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.