Role of Crystalline Lens on Angle Closure in the North Indian Population

Role of Crystalline Lens on Angle Closure in the North Indian Population

Saptarshi Mukherjee¹, Aastha Bhandari^2*, Hunny Kumar³, Jomirul Hossen⁴

1. Senior optometrist; Centre for Sight Eye Hospital, New Delhi

2 Optometrist, Rapti Academy of Health Sciences, Dang, Nepal

3 Project coordinator, Dr Shroff Charity Eye Hospital, New Delhi

4. Senior optometrist; Eye 7 hospital, New Delhi

*Correspondence to: Aastha Bhandari, Optometrist, Rapti Academy of Health Sciences, Dang, Nepal.

Copyright

© 2025 Aastha Bhandari This is an open access article distributed under the Creative Commons Attribution   License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original   work is properly cited.

Received: 08 Sep 2025

Published: 27 Sep 2025

Abstract

Purpose: To evaluate the role of crystalline lens on angle closure in the North Indian Population

Methodology: It was a prospective, comparative study. A total of 313 eyes of 162 participants underwent Anterior Segment Optical Coherence Tomography (AS-OCT) and biometry using IOL Master-700. Measurements included axial length (AL), anterior chamber depth (ACD) and lens thickness (LT). Lens vault (LV) was measured as the perpendicular distance from the anterior pole of the lens to a line connecting the scleral spur on AS–OCT. Lens position (LP) was calculated as ACD + 1/2 LT, and relative lens position (RLP) was calculated as LP / AL. The receiver operating curve (ROC) was plotted, and the Area under the curve (AUC), sensitivity, and specificity were calculated for all parameters to quantify their discriminating ability.

Results: Lens vault was significantly higher in the eyes with Primary Angle Closure Suspect (PACS: 503.85±181.03 μm), Primary angle closure (PAC: 641.69±197.04 μm) and Primary angle closure disease (PACD: 591.31±211.06 μm) compared to normal (141.39±191.33 μm) (p>0.01) Lens vault along with ACD demonstrated the highest area under curve (AUC= 0.95) with sensitivity of 89.7%, followed by lens position (AUC=0.92) with sensitivity 82.4 % and specificity 89%.

Conclusion: The eyes with angle closure have thicker lenses with a greater LV, shallower ACD, and shorter AL. Lens vault, ACD and lens position were associated strongly and independently with angle closure and distinguished eyes with angle closure from those with open angles better than traditional biometric parameters.

Keywords: Lens vault, Lens position, relative lens position, AS-OC

Introduction

Primary angle-closure glaucoma is a leading cause of blindness, for the most part in Asian countries. A survey in an urban population in southern India has reported a high prevalence of 4.3% for primary angle closure glaucoma (PACG) in the 30- to 60-year age group. (1) The Hooghly River Glaucoma Study showed that 1.54% have angle closure. (2) The Andhra Pradesh eye study showed that 41.7% of those with manifest PACG had blindness in one or both eyes resulting from PACG. (3) Previous studies have demonstrated that ocular risk factors for angle-closure glaucoma are shallow anterior chamber depth (ACD), short axial length (AL), and increased lens thickness (LT). (4–7) Among these parameters, the lens is considered to play a critical role in the pathogenesis of angle closure disease either because of an increase in its thickness or a more anterior position, causing a decrease in ACD. The result is angle crowding and a greater predisposition to pupillary block resulting from iridolenticular apposition in eyes with small anterior segments. However, the involvement of different lens parameters such as the lens position (LP; defined as ACD 1/2 LT), relative lens position (RLP; defined as LP/axial length), and LT-to-AL (LT/AL) ratio have not been recognized categorically, and there have been inconsistent reports on the importance of LP and RLP with angle closure. (8–13)

Now it is possible to capture in a single image the whole anterior chamber using anterior-segment optical coherence tomography (AS OCT). This allows enhanced imaging of the lens compared to other structures. We hypothesize that the degree of lens that is located anterior to the plane of the angles plays a role in the pathogenesis of angle closure. One way to determine the grade of this parameter is to calculate the lens vault (LV), defined as the perpendicular distance between the anterior pole of the crystalline lens and a horizontal straight line joining the two scleral spurs. The present study aimed to evaluate the relative importance of lens parameters (LV, LP, and RLP) with respect to angle closure by comparing eyes with angle closure with eyes of patients with open angles. Lens thickness increases with age and has a linear relationship. (30) Lens growth continues throughout life, and there is no difference between sexes. Although in Chinese (24) and Japanese(25)population studies, lens thickness was different between in control group and the study group, but there was a significant difference in age between the two groups.

Materials and Methods

This was a prospective, comparative study of North Indian subjects with angle closure attending a glaucoma clinic and of normal control subjects recruited from the Comprehensive Eye clinic.

Definition of Angle-closure Glaucoma: The definitions of occludable angle and manifest PACG were based on definitions used in a recent report on glaucoma in Mongolia. (14) Occludable angle was defined as pigmented posterior trabecular meshwork not visible by gonioscopy in three-quarters or more of the angle circumference, raised intraocular pressure, or both, but without glaucomatous optic neuropathy. Manifest PACG was defined as an IOP of 22 mmHg or more or glaucomatous optic disc damage with visual field loss in the presence of an occludable angle and the presence of at least 3 of the following signs: conjunctival injection, corneal epithelial oedema, mid dilated unreactive pupil, and shallow anterior chamber. (15)

 Patients diagnosed with secondary angle closure (such as neovascular or uveitic glaucoma), patients who had corneal abnormalities that would affect imaging, and patients who had a previous laser iridoplasty or intraocular surgery history were excluded. All subjects with angle closure previously had undergone laser peripheral iridotomy.

The control group of normal subjects (defined as intraocular pressure 21 mmHg with open angles, healthy optic nerves and normal visual fields, no previous ocular surgery, and no family history of glaucoma) were recruited from the Comprehensive Eye clinic, aged 25 years and older. For this report, complete data were available for 109 eyes of 58 consecutive normal North Indian subjects, and they were included as the control group. All subjects underwent a detailed routine eye examination that included visual acuity measurement using a Snellen’s chart, slit-lamp examination, stereoscopic optic disc evaluation with a 90-diopter lens (Volk Optical, Inc., Mentor, Ohio), intraocular pressure measurement by Goldmann applanation tonometer and gonioscopy, performed in a dark room. Indentation gonioscopy with the Sussman 4-mirror lens was used to determine the presence or absence of peripheral anterior synechiae. A-scan biometry (IOL master 700; Zeiss) (16, 17) was used to measure AL, ACD, and LT, and these results were used to calculate LP (defined as ACD +1/2LT) and RLP (defined as LP/AL).

Anterior segment OCT (ASOCT)

All subjects underwent imaging with ASOCT (Cirrus 5000, Carl Zeiss Meditec, Dublin, CA, USA)(18,19,20) performed in dark-room conditions (0 lux) by optometrists who were masked to the results of the clinical ophthalmic examination. Scans were centered on the pupil and taken along the horizontal axis (nasal-temporal angles at 0°–180°) using the standard anterior segment single-scan protocol. To obtain the best quality image, the examiner adjusted the saturation and noise and optimized the polarization for each scan during the examination. As several scans are acquired by the ASOCT device, the optometrist finalized the best images, without motion artefacts or eyelid image artefacts . One cross-sectional horizontal ASOCT scan of the nasal and temporal angle was evaluated for each subject. These images were processed using the in-built software, by Carl Zeiss Meditec, 2015, masked to clinical data. For each image, the only observer input was to determine the location of the two scleral spurs, defined as the point where there was a change in curvature of the inner plane of the angle wall, often appearing as an inward protrusion of the sclera. The algorithm then automatically calculated the LV, defined as the perpendicular distance between the anterior pole of the crystalline lens and the horizontal line joining the two scleral spurs. Positive values indicate that the anterior pole of the lens is located anterior to the sclera spur line, whereas negative values occur when the anterior pole of the lens is posterior to the sclera spur line.

Statistical analysis

Statistical analysis was conducted using SPSS software, version 17 (SPSS, Inc., Chicago, IL, USA). Parametric variables were assessed with ANOVA, followed by post hoc Tukey tests. Nonparametric variables were analyzed using the Kruskal–Wallis test. The ROC curve was plotted to assess the diagnostic performance of the parameters in distinguishing between cases and controls. The Area under the Curve (AUC), sensitivity and specificity were calculated for all parameters to quantify their discriminative ability. The Youden Index was used to determine the optimal cutoff point by identifying the threshold that maximized sensitivity and specificity.

Result

We have calculated 313 eyes from 163 patients, out of which 109 eyes were included in the control group and 68 PACS, 107 PAC, and 29 PACG eyes were included in the study group. The mean age group of Angle closure eyes was 52.4 ± 11.06 years, and the mean age group of Normal eyes was 45.6 ± 11.8 years. The mean lens vault of Angle closure was found to be (590.01 ± 203.26) micron, and the control group (141.39 ±191.33) micron. Significant difference between the angle closure and the control group was found for the lens vault (P=0.000). Significant difference between the angle closure and the control group was found for the LP (Lens position) (4.89±0.25 vs 5.34 ± 0.23) mm (P < 0.001) and RLP (Relative lens position) (0.21 ±0.01 vs 0.23 ±0.01) P < 0.001.

Table 1 Mean value of Lens vault, Axial length, ACD, Lens thickness, Lens position and RLP