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A Klistorner, C Balachandran, SL Graham, F Billson; Multifocal VEP latency in Glaucoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2165.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To evaluate the effect of glaucoma on multifocal VEP latency and to assess the influence of risk factors on VEP latency in pre-perimetric suspects Methods:A multifocal VEP was recorded using the AccuMap (ObjectiVision) on age-matched groups of 92 normal subjects, 158 glaucoma patients and 149 suspects. A pseudorandom cortically scaled pattern stimulus was presented at 58 locations (eccentricity 32deg) within the visual field of the individual. For each location a mean latency and standard deviation was determined from the normal population. Using these, latency values of individuals at all 58 locations, were linearly transformed to a z-score. Results: In the study eye of patients with glaucoma, the average latency z-score for the population was +0.833 , indicating a significant (p<0.001) increase in latency compared with normals (+0.04 ). The histogram of latency z-score values (from all segments) shows a positively skewed distribution with a wider spread (stdev 2.4) than in normals (stdev 1.0). The areas of increased latency z-score occurred in areas of visual field with normal and reduced amplitude. In the study eye of suspects the mean population latency z-score was 0.58. The histogram of latency z-score, shows the suspect population's distribution to lie in between that of the normal and glaucoma populations. Like the glaucoma population, it is also skewed positively and has a wider spread (stdev 1.94) than normals. In suspects a significant increase in latency z-score was noted in presence of such risk factors as high cup disc ratio and intraocular pressure. Family history alone had no significant effect on latency. Average latency z-score was found to increase with mean deviation (MD derived from subjective perimetry) in suspects and to plateau in glaucoma. Conclusion: These findings suggest that increase in latency is an early feature of glaucoma, occurring before a focal field defect develops on subjective perimetry. The increase in latency develops earlier than reduction in amplitude and plateaus in more advanced glaucoma, while VEP amplitude continues to decline.
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