Anterior segment biometry and accommodative function after orthokeratology

Objective To investigate the changes in accommodative response and anterior segment biometry during accommodation in young progressive myopes who wear overnight orthokeratology lenses. Methods Eighteen children (age: 14.4 ± 2.6 years) were enrolled in this prospective experimental study and were tested before wearing orthokeratology (OK) lenses and after wearing them for three months. Using a Badal optical system, the refractive error of each subject was corrected before and after lens wear, and then accommodative stimuli of 3 D and 5 D were presented. A custom-built optical coherence tomographer (OCT) with a long scan depth was used to image the entire anterior segment through the pupil, and to obtain the anterior segment biometry including pupil diameter (PD), anterior chamber depth (ACD), lens thickness (LT) and the lens anterior surface's radius of curvature (LAC). An auto-refractometer (WAM-5500) was used to measure ocular refraction during accommodation, which was used to calculate the accommodative response. The measurements of anterior segment biometry and accommodative response were repeated twice under each accommodative state. Results After wearing orthokeratology lenses for one to three months, an improvement in the accommodative response was evident under both the 3 D (1.72±0.59 D vs. 2.42±0.84 D) and 5 D (3.09±0.63 D vs. 3.61±0.86 D) accommodative states (paired t-test, t=2.84, 2.12, P<0.05). During accommodation, ΔPD, ΔACD, ΔLT, and ΔLAC changed obviously. Compared with baseline (before wearing OK lenses), accommodation-related changes in ΔACD (3 D: -0.11±0.04 mm vs. -0.16±0.06 mm, t=3.88, P<0.01; 5 D: -0.15±0.05 mm vs. -0.20± 0.07 mm, t=2.37, P<0.05), ΔLAC (3 D:-2.60±0.79 mm vs. -3.81±1.08 mm, t=3.96, P<0.01; 5 D:-3.57±1.14 mm vs. -4.32±1.36 mm, t=2.08, P<0.05) and ΔLT (3 D: 0.22±0.13 mm vs. 0.27±0.06 mm, t=-1.94, P<0.05; 5 D: 0.26±0.09 mm vs. 0.30±0.10 mm, t=-1.99, P<0.05) showed statistically significant increases. Conclusion After wearing orthokeratology lenses for 3 months, the accommodative response and changes in the anterior segment biometry increase in myopic children. Key words: Orthokeratology; Myopia; Accommodation,ocular; Anterior segment biometry