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K. S. Suhr, S. S. Nayak, T. S. Vajaranant, J. P. Szlyk, W. H. Seiple; Multifocal Pattern Electroretinography as a Function of Luminance and Contrast Levels. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1486.
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Multifocal pattern electroretinography (mfPERG) is an electrophysiological tool that reflects inner retinal function. The mfPERG could be a valuable diagnostic tool for detecting glaucomatous damage if used to measure visual field deficiencies caused by retinal ganglion cell degeneration. Unfortunately mfPERGs have often been difficult to record due to small signal to noise ratios (SNR). In order to determine the best stimulus parameters in an attempt to improve efficacy of mfPERG visual field testing, this study varied the stimulus luminance and pattern contrast levels for normally-sighted subjects.
Female subjects aged 20-30 with normal vision were recruited. One eye of each subject was anesthetized and underwent mfPERG testing using DTL electrodes. An eight-sector array was used with the sectors containing scaled patterns of checkerboards. MfPERGs were recorded using a 3-frame stimulus at luminance levels of either 219.6 cd/m2, 108.6 cd/m2, or 48.45 cd/m2. Subjects were also tested at contrast levels of either 50% (80.41 cd/m2, 26.08 cd/m2) or 30% (66.72 cd/m2, 35.03 cd/m2).
MfPERG response peak-to-peak amplitudes were measured. There were no significant differences between superior and inferior hemifields. As luminance decreased, the amplitudes of the responses fell. The maximum amplitude recorded was at the 219.6 cd/m2 (100%) luminance (P=0.01). Amplitudes also decreased precipitously with decreases in stimulus contrast (P=0.12). The highest amplitude recorded was at 100% contrast. Contrast levels of 50% and 30% elicited relatively equal response amplitudes that were approximately one-third the size of the responses to the 100% contrast stimuli. The largest mfPERG responses were recorded at a luminance level of 100% luminance (219.6 cd/m2) and at 100% contrast.
The largest amplitude mfPERG responses were recorded to the 216 cd/m2 100% contrast stimulus providing evidence that greater contrast and luminance levels enhances response magnitudes.
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