Hydroxychloroquine Retinopathy in a UK Single-Centre Cohort: A Retrospective Study of Risk Factors and Dosing Trends.

Background Hydroxychloroquine (HCQ) is a widely prescribed medication for autoimmune and inflammatory conditions. However, long-term use carries a risk of retinal toxicity. The prevalence of hydroxychloroquine retinopathy is higher than initially thought, and several clinical and pharmacological factors have been implicated as contributors. By optimising its prescription and monitoring, we can minimise preventable visual morbidity. Objective This study aimed to evaluate the prevalence of hydroxychloroquine retinopathy within a UK monitoring cohort and assess the impact of recognised risk factors, including daily dose relative to body weight, treatment duration, renal function and concurrent tamoxifen use. Methods A retrospective study was conducted at Watford General Hospital, West Hertfordshire NHS Trust, as part of an audit of clinical care. Patients reviewed in the dedicated hydroxychloroquine monitoring clinic between October 2023 and December 2024 were included. Demographic and clinical data were extracted, including age, sex, indication, dose (mg/kg/day), treatment duration, renal function, tamoxifen use, ocular history and evidence of toxicity. Subgroup analyses were carried out. Ethical approval was waived as the study was registered as an audit and was retrospective in nature. Results Data completeness was generally high, with six out of eight data items having reporting of over 90% of the cohort. However, treatment indication and precise dosing data were underreported in some records. A notable proportion of patients exceeded the recommended 5 mg/kg/day dosing threshold. Renal impairment and tamoxifen use were infrequent and not significantly associated with increased risk in this cohort. Subgroup analysis demonstrated that patients with toxicity were older, had been treated for a longer duration and received higher weight-adjusted doses compared to unaffected patients. Conclusion Hydroxychloroquine retinopathy was observed in association with higher doses and longer treatment duration, consistent with international literature. The enhanced reporting of dose and treatment indication, alongside stringent adherence to dosing guidelines, will improve patient safety. These findings highlight the importance of early monitoring and dose optimisation in reducing the risk of irreversible toxicity.