An Incremental Retinal-Defocus Theory of the Development of Myopia

Abstract

Previous theories of myopia development involved subtle and complex processes such as the sensing and analyzing of chromatic aberration, spherical aberration, spatial gradient of blur, and spatial frequency content of the retinal image. However, these theories have not been able to explain all the diverse experimental results, which has been accomplished by our newly proposed incremental retinal-defocus theory. Our theory is based on a relatively simple and direct mechanism for the regulation of ocular growth. It states that a time-averaged decrease in retinal-image defocus decreases the rate of release of retinal neuromodulators, which decreases the rate of retinal proteoglycan synthesis, with an associated decrease in scleral structural integrity. This increases the rate of scleral growth, and in turn the eye’s axial length, which produces permanent myopia. Schematic analysis of the theory has provided a clear explanation for the eye’s ability to grow in the appropriate direction under a wide range of experimental conditions. In addition, the theory has been able to explain how repeated cycles of nearwork-induced transient myopia leads to repeated periods of decrease in retinal-image defocus, whose cumulative effect over an extended period of time also results in an increase in axial growth that produces permanent myopia. Thus, this unifying theory forms the basis for understanding the underlying retinal and scleral mechanisms of myopia development.