There is growing evidence that oral administration of the non-selective adenosine receptor antagonist, 7-methylxanthine (7-MX), retards the development of juvenile onset myopia in children and vision-induced myopia in animals. We investigated the effects of topically instilled caffeine on lens-induced myopia in infant monkeys that were reared with -3 D spectacle lenses over their treated eyes and plano lenses over their fellow eyes. In addition, one drop of a 1.4% caffeine citrate solution was binocularly instilled twice each day until the end of lens wear. Comparison data were obtained from control animals subjected to the same lens-rearing regimen and 37 normal monkeys.
At the end of treatment, sixteen of the 17 lens-reared controls exhibited clear evidence of compensating myopic anisometropia (-2.11±1.70 D). In contrast, only 2 of the 8 caffeine treated (CT) monkeys developed myopic anisometropias (+0.60±1.82 D).
Moreover, the final ametropias in the treated (+5.06 D) and fellow eyes (+3.59 D) of the CT monkeys were significantly more hyperopic than normal monkeys (+2.44 D). The final ametropias in the CT monkeys were associated with increases in choroidal thickness and correlated with smaller vitreous chamber depths. These findings suggest that adenosine antagonists influence the vision-dependent cascade that regulates emmetropization in monkeys.
Caffeine is a safe, common dietary component in everyday life and applying caffeine topically to the eye greatly reduces any potential arousal effects. It appears that caffeine acts on local mechanisms with in the eye. Although we did not observe any adverse ocular or systemic side effects of caffeine in rhesus monkeys, from a safety perspective a thorough examination of the function and structure of the eye is warranted. Overall, our results demonstrate that adenosine receptor antagonists, specifically the caffeine eye drops, have potential as treatment strategies for preventing or slowing the progression of myopia in children.
Baskar Arumugam B.Opt., PhD., FAAO.
Research Assistant Professor
University of Houston College of Optometry
4901 Calhoun Road
Houston, Texas 77204
1 College of Optometry, University of Houston, Houston, Texas, USA
2 Brien Holden Vision Institute, Sydney, Australia
3 Department of Optometry and Vision Science, UNSW, Australia