Electroretinograma en glaucoma

Pattern electroretinogram in glaucoma
Lori M. Ventura and Vittorio Porciatti

Purpose of review Several studies have shown that the pattern electroretinogram, a direct, objective method of measuring retinal ganglion cell function, is altered early in ocular hypertension and glaucoma. Renewed interest in the pattern electroretinogram for early detection of preperimetric glaucoma has beensparked by noninvasive and reproducible methods of recording using skin electrodes. Recent findings With the noninvasive pattern electroretinogram, response abnormalities have been detected in up to 50% of glaucoma suspects with normal standard perimetry. In early glaucoma (with either normal or high intraocular pressure), a reduction of intraocular pressure has sometimes yielded improvement in patternelectroretinogram amplitude. A prolonged steady-state stimulus presentation reduces the pattern electroretinogram amplitude and increases optic nerve blood flow in normal subjects, suggesting that sustained activity of retinal ganglion cells is physiologically associated with autoregulatory changes of the neuralvascular system. It is unknown whether this autoregulation is altered in glaucoma. Themultifocal pattern electroretinogram does not seem to have an advantage over the pattern electroretinogram in the early detection of glaucoma. The photopic negative response of the diffuse flash electroretinogram has shown changes in glaucoma, but may not be able to detect retinal dysfunction in normal tension glaucoma. Summary The pattern electroretinogram is a noninvasive, direct, objectivemethod that may be useful to clinicians in detecting early retinal ganglion cell dysfunction in glaucoma suspects. The pattern electroretinogram may also optimize treatment strategies based on improvement of retinal ganglion cell function. Keywords glaucoma, neuroprotection, pattern electroretinogram, retinal ganglion cell

Abbreviations IOP MERG NTG PERG RGC intraocular pressure multifocalelectroretinogram normal tension glaucoma pattern electroretinogram retinal ganglion cell

# 2006 Lippincott Williams & Wilkins 1040-8738

Introduction
The pattern electroretinogram (PERG) is a retinal biopotential that is evoked when a high-contrast patterned stimulus (alternating stripes or checkerboards) is viewed on a television monitor [1]. When the alternation rate is slow (typically 2–4reversals per second), a transient PERG is generated with a waveform characterized by a positive wave peaking about 50 ms after the contrast reversal (P50), followed by a negative wave peaking about 95 ms after contrast reversal (N95). For faster reversal rates (typically 16 reversals per second), a steady-state, sinusoidal-like waveform is generated, whose period corresponds to the reversal frequency[2]. While the traditional flash ERG is unaltered in conditions that impair retinal ganglion cell (RGC) function, the PERG closely depends on normal RGC activity, and therefore represents an objective and direct measure of RGC function [3–5]. The PERG has been shown by many investigators to be altered in ocular hypertension [6,7], for example, and glaucoma (see [8, 9] for a review). Recentdevelopments of the technique allow easy recording in the clinical setting with good reproducibility [10••]. This article will review the PERG and the resurgence of interest in this complementary technique to aid in the earlier diagnosis and monitoring of pre-perimetric glaucoma. Recent publications comparing PERG with the photopic negative response and the multifocal PERG will also be reviewed.Pattern electroretinogram in normal subjects
Curr Opin Ophthalmol 17:196–202. # 2006 Lippincott Williams & Wilkins. Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA Correspondence to Lori M. Ventura MD, Associate Professor of Clinical Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, 900, N.W. 17th Street,...