Early detection of the retinal bioelectrical dysfunction in patients treated by chloroquine/hydroxychloroquine

Introduction
Assess the clinical application of multifocal electroretinogram in the early detection of retinal dysfunction in patients treated with chloroquine (CQ) or hydroxychloroquine (HCQ).

Material and methods
In 13 female patients – 15 eyes (9 – CQ, 6 – HCQ) mean age: 51 yrs, range: 35–66 years, treatment mean time (CQ – 8.3, HCQ – 10.4 years) with normal results of routine ophthalmological examination, retinal sensitivity (AVF – 10-2, W-W), macular structure (spectral-domain optical coherent tomography – SD-OCT) multifocal electroretinogram – mfERG (ISCEV standard) was performed. MfERG results were compared with 13, mean age 51 years range 34–66 years, and refractive error matched healthy females (15 eyes).

Results
In the group taking CQ and HCQ, a statistically significant reduction in P1-wave response density was observed in rings 2, 3, 4, 5, and 6. This reduction was accompanied by abnormal ring ratios (R1/R2, R1/R3, R1/R5) compared to the control group (p ≤ 0.016). The most prominent dysfunction of the cone system was registered in the parafoveal region (R2) and perifoveal region (R3), as well as in the mid-peripheral retina (R5) (p < 0.000). In patients treated with CQ, a significantly higher retinal dysfunction in rings 3 and 6 was detected (p ≤ 0.039). The P1-wave response density in each ring was characterized by high sensitivity and specificity values, with the highest values found in ring 2 (sensitivity and specificity – 0.93, AUC = 0.98; p < 0.001).

Conclusions
In patients treated with chloroquine/hydroxychloroquine, bioelectrical dysfunction of the cone system was observed without typical retinal signs of drug toxicity. Multifocal ERG examination demonstrated significant utility as a screening test to detect premaculopathy stages of CQ/HCQ retinopathy.