Purpose:
To investigate the peripheral refraction and image position during accommodation after orthokeratology (OK) treatment.
Methods:
Nineteen myopic children (10 to 14 years) between -2.50D and -4.50D (spherical equivalent) and astigmatism less than 1.50D participated in this study. Ten subjects were corrected by OK lens and nine were corrected by conventional single-vision spectacle lens (SVL). One month after lens delivery, non-cycloplegic autorefraction was measured at the fovea and 10°, 20° and 30° eccentricities in the nasal and temporal retina at the distance of 40cm with all tested eyes fully corrected for distant vision. Accommodative lag was monitored at the distance of 40cm for both groups.
Results:
In subjects with SVL correction, peripheral refraction became more hyperopic with increasing eccentricity relative to central refraction during accommodation. In subjects treated by OK, however, refractive errors became more myopic at 20° and 30° eccentricities in the nasal and temporal retina. Differences in refraction at 20° and 30° temporally between the two groups were statistically significant (P=0.005 and P<0.001, respectively). Mean accommodative lag was 0.86±0.27D in the OK subjects and 0.76±0.21D in the SVL subjects when viewing targets at the distance of 40cm, shifting the image-shell backward relative to the retina. In absolute terms, refraction at fovea and all tested eccentricities became hyperopic in SVL subjects. In contrast, refractions remained myopic at 20° and 30° temporally and were close to plano (retinal plane) at 20° and 30° nasally in OK subjects.
Conclusions:
Children who underwent OK treatment present relative myopia in the near periphery during accommodation. If near work and concurrent peripheral hyperopia put more stress on myopia progression in children, OK alleviates this situation by changing the peripheral refractive pattern to relative myopia at near.
Clinical Trial:
http://www.chictr.org ChiCTR-TNRC-11001210
Keywords: myopia • accommodation • contact lens