The Adenosine Receptor Antagonist, 7-Methylxanthine, Alters Emmetropizing Responses in Infant Macaques

• Published in: Investigative ophthalmology & visual science Vol. 59; no. 1; pp. 472 - 486
• Main Authors: Hung, Li-Fang, Arumugam, Baskar, Ostrin, Lisa, Patel, Nimesh, Trier, Klaus, Jong, Monica, III, Earl L. Smith
• Format: Journal Article
• Language: English
• Published: United States The Association for Research in Vision and Ophthalmology 01.01.2018
• Subjects: Anatomy and Pathology/Oncology
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.17-22337

Previous studies suggest that the adenosine receptor antagonist, 7-methylxanthine (7-MX), retards myopia progression. Our aim was to determine whether 7-MX alters the compensating refractive changes produced by defocus in rhesus monkeys. Starting at age 3 weeks, monkeys were reared with -3 diopter (D; n = 10; 7-MX -3D/pl) or +3D (n = 6; 7-MX +3D/pl) spectacles over their treated eyes and zero-powered lenses over their fellow eyes. In addition, they were given 100 mg/kg of 7-MX orally twice daily throughout the lens-rearing period (age 147 ± 4 days). Comparison data were obtained from lens-reared controls (-3D/pl, n = 17; +3D/pl, n = 9) and normal monkeys (n = 37) maintained on a standard diet. Refractive status, corneal power, and axial dimensions were assessed biweekly. The -3D/pl and +3D/pl lens-reared controls developed compensating myopic (-2.10 ± 1.07 D) and hyperopic anisometropias (+1.86 ± 0.54 D), respectively. While the 7-MX +3D/pl monkeys developed hyperopic anisometropias (+1.79 ± 1.11 D) that were similar to those observed in +3D/pl controls, the 7-MX -3D/pl animals did not consistently exhibit compensating myopia in their treated eyes and were on average isometropic (+0.35 ± 1.96 D). The median refractive errors for both eyes of the 7-MX -3D/pl (+5.47 D and +4.38 D) and 7-MX +3D/pl (+5.28 and +3.84 D) monkeys were significantly more hyperopic than that for normal monkeys (+2.47 D). These 7-MX-induced hyperopic ametropias were associated with shorter vitreous chambers and thicker choroids. In primates, 7-MX reduced the axial myopia produced by hyperopic defocus, augmented hyperopic shifts in response to myopic defocus, and induced hyperopia in control eyes. The results suggest that 7-MX has therapeutic potential in efforts to slow myopia progression.