3–9 o’clock and for STS at 4–10 versus 3–9 o’clock and at 3–9 versus 2–8 o’clock (p > 0.1). R² values ranged from 0.49 to 0.75 for ATA and STS at the different meridians, showing the best correlation at 3–9 o’clock meridian (0.64 and 0.75, respectively) and the worst at 6–12 o’clock meridian (R² = 0.49 for both ATA and STS).

Conclusions

ATA and STS distances vary radially, thus showing that the anterior chamber is vertically oval. Therefore, it is advisable to measure these two distances along the meridian to be used.

Predictability of the vault after posterior chamber phakic intraocular lens implantation using anterior segment optical coherence tomography

PURPOSE

To determine whether vault measurements after placement of a hole implantable collamer lens (hole ICL) (KS-AquaPORT) can be predicted by angle-to-angle (ATA) and white-to-white (WTW) measurements obtained with anterior segment optical coherence tomography (AS-OCT).

SETTING

Sanno Hospital, Tokyo, Japan.

DESIGN

Retrospective case series.

METHODS

Eyes were observed for 3 months after hole ICL implantation for myopia or myopic astigmatism. Central vault, ATA, and WTW measurements were obtained before and after surgery using the swept-source AS-OCT CASIA2 system.

RESULTS

The study included 44 eyes (23 patients). The mean patient age and preoperative spherical equivalent, ATA, and WTW values were 36.2 years ± 8.8 (SD), -6.23 ± 3.41 diopters (D), 12.03 ± 0.40 mm, and 11.72 ± 0.40 mm, respectively. The safety index and efficacy index 3 months postoperatively were 1.13 ± 0.21 and 0.91 ± 0.30, respectively. Regarding predictability, 93.2% of eyes were within ±0.50 D of the attempted correction and all eyes were within ±1.00 D. The reproducibility coefficients for the ATA distance and WTW distance were 0.998 and 0.960, respectively. The mean postoperative central vault was 491.6 ± 189.5 μm. There was a significant correlation between postoperative vault and the ICL size and ATA distance (Spearman rank correlation coefficient r = 0.59, P < .001) but not between the ICL size and WTW distance (r = 0.27, P = .08).

CONCLUSION

The ATA measurements had higher reproducibility than the WTW measurements on AS-OCT, making it is a more important predictor of postoperative vault.

Adjustment formulae to improve the correlation of white-to-white measurement with direct measurement of the ciliary sulcus diameter by ultrasound biomicroscopy

Purpose

This study evaluates the correlation between horizontal white-to-white (WTW) distance using Caliper and Orbscan IIz with the ciliary sulcus diameter measured by high frequency ultrasound biomicroscopy (UBM) and presents an adjustment formula to improve the correlation.

Methods

We measured horizontal sulcus-to-sulcus (STS) dimension of 273 right eyes of 273 high myopic patients with 35 MHz UBM and horizontal WTW using Orbscan IIz and Caliper. Mean WTW diameter, differences, and the correlation of measurement methods were evaluated.

Results

The mean spherical equivalent was −8.79 ± 4.87 diopters. Mean horizontal STS dimension with UBM was 12.13 ± 0.45 mm (range, 10.81–13.42 mm). Mean WTW diameter in the Caliper method was 11.70 ± 0.40 mm (range, 10.6–12.8 mm) and 11.70 ± 0.40 mm (range, 10.5–13.1 mm) in the Orbscan method. Mean difference of UBM STS and WTW with Caliper was 0.48 ± 0.28 mm (range, −0.19 to 1.37 mm). Mean difference of UBM STS diameter and Orbscan WTW was 0.38 ± 0.31 mm (range, −0.64 to 1.29 mm). The Pearson correlations of WTW diameter measured by Caliper and Orbscan with UBM's STS diameter were 0.778 and 0.773, respectively. This difference diminished after adjustment. The 95% limit of agreement was almost the same in Caliper and Orbscan (−0.07 to 1.03 compared with −0.23 to 0.99).

Conclusion

There is a significant difference in measurements between STS diameter using UBM and WTW diameter utilizing Caliper and Orbscan. This difference diminished after our recommended adjustment.

Repeatability assessment of anterior segment biometric measurements under accommodative and nonaccommodative conditions using an anterior segment OCT

PURPOSE

As accommodation is a dynamic process changing anterior ocular structures, we aim to compare the repeatability between the biometric measurements taken with and without accommodation.

METHODS

Thirty healthy right eyes were measured in a baseline and an accommodative state using Visante-OCT. Three repeated measurements were taken to obtain central corneal thickness (CCT), anterior chamber depth (ACD), angle-to-angle distance (ATA), iridocorneal angles (IA), and crystalline lens thickness (LT). Repeatability was evaluated by the calculation of coefficient of repeatability (CoR), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). In addition, the Passing-Bablok regression method was applied.

RESULTS

For the nonaccommodative state, the CoR for CCT, ACD, ATA, and LT was 20.02 μm, 0.09 mm, 0.25 mm, and 0.12 mm respectively. The CoR for CCT, ACD, ATA, and LT in the 6D-accommodative state was 20.85 μm, 0.08 mm, 0.26 mm, and 0.14 mm respectively. IA had similar results for both states; the CoR ranged between 3 and 4°, CoV was less than 4%, and the ICC was between 0.984-0.988. There were no significant differences between the three repeated measurements for any measurement.

CONCLUSIONS

Visante-OCT provides good repeatability for anterior segment measurements for both accommodative and nonaccommodative states.

Meta-analysis and review: effectiveness, safety, and central port design of the intraocular collamer lens

The purpose of this review is to summarize relevant data from publications appearing in the peer-reviewed scientific literature over the past decade since US Food and Drug Administration approval of the implantable collamer lens (ICL), and, in particular, to review studies relating to sizing methodology, safety, and effectiveness, as well as more recent studies reporting clinical outcomes of the V4c Visian ICL with KS Aquaport, VICMO. A literature search was conducted using two databases, PubMed.gov and Science.gov, to identify all articles published after 2005 related to the Visian ICL (STAAR Surgical, Inc.). Articles were examined for their relevance to sizing methodology, clinical safety, and effectiveness, and the references cited in each article were also searched for additional relevant publications. The literature review revealed that all currently reported methods of determining the best-fit size of the ICL achieve similarly satisfactory results in terms of vault, the safe distance between the crystalline lens and the ICL. Specifically, meta-analysis demonstrated that sulcus-to-sulcus and white-to-white measurement-based sizing methods do not result in clinically meaningful nor statistically significant differences in vault (two-sample two-sided t-test using pooled mean and standard deviations; t (2,594)=1.33; P=0.18). The reported rates of complications related to vault are very low, except in two case series where additional risk factors such as higher levels of myopia and older age impacted the incidence of cataract. On the basis of preclinical studies and initial clinical reports, with up to 5 years of follow-up, the new VICMO central port design holds promise for further reduction of complications. Given its safety record and the significant improvement in vision and quality of life that the ICL makes possible, the benefits of ICL implantation outweigh the risks.

Anterior segment optical coherence tomography of long-term phakic angle-supported intraocular lenses

PURPOSE

To evaluate the long-term age-related anterior chamber changes by anterior segment optical coherence tomography (OCT) and the impact of such changes on the stability and behavior of angle-supported phakic intraocular lenses (IOLs).

DESIGN

A retrospective consecutive observational cohort study.

METHODS

A total of 23 eyes with high myopia implanted with an angle-supported phakic IOL between 1990 and 1996 at Vissum Corporación Oftalmológica de Alicante were included in the study. Patients were evaluated using OCT. Anterior chamber depth, anterior chamber width, crystalline lens rise, and the distance between phakic IOL and endothelium were measured.

RESULTS

Fifteen years after implantation, anterior chamber depth was 2.9 ± 0.3 mm, crystalline lens rise 748.18 ± 393.13 μm, and phakic IOL-endothelium distance 2.1 ± 0.30 mm. The predictive model showed that 30 years after implantation, endothelial cell count was less than 600 cells/mm(2) in patients with a preoperative spherical equivalent of -25 diopters (D). Twenty years after implantation, the safety zone of 1.5 mm between endothelium and the lens will not be respected in patients with a preoperative spherical equivalent of -20 D.

CONCLUSIONS

The findings of this study could have an important influence on the decision about the indication to implant angle-supported phakic IOLs in young patients with a long postoperative life expectancy, as age-related changes in the anatomy of the anterior segment may create a long-term hazard for the implanted eye.

Posterior chamber phakic intraocular lens to correct myopia: long-term follow-up

PURPOSE

To evaluate the long-term safety and efficacy of a refractive phakic intraocular lens (pIOL) (PRL) to correct moderate to high myopia.

SETTING

Department of Ophthalmology, University Medicine Charité Berlin, Berlin, Germany.

DESIGN

Retrospective cohort study.

METHODS

Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, intraocular pressure, endothelial cell loss, and adverse events were evaluated.

RESULTS

The study enrolled 53 eyes (mean spherical equivalent [SE] -12.17 diopters [D] ± 4.12 [SD]) of 29 patients. The mean age was 34.6 ± 9.2 years and the mean follow-up, 86 ± 21.2 months. The mean UDVA improved from 1.37 ± 0.28 logMAR preoperatively to 0.14 ± 0.19 logMAR at the last postoperative visit (P<.05). The mean CDVA improved from 0.10 ± 0.18 logMAR to -0.01 ± 0.09 logMAR (P<.05). The overall mean efficacy index and mean safety index were 0.9 and 1.21, respectively, at the last follow-up visit. The mean endothelial cell loss at the last follow-up was 6.4%. The complications were slight posterior chamber (PC) pIOL decentration (5 eyes, 9.4%), severe PC pIOL decentration resulting in pIOL removal (1 eye, 1.8%), glaucoma (4 eyes, 7.5%), clinically significant cortical lens opacification resulting in cataract surgery (4 eyes, 7.5%), clinically asymptomatic anterior subcapsular cataract formation (6 eyes, 11.3%), and retinal detachment (2 eyes, 3.8%).

CONCLUSIONS

Posterior chamber phakic pIOL implantation to correct moderate to high myopia provided predictable and stable refractive results but with a high rate of serious complications over the long term.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Comparison of postoperative vault height predictability using white-to-white or sulcus diameter-based sizing for the visian implantable collamer lens

PURPOSE

To compare vault height predictability of Implantable Collamer Lens (ICL; Staar Surgical) sizing using a sulcus diameter-based formula or the manufacturer-recommended white-to-white-based method.

METHODS

In 50 myopic eyes, ICL size was calculated using both a formula including sulcus diameter and the traditional formula based on white-to-white diameter. Sulcus diameter was measured using Artemis 2 very high-frequency (VHF) digital ultrasound (ArcScan Inc). Implantation was based on the sulcus diameter derived size. Actual postoperative vault height achieved was measured by VHF digital ultrasound scanning. Circle segment trigonometry was used to calculate the vault height that would have resulted had lens sizing been based on the white-to-white formula.

RESULTS

The same lens size would have been used in 60% of eyes, a smaller lens would have been used in 34% of eyes and a larger lens in 6% of eyes had lens sizing been based on the white-to-white formula. Mean vault for eyes with lenses sized using the sulcus diameter formula was 0.37±0.16 mm (range: 0.08 to 0.92 mm), with 2% <0.09 mm, the recognized low-vault height for risk of cataract. Circle segment trigonometry predicted that the vault height would have been 0.24±0.28 mm (range: -0.31 to 0.92 mm), with 26% <0.09 mm had lens sizing been based on the white-to-white formula.

CONCLUSIONS

Significantly better predictability of postoperative vault height was achieved by including sulcus diameter into the ICL sizing formula compared with using the traditional white-to-white-based formula.

The posterior chamber phakic refractive lens (PRL): a review

Implantation of phakic intraocular lenses (pIOLs) is a reversible refractive procedure, preserving the patient's accommodative function with minimal induction of higher order aberrations compared with corneal photoablative procedures. Despite this, as an intraocular procedure, it has potential risks such as cataracts, chronic uveitis, pupil ovalization, corneal endothelial cell loss, pigmentary dispersion syndrome, pupillary block glaucoma, astigmatism, or endophthalmitis. Currently, only two models of posterior chamber pIOLs are commercially available, the implantable collammer lens (STAAR Surgical Co.) and the phakic refractive lens (PRL; Zeiss Meditec). The number of published reports on the latter is very low, and some concerns still remain about its long-term safety. The present article reviews the published literature on the outcomes after PRL implantation in order to provide a general overview and evaluate its real potential as a surgical refractive option.

Medium-term visual, refractive, and intraocular stability after implantation of a posterior chamber phakic intraocular lens to correct moderate to high myopia

PURPOSE

To evaluate the medium-term refractive and visual outcomes and the complications after implantation of a silicone posterior chamber phakic intraocular lens (PC pIOL) for moderate to high myopia.

SETTING

Oftalmar, Medimar International Hospital, Alicante, Spain.

DESIGN

Retrospective case series.

METHODS

Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, and intraocular pressure were evaluated during a medium-term follow-up. Postoperative complications were also studied.

RESULTS

The study enrolled 35 eyes (mean preoperative spherical equivalent [SE] -10.25 diopters [D] ± 3.19 [SD]) of 20 patients with a mean age of 31.83 ± 8.87 years and a mean follow-up of 57.34 ± 9.24 months. The mean UDVA improved from 2.40 ± 0.20 logMAR preoperatively to 0.08 ± 0.13 logMAR at the last postoperative visit (P<.01). The mean CDVA improved from 0.11 ± 0.09 logMAR to 0.02 ± 0.09 logMAR, respectively (P<.01). The postoperative CDVA was 0.1 or better in 30 eyes (85.71%), with 22 eyes (62.86%) gaining lines of CDVA. The final efficacy index was 1.16 and the final safety index, 1.26. Regarding predictability, 34 eyes (97.14%) had an SE within ± 1.00 D and 33 eyes (94.28%) within ± 0.50 D. The complications were PC pIOL decentration (2 eyes, 5.71%), cortical lens opacification (1 eye, 2.86%), and retinal detachment (1 eye, 2.86%).

CONCLUSIONS

Implantation of a PC pIOL to correct moderate to high myopia was efficient and predictable in the medium term, with intraocular stability in most cases. New designs and criteria for PC pIOL size selection should be developed.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.