Pattern Electroretinogram (PERG) in Glaucoma Suspects: Comparison Between DTL and Palpebral Electrodes

Purpose to compare two available types of electrodes used to record the pattern electroretinogram (PERG), DTL and palpebral, and to identify the better one to apply in clinical practice. Methods 68 patients with glaucoma suspect were selected from the Glaucoma Service of the University Eye Clinic and submitted to complete ocular examination and to visual field (VF). They were then submitted to PERG after being randomized to one of the two groups: group 1 (35 subjects) performed PERG with DTL electrodes and group 2 (33 patients) with the palpebral ones. All patients underwent Visual Evoked Potential (VEP) as well. The following parameters have been considered: Mean Defect (MD) for VF; P50 and N95 latency and amplitude for PERG, and P100 amplitude and latency for VEP. For the statistical analysis, the Pearson correlation coefficient and the Mann-Whitney test have been applied as appropriate . Results The two groups presented an equivalent mean age. The P50 and N95 amplitudes resulted statistically different by group (p=.001), with DTL electrodes recording statistically higher values. VEP values were similar (p=.5). About the correlation between MD of VF and electro-physiologic parameters, the better correlation was recorded between MD and both P50 and N95 latencies (p=.008 and p=.026, respectively) in group 1 and between MD and P50 latency in group 2 (p=.001). No correlation was found between VF and VEP. Conclusions PERG records the ganglion cell response and, therefore, may play a role in the diagnosis of glaucoma. The DTL electrodes have been shown to be better than the palpebral ones since DTL’s amplitudes are statistically higher without influencing the latencies that, in our study, remain equivalent. DTL electrodes are therefore able to record smaller signals and are preferable to use in clinical practice to detect early defects in ganglion cells.