Relationship between Crystalline Lens Thickness and Shape and the Identification of Anterior Ocular Segment Parameters for Predicting the Intraocular Lens Position after Cataract Surgery

Lens Thickness in Infants and Children with Cataracts

Purpose

The purpose of this study was to determine the association between lens thickness and cataract in participants aged 0 to 5 years.

Design

This was a prospective, multicenter, case-control study.

Participants

We enrolled 118 participants (171 eyes) aged 0 to 5 years, mean age 14.6 ± 17.0 months, range 0 to 60 months.

Methods

Lens thickness was measured on 342 ultrasound biomicroscopy (UBM) images.

Main Outcome Measures

Lens thickness; feasibility of lens thickness measurement from UBM images.

Results

The mean lens thickness among noncataracts was 3.60 ± 0.17 mm, compared with 3.16 ± 0.61 mm among cataracts (P < 0.0001). Lens thickness <3.5 mm was significantly associated with increased odds of cataract; adjusted odds ratio = 5.99 (95% confidence interval, 2.41-14.88; P < 0.0003) among participants age 0 to 7 months. Lens thickness was significantly associated with cataract laterality among participants age 0 to 7 months (P < 0.0001).

Conclusions

Quantitative UBM can be used to evaluate lens thickness in infants and children with congenital cataracts. The lens in congenital cataract eyes was thinner than that of controls among infants. Abnormal lens thickness was significantly associated with cataract. Future longitudinal studies will examine the association between lens thickness and postcataract surgery outcomes.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Influence of Lens Thickness on Accuracy of Kane, Hill-RBF 3.0, Barrett Universal II, Emmetropia Verifying Optical, and Pearl-DGS Formulas in Eyes with Nonhigh Myopia and High Myopia

PURPOSE

To investigate the influence of lens thickness (LT) on accuracy of Kane, Hill-RBF 3.0 Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO), and Pearl-DGS formulas in eyes with different axial lengths (AL).

METHODS

The prospective cohort study was conducted at Eye and ENT Hospital of Fudan University. Patients who had uneventful cataract surgery between March 2021 and July 2023 were recruited. Manifest refraction was conducted two-month post-surgery. Eyes were divided into 4 groups based on AL: short (<22mm), medium (22-24.5 mm), medium long (24.5-26mm) and very long (≥26mm). In each AL group, eyes were then divided into 3 subgroups based on the LT measured with IOLmaster700: thin (<4.5 mm), medium (4.5-5.0 mm), and thick (≥ 5 mm). The influence of LT on accuracy of Kane, Hill-RBF 3.0, BUII, EVO, and Pearl-DGS formulas were investigated in each AL group.

RESULTS

A total of 327 eyes from 327 patients were analyzed, with 64, 102, 73 and 88 eyes in each AL group, respectively. In eyes with AL < 24.5 mm, myopic PE was significantly associated with greater LT using all the 5 formulas (all p < 0.05). Backward stepwise multivariate regression analyses revealed that LT was an important influencing factor for PE in all 5 formulas, particularly in eyes with AL <24.5 mm. In eyes with AL <24.5 mm and LT > 5.0 mm, PE of all 5 formulas calculated with the optional parameter LT were more myopic than those calculated without LT.

CONCLUSIONS

Thicker LT was associated with more myopic PE among eyes with AL <24.5 mm when using all 5 formulas. Further optimization of current formulas is necessary, especially for eyes with short AL and thick LT.

Research progress on prediction of postoperative intraocular lens position

With the progress in refractive cataract surgery, more intraocular lens (IOL) power formulas have been introduced with the aim of reducing the postoperative refractive error. The postoperative IOL position is critical to IOL power calculations. Therefore, the improvements in postoperative IOL position prediction will enable better selection of IOL power and postoperative refraction. In the past, the postoperative IOL position was mainly predicted by preoperative anterior segment parameters such as preoperative axial length (AL), anterior chamber depth (ACD), and corneal curvature. In recent years, some novel methods including the intraoperative ACD, crystalline lens geometry, and artificial intelligence (AI) of prediction of postoperative IOL position have been reported. This article attempts to give a review about the research progress on prediction of the postoperative IOL position.

Influence of Ocular Biometry Parameters on the Predictive Accuracy of IOL Power Formulas in Patients with High Myopia

INTRODUCTION

The aim of this study was to investigate the influence of ocular biometry parameters on the predictive accuracy of 10 intraocular lens (IOL) power formulas in patients with high myopia (HM).

METHODS

We analyzed 202 eyes of 202 patients. The ocular biometry was determined preoperatively using an IOLMaster 700. The associations between the biometry parameters and the prediction error (PE) 1 month postoperatively were assessed. HM was defined as an axial length exceeding 26.50 mm.

RESULTS

In patients with HM (n = 108), the K6, Emmetropia Verifying Optical (EVO), Olsen, and Barrett Universal II (BUII) formulas had the lowest absolute PEs among the 10 formulas. The ocular biometry parameters were not associated with the PE of K6, EVO, Olsen, or BUII. A longer axial length in HM eyes was associated with myopic outcomes by Kane, Hoffer QST, and VRF and hyperopic outcomes by Holladay 2 and T2. Steeper keratometry, a deeper anterior chamber, and a thicker lens were associated with a hyperopic shift in HM eyes when using VRF, Kane, and Hoffer QST, respectively. In patients without HM (n = 94), there was no difference between the formulas in absolute PE. The significant associations between the biometry parameters and PE in patients with HM were not present in patients without HM.

CONCLUSIONS

K6, EVO, Olsen, and BUII displayed high accuracy in HM eyes and were not influenced by preoperative biometry parameters. For the remaining formulas, the preoperative keratometry, anterior chamber depth, lens thickness, and axial length were possible error sources underlying an inaccurate IOL power prediction in patients with HM.

Estimation of the full shape of the crystalline lens from OCT: validation using stretched donor lenses

Quantifying human crystalline lens geometry as a function of age and accommodation is important for improved cataract and presbyopia treatments. In previous works we presented eigenlenses as a basis of 3-D functions to represent the full shape of the crystalline lens ex vivo. Also, we presented the application of eigenlenses to estimate the full shape of the lens in vivo from 3-D optical coherence tomography (OCT) images, where only the central part of the lens -visible through the pupil- is available. The current work presents a validation of the use of eigenlenses to estimate in vivo the full shape of dis-accommodated lenses. We used 14 ex vivo crystalline lenses from donor eyes (11-54 y/o) mounted in a lens stretcher, and measured the geometry and the power of the lenses using a combined OCT and ray tracing aberrometry system. Ex vivo, the full extent of the lens is accessible from OCT because the incident light is not blocked by the iris. We measured in non-stretched (fully accommodated) and stretched (mimicking in vivo dis-accommodated lenses) conditions. Then, we simulated computationally in vivo conditions on the obtained ex vivo lenses geometry (assuming that just the portion of the lens within a given pupil is available), and estimated the full shape using eigenlenses. The mean absolute error (MAE) between estimated and measured lens' diameters and volumes were MAE = 0.26 ± 0.18 mm and MAE = 7.0 ± 4.5 mm3, respectively. Furthermore, we concluded that the estimation error between measured and estimated lenses did not depend on the accommodative state (change in power due to stretching), and thus eigenlenses are also useful for the full shape estimation of in vivo dis-accommodated lenses.

Spectral-Domain OCT Lens Meridian Position as a Metric to Estimate Postoperative Anatomical Lens Position

PURPOSE

To evaluate the prediction of postoperative anatomical lens position (ALP) using intraoperative spectral-domain optical coherence tomography (SD-OCT) lens anatomy metrics in patients who underwent femtosecond laser-assisted cataract surgery.

METHODS

Intraoperative SD-OCT (Catalys; Johnson & Johnson Vision) and postoperative optical biometry (IOLMaster 700; Carl Zeiss Meditec AG) were used to assess anterior segment landmarks, including lens thickness, lens volume, anterior chamber depth, lens meridian position (LMP), and measured ALP. LMP was defined as the distance from the corneal epithelium to the lens equator, and ALP was defined as the distance from the corneal epithelium to the IOL surface. Eyes were divided into groups according to axial length (> 22.5 mm, 22.5 to 24.5 mm, and > 24.5 mm) and IOL type (Tecnis ZCB00 [Johnson & Johnson Vision]; AcrySof SN-60WF [Alcon Laboratories, Inc], or enVista MX60E [Bausch & Lomb]) to further analyze the correlation between LMP and ALP. Theoretical effective lens position was back-calculated using a specific formula. Primary outcome was correlation between postoperative measured ALP and LMP.

RESULTS

A total of 97 eyes were included in this study. Linear regression analysis displayed a statistically significant correlation between intraoperative LMP and postoperative ALP (R² = 0.522; P < .01). No statistically significant correlation was observed between LMP and lens thickness (R² = 0.039; P = .06) or between ALP and lens thickness (R² = 0.02; P = .992). The greatest predictor for ALP was LMP (β = 0.766, P < .001; R² = 0.523).

CONCLUSIONS

Intraoperative SD-OCT-measured LMP correlated better than anterior chamber depth and axial length to postoperative ALP. Further studies are necessary to analyze the impact of preoperative or intraoperative LMP measurements on postoperative refractive outcomes. [J Refract Surg. 2023;39(3):165-170.].

Estimation of the full shape of the crystalline lens in-vivo from OCT images using eigenlenses

Quantifying the full 3-D shape of the human crystalline lens is important for improving intraocular lens power or sizing calculations in treatments of cataract and presbyopia. In a previous work we described a novel method for the representation of the full shape of the ex vivo crystalline lens called eigenlenses, which proved more compact and accurate than compared state-of-the art methods of crystalline lens shape quantification. Here we demonstrate the use of eigenlenses to estimate the full shape of the crystalline lens in vivo from optical coherence tomography images, where only the information visible through the pupil is available. We compare the performance of eigenlenses with previous methods of full crystalline lens shape estimation, and demonstrate an improvement in repeatability, robustness and use of computational resources. We found that eigenlenses can be used to describe efficiently the crystalline lens full shape changes with accommodation and refractive error.

Influence of lens position as detected by an anterior segment analysis system on postoperative refraction in cataract surgery

AIM

To predict postoperative intraocular lens (IOL) position using the Sirius anterior segment analysis system and investigate the effect of lens position and IOL type on postoperative refraction.

METHODS

A total of 97 patients (102 eyes) were enrolled in the final analysis. An anterior segment biometry measurement was performed preoperatively with Sirius and Lenstar. The results of predicted lens position (PLP) and IOL power were automatically calculated by the software used by the instruments. Effective lens position (ELP) was measured manually using Sirius 3mo postoperatively. Pearson's correlation analysis and linear regression analysis were used to determine the correlation of lens position to other parameters.

RESULTS

PLP and ELP were positively correlated to axial length (AL; r=0.42, P<0.0001 and r=0.49, P<0.0001, respectively). There was a weak correlation between the peLP (ELP-PLP) and the prediction error of spherical refraction (peSR; r=0.34, P<0.0001). The peLP of Softec HD IOL differed statistically from those of both the TECNIS ZCB00 and Sensor AR40E IOLs. Multiple linear regression was used to obtain the prediction formula: ELP=0.66+0.63×[aqueous depth (AQD)+0.6LT] (r=0.61, P<0.0001), and a new variable (AQD+0.6 LT) was found to have the strongest correlation with ELP.

CONCLUSION

The Sirius anterior segment analysis system is helpful to predict ELP, which reduces postoperative refraction error.

Determining the Theoretical Effective Lens Position of Thick Intraocular Lenses for Machine Learning-Based IOL Power Calculation and Simulation

Purpose

To describe a formula to back-calculate the theoretical position of the principal object plane of an intraocular lens (IOL), as well as the theoretical anatomic position in a thick lens eye model. A study was conducted to ascertain the impact of variations in design and IOL power, on the refractive outcomes of cataract surgery.

Methods

A schematic eye model was designed and manipulated to reflect changes in the anterior and posterior radii of an IOL, while keeping the central thickness and paraxial powers static. Modifications of the shape factor (X) of the IOL affects the thick lens estimated effective lens position (ELP). Corresponding postoperative spherical equivalent (SE) were computed for different IOL powers (-5 diopters [D], 5 D, 15 D, 25 D, and 35 D) with X ranging from -1 to +1 by 0.1.

Results

The impact of the thick lens estimated effective lens position shift on postoperative refraction was highly dependent on the optical power of the IOL and its thickness. Design modifications could theoretically induce postoperative refraction variations between approximately 0.50 and 3.0 D, for implant powers ranging from 15 D to 35 D.

Conclusions

This work could be of interest for researchers involved in the design of IOL power calculation formulas. The importance of IOL geometry in refractive outcomes, especially for short eyes, should challenge the fact that these data are not usually published by IOL manufacturers.

Translational Relevance

The back-calculation of the estimated effective lens position is central to intraocular lens calculation formulas, especially for artificial intelligence-based optical formulas, where the algorithm can be trained to predict this value.

Lens thickness and associated ocular biometric factors among cataract patients in Shanghai

Background

To evaluate the distribution of lens thickness (LT) and its associations with other ocular biometric factors among cataract patients in Shanghai.

Methods

Twenty-four thousand thirteen eyes from 24,013 cataract patients were retrospectively included. Ocular biometric factors including LT, central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white (WTW) distance, anterior corneal curvature, and axial length (AL) were obtained using the IOLMaster700. The associations between LT and general or ocular factors were assessed.

Results

The mean age was 62.5 ± 13.6 years and 56.1% were female. The mean LT was 4.51 ± 0.46 mm. The LT was greater in older patients (P < 0.001). LT was positively correlated with CCT, while negatively correlated with ACD, WTW, and anterior corneal curvature (P < 0.001). Multivariate analysis revealed that increased LT was associated with older age, male gender, thicker CCT, shallower ACD, larger WTW, and flatter anterior corneal curvature (P < 0.001). LT changed with a variable behavior according to AL. In short eyes LT increased as AL increased, then decreased with longer AL in normal eyes and moderate myopic eyes, but increased again as AL increased in highly myopic eyes. Thickest LT was found in the 20.01–22 mm AL group. The correlation between LT and other biometric factors remained significant when stratified by ALs.

Conclusions

In a large Chinese cataractous population, we found that the thicker lens may be associated with older age, male gender, thicker CCT, shallower ACD, larger WTW, and flatter anterior corneal curvature. As AL increased, the change of LT was nonlinear, with the thickest lens seen in the 20–22 mm AL group.

Anterior segment optical coherence tomography imaging and ocular biometry in cataract patients with open angle glaucoma comorbidity

BACKGROUND

Anterior chamber angle anatomy in perspective of ocular biometry may be the key element to intraocular pressure (IOP) reduction, especially in glaucoma patients. We aim to investigate anterior chamber angle and biometrical data prior to cataract surgery in patients with and without glaucoma comorbidity.

MATERIALS AND METHODS

This prospective comparative case-control study included 62 subjects (38 with cataract only and 24 with cataract and glaucoma). A full ophthalmic examination including, Goldmann applanation tonometry, anterior chamber swept source optical coherence tomography (DRI OCT Triton plus (Ver.10.13)) and swept source optical biometry (IOL Master 700 v1.7) was performed on all participants.

RESULTS

We found that ocular biometry parameters and anterior chamber parameters were not significantly different among groups. However, when we added cut-off values for narrow angles, we found that glaucoma group tended to have more narrow angles than control group. IOP was higher in glaucoma group despite all glaucoma patients having medically controlled IOP. In all subjects, anterior chamber parameters correlated well with lens position (LP), but less with relative lens position, while LP cut-off value of 5.1 mm could be used for predicting narrow anterior chamber angle parameters.

CONCLUSIONS

Cataract patients tend to develop narrow anterior chamber angles. Anterior chamber angle parameters have a positive moderate to strong relationship with lens position. LP may be used predicting narrow angles.

New IOL formula using anterior segment three-dimensional optical coherence tomography

This retrospective study was aimed to compare prediction errors from various combinations of biometric data generated using optical coherence tomography (OCT) and develop a new intraocular lens (IOL) formula using biometric data. 145 eyes from 145 patients who underwent femtosecond laser-assisted cataract surgery (FLACS) were enrolled to the present study and they were divided into a training set (n = 92) and a test set (n = 53). Preoperative axial length (AL) and corneal radius were measured using partial coherence interferometry. The anterior chamber depth (ACD), lens meridian parameter (LMP), lens thickness (LT), thickness of anterior and posterior parts of the crystalline lens (aLT and pLT), and anterior segment length were measured by OCT. From a training set, we developed eight regression equations and analyzed the predictive accuracy. The regression equation using AL, LMP, and pLT (-1.143 + 0.148*AL + 0.428*LMP + 0.254*pLT) showed the strongest correlation with effective lens position (ELP) and smallest standard deviation of ELP prediction error. IOL formula generated using AL, LMP, and pLT yielded the highest predictive accuracy. In a test set, the new IOL formula also produced narrowest range of prediction error, smallest median absolute error, and highest percentages within ±0.25, ±0.50 than existing IOL formulas. The IOL formula considering AL, LMP and pLT will help to improve predictive accuracy in FLACS.

Development of a new intraocular lens power calculation method based on lens position estimated with optical coherence tomography

A new method is developed and validated for intraocular lens (IOL) power calculation based on paraxial ray tracing of the postoperative IOL positions, which are obtained with the use of anterior segment optical coherence tomography. Of the 474 eyes studied, 137 and 337 were grouped into training and validation sets, respectively. The positions of the implanted IOLs of the training datasets were characterized with multiple linear regression analyses one month after the operations. A new regression formula was developed to predict the postoperative anterior chamber depth with the use of the stepwise analysis results. In the validation dataset, postoperative refractive values were calculated according to the paraxial ray tracing of the cornea and lens based on the assumption of finite structural thicknesses with separate surface curvatures. The predicted refraction error was calculated as the difference of the expected postoperative refraction from the spherical-equivalent objective refraction values. The percentage error (within ±0.50 diopters) of the new formula was 84.3%. This was not significantly correlated to the axial length or keratometry. The developed formula yielded excellent postoperative refraction predictions and could be applicable to eyes with abnormal proportions, such as steep or flat corneal curvatures and short and long axial lengths.

Correlation between lens thickness and lens density in patients with mild to moderate cataracts

PURPOSE

To determine the relationships between lens thickness (LT), lens density and anterior segment parameters in patients with mild to moderate cataracts.

SETTING

Oftalmosalud Instituto de Ojos, Lima, Perú.

DESIGN

Prospective, single-centre, cross-sectional study.

METHODS

169 eyes with age-related mild to moderate cataracts had lens density assessed using the Lens Opacification Classification System III, the built-in Pentacam HR Nucleus Staging software and ImageJ software. LT and axial length (AL) were measured with the IOLMaster 700, and angle parameters were measured using anterior segment optical coherence tomography. Pearson correlation coefficients and Kruskal-Wallis tests were used for statistical analyses.

RESULTS

Nuclear colour score was the only clinical parameter with a weak significant correlation with LT (r=0.24, p=0.003) after accounting for age, AL, gender and anterior chamber depth (ACD). The maximum value of average lens density and the mean nuclear density were significantly correlated with LT (r=0.24, p=0.003 and -0.17, p=0.03, respectively) after controlling for the same factors. Central LT greater than 4.48 mm was present in 54.5% of the eyes with a nuclear opalescence grade 1.

CONCLUSIONS

LT is independent of lens density in mild to moderate cataracts after accounting for age, AL, ACD and gender contrary to previous studies.