Hydroxychloroquine-related retinal toxicity

HCQ is widely used for the treatment of rheumatic diseases, particularly lupus and RA. It is generally well tolerated, but retinopathy is a concern. Retinopathy is rare, but is sight threatening, generally irreversible and may progress even after cessation of therapy. Damage may be subclinical. Although a number of risk factors have been proposed (such as duration of therapy and cumulative dose), the many exceptions (e.g. retinopathy on low-dose HCQ, or no retinopathy after a very large cumulative dose of HCQ) highlight our limited understanding of the disease process. Novel technologies such as optical coherence tomography (OCT), fundus autofluorescence (FAF) and multifocal electroretinogram (mfERG) may provide the earliest structural and functional evidence of toxicity in these stages. Along with the well-established technique of central visual field testing (10-2 visual fields), these modalities are increasingly being used as part of screening programmes. The ideal single test with high sensitivity and high specificity for HCQ retinopathy has still not been achieved. Screening for HCQ retinopathy remains an area of considerable debate, including issues of when, who and how to screen. Commonly accepted risk factors include receiving > 6.5 mg/kg/day or a cumulative dose of > 1000 g of HCQ, being on treatment for > 5 years, having renal or liver dysfunction, having pre-existing retinopathy and being elderly. HCQ continues to be a valuable drug in treating rheumatic disease, but clinicians need to be aware of the associated risks and to have arrangements in place that would enable early detection of toxicity.