Abstract
BACKGROUND: Hydroxychloroquine (HCQ) maculopathy is irreversible; primary prevention is done by regular monitoring. Guidelines of the Royal College of Ophthalmologists identify definite toxicity as having abnormal results of two screening tests, we present a quantitative method for interpreting these guidelines. METHODS: We obtained ocular coherence tomography (OCT) scans of 100 patients who have been on HCQ for 5 years or more (patients) and 70 age-matched controls. Both groups had 10'2 visual field (VF) test. We used linear regression to determine the cut-off points for each of the eight Early Treatment of Diabetic Retinopathy Study (ETDRS) macular sectors for the VF and OCT. We calculated the probability of developing maculopathy using logistic regression. RESULTS: Mean patient age: 59.9 years, 85% females, no statistically significant age difference between the patients and the control groups. DIAGNOSIS: 64% rheumatoid arthritis, 14% Sjogren's syndrome, 16% systemic lupus and 6% various other rheumatology conditions. Mean duration of use was 6.3 years. Logistic regression results show strong negative correlation between the outer nuclear layer (ONL) volume and probability of toxicity. Goodness of fit was tested using Hosmer and Lemeshow test that indicates a high significance with a high P-value of 1. CONCLUSIONS: Combining the ONL volume reduction and VF retinal sensitivity reduction per each of the eight ETDRS macular sectors provides an accurate and objective way of diagnosing HCQ maculopathy, this helps busy eye units establishing an optometrist-led or virtual service because it is independent of the assessor's level of experience.