Peripheral Defocus and Myopia Management: A Mini-Review

Abstract

Myopia is the most common refractive error in the world, and its' prevalence continually increases. The potential pathological and visual complications of progressive myopia have inspired researchers to study the sources of myopia, axial elongation, and explore modalities to arrest progression. Considerable attention has been given over the past few years to the myopia risk factor known as hyperopic peripheral blur, the focus of this review. The primary theories currently believed to be the cause of myopia, the parameters considered to contribute and influence the effect of peripheral blur, such as the surface retinal area or depth of blur will be discussed. The currently available optical devices designed to provide peripheral myopic defocus will be discussed, 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 mentioned in the literature to date.

Keywords: Hyperopic peripheral blur; Myopia; Peripheral defocus.

Fig. 1

Myopic correction with single vision contact lenses or single vision spectacles correct myopia at both the fovea and the peripheral retina in equal amounts. This causes the myopic eye’s fovea and peripheral retina to be in different myopic states. (A) The peripheral retina is more hyperopic; therefore, equal myopic correction peripherally and centrally is likely to enhance myopia progression. (B) As illustrated, myopic correction with peripheral myopic defocus contact lenses or spectacle lenses correct the full degree of myopia at the fovea but create myopic defocus in the peripheral retina by providing additional positive power in the periphery, thus retarding myopia progression.

Fig. 2

Reduction of myopia progression (RMP) expressed as the percentage of sphere equivalent decrease. A 3-year study: (A) dual-focus MiSight 1 day (CooperVision) and (B) multifocal Biofinity (CooperVision) contact lenses. A 2-year study: extended depth of focus (C) Mylo (Mark’ennovy) and (D) 1dayPure (SEED) contact lenses. A 3-year study: (E) single vision MiyoSmart (Hoya), (F) multifocal Myopilux (Essilor), (G) single vision Stellest (Essilor), and (H) single vision MyoVision (Zeiss) spectacle lenses.