Quantification of Goldmann visual field volume to track the progression of Choroideremia in a large retrospective cohort

Abstract

Purpose : Choroideremia is an X-linked choroidopathy caused by mutations in the CHM gene and characterized by the early appearance of multiple scotomas in the periphery that spread and coalesce, often sparing the fovea until late in the disease. This makes quantitative monitoring of the decline in visual function particularly challenging. Therefore, we set out to track the progression of choroideremia in a longitudinal, retrospective cohort using Goldmann visual field volume and visual acuity.

Methods : Molecularly confirmed choroideremia patients who had Goldmann visual fields available were collected from the records of the University of Iowa retina service. The Goldmann visual fields were traced using an iPad-based application, and the three-dimensional hill of vision was interpolated. This interpolation allowed quantification of visual field loss from data collected over decades with differing protocols (different or incomplete isopters etc.). Best-corrected visual acuities were collected and converted to LogMAR. An exponential mixed effects model was used to evaluate the loss of visual field volume over time.

Results : We analyzed data from 191 clinic visits of 56 molecularly confirmed choroideremia patients (range 1–19 visits per patient). Patients had a median follow up of 3 years (range 0–53 years) with an age range of 6 to 78 at the time of their visits. Mean field volume loss was 5.7 ± 0.6% (range 1.2–12.6%) per year based on exponential modelling. Visual field volume was strongly correlated between eyes (r-squared = 0.94) compared to best corrected visual acuity (r-squared = 0.31).

Conclusions : Volumetric analysis of kinetic perimetry data enables quantification of peripheral visual function in choroideremia patients and monitoring of disease progression over time. Because of the minimal inter-eye variability, this metric is potentially useful in fellow-eye control trials. The methods presented here will allow us to unlock decades worth of retrospective visual field data from patients with inherited retinal diseases. To date, we have collected and traced 14,151 visual fields from 2,215 patients with inherited retinal diseases. This will be particularly valuable in rare and very slowly progressing diseases where prospective natural history studies are not feasible.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.