Effect of Overnight Wear Orthokeratology Lenses on Corneal Shape and Tears.

Abstract

The aim of this study was to explore the effects of the overnight wear orthokeratology (OK) lenses on corneal shape and tear film stability. Forty patients with myopia aged between 11 and 18 years who wore OK lens continuously for more than 1 year were selected. Refractive error (D), corneal curvature, corneal surface regularity index (SRI), tear breakup time (TBUT), Schirmer I test score, and corneal staining were measured at the following time points: 1 week before wearing the OK lens (T0) and 1 week (T1), 1 month (T2), 3 months (T3), 6 months (T4), and 12 months (T5) after wear. Compared with T0, the average spherical refractions at other time points had become less myopic, flattens the central cornea, the SRI increased, and the TBUT decreased (P<0.01). All the aforementioned variables became stable at T1. Conversely, results of the Schirmer I test showed no significant changes. The number of patients with a corneal epithelium stained with fluorescein increased; staining was mainly of the grade I type. At each time point, the TBUT in patients with grade I corneal fluorescein staining was significantly lower than in patients with grade 0 staining (P<0.05). The overnight wear OK lenses may have decreased the degree of myopia and flattened the cornea while leaving basal tear secretion unaffected; however, the stability of tears decreased, therefore regular follow-ups are recommended.