Incidence of blindness in a population of rheumatic patients treated with hydroxychloroquine

Long-term HCQ use for the treatment of rheumatic diseases has been associated with retinopathy in a daily and cumulative dose-dependent manner by weight. We examined the incidence of ocular toxicity in a large population of patients treated with HCQ for inflammatory arthritis and SLE and followed long term in a tertiary centre.

Our retrospective longitudinal review identified 2867 rheumatic patients from 1999 to August 2017 who had a prescription written for HCQ. Thirty-one patients were identified as having a diagnosis of blindness or toxic maculopathy in their electronic medical record, and we carried out an extensive chart review.

Of our 31 patients with a diagnosis of blindness or toxic maculopathy, 11 had documented blindness, in all cases attributed to a cause other than HCQ-related ocular toxicity: stroke (27%), pre-existing macular disease (18%), diabetic retinopathy (18%), hypertensive retinopathy (9%) and cataracts (9%). Seventeen of 31 patients had visual impairment that was multifactorial and unrelated to HCQ. We identified two patients with bull's eye maculopathy [person-time incidence rate, 0.12 cases per 1000 person-years (95% CI: 0.01, 0.43)] and one with early HCQ toxic maculopathy [person-time incidence rate, 0.06 cases per 1000 person-years (95% CI: 0.002, 0.33)]. All three patients received HCQ for >18 years, and none had functional vision loss at diagnosis.

HCQ-induced macular toxicity is rare in routine clinical practice, seems to require prolonged HCQ therapy (>18 years) and is not necessarily associated with functional visual loss. Our findings suggest that co-morbid conditions that are common in RA and SLE contribute substantially to vision loss and should not be ignored.