Analysis of the effects and safety of wearing orthokeratology lenses

Abstract

Objective To investigate the effects and safety of wearing orthokeratology lenses for 2 years. Methods This was a retrospective analysis. The left eyes of 58 subjects (11.1 ± 2.0 years old with a spherical equivalent of -3.68±1.36 D) were examined by measuring refraction, axial length, corneal endothelial cells, central corneal thickness, corneal horizontal curvature, corneal vertical curvature and corneal astigmatism. The same data were also collected four weeks after removal of the orthokeratology lenses that had been worn every night for two years. Patients were divided into group A (38 eyes) and B (20 eyes) based on the type of materials used for the orthokeratology lenses (Boston EqualensⅡ for group A and Boston XO for group B) and data were analyzed for the two groups. A value of-3.00 D was used to further divide the patients in a low myopia group (19 eyes) and a moderate myopia group (39 eyes). All the data were analyzed by an independent t test, rank sum test and correlation analysis. Results After 2 years of wearing orthokeratology lenses, four values were significantly different from baseline four weeks after removing the orthokeratology lenses: spherical equivalent (-0.35±0.64 D, t=4.132, P<0.01), axial length (0.33±0.33 mm, t=4.411, P<0.01), corneal flat curvature (-0.33 ± 0.25 D, t=10.001, P<0.01), and corneal astigmatism (-0.34 ± 0.38 D, t=6.873, P<0.01). Significant differences were found between the two groups when SE, AL and corneal astigmatism were compared. For the low myopia group, the variations in spherical equivalent (-0.70 ± 0.68 D), axial length (0.47 ± 0.36 mm) and corneal astigmatism (-0.54 ± 0.37 D) differed from the moderate myopia group, which were-0.17 ± 0.54 D, 0.26 ± 0.29 mm, and-0.25(-1.00, 0.25)D, respectively. The differences were significant (t=3.193,-2.384, Z=-2.598, P<0.05). Conclusion The results suggest that there is slightly greater myopia and a longer axial length after 2 years of wearing orthokeratology lenses. And the lens seems to control myopia better in moderate myopes than in low myopes. Key words: Orthokeratologic procedures; Myopia; Astigmatism; Treatment outcome; Safety