Retinal ganglion cells function measured by the PERG test in patients with ocular hypertension

Introduction
To assess the retinal ganglion cells function in patients with ocular hypertension (OHT).

Material and methods
In one hundred eyes of 50 patients with ocular hypertension [mean age: 48 ± 13 years, intraocular pressure mean: 26 ± 3.0 mmHg; Humphrey Field Analyzer (HFA) 24-2 W-W mean deviation (MD) > -2 decibels (dB), normal optic nerve fiber layer results in scanning laser polarimetry (GDX)], PERG recordings were performed according to the modified methodology described by Parisi V et al. (Ophthalmology 2006; 113: 216-228). Main parameters measured in the PERG test were as follows: amplitude of the P50 and N95 waves, AN95/AP50 ratio as well as implicit time of P50 wave. Pattern Electroretinogram P50 implicit times were considered delayed when exceeding the limit of mean values plus 2 standard deviations (SDs) from controls. PERG amplitudes of P50, N95 waves and AN95/AP50 ratio were considered reduced when they were below the mean values minus 2 SDs from controls. Control group consisted of age, sex, and refractive error matched one hundred eyes of 50 healthy subjects with intraocular pressure mean equal to 16 ± 4.0 mmHg.

Results
In the OHT eyes, significant reductions of AN95-wave (p < 0.0002) and AN95/AP50 ratio (p < 0.002) were obtained in comparison to controls. The PERG test revealed the abnormalities mostly in AN95/AP50 ratio (32/100 of OHT eyes – 32%). Other less frequent abnormalities were observed in amplitude of N95-wave (10/100 of OHT eyes – 10%) and in amplitude of P50-wave (6/100 of OHT eyes – 6%). The implicit times of P50 and N95-waves were within normal limits.

Conclusions
In the eyes of the OHT patients, retinal ganglion cells dysfunction is present and can be detected by the PERG test. Longer follow-up is necessary to show predictable value of the PERG examination in separation of the OHT patients with a high risk of glaucoma development.