Role of multifocal electroretinogram in the prediction of visual prognosis in patients with occult macular dystrophy

Abstract

Background Occult macular dystrophy (OMD) is a rare hereditary macular dystrophy characterized by severe bilateral progressive loss of central vision with normal fundus appearance and normal fundus fluorescein angiography.Aim The aim of this study was to assess the correlation between multifocal electroretinogram (mf-ERG) parameters and best-corrected visual acuity (BCVA) in patients with OMD.Patients and methods In all, 20 eyes of 10 patients with OMD and 20 eyes of 10 age-matched and sex-matched normal individuals were included in this study. Full ophthalmic examination, fundus fluorescein angiography, optical coherence tomography, full-field ERG and mf-ERG were performed for all participants. The average amplitude density of P1 wave, amplitude, and implicit time of P1 and N1 waves were recorded in the five concentric hexagonal rings. Correlation between these mf-ERG parameters and BCVA (LogMAR) was analyzed.Results There were no statistically significant differences in age, sex, and refraction between the studied groups (P=0.54, 1.0, and 0.82, respectively). Mf-ERG parameters in OMD patients showed significant central depression with less affection of peripheral rings. The average amplitude density of P1 wave and the amplitude of P1 and N1 waves were significantly reduced in the central rings (rings 1, 2, and 3), with less impairment in paracentral areas (rings 4 and 5). The implicit time of P1 and N1 waves were significantly delayed across the central rings in OMD patients. The BCVA (LogMAR) was significantly negatively correlated with the amplitude of P1 and N1 waves (P≤0.001). The BCVA (LogMAR) was significantly positively correlated with the implicit time of P1 and N1 waves (P≤0.001). Multiple regression analysis demonstrated that the amplitude and latency of P1 and N1 waves in the central rings (1 and 2) were the most important determinants for BCVA.Conclusion Mf-ERG has a key role in the detection of OMD and can be considered as a valuable objective test for the detection of central/macular dysfunction. The amplitude and latency of P1 and N1 waves in rings 1 and 2 may be used as biomarkers for the prediction of visual prognosis in these patients.