Pattern electroretinogram in glaucoma suspects: new findings from a longitudinal study.

PURPOSE Early detection of glaucoma remains a challenging problem and needs long-term, prospective studies. The pattern electroretinogram (PERG) directly reflects retinal ganglion cell function. The PERG was evaluated by extending a prospective study of patients with ocular hypertension and evaluated amplitude, PERG ratio, peak time, and trends thereof. METHODS One hundred twenty eyes of 64 patients with intraocular pressure greater than 25 mm Hg (or ≥ 23 mm Hg with additional risk factors), normal visual fields, normal optic disc appearance, and visual acuity ≥ 0.8 were included in the study. Mean follow-up time was 10.3 years. The per-visit measures of amplitude at 15 reversals/s to 0.8° check size, PERG ratio (0.8°/16°), peak time, visual field, and their trends were analyzed. RESULTS Over the course of the study 13 eyes converted to glaucoma according to a visual field definition. Amplitude to 0.8° check size, PERG ratio, and peak time were significantly lower in converters. Amplitude and PERG ratio predicted conversion 4 years ahead with a sensitivity/specificity of 67%/64% and 75%/76%, respectively. At this time, the ROC area was already significantly above chance for the PERG ratio. Comparison of the trends of converters and nonconverters revealed significant differences in the PERG ratio; however, trends did not predict conversion as successfully as single-visit measures. CONCLUSIONS The PERG, especially the PERG ratio, detected glaucoma patients 4 years before visual field changes occurred, with a sensitivity/specificity of 75%/76%. Slope analysis required multiple visits, but provided little additional information in detecting converters.