The influence of orthokeratology on peripheral refraction during accommodation.

SIGNIFICANCE

The change in peripheral refraction from hyperopic to myopic defocus following orthokeratology (OK) has been recognized as a main factor in myopia control. However, the impact of OK lenses on peripheral refraction at nearpoints in myopic eyes still requires further investigation.

PURPOSE

This study aims to investigate changes in peripheral refraction during accommodation in myopic adults after orthokeratology (OK) wear.

METHODS

Twenty-four selected myopic adults (mean spherical equivalent: -2.70 ± 1.04 D) participated in this study. Peripheral refractions were measured by an auto-refractor with targets located at 25 cm and 50 cm from the eye. Measurements were performed across ± 30º of the horizontal field in 5º steps from the visual axis of subject's right eye before and after wearing the OK lens. The statistical package SPSS was used to analyze the data to determine the relationship between peripheral refractions and accommodation.

RESULTS

After wearing the OK lens, the peripheral refraction became more myopic with increasing eccentricity during accommodation (t > 2.80, p < 0.01, N30º, N25º, N20º, T15º, T20º, T25º and T30º, for 25 cm and 50 cm). While relative hyperopic reflective errors were observed in the central (accommodative lag) and near peripheral (= < 15 º) retinal fields (t < -2.5, p < 0.02, for 0º, N5º, N10º, N15º and T10º for 25 cm and 50 cm), relative myopic refractive errors were evident in the farther periphery (> 15 º). (for 25 cm, -0.45 ± 1.18, -0.71 ± 1.47, -1.00 ± 1.31 and -1.70 ± 2.16D, for N30º, T20º, T25º, and T30º; for 50 cm, -0.76 ± 1.28, -0.84 ± 1.05; -1.17 ± 1.30 and -2.15 ± 1.81D, for N30º, T20º, T25º, and T30º; t > 2.5, P < 0.02).

CONCLUSION

The myopic shift of peripheral refraction from the OK lens was partly counteracted by an insufficient change in refractive power of the eye during accommodation. Even though the refractive errors become relative hyperopic in the central and near peripheral retinal fields, relative myopic refraction was still maintained in the farther periphery for the accommodated myopic eyes treated with OK lenses.