Comparison of ganglion cell layer thickness and pattern electroretinography among glaucoma suspects and healthy controls.

Purpose: To evaluate the difference in ganglion cell layer (GCL) thickness on optical coherence tomography (OCT) and waveform on pattern electroretinography (PERG) among glaucoma suspects and healthy controls.

Methods: An analytical, cross-sectional study was done on 100 eyes of 50 subjects, equally divided in the glaucoma suspect and control group. Subjects with an asymmetrically increased vertical cup-to-disc ratio and without any perimetric change were taken as suspects, and subjects with normal findings were taken as controls. GCL thickness was evaluated on spectral domain OCT at 3 mm, 3.45 mm, and 6 mm centering the foveola, and P50, N95 wave forms were recorded according to the standard PERG protocol.

Results: In this study, we observed that the average GCL thickness is significantly less in glaucoma suspects at 3.45 mm (p = 0.045) and at 6 mm (p < 0.001) circle zone. On PERG, P50 amplitude was significantly low in glaucoma suspects in comparison to controls (p = 0.007). There was significantly increased implicit time for both P50 and N95 in glaucoma suspects (p < 0.001). For N95 amplitude, a non-significant (p = 0.127) difference was observed among the two groups. At 3.45 mm, average GCL thickness showed a weak negative correlation with N95 implicit time (r = - 0.286, p = 0.044), a weak positive correlation with P50 amplitude (r = 0.349, p = 0.013), and at 6 mm, a weak positive correlation with P50 amplitude (r = 0.311, p = 0.028) in glaucoma suspects.

Conclusions: Analysing GCL thickness can help in the structural assessment of preperimetric glaucoma. PERG can be used as a valuable tool for the detection of ganglion cell dysfunction, even before cell loss.