The Role Of Peripheral Refractive Errors In the Development of Myopia

Abstract

Aim: To investigate the relationship between peripheral retinal refractive errors and progression of refractive errors, especially myopia in terms of spherical equivalent and axial length in Chinese children. Methods: A pilot study investigated the impact of single-vision spectacle correction for their effect on peripheral refractive errors. Then, Eighty-six healthy Chinese children (mean age: 9.9± 0.58 yrs, 9-11 yrs) were enrolled in a longitudinal trial and screened at baseline and 6 monthly in tervals for 18 months. Statistical significance was set at p < 0.05. Results: The pilot study found absolute hyperopic peripheral defocus with eyes corrected with single vision spectacles. In the longitudinal study, age significantly influenced progression (younger children progressed faster than older children p=0.009). With respect to central and peripheral refractive error profile, from baseline to 18 months, the central myopic shift was most in myopic eyes and least in hyperopic eyes (-1.34±0.27 D vs -0.49±0.14 D respectively). In the hyperopic eyes, the myopic shift was mostly central and in the temporal visual field. This resulted in the difference between central and nasal field refractive errors increasing with time and resulting in re lative hyperopia in the nasal visual field. In the moderate myopes, the magnitude of myopic shift was similar for both central and peripheral retinal points whereas in low myopic eyes the magnitude of myopic shift was similar for central and nasal visual field. Conclusion: Absolute hyperopic peripheral defocus was found within myopic eyes corrected with single vision spectacles. It appeared that in eyes that emmetropic and hyperopic, whilst there was a myopic shift over time, this was mostly limited to the central 20 degrees of the retina and indicative of an axial stretch ing. This predominantly central shift also resulted in hyperopic defocus at the retinal periphery. In those eyes that were myopic eyes, over time, there was a myopic shift at both the central and peripheral retina and was suggested of a global stretching. It may be that the initiation of hyperopic retinal defocus at the retinal periphery possibly plays a role in the initiation of this global stretching, but the evidence is not clear.