Pattern ERG as a predictor in ocular hypertensive
Purpose: To report the repeatability of Pattern Electrotretinogram (PERG) and its findings in ocular hypertension (OHT) and normal eyes.
Methods: A cross-sectional study where PERG responses were compared between the study group comprising of 80 eyes of 80 patients with intraocular pressure (IOP)>21 mmHg and the control group with 80 eyes of 80 normal individuals (IOP≤21mmHg). The optic disc and the visual fields were normal with a visual acuity of ≥ 0.8 in both groups. PERG was recorded twice for each individual in the control group by a single operator on 2 consecutive days to assess the repeatability.
Results: The mean age in the study and control groups was 50.05±10.03 and 54.8±7.66 years
(p=0.44) respectively. The mean IOP was 26.55±3.9 mmHg for the study group as opposed to 14.45±2.9 mmHg for the controls (p<0.001). The central corneal thickness and the cup-disc ratio was similar between the groups (p>.05). The P50-N95 amplitude (p=0.01) and the P50 latency (p<0.001) was statistically significantly different between both the groups. The intra-class correlation coefficient (ICC) showed poor agreement for all parameters except for N35-P50 0.8 to 16 degree check size amplitude ratio (PERG ratio).
Conclusion: Increase in P50 latency emerges as a new candidate for early glaucoma indicator in addition to reduction in P50-N95 amplitude. PERG parameters suffer from high test-retest variability. Deterioration in PERG recordings should be interpreted with caution. The variability is lesser for the PERG ratio which maybe more meaningful while monitoring for change over time.