Peripheral defocus as it relates to myopia progression: A mini-review

Abstract

Myopia is the most common refractive error in the world and has reached a pandemic level. The potential complications of progressive myopia have inspired researchers to attempt to understand the sources of myopia and axial elongation and to develop modalities to arrest progression. Considerable attention has been given over the past few years to the myopia risk factor known as hyperopic peripheral blur, which is the focus of this review. It will discuss the primary theories believed to be the cause of myopia and the parameters considered to contribute to and influence the effect of peripheral blur, such as the surface retinal area of blur or the depth of blur. The multitude of optical devices designed to provide peripheral myopic defocus will be mentioned, including bifocal and progressive addition ophthalmic lenses, peripheral defocus single-vision ophthalmic lenses, orthokeratology lenses, and bifocal or multifocal center distance soft lenses, as well as their effectivity as discussed in the literature to date.

Keywords: Hyperopic peripheral blur; myopia; peripheral defocus.

Figure 1

Myopic correction with single-vision contact lenses or single-vision spectacles equally corrects myopia at the fovea and the peripheral retina. The myopic eye’s fovea and peripheral retina are in different myopic states. The peripheral retina is more hyperopic; therefore, equal correction, peripherally and central, is likely to enhance myopia progression (a). As illustrated, myopic correction with peripheral defocus contact lenses or spectacle lenses correct the degree of myopia at the fovea but creates myopic defocus in the peripheral retina by providing additional positive power in the periphery, thus retarding myopia progression (b)