[Early diagnosis of glaucoma with pattern-ERG]

Current electrophysiological techniques for diagnosis of glaucoma include pattern-electroretinogram (PERG) and visual evoked potentials (VEP) but PERG has been recognized over the last decade as a good functional indicator of retinal ganglion cells.

An investigation has been carried out on 171 eyes of 89 subjects using both PERG (gold foil electrodes) and VEP. One group of 32 subjects with ocular hypertension (OHT) and another group of 27 subjects having simple chronic glaucoma (SCG) were compared with a control group of 30 healthy age-matched subjects.

For PERG, the amplitude of the P50 and N95 components was measured but statistically significant differences were shown for N95 only in SCG (p < 0.01) and OHT (p < 0.05). FFT analysis on each PERG showed a dominant frequency of 3.3 Hz for OHT subjects versus 9.9 Hz for those of the control group. For VEP, the amplitude and latency of P100 was analysed. P100 latency showed significant delay (p < 0.05) in the SCG group only.

These findings suggest that N95-amplitude is the most sensitive electrophysiologic parameter for early glaucoma detection. By comparing data of this work with a previous study using wire (anchor shaped) electrodes we demonstrate higher amplitude and lesser variability of the N95 component for gold foil electrodes, therefore this latter type of recording is acknowledged as the most sensitive for detection of early impairment of ganglion cells in HTO patients.