Pointwise linear regression analysis of serial Humphrey visual fields and a correlation with electroretinography in...

To investigate deterioration in serial Humphrey visual fields (HVFs) using pointwise linear regression (PLR) analysis in patients with birdshot chorioretinopathy (BCR) monitored with full field electroretinography (ERG).

Retrospective review of the case notes, HVFs and ERG of patients under treatment for BCR at Moorfields Eye Hospital between 1998 and 2014. Eyes with ERG recorded using protocols to incorporate International Society for Clinical Electrophysiology of Vision standards and at least five reliable Swedish Interactive Testing Algorithm standard 24-2 HVFs were included. HVFs were analysed by PLR analysis of luminance sensitivity using the Progressor software and linear regression analysis of mean deviation (MD).

202 HVFs from 31 eyes of 16 patients were analysed. Mean follow-up was 60.25 months. MD remained stable in all eyes. PLR analysis detected progressive field loss in 10 eyes (seven patients). The mean (SD) slope of change at progressing points was -1.83 (0.90) db/year (p<0.05). ERG worsened in 3 of the 10 eyes with field loss. Although there was no clear relationship between patterns of field loss and electrophysiological dysfunction, more extensive field loss was associated with more marked ERG abnormalities and rod system involvement.

This study demonstrates that PLR analysis can identify field loss despite a stable MD and stable and even normal electrophysiology in BCR, thus establishing a role for regular standardised monitoring of visual fields as an adjunct to electrophysiology in order to facilitate more accurate characterisation of retinal dysfunction and hence enabling better-informed treatment decisions and monitoring of treatment efficacy.