Clock-hour topography and extent of outer retinal damage in hydroxychloroquine retinopathy

In this study, we investigated the clock-hour topographic characteristics and extent of photoreceptor and retinal pigment epithelium (RPE) damage and correlated the extent with functional defects in eyes with hydroxychloroquine retinopathy. A total of 146 eyes of 75 patients diagnosed with hydroxychloroquine retinopathy were included. The clock-hour topographic characteristics (relative to the fovea) and extent of the photoreceptor and RPE defects in the parafoveal and pericentral areas were evaluated by reviewing the radial-scan optical coherence tomography (OCT) and wide-field fundus autofluorescence (FAF) images. The extent of outer retinal damage in the parafoveal and pericentral areas were correlated with the perimetric parameters of the Humphrey 10–2 and 30–2 tests, respectively. Although the photoreceptor damage was most commonly noted at the temporal to inferior locations in both parafoveal and pericentral areas, the RPE damage in the pericentral eyes was most commonly noted in the nasal area and showed topographic discrepancies with photoreceptor damage. The extent of RPE damage was almost identical between OCT and FAF images, whereas photoreceptor defect extent was significantly greater on OCT images. The extent of parafoveal and pericentral photoreceptor damage on OCT images was significantly correlated with perimetric parameters of the 10–2 and 30–2 tests, respectively (all P < 0.05). Our findings on the detailed topographic characteristics using a clock-hour-based system and significant correlation between the structural extent and perimetric parameters suggest that this evaluation may facilitate more comprehensive descriptions of structural damage extent and predictions of visual function.