Increased Corneal Toricity after Long-Term Orthokeratology Lens Wear

摘要

Purpose. To investigate the change in corneal toricity and associated refractive astigmatism after discontinuation of long-term orthokeratology (ortho-k) lens wear. Methods. This study investigated 136 subjects aged between 6 and 14 (9.1 ± 1.5) years old at the commencement of ortho-k treatment, who had been undergoing overnight ortho-k treatment for 24 to 72 (37.4 ± 11.9) months. Corneal refractive power and manifest refraction were measured and compared before ortho-k and 1 month after discontinuation of ortho-k lens wear. Changes in corneal curvature were analyzed. Corneal curvature data from a historical longitudinal study were used as control. Results. Compared to pre-ortho-k values, the corneal curvature became significantly flatter in the flatter meridian (?0.22 ± 0.27 D, ) and steeper in the steeper meridian (0.06 ± 0.34 D, ) after cessation of ortho-k lens wear, resulting in a significant increase in corneal toricity (0.28 ± 0.43 D, ), which is associated with an increase in refractive astigmatism (0.57 ± 0.57 D, ,). The amount of residual corneal flattening in the flatter meridian is significantly affected by the length of ortho-k treatment (,) and the baseline age of subject (,), but not by the baseline spherical or cylindrical refractive error (both ). In the historical control group, there is no significant change in the corneal curvature over two years in children wearing spectacle lenses (both meridians, ). Change of corneal toricity was more significant in the ortho-k group than in the spectacle control group ().Conclusions. Long-term ortho-k lens wear increases corneal toricity after discontinuation of the treatment, which is associated with an increase in refractive astigmatism. A more pronounced change in corneal toricity was found in subjects who were younger to start ortho-k and have been in a longer period of treatment. This trial is registered with http//www.chictr.org.cn (ChiCTR-TNRC-11001210).