By Dr André Horak MBChB, MMed, FRCSEd, FRANZCO

Retinal toxicity from Plaquenil has a low incidence, 6.8/1000 users, and the prevalence is dependent on duration of use (cumulative dosage >1000g).  Toxicity from these drugs is however of serious ophthalmologic concern because even after cessation of the drugs, there is little if any visual recovery and sometimes progression of visual loss.

Screening by a retinal specialist is recommended for all individuals taking the drug. Following a baseline evaluation, screening for toxicity should be initiated annually, no later than 5 years after starting the medication.

Routine screening test should include: A thorough ophthalmic examination with documentation of visual status and ocular findings. Automated threshold visual field testing with a white 10-2 pattern. The finding of any reproducibly depressed central or parafoveal spots can be indicative of early toxicity. At least one or more of the following objective tests should be considered, spectral domain-OCT (can show localized thinning in the parafoveal region), fundus autofluorescence (may reveal subtle RPE defects or areas of photoreceptor damage before visual field loss) and a multifocal electroretinogram (can objectively document localized paracentral depression in early toxicity). Amsler grid and color vision testing can be used as supplemental tests but are not consistent and specific enough as screening tools.

Particular risk factors for developing visual loss include the elderly, drug usage for more than 5 years, exceeding the recommended daily dosage and suffering from existing macular, kidney or liver disease.

The goal is to recognize early signs of paracentral field loss, or paracentral tissue damage, before the development of visible bulls eye maculopathy. Screening can recognize toxicity early and minimize visual loss, but cannot necessarily prevent all toxicity or guarantee there will be no visual loss.