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P.A. Gonzalez, S. Parks, D. Keating; The Effect of pupil size on the multifocal electroretinogram . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4246.
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Abstract: : Purpose:To investigate the effect of changing the pupil diameter on the amplitude and latency of the multifocal electroretinogram. Methods:Multifocal elctroretinograms were recorded using a custom built electrophysiological system. An array of sixty one empirically scaled hexagons was used to stimulate the visual field. The duration of overall recording period was eight minutes, segmented into sixteen intervals each lasting thirty seconds. An amplifier gain of 100,000 with an ADC digitization rate of 1200Hz and a dual high/low pass filter of 3–300Hz and 10–100Hz was used. Four normal subjects were recruited and both eyes were tested. Mydriasis and miosis were obtained with tropicamide (1%) and pilocarpine (1%) respectively. Pupil diameters between 9mm and 1mm were measured. All patients were emmetropic. Results:For a change in pupil diameter of 8mm there was a drop in amplitude in some cases greater than 50% (amplitude 53nV at 8mm to 25nV at 1 mm). Also there was an increase in latency in some cases as much as 8ms in the central 40° (39ms at 8mm to 47ms at 1mm.) Conclusions:Pupil size has significant effects on both amplitude and latency of multifocal electroretinograms and should be measured carefully to provide accurate interpretation of results
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