To evaluate retinal function in patients on hydroxychloroquine using multifocal electroretinography.
A retrospective chart review was performed for 23 patients (46 eyes) on hydroxychloroquine therapy and referred for multifocal electroretinogram (mfERG) testing. Duration of treatment, daily hydroxychloroquine dose, visual acuity, fundus examination, color vision testing, Amsler grid testing, visual field examination, and fluorescein angiography results were obtained when available. Multifocal electroretinogram response amplitudes were calculated for the central and paracentral regions and compared with previously published normal values. The central and paracentral regions of the mfERG color difference plot, which assigns colors to localized areas of the mfERG based on deviation from normal, were assessed using a novel Color Difference Plot Scoring System which relies on the color pattern observed within each region.
Ninety-two regions were assessed for response amplitudes, 31 of which showed a depressed response amplitude. Of the 17 eyes which had at least one region with a depressed response amplitude, clinical examination findings were relatively benign. Color difference plot scoring showed strong agreement with response amplitude, with a Color Difference Plot Scoring System score of 2 or 3 showing 93.55% sensitivity and 60% specificity for a depressed response amplitude. Interrater reliability of the scoring system as measured by Kendall's W coefficient of concordance was 0.6484 (P < 0.00001).
The mfERG appears to be able to detect decreased retinal function in hydroxychloroquine patients with normal clinical examinations, and may be useful in identifying patients that require close monitoring for the development of clinically relevant toxicity. The Color Difference Plot Scoring System may be used as a tool to aid in the interpretation of results of the mfERG in the clinic setting.