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Acute Effects of Oral Caffeine Intake on Human Global-Flash mfERG Responses: A Placebo-Controlled, Double-Masked,
Jesús Vera1,2, Beatriz Redondo1,2, Fuensanta A Vera-Diaz2
1CLARO (Clinical and Laboratory Applications of Research in Optometry) Research Group, Department of Optics, Faculty of Sciences, University of Granada, Spain.
Purpose:
To determine the acute effect of caffeine intake on the retinal responses as measured with a global-flash multifocal electroretinogram (gfmERG) protocol at different contrast levels.
Methods:
Twenty-four young adults (age = 23.3 ± 2.4 years) participated in this placebo-controlled, double-masked, balanced crossover study. On two different days, participants orally ingested caffeine (300 mg) or placebo, and retinal responses were recorded 90 minutes later using a gfmERG at three contrast levels (95%, 50%, and 29%). The amplitude response density and peak time of the direct and induced components (direct component [DC] and induced component [IC], respectively) were extracted for five different eccentricities (1.3°, 5.0°, 9.6°, 15.2°, and 21.9°). Axial length, spherical equivalent refraction, habitual caffeine intake, and body weight were considered as continuous covariates.
Results:
Increased IC amplitude response density was found after caffeine ingestion in comparison to placebo (P = 0.021, ƞp2 = 0.23), specifically for the 95% and 50% stimulus contrasts (P = 0.024 and 0.018, respectively). This effect of caffeine on IC amplitude response density was independent of the retinal eccentricity (P = 0.556). Caffeine had no effect on DC amplitude response density or DC and IC peak times.
Conclusions:
Our results show that oral caffeine intake increases the inner electro-retinal activity in young adults when viewing stimuli of high- (95%) to medium-contrast (50%). Given the increasing evidence that the inner retinal function is involved in the emmetropization process, these results may suggest that caffeine or its derivatives could potentially play a role in the mechanisms involved in eye growth.
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