Peripheral refraction in orthokeratology patients

Abstract

Purpose. The purpose of this study is to measure refraction across the horizontal central visual field in orthokeratology patients before and during treatment.

Methods. Refractions were measured out to 34[degrees] eccentricity in both temporal and nasal visual fields using a free-space autorefractor (Shin-Nippon SRW5000) for the right eyes of four consecutively presenting myopic adult patients. Measurements were made before orthokeratology treatment and during the course of treatment (usually 1 week and 2 weeks into treatment). Refractions were converted into mean sphere (M), 90[degrees] to 180[degrees] astigmatism (J180), and 45[degrees] to 135[degrees] astigmatism (J45) components.

Results. Before treatment, subjects had either a relatively constant mean sphere refraction across the field or a relative hypermetropia in the periphery as compared with the central refraction. As a result of treatment, myopia decreased but at reduced rate out into the periphery. Most patients had little change in mean sphere at 30[degrees] to 34[degrees]. In all patients, the refraction pattern altered little after the first week.

Conclusion. Orthokeratology can correct myopia over the central +/- 10[degrees] of the visual field but produces only minor changes at field angles larger than 30[degrees]. If converting relative peripheral hypermetropia to relative peripheral myopia is a good way of limiting the axial elongation that leads to myopia, orthokeratology is an excellent option for achieving this.