Relation between pre- and post-operative iris depth and IOL position in cataract surgery patients measured using extended-depth OCT

Abstract

Purpose : The gap between the post-operative iris plane and anterior IOL surface may contribute to undesired visual effects in cataract surgery patients, such as dysphotopsia. The purpose of this study was to measure the position of the iris plane and its changes in subjects before and after cataract surgery in relation to IOL position.

Methods : Twenty-two eyes from 17 subjects (age: 70.4 ± 10.8 years) who underwent cataract surgery and IOL implantation at Bascom Palmer Eye Institute were imaged with a custom-built extended-depth OCT system (Ruggeri et al, Biomed Opt Exp 2012) before and one to six months after surgery. All surgeries were performed by one of two surgeons using a standard monofocal IOL (Alcon Acrysof). A custom-made MATLAB program was used to measure the iris depth in the pre- and post-operative images and the IOL position in the post-op image. To measure iris depth, a line was drawn between the left and right tip of the iris in the OCT image. Iris depth was defined as the distance from this line to the posterior corneal surface measured along the A-line passing though the mid-point of line. Iris to IOL distance was measured along the same A-line in the post-operative images. The position of the iris pre-op and post-op were compared and the variability of the iris to IOL distance was quantified.

Results : The iris shifted downwards (iris depth increased) in 21 of the 22 subjects following cataract surgery. The average pre-op iris depth was 2.91 ± 0.45 mm (range: 2.17 - 3.78 mm). The average post-op iris depth was 3.48 ± 0.29 mm (range: 4.40 - 5.34 mm). Post-op iris to IOL distance was 0.71 ± 0.23 mm (range: 0.45 - 1.50 mm). The relative change in iris depth (post-op – pre-op) for individual subjects was 0.57 ± 0.34 mm (range: -0.02 - 1.15 mm).

Conclusions : There a significant shift of the iris plane after cataract surgery and a large variability in the post-op iris to IOL distance, which may contribute to dysphotopsia.

This is a 2020 ARVO Annual Meeting abstract.

 

Figure 1. OCT images of a subject taken before (left) and after (right) cataract surgery. The distance between the posterior corneal surface and the average position between the left and right tip of the iris, indicated by the dotted line, is the pre-op and post-op iris depth. The distance between the average position between the left and right tip of the post-op iris and the IOL anterior surface is the iris to IOL distance.