Prolonged use of hydroxychloroquine is common in patients with rheumatoid arthritis. Retinal toxicity due to hydroxychloroquine is known, and is monitored by investigations such as visual acuity, Amsler chart, colour vision, automated perimetry, full-field electroretinogram, and electrooculogram. Multifocal electroretinogram can suggest macular toxicity due to hydroxychloroquine even when the other investigations have normal results. Hence, multifocal electroretinogram has a role in the screening and follow-up of patients with suspected hydroxychloroquine toxicity.