Effect of Overnight Wear Orthokeratology Lenses on Corneal Shape and Tears

OBJECTIVE: The aim of this study was to explore the effects of the overnight wear orthokeratology (OK) lenses on corneal shape and tear film stability. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.