Scleral capsule biophysical properties in the prognosis of the stabilizing effectiveness of orthokeratological myopia correction

Abstract

Purpose: determine the impact of biophysical properties of the scleral capsule on the stabilizing effect of orthokeratological correction in progressive myopia.
 Material and methods. In 57 patients (114 eyes) aged 8-18 (average age 12.5 0.6 years) with myopia from 1.0 to 7.0 D, acoustic scleral density (ASD) was tested. All patients used (during different terms) orthokeratological (OK) lenses Contex OKE-System during the night time. To measure ASD (in conventional units) we used digital analysis of ultrasound tissue histograms obtained with a multifunctional ultrasound diagnostic device Voluson 730 Pro (Kretztechnik AG) with a linear frequency sensor of 10 to 16 mHz. ASD was measured in the posterior pole and in the superior temporal quadrant of the equatorial zone. The anteroposterior axis (APA) was measured by ultrasound biometry using an ultrasound device A/B Scan System Model 837 (Allergan Humphrey, USA). Myopia progression was found in 18 eyes of 9 patients with APA increase over 0.1 mm in 6 months, i. e. in 15.5% of cases, while the remaining 48 patients (96 eyes) showed no myopia progression over the follow-up period.
 Results. APA was less in eyes with progressive myopia as compared to those with stabilized myopia, both in the equatorial and the posterior pole zones. In progressive myopia, mean APA was 213 3.6 units in the posterior pole and 208 2.19 units in the equatorial zone. In cases of stable myopia, APA was 2.1% higher in the posterior pole area (217 1.3 units) and 1.86% higher in the equatorial area (212 1.4 units). On average, APA in stable myopia was 4 2.0 units higher than in progressive myopia (р 0.05).
 Conclusion. The APA parameter could serve as a prognostic criterion for the myopia course by OK-correction, and as an indicator for choosing treatment tactics.