Effect of Refractive Error on the Multifocal Electroretinogram

ABSTRACT

PURPOSE: To evaluate the influence of refractive blur on the results of mfERG. METHODS: mfERG was performed on 10 healthy volunteers with a refractive error within +/- 1 diopter. The central 30 degrees of the ocular fundus were stimulated by an array of 103 hexagonal elements, for four minutes, using VERISTM. To change the refractive status, 6-cm diameter corrective lens, of -6, -4, -2, plano, +2, +4, and +6 diopters, were placed in front of the eyes, and the examination distance adjusted to compensate retinal image size changes due to corrective lens. The mfERG responses were grouped by 6 concentric rings, and then averaged. For each ring, the latencies and amplitudes of the N1, P1 and N2 were analyzed. The 6 rings were divided into the central (ring 1, 2) and peripheral (ring 3~6) retina, and the latencies and amplitudes of the N1, P1 and N2 were then also analyzed. RESULTS: Refractive blur can affect the results of the mfERG. Latency delay was more common at the peripheral than central retina, but had no statistically significant correlations with the refractive power increase. CONCLUSIONS: When the viewing distance was adjusted to create a constant retinal image size, the influence of refractive blur may cause some changes in the mfERG results. Therefore, when evaluating the results of an mfERG, the effects of the refractive error should be borne in mind.