Macular Dysfunction in Glaucoma Detected by Focal and Multifocal ERG

Abstract

Abstract: : Purpose: To evaluate macular function in patients with open angle glaucoma (OAG) by means of Focal (FERG) and Multifocal (MERG) electroretinograms. Methods: 48 subjects (34 OAG patients, mean age 57±7.4 years, and 14 age–matched control subjects) were enrolled. OAG patients had IOP < 21 mmHg in topical medical treatment, 24/II HFA with Mean Deviation (MD) between –2 and –10 dB, no history of other optic nerve or macular disease and a best corrected visual acuity of 20/20 with a refraction between ± 2 diopters. OAG patients were randomly divided into two age and MD matched groups. On 20 OAG patients (Group OAG1, 20 eyes), Focal (9 x 9 central degrees) ERGs in response to a 32 Hz sinusoidally flickering uniform field was recorded. The amplitude and phase of the fundamental harmonic of FERG response (1F) was measured. On 14 OAG patients (Group OAG2, 14 eyes) MERGs in response to 61 M–stimuli presented to the central 20 degrees of the visual field was assessed. Ring analysis, was performed every five retinal eccentricities areas between fovea and mid–periphery: 0–2.5 (R1), 2.5–5 (R2), 5–10 (R3), 10–15 (R4) and 15–20 (R5) degrees. On R1–R5, MERG response amplitude density (RAD, nV/deg²) and time–to–peak (TP, ms) of the N1–P1 components of first order binary kernels were measured. In control subjects both FERG and MERG were recorded. Results: In OAG1 patients, mean FERG 1F amplitude was significantly reduced compared to controls(p=0.01): No correlations between the MD of HFA and 1F amplitudes and phases were found. OAG2 patients showed a significant (p<0.01) delay in mean TP in all MERG ring analysis (R1–R5) when compared to controls. Significantly(p=0.01)reduced RAD in R3, R4 and R5 MERGs with respect to control values were observed. The reduction in RAD of R1 was positively correlated (r = 0.694, p=0.0058) with the MD of HFA. No other significant correlations were found. Conclusions: OAG patients show a macular dysfunction testable by both FERG and MERG techniques. Since FERG 1F and MERG N1 are thought to be generated respectively by macular preganglionic elements and by photoreceptors and off bipolar cells¹, our data suggest a functional impairment of these neural generators of the macular region in patients with glaucoma. ¹Hood, Prog Ret Res 2000, 19: 607–646

Keywords: electroretinography: clinical • macula/fovea • photoreceptors