Subclinical Detection of Hydroxychloroquine-Induced Retinopathy in Patients with Systemic Lupus Erythematous Using Multifocal Electroretinography and Optical Coherence Tomography

Background/Objectives: Although hydroxychloroquine (HCQ) is used to treat systemic lupus erythematosus (SLE), it is associated with retinal toxicity. Early diagnosis can prevent the further progression of HCQ-associated retinopathy by discontinuing HCQ treatments. This study aimed to evaluate the early diagnostic parameters in patients with SLE treated with HCQ and identify the best approach using multifocal electroretinography (mfERG) and swept-source optical coherence tomography (SS-OCT) to reflect subclinical retinal toxicity. Methods: Thirty-eight patients with SLE (76 eyes) and 18 healthy controls (36 eyes) were enrolled. They were referred for HCQ retinopathy screening without visual field defects. The patients were tested using a standard 61-hexagon mfERG stimulus and SS-OCT. Ten groups of the mfERG responses from the sectors were averaged to compare the quadrants, hemiretinal areas, consecutive ring amplitudes, and ring ratios (R1/R2–R5) from the center to the periphery. Additionally, the ganglion cell complex (GCC) analyses were performed using SS-OCT. Results: No difference was observed in GCC thickness on the OCT images, in the P1 amplitudes, and in the implicit time of mfERG. However, the R1/Rx ring ratios, except the R1/R2 ratio, showed significant differences among the three groups (p = 0.759, 0.018, 0.029, and 0.029, respectively). The R1/R3, R1/R4, and R1/R5 ring ratios demonstrated a correlation with the duration of HCQ therapy (r = −0.303, −0.279, and −0.266; p = 0.003, 0.006, and 0.009). The areas under the receiver operating characteristic curve of the ring ratios R1/R3–R5 were 0.730, 0.702, and 0.724, respectively (p = 0.004, 0.012, and 0.006), indicating the likelihood of being categorized as a high-risk group for subclinical HCQ retinopathy. Conclusions: The ring ratio of mfERG reflects the subclinical electrophysiological alterations induced by HCQ and can become more clinically useful by simplifying screening examinations.