Good Visual Performance Despite Reduced Optical Quality during the First Month of Orthokeratology Lens Wear

ABSTRACT

Purpose: To measure changes in visual performances and optical quality in myopic children during the first month of wearing orthokeratology lens, and to reveal the association between those two.

Methods: Thirty-five myopic children participated in this study. Visual performances were evaluated with visual acuity and shape discrimination threshold (SDT) for radial frequency patterns. Placido disc-based corneal topography for central 4 mm and 6 mm zones was collected and decomposed by Fourier analysis into the spherical, asymmetric, and regular astigmatic components. Root-mean-square of third-order, fourth-order, and total higher-order aberrations (HOA) were extracted for the 4 mm and 6 mm zones. All examinations were conducted at baseline, 1-week, and 1-month after lens dispensing. The changing trends over time and association between SDT and optical quality were analysed with linear-mixed model.

Results: All subjects’ uncorrected visual acuity improved to 0.1 logMAR or better at 1-week and 1-month lens wear (P < .01). SDT did not change significantly from the baseline at 1-week and 1-month after lens wear (P > .05). For the two zones with diameters of 4 mm and 6 mm, the spherical component decreased significantly at 1-week (P < .01) and remained stable thereafter (P < .01); the asymmetric component increased significantly at 1-week (P < .01) and remained high at 1-month (P < .01); and the regular astigmatism did not show any significant change throughout (P > .05). At the two zones with diameters of 4 mm and 6 mm, the third-order, fourth-order, and total HOA increased significantly over time (P < .05). Change of SDT did not correlate with impairments in optical quality (P > .05 for all parameters).

Conclusions: While corneal optical quality decreased steadily during the first month following lens wearing, the visual acuity and shape discrimination sensitivity assessed by SDT remained very satisfactory.

KEYWORDS:

• RF pattern
• shape discrimination
• orthokeratology
• Fourier analysis
• corneal optical quality

Summary statement

The subjectively perceived visual distortion, which was quantified by shape discrimination threshold, did not show significant change before lens wear and 1 week and 1 month after lens wear. Meanwhile, the optical aberration, which was objectively extracted through Zernike or Fourier decomposition of corneal topography, showed steady increment.

Declaration of interest

The authors report no conflicts of interest.

Additional information

Funding

This study was supported by grants from project of medical and health technology program in Zhejiang Province, China (Grant No. 2018KY542);project of medical and health technology program in Zhejiang Province, China [Grant No. 2018KY542].