Purpose: To compare peripheral refraction along both the horizontal and vertical retinal meridians before and after orthokeratology (OK) lens wear.
Methods: Nineteen young adult myopic subjects (mean age, 28 ± 7 years) were fitted with OK lenses in both eyes. Central and peripheral refraction and corneal topography measurements were taken before and after 14 nights of OK. All measurements were taken with no correction or OK lens in place.
Results: At baseline before OK, peripheral spherical equivalent refraction (M) across the horizontal meridian did not vary significantly from center. M across the vertical meridian was more myopic than the center (p < 0.05). After OK, there was a significant hyperopic shift in M (p < 0.001); both meridians now experienced myopic peripheral refraction. At baseline, J180 across the horizontal meridian was more negative than the center, and along the vertical meridian, it was more positive than the center (all p < 0.05). At baseline, J45 was more positive than center with increased eccentricity in the temporal and inferior retina and more negative than center with increased eccentricity in the nasal and superior retina. Orthokeratology caused greater rate of change of peripheral J180 across both retinal meridians (p < 0.001). Furthermore, compared with baseline, J45 became more positive in the nasal and superior retina and more negative in the temporal and inferior retina (all p < 0.05).
Conclusions: Orthokeratology lenses induced significant changes in peripheral refraction along the horizontal and vertical meridians. As peripheral myopia was measured at baseline along the vertical meridian, the results of our study suggest that inducing greater degrees of myopic defocus on to the peripheral retina, more than habitually experienced, may be required for effective myopia control. Further investigation into the critical threshold of retinal area receiving myopic defocus and the impact of duration of exposure is necessary to improve the efficacy of current myopia control treatments.