Orthokeratology Increases Myopic Defocus and Slows Axial Growth

The relative peripheral refraction (RPR) of children with myopia demonstrates relative myopic defocus after wearing orthokeratology (OK) lenses, according to a study published in Clinical and Experimental Optometry. Axial length (AL) growth rate is smaller among these children compared with children who wear spectacle lenses.

Researchers enrolled 31 children wearing OK lenses (mean age, 10.9years) in the study and compared them with a control group (n=31) wearing single vision spectacles. Participants in the OK lens group were further stratified into 2 groups according to AL growth progression consisting of fast (n=15; >0.017 mm/month) and slow (n=16; <0.017 mm/month) progressors.

Participants underwent multispectral refraction topography to obtain total RPR along with RPR in the superior area, inferior area, temporal area and nasal areas. RPR was also obtained in the visual fields of 15°, 30°, and 45°. Investigators compared AL and RPR of the children in the OK lens group with control individuals and examined differences in age, initial spherical equivalent (SE), and initial wearing period, and compared AL and RPR growth among fast and slow progressors in the OK lens group.

According to the report, RPR among all measured visual fields, total RPR, and RPR in the inferior, temporal, and nasal regions were significantly smaller among children treated with OK lenses compared with control group participants (all P < .05). Slow progressing OK group members exhibited smaller total RPR, RPR in the nasal area, and RPR at all measured visual fields compared with fast progressing OK group participants (all P < .05). 

AL growth rate positively correlated with total RPR (R, 0.383; P =.040), RPR in the nasal area (r, 0.395; P =.034), RPR at 30° (r, 0.408; P =.028), RPR at 45° (r, 0.377; P =.044), and RPR in the visual field from 15 to 30° (r, 0.390; P =.036).

“The growth rate of AL was positively correlated with [nasal RPR], which suggested that imaging signals of temporal external objects (wider than centre fixation targets and nasal objects) on the retina may be associated with eye development,” according to researchers. “The growth rates of AL were positively correlated with [total RPR, RPR at 30°, RPR at 45°, RPR in the visual field from 15-30°], which suggests that the more retinal peripheral relative myopic defocus induced by OK lenses, the less AL grew.”

Study limitations include a small sample size, short observation time, poor repeatability of peripheral refraction measurements in the various quadrants, and the inability to measure RPR before OK lens treatment.