Bilateral axial length growth patterns of myopic anisometropes undergoing sequential monocular to binocular...

To investigate bilateral axial length (AL) growth patterns and interactions of myopic eyes in anisometropic children during unilateral orthokeratology (OK) treatment in their singularly myopic eyes (Eyes1), followed by bilateral treatment when their second eyes (Eyes2) developed myopia.

This study enrolled 94 eyes from 47 anisometropes (20 males). All patients had undergone monocular OK treatment for > 1 year followed by binocular treatment for > 1 year. Axial growth of Eyes1 and Eyes2 during the first year of monocular treatment (Stage 1), average annual axial elongation during the monocular treatment period, and axial elongation during the first year of binocular treatment (Stage 2) were respectively termed: S1E1 and S1E2, Annual E1 and Annual E2, and S2E1 and S2E2. Associations between AL growth and age, sex, interval time, and ocular parameters were analysed using correlation and generalised estimating equation (GEE) analysis.

During the monocular period, Eyes1 showed less AL growth (S1E1: 0.05 ± 0.18 mm; Annual E1: 0.05 ± 0.21 mm) than Eyes2 (S1E2: 0.51 ± 0.24 mm; Annual E2: 0.52 ± 0.25 mm) (all p < 0.001). During the binocular period, there was no significant difference between S2E1 and S2E2(0.21 ± 0.14 mm v. 0.19 ± 0.17 mm, p = 0.951). Between monocular and binocular periods, Eyes1 had significantly higher S2E1 compared to S1E1 and Annual E1 (both p < 0.001), and Eyes2 had significantly lower S2E2 than S1E2 and Annual E2 (both p < 0.001). In the GEE model, spherical equivalent refraction (SER) and between periods interval time showed independently significant associations with AL growth after adjusting for age and sex.

Orthokeratology can significantly control AL growth in unilateral myopia. AL growth of the initial myopic OK-treated eyes accelerated relative to the monocular period when contralateral eyes developed myopia and assumed OK treatment. During the binocular treatment phase, OK lenses showed moderate and comparable effects on AL retardation across both eyes.