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Mineo Kondo, Kumiko Kato, Ryunosuke Nagashima, Yoshitsugu Matsui, Masahiko Sugimoto, Hisashi Matsubara; Effect of Pupil Size on ERGs Recorded by New Mydriasis-Free Full-Field Flicker ERG System (Reteval™). Invest. Ophthalmol. Vis. Sci. 2014;55(13):5119.
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To study the effect of pupil size on the amplitude and implicit time of 28.3-Hz flicker electroretinograms (ERGs) recorded with a new mydriasis-free full-field flicker ERG system (RETeval™, LKC Technologies, Gaithersburg, MD). This system was designed to deliver constant retinal illumination by adjusting the light intensity to compensate for the pupil size.
Ten healthy volunteers (age, 25 to 46 years) were studied. After 10 minutes of light adaptation, 28.3-Hz flicker ERGs were repeatedly recorded every three minutes after starting the pupil dilation by drops of 0.5% tropicamide and 0.5% phenylephrine over a period of 21 minutes. The pupil size was measured by an automated pupil area measuring device. The amplitudes and implicit times of 28.3-Hz flicker ERG were plotted against the time after the installation of the mydriatics.
The average pupil area was 14.39 ± 4.78 mm^2 at the beseline, and it gradually increased to 46.50 ± 12.20 mm^2 at 21 minutes after starting the mydriatic drops. There was no statistically significant change in the amplitude of flicker ERG during the 21 minutes. However, the average implicit time of the flicker ERGs was 32.80 ± 1.03 ms at the baseline, and it significantly increased with time, then reached 34.20 ± 1.12 ms at 21 min (p<0.05, two-way layout ANOVA and Bonferroni type multiple comparisons). There was a significant positive correlation between the pupil area and implicit time (Pearson product-moment correlation: p<0.001, r = 0.62). A simple regression equation showed that a 1 mm^2 increase of pupil area caused approximately 0.05 msec implicit time delay.
These results suggest that the implicit time of 28.3-Hz flicker ERGs recorded with mydriasis-free flicker ERG System (Reteval™) can be influenced by the pupil size.
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