Incidence of electronegative findings in tertiary ophthalmology referral centre

Abstract

Purpose : Negative electroretinogram (ERG) reflecting inner retinal dysfunction can be used as diagnostic tool to determine the anatomical abnormality location in eye disease. The aim of this study is to determine the frequency and etiology of negative ERG in an electrophysiology referral centre.

Methods : Retrospective review of ERGs performed at the Save Sight Institute from January 2011 to December 2020 . ERGs were performed according to ISCEV standard. The b:a ratio was analyzed in Dark Adapted (DA) 3.0 or 12.0. Data were then divided into 2 groups: Group A true negative ERGs (b:a wave ratio of ≤1.0) and group B mild negative ERG (b:a wave ratio between 1 and 1.5).

Results : 4,530 patients had ERGs performed, of which 178 (3.9%) had an electronegative ERG consisting of 112 male and 66 female. 142 (3.1%) patients were in Group A and 36 (0.8%) patients were in Group B indicating that 20.2% of the electronegative ERG diagnoses were mild type. The median age at referral time was 36 (2-91) years. Photoreceptor dystrophy was the largest causative etiology with 53 (45A+8B) patients (28%) followed by Congenital Stationary Night Blindness (CNSB) with 42 (33A+9B) (16.5%), retinoschisis with 18 (15A+3B) (7.1%), retinal ischemia with 16 (15A+1B)(6.3%) and Paraneoplastic Autoimmune Retinopathy (PAIR) and nonPAIR with 14 patients (11A+3B)(5.5%). Batten disease, inflammatory retinopathy, Melanoma Associated Retinopathy and retinal detachment each had 5 (4A+1B)(2%), 3 (3A)(1.2%), 2 (2A)(0.8%), 2 (1A+1B) (0.8%) patients respectively. Birdshot chorioretinopathy, vigabatrin toxicity and foveal hypoplasia were diagnosed in 3 patients (0.4%) and 20 patients had an unclassified diagnosis.

Conclusions : The incidence of true negative ERG and mild negative ERG in our referral center was 3.1% and 0.8% with photoreceptor dystrophy as the main etiology followed by CSNB, retinoschisis, ischemia, and PAIR and nonPAIR. Classic negative ERG diagnoses such as CSNB and retinoschisis both had patients with mild negative ERG (Group B) suggesting the conceivable need to reconsider the traditional negative ERG definition of ≤1.

This is a 2021 ARVO Annual Meeting abstract.