Authors: Zhang Xu, Wang Yan, Xu Lulu
To evaluate changes in corneal high-order aberrations after the wearing of orthokeratology contact lenses and to study the factors influencing those changes.
A series of case-observational method was used.Data on 46 right myopic eyes of 46 children fitted for orthokeratology were continuously collected from January to April 2018.The corneal morphology, the e values of the anterior and posterior corneal surface in the nasal, temporal, superior and inferior zones within 6 mm were measured with Pentacam Anterion Segment Analysis System before and one month after the wearing of orthokeratology contact lens.Zernike Analysis System was used to calculate the values of Z33, Z3-3, Z31, Z3-1, and Z40 on the anterior and posterior surfaces and on the total cornea within a diameter of 6 mm.This study conformed to the tenets of the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Baoding Yinghua Eye Hospital (No.YKLL-2018-1-01). Written informed consent was obtained from each child and their guardians prior to entering the study cohort.
Compared to the values recorded prior to orthokeratology contact lens wear, the horizontal coma, vertical coma, and spherical aberration of the total cornea and anterior corneal surface were drifted positively after lens wear; the horizontal coma and spherical aberration of the posterior corneal surface were drifted negatively after lens wear; and the differences were statistically significant (all at P<0.05). Before wearing orthokeratology contact lenses, eNf, eTf, eIf, eSf and eMf values were 0.580(0.450, 0.670), 0.455(0.378, 0.513), 0.485(0.268, 0.553), 0.665(0.578, 0.740) and 0.505±0.015, respectively, and after wearing orthokeratology contact lenses, eNf, eTf, eIf, eSf and eMfvalues were 0.285(-0.635, 0.665), -0.605(-0.813, -0.335), -0.545(-0.765, 0.305), -0.335(-0.705, 0.423) and -0.247±0.058, respectively.Compared with the conditions prior to wearing orthokeratology contact lens, the anterior corneal surface in all parts changed from steep to flat after lens wear, with statistically significant differences between them (all at P<0.05). The results of multiple stepwise linear regression showed that after wearing orthokeratology contact lens, the spherical aberration of the total cornea was moderately negatively correlated with the corneal e value and the initial diopter (rs=-0.626, -0.450; both at P<0.05), the horizontal coma of the total cornea was moderately negatively correlated with the temporal e value (rs=-0.391, P=0.004); the spherical aberration of the anterior corneal surface was moderately negatively correlated with the corneal e value and the initial diopter (rs=-0.612, -0.432; both at P<0.05); the horizontal coma of the anterior corneal surface was moderately negatively correlated with the temporal e value (rs=-0.400, P=0.003); and the horizontal coma of the posterior corneal surface was negatively correlated with the horizontal coma of the anterior corneal surface (rs=-0.380, P=0.009).
The spherical aberration and coma of the total cornea and anterior corneal surface drift positively after wearing orthokeratology contact lens, and the spherical aberration and horizontal coma of the posterior corneal surface drift negatively.The refraction and deformation of the anterior surface of the cornea are important factors affecting variation in corneal high-order aberrations.