Effects of Orthokeratology on Axial Length Elongation in Anisometropes

This study aimed to investigate the therapeutic effects of overnight orthokeratology (OK) lenses on anisometropes.

We enrolled 178 anisometropes from August 2015 to August 2017. We then divided these patients into 2 parts depending on them wearing either monocular or binocular OK lenses. In part one, 47 monocular myopic subjects (25 males and 22 females) were treated with OK lenses in the myopic eyes only. We also labeled the myopic eyes as the OK group and the contralateral nonmyopic eyes as the control group. The initial average wearing age of the subjects was 12.35 ± 2.37 years (8-16 years). The mean follow-up duration was 15.43 ± 4.88 months (7-25 months). The average spherical equivalent refraction (SER) was -2.31 ± 1.16 diopter (D) in the OK group and 0.15 ± 0.49 D in the control group (p < 0.001). In part 2, 131 binocular myopic anisometropes (56 males and 75 females) were involved in the study. The eyes with more severe myopia were assigned to the G group and the contralateral eyes to the L group. The initial average wearing age of the subjects was 12.92 ± 2.60 years ( 8-16 years). The mean follow-up duration was 17.83 ± 5.02 months (7-26 months). The average SER was -4.79 ± 1.90 D in the G group and -3.14 ± 1.88 D in the L group (p < 0.001). We calculated the axial length (AL) difference and AL elongation as our primary outcome measures.

In part one, the AL elongation in the OK group (0.21 ± 0.09 mm) was significantly lower than that in the control group (0.70 ± 0.17 mm) at 24 months (p < 0.001). Meanwhile, the AL difference exhibited a decrease of 0.50 ± 0.29 mm from a baseline of 1.08 ± 0.35 to 0.58 ± 0.25 mm at 24 months (F = 24.539, p < 0.001). In part 2, the AL had increased by 0.17 ± 0.13 mm in the G group and 0.24 ± 0.18 mm in the L group after 24-month follow-up, respectively (p < 0.001). While the AL difference decreased from 0.55 ± 0.11 mm at the baseline, to 0.48 ± 0.08 mm at 24 months, eliciting a decrement in AL difference of 0.07 ± 0.09 mm (F = 3.884, p = 0.030).

OK lenses can slow down AL growth in anisometropes and has a greater effect on reducing AL elongation in the more severely affected myopic eyes of anisometropic patients.