Comparison of Phakic Intraocular Lens Vault Using Conventional Nomogram and Prediction Formulas

Prediction of footplate position after implantable collamer lens implantation based on iris and ciliary body morphologies

PURPOSE

To investigate the factors affecting footplate position and its influence on vault characteristics after implantable collamer lens (ICL) implantation.

SETTING

Hunan Provincial People's Hospital, Changsha, China.

DESIGN

Retrospective case series.

METHODS

This study included 124 patients (124 eyes). Ultrasound biomicroscopy (UBM) was performed to assess the iris and ciliary body morphologies and observe the footplate position. Using multiple linear regression, the relationship between various ocular and ICL parameters and the vault as well as the factors affecting the footplate distance (FD) were analyzed. Based on the FD, 3 groups were formed: group 1 (<500 μm), group 2 (500 to 1000 μm), and group 3 (>1000 μm). The distribution of the vault range postoperatively was observed for the 3 groups.

RESULTS

Ciliary sulcus angle and FD significantly affected the vault (adjusted R2 = 0.190, F = 6.763, P < .001), with FD being the most important factor influencing the vault (β = -0.383, P < .001). Postoperative UBM revealed that the footplate was located at different positions in the posterior chamber, with the majority (52%) being located on the ciliary body. The mean size of the 4 footplate orientations was 0.88 ± 0.24 mm. Multiple linear regression analysis revealed that ciliary body thickness (CBT), iris curvature (IC), and ICL iris contact length (IRCL) significantly influenced the FD (adjusted R2 = 0.373, F = 11.432, P < .001). The vault range differed significantly among the 3 groups (X 2 = 32.33, P < .001).

CONCLUSIONS

Different postoperative ICL footplate positions significantly affect the vault. CBT, IC, and IRCL can alter the position of the footplate from the expected position. This study provides reference for ICL size selection and vault prediction.

Lens height paraments comparison according to ciliary sulcus width (CSW): a pilot study of the predictive role of CLR and STSL for vault after ICL implantation

BACKGROUND

To assess the relationship between postoperative implantable collamer lens (ICL) vault and lens height obtained from two different measurements.

METHODS

A retrospective case series study enrolled eyes with horizontally implanted ICL. Crystal lens rise (CLR) and the distance between STS plane and anterior crystalline lens surface (STSL) were measured in the horizontal and vertical directions using ultrasound biomicroscopy (UBM). We compared the differences in the parameters measured in both horizontal and vertical directions. The participants were categorized into three groups according to ciliary sulcus width (CSW) which is defined as the distance between the posterior angle of the iris and the anterior angle of the ciliary process: narrow CSW group (NSG); medium CSW group (MSG); and wide CSW group (WSG). The correlations between CLR/STSL and vault were examined in each of the three groups. Biased correlation analysis was used further to contrast the correlation between CLR/STSL and vault.

RESULTS

This retrospective study included 223 myopic eyes. Vertical STSL (VSTSL) and vertical CLR (VCLR) exhibited significantly greater values compared to their horizontal counterparts (both P < 0.05). None of the indicators were statistically different between the three groups. In both NSG and MSG, STSL/CLR correlated with vault, while in WSG, only STSL correlated with vault (r=-0.316, P = 0.013). In contrast to HCLR, the correlation between HSTSL and vault remained after controlling for HCLR (r=-0.162, P = 0.015).

CONCLUSIONS

STSL should deserve more attention in the preoperative evaluation of ICL compared to CLR especially when CSW is large.

Development and validation of a novel vault prediction formula based on structural parameters of the anterior and posterior chambers

BACKGROUND

Accurate prediction of postoperative vault in implantable collamer lens (ICL) implantation is crucial; however, current formulas often fail to account for individual anatomical variations, leading to suboptimal visual outcomes and necessitating improved predictive models. We aimed to verify the prediction accuracy of our new predictive model for vaulting based on anterior and posterior chamber structural parameters.

METHODS

This retrospective observational study included 137 patients (240 eyes) who previously underwent ICL surgery. Patients were randomly divided into the model establishment (192 eyes) or validation (48 eyes) groups. Preoperative measurements of the anterior and posterior chamber structures were obtained using Pentacam, CASIA2 anterior segment optical coherence tomography (AS-OCT), ultrasound biomicroscopy, and other devices. Stepwise multiple linear regression analysis was used to evaluate the relationship between the vault and each variable (WL formula). The Friedman test was performed for the vaulting prediction results of the WL, NK (Ver. 3), and KS formulas (Ver. 4) in CASIA2 AS-OCT, as well as the Zhu formula and vault measurements. The proportions of prediction error within ± 250 μm per formula were compared.

RESULTS

The predicted vault values of the WL, NK, KS, and Zhu formulas and vault measurements were 668.74 ± 162.12, 650.85 ± 248.47, 546.56 ± 128.99, 486.56 ± 210.76, and 716.06 ± 233.84 μm, respectively, with a significant difference (χ2 = 69.883, P = 0.000). Significant differences were also found between the measured vault value and Zhu formula, measured vault value and KS formula, WL formula and Zhu formula, WL formula and KS formula, NK formula and KS formula, and NK formula and Zhu formula (P < 0.001) but not between other groups. The proportions of prediction error within ± 250 μm per formula were as follows: WL formula (81.3%) > NK formula (70.8%) > KS formula (66.7%) > Zhu formula (54.2%).

CONCLUSIONS

The WL formula, which considers the complexity of the anterior and posterior chamber structures, demonstrates greater calculation accuracy, compared with the KS (Ver. 4) and Zhu formulas. The proportion of absolute prediction error ≤ 250 μm is higher with the WL formula than with the NK formula (ver. 3). This enhanced predictive capability can improve ICL sizing decisions, thereby increasing the safety and efficacy of ICL implantation surgeries.

Comparison of Predictability in Vault Using NK Formula and KS Formula for the Implantable Collamer Lens Surgery

Background

This study aims to investigate the agreement between the NK and KS formulas in predicting the vault after implantation of an EVO-implantable collamer lens (ICL).

Methods

This retrospective study included 106 eyes of 57 patients who underwent ICL-V4c implantation. Preoperative vault prediction was conducted by utilizing the NK and KS formulas, with postoperative measurements by anterior segment optical coherence tomography (AS-OCT) at one month. The analysis focused on the consistency between predicted and achieved vaults, as well as the correlation between the achieved vault and various biometric parameters.

Results

The mean achieved vault was 605.25 ± 212.72 µm, which was significantly smaller than the predicted vaults of 710.08 ± 195.08 and 673.80 ± 212.76 µm, using the NK and KS formulas, respectively (P < 0.05). The mean differences between the achieved vault and the predicted vault using the NK formula and KS formula were -104.82 μm (95% LoA: -600.38-391.19 μm) and -68.55 μm (95% LoA: -628.91-491.82 μm), respectively. Anterior chamber depth (ACD), vertical sulcus-to-sulcus (V-STS) diameter, and crystalline lens rise (CLR) were independent factors associated with the achieved vault (P < 0.05). The two formulas showed no statistically significant difference in absolute prediction error (APE).

Conclusion

The NK formula exhibited superior consistency and low predictive error compared to the KS formula in the 12.6 mm ICL group. AS-OCT measurements overestimated the predicted ICL vault, especially in the 13.2 mm ICL size selection. Relying solely on the NK or KS formulas for predicting vaults before ICL surgery is not recommended.

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.

Predicting Implantable Collamer Lens Vault Using Machine Learning Based on Various Preoperative Biometric Factors

Purpose

To predict the vault size after Implantable Collamer Lens (ICL) V4c implantation using machine learning methods and to compare the predicted vault with the conventional manufacturer's nomogram.

Methods

This study included 707 patients (707 eyes) who underwent ICL V4c implantation at the Department of Ophthalmology, Peking Union Medical College Hospital, from September 2019 to January 2022. Random Forest Regression (RFR), XGBoost, and linear regression (LR) were used to predict the vault size 1 week after ICL V4c implantation. The mean absolute error (MAE), median absolute error (MedAE), root mean square error (RMSE), symmetric mean absolute percentage error (SMAPE), and Bland-Altman plot were utilized to compare the prediction performance of these machine learning methods.

Results

The dataset was divided into a training set of 180 patients (180 eyes) and a test set of 527 patients (527 eyes). XGBoost had the lowest prediction error, with mean MAE, RMSE, and SMAPE values of 121.70 µm, 148.87 µm, and 19.13%, respectively. The Bland‒Altman plots of RFR and XGBoost showed better prediction consistency than LR. However, XGBoost showed narrower 95% limits of agreement (LoA) than RFR, ranging from -307.12 to 256.59 µm.

Conclusions

XGBoost demonstrated better predictive performance than RFR and LR, as it had the lowest prediction error and the narrowest 95% LoA. Machine learning may be applicable for vault prediction, and it might be helpful for reducing the complications and the secondary surgery rate.

Translational Relevance

Using the proposed machine learning model, surgeons can consider the postoperative vault to reduce the surgical complications.

Effect of ciliary sulcus angle on the prediction of the vault for phakic implantable collamer lens in the KS formula

PURPOSE

We aimed to explore the effects of the ciliary sulcus angle (CSA) on accurate prediction of the vault after phakic implantable collamer lens (EVO ICL Model V4c) using the KS formula.

METHODS

Patients were classified according to the size of CSA: group A, narrow angle (CSA < 30°); group B, normal angle (CSA = 30-90°); and group C, wide angle (CSA > 90°). Further, differences between the actual vault dimensions at 3 months postoperatively and the preoperatively predicted vault dimensions in the three groups were analyzed.

RESULTS

This study included 223 eyes of 223 individuals. In groups A-C, the difference in the preoperative vault dimensions of the three groups predicted with the KS formula was not statistically significant (P = 0.056). The actual vault dimensions at 3 months postoperatively were significantly different between the three groups (P < 0.001). Moreover, the difference between the actual and predicted vaults by the KS formula was statistically significant (P < 0.001). In the 3 months, after surgery, the percentages of patients with a low vault (< 250 μm) were 0%, 3%, and 29% in groups A, B, and C, respectively. Further, the percentages of patients with an ideal vault (250-750 μm) in the postoperative period were 66%, 84%, and 71% in groups A, B, and C, respectively. Finally, the percentages of patients with a high vault (> 750 μm) in the postoperative period were 34%, 13%, and 0% in groups A, B, and C, respectively. Notably, the distribution of the vault among the three groups was statistically significant (P < 0.001).

CONCLUSION

The size of CSA significantly affects the predictiveness of the vault by the KS formula, with the most pronounced effect on the angles < 30° and > 90°. Therefore, CSA should be considered when selecting the lens size using the KS formula preoperatively.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2200065501.

Comparative evaluation of multiple nomograms for predicting postoperative vault after implantable collamer lens surgery

PURPOSE

To compare the vault predictability of most available implantable collamer lens (ICL) sizing nomograms and identify which preoperative measurements are predictive of vault.

SETTING

Private practice in Draper, Utah.

DESIGN

Retrospective chart review.

METHODS

This study was a retrospective analysis of 209 eyes of 106 patients who underwent STAAR Surgical ICL implantation. Analyses were performed based on the availability of preoperative parameters, varying the number of eyes for each test. Mean absolute error (MAE) of predicted vs actual postoperative vault was calculated for each nomogram. The frequency of Kim, Rocamora (least absolute shrinkage and selection operator-optical coherence tomography), Russo, and Reinstein recommending the correct ICL size in instances when Parkhurst, optimized white-to-white (WTW), and STAAR could not recommend a definitive ICL size was determined. Univariate and multivariate linear regression analysis was performed between preoperative measurements and vault.

RESULTS

The Kim, Rocamora, Russo, and Reinstein nomograms had significantly lower MAE of predicted vs actual postoperative vault than the KSV2 and Nakamura V3 nomograms. The Russo formula most frequently recommended the correct ICL size when the Parkhurst, Optimized WTW, and STAAR nomograms could not provide ICL size recommendations. At the 0.05 significance level, anterior chamber depth (ACD), ciliary body inner diameter (CBID), and pupil diameter were the parameters found to have significant correlation with postoperative vault.

CONCLUSIONS

The Kim, Rocamora, Russo, and Reinstein nomograms were the most predictive of vault. Additionally, ACD, CBID, and pupil diameter were found to be significantly correlated with vault and should be considered for use in future ICL sizing nomograms.

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.

Comparison of formulas in the implantable collamer lens vault prediction

To compare the predictability of different formulas in the postoperative vault of an implantable collamer lens (ICL) surgery and assist physicians for formula selection in ICL implantation. This is a retrospective study. Patients who underwent ICL implantation between August 31, 2021 and October 29, 2021 at our clinic were reviewed. The clinical data, predicted ICL sizes and vaults, actual ICL size implanted and vaults at 1 month after surgery, and corresponding prediction formulas used were collected and analyzed. This study included 140 eyes from 72 patients (15 males and 57 females). Differences between ICL sizes recommended by the Visian ICL Online Calculation & Ordering System (OCOS) and NK formula (Version. 3) or KS formula (Version. 4) were statistically significant (P < .0001), except for the recommended ICL sizes between the NK and KS formulas (P > .05). Better consistency between predicted ICL vaults and achieved ICL vaults was observed when using the KS formula compared to the NK formula. The actual ICL vaults were 250 to 750 μm at 1 month after surgery in 66.4%, 76.5%, and 80.5% eyes of the OCOS, NK, and KS groups, respectively. There was significant difference between the OCOS and KS groups (P < .05), especially in the 12.6 mm ICL group. The KS formula is the most accurate formula for recommending an ICL size and vault prediction when compared to the NK formula and OCOS. Further studies for a more accurate formula are warranted.

Assessing the efficacy of four methods established by four parameters in ICL size selection and relevant influencing factors: a prospective cohort study

PURPOSE

To compare the efficacy and relevant influencing factors of four ICL size selection methods established by four different parameters.

METHODS

This prospective study included 60 patients (120 eyes) who underwent bilateral ICL implantation. Patients were equally divided into four groups, and each group used the Parkhurst nomogram based on sulcus-to-sulcus (STS), the manufacturer's Online Calculation & Ordering System (OCOS) nomogram based on white-to-white (WTW), the KS formula based on angle-to-angle (ATA) and the NK formula based on anterior chamber width (ACW) to determine the ICL size. Recorded the vault one month after operation and compared the consistency between STS and WTW, ATA and ACW and their effects on the vault of different groups.

RESULTS

The Parkhurst nomogram, OCOS nomogram, KS formula and NK formula determined 86.7%, 70.0%, 83.3% and 66.7% of properly sized ICL, respectively. STS and ATA were correlated (P < 0.05). The mean difference between the STS and WTW, ATA and ACW was -0.37 ± 0.62 mm, -0.42 ± 0.53 mm and -0.44 ± 0.52 mm, respectively. The vault in the OCOS group was negatively correlated with △STS-WTW, and the vault in the NK group was negatively correlated with △STS-WTW, △STS-ATA and △STA-ACW. The vault in the Parkhurst group and KS group was not affected by anterior segment biometry variables.

CONCLUSION

ATA can be served as an alternative parameter to STS, and STS-based Parkhurst nomogram and ATA-based KS formula determined the most appropriate ICL size. When using OCOS nomogram and NK formula to select ICL size, postoperative abnormal vault was associated with a larger difference between STS and other anterior segment parameters.

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.

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.].

Predicting post-operative vault and optimal implantable collamer lens size using machine learning based on various ophthalmic device combinations

BACKGROUND

Implantable Collamer Lens (ICL) surgery has been proven to be a safe, effective, and predictable method for correcting myopia and myopic astigmatism. However, predicting the vault and ideal ICL size remains technically challenging. Despite the growing use of artificial intelligence (AI) in ophthalmology, no AI studies have provided available choices of different instruments and combinations for further vault and size predictions. This study aimed to fill this gap and predict post-operative vault and appropriate ICL size utilizing the comparison of numerous AI algorithms, stacking ensemble learning, and data from various ophthalmic devices and combinations.

RESULTS

This retrospective and cross-sectional study included 1941 eyes of 1941 patients from Zhongshan Ophthalmic Center. For both vault prediction and ICL size selection, the combination containing Pentacam, Sirius, and UBM demonstrated the best results in test sets [R² = 0.499 (95% CI 0.470-0.528), mean absolute error = 130.655 (95% CI 128.949-132.111), accuracy = 0.895 (95% CI 0.883-0.907), AUC = 0.928 (95% CI 0.916-0.941)]. Sulcus-to-sulcus (STS), a parameter from UBM, ranked among the top five significant contributors to both post-operative vault and optimal ICL size prediction, consistently outperforming white-to-white (WTW). Moreover, dual-device combinations or single-device parameters could also effectively predict vault and ideal ICL size, and excellent ICL selection prediction was achievable using only UBM parameters.

CONCLUSIONS

Strategies based on multiple machine learning algorithms for different ophthalmic devices and combinations are applicable for vault predicting and ICL sizing, potentially improving the safety of the ICL implantation. Moreover, our findings emphasize the crucial role of UBM in the perioperative period of ICL surgery, as it provides key STS measurements that outperformed WTW measurements in predicting post-operative vault and optimal ICL size, highlighting its potential to enhance ICL implantation safety and accuracy.

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.

Evaluation of implantable collamer lens sizing developed by reviewing the horizontal compression-vault coefficient

PURPOSE

To evaluate the implantable collamer lens (ICL)-sizing method using the partial regression coefficient of the implanted ICL size to review the conventional horizontal compression coefficient and match the results of clinical observation.

SETTING

Nagoya Eye Clinic, Nagoya, Japan.

DESIGN

Interventional case series.

METHODS

Patients who underwent ICL V4c implantation to correct myopia and myopic astigmatism were enrolled. The stepwise multiple regression analysis used achieved vault as a dependent variable and preoperative biometric parameters as explanatory variables. The partial regression coefficient of the implanted ICL size was obtained to develop the optimal ICL-sizing formula, the Nakamura-Kojima formula version 3 (NK-formula V3). 85 eyes of 45 patients were implanted with an ICL size recommended by the NK-formula V3. At 3 months postoperatively, the achieved vault was measured using anterior segment optical coherence tomography to validate the NK-formula V3.

RESULTS

The study enrolled 174 patients (174 eyes). The partial regression coefficient of the implanted ICL size adopted as the compression-vault coefficient in the multiple regression equation predicting the vault was 0.729. To validate the NK-formula V3, 77 (90.6%), 7 (8.2%), and 1 (1.2%) eyes were in the moderate-vault, low-vault, and high-vault categories, respectively. The mean difference between the achieved and predicted vaults was 0.064 ± 0.190 (range: -0.264 to 0.742) mm for the NK-formula V3 and 0.176 ± 0.217 (range: -0.254 to 0.907) mm for the NK-formula V2.

CONCLUSIONS

As in vivo coefficient measurement experiments are not possible, the partial regression coefficient is the best option for developing a formula to predict the optimal ICL size.

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.

Vertically Fixated Posterior Chamber Phakic Intraocular Lens Implantation Through a Superior Corneal Incision

Introduction

To assess the 1-year outcomes of vertically fixated posterior chamber phakic intraocular lens implantation through a superior corneal incision.

Methods

This pilot study comprised 78 eyes of 53 consecutive patients undergoing vertically fixated implantable collamer lens (ICL) implantation through a superior corneal incision to correct moderate to high myopia and myopic astigmatism. We prospectively determined the safety, efficacy, predictability, stability, and adverse events preoperatively, and at 1 week and 1, 3, and 12 months postoperatively.

Results

The mean follow-up period was 10.4 ± 5.4 months. Uncorrected and corrected visual acuity were −0.20 ± 0.10 and −0.25 ± 0.07 logMAR, respectively, at 1 year postoperatively. At 1 year postoperatively, 98% and 100% of eyes were within 0.5 and 1.0 D, respectively, of the targeted correction. A nonsignificant change in manifest refraction of −0.01 ± 0.08 D occurred from 1 week to 1 year. The manifest astigmatism decreased significantly, from 0.69 ± 0.73 D preoperatively to 0.21 ± 0.27 D at 1 year postoperatively (Mann–Whitney U test, p < 0.001). No vision-threatening complications occurred at any time in this series.

Conclusions

According to our experience, the vertically fixated ICL through a superior incision achieved good results, without significant complications. Considering that younger patients requiring ICL surgery tend to have with-the-rule astigmatism, this surgical technique may be a viable option for reducing astigmatism without using toric ICLs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40123-022-00470-6.

Assessment of the Vault After Implantable Collamer Lens Implantation Using the KS Formula

PURPOSE

To examine the vault size after Implantable Collamer Lens (ICL) (KS-AquaPORT; STAAR Surgical) surgery using the KS formula.

METHODS

In this prospective study, the postoperative vault was examined using the KS formula in 121 eyes of 65 patients (28 men and 37 women) who underwent ICL implantation for myopia and myopic astigmatism. The mean horizontal angle-to-angle (ATA), anterior chamber depth, and axial length before surgery were 11.83 ± 0.40, 3.25 ± 0.34, and 26.52 ± 1.17, respectively. Anterior segment optical coherence tomography (CASIA2; Tomey Corporation) was used for ATA measurement.

RESULTS

Multiple regression analysis of the potential factors influencing the predicted vault error (postoperative vault - predicted vault by KS formula) showed that only ICL size was a significant factor (P < .001, r = 0.36). At an ICL size of 12.1 mm, the postoperative vault was smaller than the predicted vault, and the postoperative vault tended to be larger than the predicted vault at ICL sizes of 13.2 and 13.7 mm.

CONCLUSIONS

Vault prediction by the KS formula was generally good, but the ICL size influenced the vault prediction error; therefore, a modified KS formula was created to reduce the error in measurements of the postoperative vault. [J Refract Surg. 2021;37(9):636-641.].

Biometric and ICL-related risk factors associated to sub-optimal vaults in eyes implanted with implantable collamer lenses

Background

To identify biometric and implantable collamer lens (ICL)-related risk factors associated with sub-optimal postoperative vault in eyes implanted with phakic ICL.

Methods

This study reports a retrospective case series of the first operated eye in 360 patients implanted with myopic spherical or toric ICL. Preoperatively, white-to-white (WTW), central keratometry (Kc) and central corneal thickness (CCT) were measured using the Pentacam. Anterior-segment optical coherence tomography (AS-OCT, Visante) was applied preoperatively for measuring the horizontal anterior-chamber angle-to-angle distance (ATA), internal anterior chamber depth (ACD), crystalline lens rise (CLR), anterior-chamber angle (ACA) and postoperatively the vault. Eyes were divided into three vault groups: low (LVG: ≤ 250 μm), optimal (OVG: > 250 and < 1000 μm) and high (HVG: ≥ 1000 μm). Multinomial logistic regression (MLR) was used to find the sub-optimal vault predictors.

Results

MLR showed that CLR, ICL size minus the ATA (ICL size-ATA), age, ICL spherical equivalent (ICLSE) and ICL size as contributing factors for sub-optimal vaults (pseudo-R² = 0.40). Increased CLR (OR: 1.01, CI: 1.00–1.01) and less myopic ICLSE (OR: 1.22, CI: 1.07–1.40) were risk factors for low vaults. Larger ICL size-ATA (OR: 41.29, CI: 10.57–161.22) and the 13.7 mm ICL (OR: 7.08, CI: 3.16–15.89) were risk factors for high vaults, whereas less myopic ICLSE (OR: 0.85, CI: 0.76–0.95) and older age (OR: 0.92, CI: 0.88–0.98) were protective factors.

Conclusion

High CLR and low ICLSE were the major risk factors in eyes presenting low vaults. In the opposite direction, ICL size-ATA was the major contributor for high vaults. This relationship was more critical in higher myopic ICLSE, younger eyes and when 13.7 mm ICL were used. The findings show that factors influencing the vault have differentiated weight of influence depending on the type of vault (low, optimal or high).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00250-6.

Development of a Web-Based Ensemble Machine Learning Application to Select the Optimal Size of Posterior Chamber Phakic Intraocular Lens

Purpose

Selecting the optimal lens size by predicting the postoperative vault can reduce complications after implantation of an implantable collamer lens with a central-hole (ICL with KS-aquaport). We built a web-based machine learning application that incorporated clinical measurements to predict the postoperative ICL vault and select the optimal ICL size.

Methods

We applied the stacking ensemble technique based on eXtreme Gradient Boosting (XGBoost) and a light gradient boosting machine to pre-operative ocular data from two eye centers to predict the postoperative vault. We assigned the Korean patient data to a training (N = 2756 eyes) and internal validation (N = 693 eyes) datasets (prospective validation). Japanese patient data (N = 290 eyes) were used as an independent external dataset from different centers to validate the model.

Results

We developed an ensemble model that showed statistically better performance with a lower mean absolute error for ICL vault prediction (106.88 µm and 143.69 µm in the internal and external validation, respectively) than the other machine learning techniques and the classic ICL sizing methods did when applied to both validation datasets. Considering the lens size selection accuracy, our proposed method showed the best performance for both reference datasets (75.9% and 67.4% in the internal and external validation, respectively).

Conclusions

Applying the ensemble approach to a large dataset of patients who underwent ICL implantation resulted in a more accurate prediction of vault size and selection of the optimal ICL size.

Translational Relevance

We developed a web-based application for ICL sizing to facilitate the use of machine learning calculators for clinicians.