BackgroundThe risk of developing hydroxychloroquine retinopathy is considered sufficient to justify national monitoring programmes. There are an estimated 71,144–77,170 long-term hydroxychloroquine users in the UK. However, the number of patients diagnosed with retinopathy is unknown. This study aimed to identify the number of cases and clinical characteristics of hydroxychloroquine retinopathy diagnosed annually in hospital eye services across the UK.MethodsA nationwide, prospective case ascertainment study was undertaken using the British Ophthalmological Surveillance Unit, which sends approximately 1420 reporting cards to UK Ophthalmologists monthly. The case definition was two abnormal tests suggestive of hydroxychloroquine retinopathy. Demographic and clinical data relating to hydroxychloroquine use and retinopathy were collected from identified cases using a standardised questionnaire over a 1-year period (2018–2019).ResultsSixty-six cases of hydroxychloroquine retinopathy were reported, and 46 questionnaires were received (73% response rate). Twenty-four incident cases of hydroxychloroquine retinopathy were identified (24-43 cases following adjustment). The median duration of drug therapy was 19 years (range: 4–50 years, IQR: 14.5–23 years). Fourteen patients were asymptomatic, and 9 symptomatic at diagnosis. A trend towards a lower mean deviation on visual field testing was observed in the symptomatic group (−11.55 dB versus −6.9 dB;P= 0.15).ConclusionBetween 1 in 1655 and 3215 (0.03–0.06%) long-term hydroxychloroquine users were diagnosed with retinopathy over the study period. We estimate that monitoring was available for 1.9–3.8% of long-term users, accounting for a lower than expected incidence. The high proportion of symptomatic retinopathy at diagnosis underlines the importance of monitoring to detect pre-symptomatic disease.