Hydroxychloroquine Dosing and Toxicity in Ophthalmology Clinics

Hydroxychloroquine (HCQ) is an anti-malarial drug that is used to treat a variety of autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus, juvenile idiopathic arthritis and Sjogren's syndrome. Hydroxychloroquine is a less toxic metabolite of chloroquine. There is an ongoing increase in the number of patients who are using HCQ for prolonged duration because of the expanding indications and the relatively safe systemic profile. Hydroxychloroquine can cause variable ocular adverse effects including corneal deposits, posterior sub-capsular cataract, ciliary body dysfunction and toxic retinopathy. Toxic retinopathy caused by HCQ has been recognized for many years. Patients with toxic retinopathy usually complain of blurry vision. The classical clinical picture of HCQ toxic retinopathy is a bilateral bull's-eye maculopathy, which is caused by a ring of parafoveal RPE depigmentation that spares the fovea. The exact mechanism responsible for the development of this pattern is not fully understood, however, it is believed that the primary damage is in the photoreceptors and outer nuclear layer leading to secondary disruption of the RPE.