Cone Density Distribution and Related Factors in Patients Receiving Hydroxychloroquine Treatment

PURPOSE: Hydroxychloroquine is an effective treatment for rheumatic diseases; however, retinal damage is a possible side effect. We aimed to identify the retinal area and related risk factors associated with cone density reduction caused by hydroxychloroquine. METHODS: We recorded the retinal images of patients with rheumatic diseases taking hydroxychloroquine (n = 44) and compared them with images of healthy controls (n = 107). Cone density was obtained in vertical and horizontal axes. Regions of decreased cone density and associations between age, rheumatic disease type, dosage for ideal body weight, and cone density were evaluated. RESULTS: Cone densities were significantly lower in hydroxychloroquine-treated patients than in sex- and age-matched controls in the vertical axis (P < 0.001), with no significant difference in the horizontal axis (P = 0.120); in healthy elderly than in healthy young people in the horizontal axis (P < 0.001), with no significant difference in the vertical axis (P = 0.100); in hydroxychloroquine-treated elderly than in hydroxychloroquine-treated young patients in both axes (both P < 0.05); among patients with different rheumatic disease types, with no significant difference in the vertical axis (P = 0.294). The daily dose was negatively correlated with cone density in the vertical axis and inferior quadrant. CONCLUSIONS: Hydroxychloroquine reduces retinal cone cell density in the vertical axis. Cone density loss in the horizontal axis increases with age; further, hydroxychloroquine dosage is negatively correlated with cone density in the vertical axis and inferior quadrant. Early screening of hydroxychloroquine-related retinal injury should consider changes in cone density in the vertical axis.