Effects of 7-Methylxanthine on Form Deprived Myopia in Guinea Pig

Abstract

Purpose: : To determine the effect of the adenosine receptor antagonist 7-methylxanthine on the development of form-deprived myopia in guinea pig.

Methods: : Three-week old Guinea pigs were monocularly deprived (MD) using a diffuser for a period of 21 days. Two groups of guinea pigs were fed either 7-methylxanthine (300 mg per kg body weight; n = 7) or vehicle control (saline equal volume with 7-methylxanthine; n = 7). A normal control group (n = 6) was not subjected to form-deprivation. Ocular refractions, axial lengths and body weights were measured at the start and the end of the experiment 21 days later. Light and electron microscopy were used to measure scleral thickness and to determine the collagen fibril diameters in the posterior of sclera.

Results: : In vehicle control MD guinea pigs, 21 days of MD produced-5.40 D +/- 1.08 D of myopia and the axial length increased 1.00 mm +/- 0.07 mm. In MD guinea pigs fed with 7-methylxanthine, 21 days of MD induced only -2.75 D +/- 0.50 D of myopia and the axial length increased 0.66 mm +/- 0.21 mm. Compared with the control group, the changes in refraction and axial length of two MD groups’ contralateral eyes during the 21 days were not significantly different (2.15 D +/- 0.22 D and 2.85 D +/- 1.45 D versus 2.70 D +/- 1.15 D, p>0.05; 0.41 mm +/- 0.12 mm and 0.53 mm +/- 0.07 mm versus 0.37 mm +/- 0.10 mm, p>0.05). The weights of the three groups guinea pigs had no significant changes (300g +/- 6.12g versus 306g +/- 8.22g versus 308g +/- 5.70g, p>0.05). The sclera thickened and the diameter of scleral collagen fibers increased in both eyes of 7-methylxanthine treated guinea pigs.

Keywords: myopia • drug toxicity/drug effects • sclera