AIM: To observe and analyze the effectiveness and safety of wearing corneal refractive therapy(CRT)and vision shaping treatment(VST)designed orthokeratology in controlling myopic progression in adolescents with low E-value corneal morphology.

METHODS: This prospective study involved 100 cases(100 eyes)of adolescent myopia patients fitted with orthokeratology at our optometry clinic from January 2020 to December 2021. The data of right eye were collected for research, and they were divided into low myopia group(-1.00 to -3.00 D)and moderate myopia group(-3.25 to -5.00 D)according to spherical equivalent, with 50 cases in each group. Each group of patients was further randomly divided into the CRT group and the VST group, with 25 cases in each group. Uncorrected visual acuity, refractive error, axial length(AL), tear film break-up time(BUT), corneal endothelial cell density, corneal staining grading, lens decentration, and refractive power at 15°-30° were measured before and after wearing orthokeratology, with a follow-up duration of 1.5 a.

RESULTS: The uncorrected visual acuity of CRT and VST subgroups in the low myopia group showed no statistical significance at any time point after wearing orthokeratology. However, in the moderate myopia group, CRT subgroup showed better uncorrected visual acuity than the VST subgroup, with significant differences at 1 d and 1 wk(t=-9.474, -12.067, both P<0.01); no significant differences were noted at other time points. After wearing lens for 6 mo and 1.5 a, the AL growth for the CRT subgroup in low and moderate myopia was less than the VST subgroup, with no statistically significant differences. There were no statistically significant differences in binocular BUT and corneal endothelial cell density after wearing lens for 6 mo and 1.5 a. Corneal injury was lower in the CRT subgroup than that in the VST subgroup, but the difference was not statistically significant(Z=-1.803, P=0.071). Lens decentration was significantly better in the CRT subgroup than in the VST subgroup(Z=-4.629, P<0.001). In the periphery of the retina at 15°-30°, there were no significant differences in the amount of myopic defocus between the two groups, while it was statistically significant at 1, 3, and 6 mo in the moderate myopia subgroup(t=-3.949, P=0.008; t=-5.833, P<0.001; t=-6.231, P<0.001), indicating that CRT subgroup could produce a greater amount of myopic defocus.

CONCLUSION: For patients with low E-value corneal morphology, CRT, using the vector height at 8 mm on the cornea for fitting, is not limited to the corneal E-value. It shapes faster and improves uncorrected visual acuity after shaping, especially for moderate myopia, achieving better daytime vision. In terms of controlling myopia, CRT fitting elevates return zone depth(RZD), creating a small central optical zone to produce more peripheral myopic defocus. However, there was no significant difference between the two groups in controlling AL growth. Both groups showed minimal corneal damage, indicating consistent safety in myopia control.