Clinical electrophysiology relevant for early glaucoma diagnosis

This review reports findings of the recent literature about electrophysiologic techniques that are used in glaucoma diagnosis and research. Included in this review are results obtained by recording electrical responses from the eye (electroretinograms) and from the brain (visual evoked potentials). Studies concerned the electroretinogram evoked by patterned stimuli that originates in the proximal retina and with flash-evoked responses that originate from the proximal retina, such as oscillatory potentials and scotopic threshold responses, from middle layers of the retina (B wave), and from the outer retina (A waves and C waves). Regarding the pattern electroretinogram, the authors agree on its usefulness in the diagnosis of glaucoma. However, the optimal stimulus conditions (temporal and spatial frequency, retinal location, contrast, and color), which component of the response to evaluate, and the value of the pattern electroretinogram in follow-up treatment are debatable. Flash-evoked components of the electroretinogram that have been considered in the past to be of low value in diagnosis of glaucoma now seem to be more important. New developments in visual evoked potentials techniques, such as photostress methods, contrast sensitivity measurements, ramp stimulation, and selective adaptation for isolating blue-cone activity seem to be promising in further increasing the diagnostic value of visual evoked potential measurements.