Short-term changes in light distortion in orthokeratology subjects

Abstract

Purpose: Quantifying adaptation to light distortion of subjects undergoing orthokeratology (OK) for myopia during the first month of treatment.

Methods: Twenty-nine healthy volunteers (age: 22.34 ± 8.08 years) with mean spherical equivalent refractive error -2.10 ± 0.93D were evaluated at baseline and days 1, 7, 15, and 30 of OK treatment. Light distortion was determined using an experimental prototype. Corneal aberrations were derived from corneal topography for different pupil sizes. Contrast sensitivity function (CSF) was analyzed for frequencies of 1.50, 2.12, 3.00, 4.24, 6.00, 8.49, 12.00, 16.97, and 24.00 cpd under photopic conditions.

Results: Average monocular values of all light distortion parameters measured increased significantly on day 1, returning to baseline after 1 week (P < 0.05 in all cases). Spherical-like aberration stabilized on day 7 for all pupil diameters, while coma-like for smaller pupils only. CSF was significantly reduced on day 1 for all spatial frequencies except for 1.5 cpd, returning to baseline afterwards. Significant correlation was found between light distortion and contrast sensitivity for middle and high frequencies (P < 0.05) after 15 days.

Conclusion: Despite consistently increased levels of corneal aberrations, light distortion tends to return to baseline after one week of treatment, suggesting that neural adaptation is capable of overcoming optical quality degradation.

Figure 1

Distribution of main central source of light and peripheral stimuli.

Figure 2

Monocular and binocular Best Fit Circle Radius (BFCr) (a), Light Distortion Index (LDI) (b), and BFC Irregularity (BFC Irregularity) parameter (c) of light distortion. Bars represent the Standard Error of the Mean (SEM).

Figure 3

Optical quality of the corneal front surface for different pupil sizes represented by the root mean square (RMS) of spherical-like aberrations (a), coma-like aberrations (b), and secondary astigmatism (c). Bars represent the Standard Error of the Mean (SEM).

Figure 4

Monocular (a) and binocular (b) log contrast sensitivity (CS). Bars represent the Standard Error of the Mean (SEM) only for visits on days 1 and 30; the remaining error bars are omitted for clarity.