Analysis of the outer retinal thickness pixel maps for the screening of hydroxychloroquine retinopathy

Purpose To describe the findings and new interpretation methods of retinal thickness maps in the setting of hydroxychloroquine (HCQ) therapy. Methods A case series of 27 patients with a history of HCQ intake of more than 5 years and 21 normal subjects as the control group were studied. Patients were tested using swept-source optical coherence tomography (OCT). Custom-made 10 × 10 retinal thickness pixel maps of the 6 mm⨯6 mm area centered on the fovea were created for the full, inner, and outer retina of each eye and normal values obtained from the control group were used to calculate the statistical significance of each pixel and highlight suspicious pixels. A pixel was shown with light or dark gray color if its p value was ≤ 0.05 or ≤ 0.01, respectively. Cross-sectional OCT images and visual fields were examined as well and used to confirm the diagnosis of HCQ retinopathy. Results The pixel outer retinal thickness maps appeared accurate in detecting lesions even in eyes with unremarkable full retina thickness maps. The size and location of atrophic retinal defects were shown on pixel maps. Outer retinal thickness maps were able in differentiating outer retinal thinning from inner retinal thinning as the hallmark of HCQ retinopathy. Conclusion Outer retinal thickness pixel maps can be used for the screening of HCQ retinopathy.