Functional characteristic of the retina in glaucoma

Abstract

Abstract Purpose: Purpose: To investigate bioelectrical activity of the retina in normal subjects and patients with primary open angle glaucoma (POAG). Methods: Methods: 40 eyes of 20 normal subjects and 80 eyes of 45 patients with different stages of glaucoma were examined with electroretinogram (full‐field, flicker, pattern, multifocal ERG, ERG to long duration stimulus and chromatic ERG to red, green and blue stimulus). Intraocular pressure was 21 mm Hg or less in all patients. All patients were also tested on HRT II. Results: Full‐field ERG recordings showed a decrease of b‐wave amplitude and an increase of implicit time in advanced and late stages of POAG. Macular chromatic ERG to red stimulus of 15° area was subnormal in all stages of POAG (p<0,01). The density of retinal responses of multifocal ERG was progressively decreased in all stages. An amplitude of P50 component of pattern ERG in initial stage of glaucoma was decreased (p<0,05). In advanced stage of glaucoma a significant decrease of amplitudes of P50 and N95 components and prolonged implicit time of N95 component were observed.The off‐component of long duration stimulus flash ERG in all stages was subnormal. The on‐component in early stage was supernormal, whereas in advanced and late stages was subnormal. A damage of off‐cone system of the retina was the first symptom of retinal changes in glaucoma. In initial stage of glaucoma ERG symptoms of glaucomatous neuropathy were first detected even before changes on HRT test. Conclusions: The retinal pathology presented in ERG symptoms may probably reflect some pathogenetic mechanisms of development of glaucomatous damage, including excitotoxcic factors and ischemia.