Decreased peri-parafoveal RPE, EZ and ELM intensity: A novel predictive biomarker for hydroxychloroquine retinal toxicity

Purpose To evaluate the reflectivities of the retinal pigment epithelium (RPE), ellipsoid zone (EZ), and external limiting membrane (ELM) in the central fovea, perifoveal, and parafoveal regions with Optical Coherence Tomography (OCT) and the change in choroid vascular index (CVI) in patients using hydroxychloroquine (HCQ). Methods Sixty-one patients underwent HCQ treatment; age and sex-matched 44 control group subjects were included in the study. The RPE, EZ, and ELM reflectivities were measured with the ImageJ program at 5 points, and CVI was calculated. Results RPE, EZ, and ELM reflectivities in the central fovea were higher in the HCQ group than in the control group (p < 0.001, p = 0.013, p = 0.022). In the HCQ group, there was a decrease in RPE reflectivities in the temporal, nasal parafovea, and nasal perifovea (p = 0.001, p = 0.03, p = < 0.001). EZ and ELM reflectivity in the nasal parafovea and nasal perifovea was lower in the patient group than in the control group (p = 0.007, p = 0.005, p = 0.009, p = 0.001). In the HCQ group, all absolute para and perifoveal reflectivities relative to the fovea decreased significantly more than in the control group (p < 0.05). Conclusion In patients who underwent HCQ treatment, there is a decrease in the reflectivities of the para and perifoveal RPE, EZ, and ELM compared to the fovea. This decrease is more pronounced than the decrease in reflectivity in the para and perifoveal regions compared to the fovea in people who do not use HCQ. This situation can be considered as a sign of toxicity that is a precursor to overt maculopathy.