Axial Length in Orthokeratology Patients: Large Case Series

1.1.Purpose: To evaluate axial length measurements obtained over a three-year period in children undergoing Orthokeratology (Ortho-K). 1.2.Methods: Patient records were identified from a specialty contact lens practice. Data were obtained from myopic patients who were prescribed Ortho-K wear. Demographic data at baseline included age at commencement of Ortho-K and ethnicity. Clinical data recorded at baseline and at years 1, 2 and 3 included subjective refraction, corneal topography, corneal curvature, axial length, pupil size, and lens design, changes in lens parameters, lens wear habits, wearing time and unaided visual acuity. The primary outcome measure was change in axial length during the study period. 1.3.Results: 194 eyes of 97 subjects were included in data analysis. Mean age at start of Ortho-K was 10.4 years (SD=1.9). Mean axial length was 24.59 mm (SD=0.85) at baseline and 24.87 mm (SD=0.87) at the three year evaluation, for a mean change in axial length of 0.28 mm (SD=0.64). 65.5% of eyes (n=127) showed little or no change ( 1.0 mm increase in axial length during the 3-year study period. Linear mixed regression analysis showed a significant association between older age at initiation of Ortho-K and less increase in axial length (p=0.0077). Axial length changes were not associated with duration of wear (both hours/night and nights/week) or baseline corneal curvature. 1.4.Conclusion: Use of Ortho-K may help reduce axial length elongation in myopic eyes. Age of the initial treatment is a key factor. The baseline of cornea curvature and duration of the wear are not directly associated with treatment outcome. Of note, during the three-year study, 65.5% of treated eyes (n=127) showed a minimal or clinically insignificant increase of axial length (<0.5mm). Early treatment should be considered.