Biomedical Research

Purpose: Our study aimed to investigate and compare the effectiveness of general and toric orthokeratology lenses in corneal toricity using the vector analysis.

Methods: A retrospective observational study was carried out. 19 patients, 37 eyes, (spherical group) were fitted with spherical ortho-k lenses and 15 patients, 30 eyes, (toric group) were fitted with toric ortho-k lenses. Data collection was performed at baseline and 1 d, 1 week, 1 month, 3 months after the commencement and included visual acuity, corneal topography, axial length and biomicroscopy examinations. Changes in corneal toricity were evaluated using vector analysis.

Results: Ortho-k significantly reduced the manifest myopia and improved UCVAs in both groups after 1 d, 1 week, 1 month and 3 months of lens wear. The median subjective myopia of spherical group and toric group at base line was -3.85 ± 1.29 D and -3.66 ± 1.69 D (P>0.05). After wearing ortho-k lenses for 1 d, 1 week, 1 month and 3 months, the UCVAs improved steadily in both groups, the differences between the two groups were insignificant in 1 d, 1 week, 1 month, but with significant difference only in 3 months (0.07 ± 0.05 vs. 0.00 ± 0.07, P<0.05). The corneal J0 vector values were -0.98 ± 0.60 and -1.19 ± 0.25 D (P>0.05) and the J45 vector values were 0.09 ± 0.20 and 0.09 ± 0.46 D (P>0.05), respectively. The differences of corneal J0 vector values between the two groups were significant for all the time points (t=-3.34, -1.94, -1.41, -1.82, P<0.05). The differences of corneal J45 vector values between the two groups were not significant. The percent of patients in spherical group and toric group who reported visual disturbance symptoms were 15% and 0%, respectively.

Conclusions: For low-moderate myopias with moderate-high astigmatism, despite the similar UCVAs achieved in two groups, Toric design lens were more effective in reducing corneal toricity.

Author(s): Chang Feng, Wang Tao, Chen Xiao, Chen Yunhui, Li Mei, Zhou Ping, Zhou Hezheng
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