Abstract
Purpose :
Recent studies showed that oral administration of 7-methylxanthine (7-MX), an adenosine receptor antagonist, can retard the development of myopia in children and lens-induced myopia in laboratory animals. Our aim was to investigate the effects of topically instilled caffeine, also a strong adenosine receptor antagonist, on the compensating refractive changes produced by defocus in rhesus monkeys.
Methods :
Starting at 24±2 days of age, 14 infant monkeys were reared with either -3D (CT -3D; n=8) or +3D (CT +3D; n=6) lenses over their treated eyes and plano lenses over their fellow eyes. In addition, one drop of 1.4% caffeine citrate solution (in sterile 0.3% hydroxyl-propyl methyl cellulose) was topically instilled into both eyes twice a day until the end of lens wear (136±3 days of age). Comparison data were obtained from control infants reared with unrestricted vision (n=37), monocular -3D (n=17) and monocular +3D lenses (n=9). Refractive status, corneal power and axial dimensions were assessed periodically throughout the treatment period.
Results :
At the end of treatment period, the control animals reared with monocular +3 and -3D lenses exhibited significant compensating hyperopic (+1.86±0.54D) and myopic anisometropia (-2.15±1.07D), respectively. In contrast, the CT -3D monkeys exhibited significant hyperopic ametropia in both eyes (median: treated eye, +5.06D, p=0.0003; fellow eye, +3.60D, p=0.007) and remained isometropic (+0.60±1.82D); the CT +3D monkeys manifested hyperopic shifts that are larger than those observed in +3D controls (treated eyes:1.74±1.88D vs 0.30±1.36D, p=0.05; fellow eyes: -0.09±2.31D vs -1.72±1.33D, p=0.05) and similar amount of hyperopic anisometropia (+1.93±0.82D, p=0.84). The relative hyperopic changes in the CT monkeys were associated with increases in choroidal thickness and reduced vitreous chamber elongation rates.
Conclusions :
In infant monkeys, topical caffeine slows axial elongation rates, increases choroidal thickness, produces absolute hyperopic shifts in refractive error, retards the myopic compensation normally produced by hyperopic defocus, and augments hyperopic shifts in response to imposed myopic defocus. These results suggest that adenosine receptor antagonists have potential in efforts to slow myopia progression.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.