Hydroxychloroquine for treatment of rheumatoid arthritis: multifocal electroretinogram and laser flare-cell photometry study

PURPOSE To evaluate early changes in multifocal electroretinogram (mfERG) and subclinical aqueous humor flare and cellularity in patients receiving hydroxychloroquine (HCQ) as treatment for rheumatoid arthritis. METHODS Ten patients receiving treatment with HCQ and no ophthalmic symptoms were enrolled. After complete ocular examination, mfERG and laser flare-cell photometry were performed. Patients were also divided into two subgroups with HCQ cumulative dose (CD) higher or lower than 500 g. Results obtained were compared with a control group of ten healthy subjects and statistical analysis was performed. RESULTS In patients receiving HCQ treatment, mfERG P1-wave in ring 2 showed a significant reduction in amplitude and a significant increase in latency compared to healthy control subjects, respectively resulting in 1.143 μV vs 1.316 μV (P=0.040) and 38.611 ms vs 36.334 ms (P=0.024). These changes are highly related to CD. Furthermore, when using the laser flare-cell photometry, a significant increase in aqueous humor flare and cellularity was shown in patients with CD higher than 500 g, resulting in a mean value of 14.4 ph/ms compared to 8.1 ph/ms in patients with CD lower than 500 g (P=0.0029). These reports appear highly related to CD (P=0.001). Receiver operating characteristic curve analysis showed mfERG P1-wave amplitude in ring 2 as the most sensitive value in detecting early HCQ-related retinopathy. CONCLUSION MfERG was shown to be a very sensitive test in detecting early retinal toxicity and should be used for the screening of patients receiving HCQ treatment. Although less sensitive, laser flare-cell photometry can provide further information to evaluate early toxic retinal cell damage.