Luminescent threshold comparisons, flicker fusion discrimination, and repetition blindness in response to trimethylxanthine (caffeine) ingestion

Scope and method of study. The purpose of this study was to investigate the influences of two doses of caffeine (2.5 mg./kg. bwt. and 5.0 mg./kg. bwt.) and a placebo on three aspects of vision: luminescent threshold comparisons, flicker fusion discrimination, and repetition blindness. Subjects consisted of 9 male and 14 female college age students. All subjects were moderate to low caffeine consumers. The study utilized a within subject research design with treatments administered randomly using a double-blind format. A pre and post-test protocol enabled subjects to serve as their own control. Each participant was tested utilizing Lafayette Instrument Company's Light Discrimination Apparatus, Lafayette's Visual Perception Control and a computer program designed by Dr. Larry Hochhaus, Oklahoma State University, to measure repetition blindness. Repeated measures ANOVAs combined with Newman-Keuls post hoc analyses were used to analyze all data.; Findings and conclusions. Caffeine's effects on three visual tests appear to be dose related with the 2.5 mg./kg. dose being the most influential. At low luminescence, caffeine at 2.5 mg./kg. bwt. produced significantly greater variations between pre and post-test scores compared to the 5.0 mg./kg. bwt. dose. Similar results occurred with the 5.0 mg./kg. bwt. dose at moderate luminescence compared to both the placebo and the 2.5 mg./kg. bwt. dose. Flicker fusion comparisons revealed that flicker fusion was postponed after consuming 2.5 mg./kg. bwt. caffeine. Repetition blindness decreased after ingesting 2.5 mg,/kg. bwt. caffeine. Higher levels of caffeine were required to produce significant findings as luminescence increased. However, no significance was reported at high luminescence.