Purpose
The hallmark of hydroxychloroquine retinal (HCQ) damage is bilateral pigmentary retinopathy due to long term effect of the drug on the photoreceptors. We performed a retrospective, SD-OCT clinical study to quantify the disruption of the external limiting membrane (ELM) and the volumetric photoreceptors changes in eyes with HCQ toxic effects after discontinuation of drug therapy.
Methods
A retrospective medical record review identified patients taking HCQ who were diagnosed with HCQ toxic effects at the ophthalmology department of Northwestern University. The SD-OCT images were obtained using the Spectralis HRA-OCT (Heidelberg Engineering, Heidelberg, Germany) and the images were analysed with ImageJ software (United States of National Institutes of Health). Individual b-scans from the volumetric scans were examined and manually marked for ELM disruption (Fig 1), as well as measure the volume (mm3) of the area between the ELM and Bruch’s Membrane (BM) (Fig 2) at baseline, intermediate follow up and final visit. Two trained graders marked these changes and intraclass correlation coefficients (ICCs) were calculated in order to assess inter-observer variability of the OCT measurements.
Results
Eighteen eyes of 9 patients were identified as having HCQ toxic effects and were included. The mean treatment duration was 11.2 years ±5.3. The mean cumulative dose of HCQ was 1671.62 g ±843.6. The mean follow up was 35.3 months. 12 out of 18 (66.6%) eyes showed damaged ELM at baseline, which showed progressive loss in 4/12 eyes over time. 6 of 3 patients did not have any ELM damaged during the entire follow up. Looking at the overall results for ELM disruption 3 types of effects was identified: 1) progressive worsening (4/18), 2) stable disruption (8/18), and 3) eyes with no ELM damage (6/18). Overall, the mean percentage photoreceptor volume change was -5.8% ±21.6 between baseline and the last visit. 7 out of 18 eyes showed progressive volumetric thinning of the photoreceptors during follow up. ICCs of the manually measurement of ELM disruption and the volume were reliable (0.94 and 0.96, respectively).
Conclusions
Using quantitative measurements on SD-OCT, this study showed that measuring the ELM disruption and the volume of the area between the ELM and the BM seems to be an appropriate tool for evaluating the course of HCQ lesions over time, identifying three patterns of outer retinal affection.