Changes in Peripheral Refractive Profile after Orthokeratology for Different Degrees of Myopia

Abstract

Purpose: The purpose of this study was to evaluate the effect of orthokeratology for different degrees of myopia correction in the relative location of tangential (F_T) and sagittal (F_S) power errors across the central 70° of the visual field in the horizontal meridian.

Methods: Thirty-four right eyes of 34 patients with a mean age of 25.2 ± 6.4 years were fitted with Paragon CRT (Mesa, AZ) rigid gas permeable contact lenses to treat myopia (−2.15 ± 1.26D, range: −0.88 to −5.25D). Axial and peripheral refraction were measured along the central 70° of the horizontal visual field with the Grand Seiko WAM5500 open-field auto-refractor. Spherical equivalent (M), as well as tangential (F_T) and sagittal power errors (F_S) were obtained. Analysis was stratified in three groups according to baseline spherical equivalent: Group 1 [M_Baseline = −0.88 to −1.50D; n = 11], Group 2 [M_Baseline = −1.51 to −2.49D; n = 11], and Group 3 [M_Baseline = −2.50 to −5.25D; n = 12].

Results: Spherical equivalent was significantly more myopic after treatment beyond the central 40° of the visual field (p < 0.001). F_T became significantly more myopic for all groups in the nasal and temporal retina with 25° (p ≤ 0.017), 30° (p ≤ 0.007) and 35° (p ≤ 0.004) of eye rotation. Myopic change in F_S was less consistent, achieving only statistical significance for all groups at 35° in the nasal and temporal retina (p ≤ 0.045).

Conclusions: Orthokeratology changes significantly F_T in the myopic direction beyond the central 40° of the visual field for all degrees of myopia. Changes induced by orthokeratology in relative peripheral M, F_T and F_S with 35° of eye rotation were significantly correlated with axial myopia at baseline.

• Field curvature
• myopia
• orthokeratology
• peripheral astigmatism

Acknowledgments

The authors want to thank Paragon Vision Science (Mesa. AZ) for donating the lenses.

Declaration of interest

This work was partially funded by Fundação para Ciência e Tecnologia, Portugal, Projects: PTDC/SAU-BEB/098392/2008 and PTDC/SAU-BEB/098391/2008 and the Strategic Project PEST-C/FIS/UI607/2011.