Reproducibility of multifocal ERG (mfERG) in patients with macular disease.

Abstract

Abstract: : Purpose:Reproducibility of mfERGs has been investigated in normal but not in pathologic eyes. Our goal was to assess the reproducibility of mfERG in eyes with macular diseases. Methods: In 12 eyes of 11 patients with documented macular disease, mfERG and visual acuity were measured twice, 4–6 weeks apart. Patients had a complete ophthalmologic exam prior to entering the study. Mean age was 65 ± 17 y.o., (8 M; 3F). Diagnosis were cystic macular edema 2^nd to pars planitis (1), AMD (6), diabetic macular edema (3), nonproliferative diabetic retinopathy (1), changes in retinal pigment epithelium 2^nd to an old central serous retinopathy treated with Argon laser (1). The mfERG stimulus consisted of a 61–hexagon matrix (mean luminance 400 cd.m^–2). Recordings (DTL, non dilated eye) were obtained using 16 segments of 15 sec each. Signal was filtered (10–100 Hz) and amplified (100,000x). P1 latency and amplitude were measured for each ring (5) and for the central 5–degree. Results: Median visual acuity was 6/15 (range: 6/6 to 6/32) and 6/12 (range: 6/6 to 6/60) at the time of first and 2nd mfERG respectively. Mean delay between the two mfERG was 36 ± 4 days except in one patient where the two mfERGs were 3 months apart. For P1 latencies, the intraclass correlation coefficient of reliability was R=0.87, 0.71, 0.84, 0.80, 0.81 and 0.90 for the central 5–degree and ring 1 to 5 respectively. For P1 amplitude, R=0.89, 0.73, 0.90, 0.91, 0.91 and 0.88 for central 5–degree and ring 1 to 5 respectively. Conclusions:Despite the use of the DTL electrode (which may be more prone to displacement), multifocal ERGs are highly reproducible even in eyes affected with different maculopathies. Interestingly, the mfERGs of ring 1 are the least reproducible (amplitude and peak time). The weaker reproducibility of this segment of the mfERG is not due to progression of the maculopathy (as there was a short interval between tests) but rather due to the lower signal to noise ratio for ring 1 in patients with central retinal dysfunction.

Keywords: electroretinography: clinical • visual acuity • macula/fovea