Purpose
to evaluate the electrophysiological response in patients with preperimetric glaucoma (PPG) compared to control subjects and to patients with perimetric glaucoma (POAG) using a two- global- flash paradigm mfERG.
Methods
A two- global- flash mfERG (VERIS 6.06TM, FMSIII) was recorded in 6 eyes with PPG. The control group consisted of 20 healthy subjects and POAG group - of 25 patients (8- high tension glaucoma (HTG) and 17- normal tension glaucoma (NTG)). Recording parameters: bandpass filter (BPF): 1-300Hz, 103 Hexagons, M-sequence stimulus: LMax 100cd/m^2, Lmin <1cd/m^2, global flash: 200cd/m^2. Responses were filtered at 1-200 Hz. RMS was calculated. Three response epochs were analysed: the response to the focal flash, at 15-45ms (DC) and the response to the global flashes at 45-75ms (IC-1) and at 75-105ms (IC-2). Automated perimetry (Octopus 101, G2) was performed in all glaucoma patients. Measurement of RNFL thickness around the optic disc head was used to determine PPG patients (Cirrus SD-OCT, Carl Zeiss). Statistical analysis was performed using linear mixed effects models in the statistical package R version 12.1.
Results
The mean deviation (MD) of the PPG patients was 0.8±1.2 (dB) and of the POAG was 5.9±3.9 (dB). Visual acuity and IOP did not differ significantly between both patients groups (p=0.57 and p=0.14 respectively). The mfERG response of the PPG group differed most from control subjects in the central 10° (diameter). When compared to controls, PPG differed more than POAG in IC1&IC2. However for the DC POAG differed more than PPG. (see Table for details).
Conclusions
Multifocal ERG has been shown to be sensitive to detect glaucomatous damages in established glaucoma. In this study we could show, that in preperimetric glaucoma patients, the mfERG response is also reduced in the central 10°. These findings provide additional objective information on early retinal dysfunction in patients with beginning changes in the OCT but without visual field defects on standard automated perimetry.
Keywords: 509 electroretinography: clinical