Laboratory investigationsEffects of Caffeine on Microcirculation of the Human Ocular Fundus
Introduction
In addition to intraocular pressure (IOP), ocular blood flow has also recently been shown to play a role in the development and progression of glaucoma.1, 2, 3, 4, 5 Interest is now being focused on how this affects the microcirculation of the optic nerve head (ONH). The recent heightened interest in general health maintenance has also led to a growing interest in the effects of food products such as coffee and tea. Research on the effects of caffeine on blood circulation has demonstrated a decrease in cerebral blood flow.6, 7, 8 Studies of the relationship between caffeine and ocular blood flow have thus far been limited to investigation by blue field entoptoscopy of the effects on macular blood flow.9 There have been no reports concerning caffeine ingestion and its effects on serial changes in ONH microcirculation. Therefore, in the present study, we used the laser speckle method to evaluate the effects of caffeine ingestion on human ocular microcirculation.
Section snippets
Materials and Methods
The subjects in this study were 10 healthy volunteers (10 eyes) without any ophthalmologic disorders (other than simple myopia), and comprised 5 men and 5 women ranging in age from 25 to 44 years (mean ± SD, 30.7 ± 6.4 years). Caffeine ingestion, food and drink of any kind, and exercise were prohibited for 6 hours, 2 hours, and 30 minutes before testing, respectively. The study was conducted in a double-blind manner. All subjects underwent the same experimental procedure.
During the study
Results
Figure 1 shows the relative SBR values (ie, sequential changes in relative SBR values), compared to values obtained before the administration of caffeine or placebo (Figure 1A, in ONH; Figure 1B, in choroid-retina). The relative SBR values in the ONH were lowest from 45 to 60 minutes after administration. The values decreased from the baseline (before administration) by 10% at 45 minutes and by 8% at 60 minutes. Analysis of the data at 60 minutes by paired t-test with Bonferroni's correction
Discussion
Whether patients with glaucoma should consume products containing caffeine is still a matter of debate. Some investigators have shown that caffeine increases IOP, and recommended that it be avoided.17, 18 Other studies have shown that ingestion of as much as 400 mg of caffeine does not raise IOP in normal volunteers.19 Recently, ONH microcirculation, in addition to IOP, has been shown to be a factor in the development of glaucoma. No previous studies have investigated the effects of caffeine on
Acknowledgements
This paper was originally published in Japanese in the Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 2001;105:308–13. It appears here in a modified form after peer review and editing for the Japanese Journal of Ophthalmology.
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