While both axial length and central corneal power change after two years of myopia therapy with orthokeratology (OK), a new study suggests the two measures do not correlate with each other.

European researchers studied 31 pediatric patients with myopia −0.75D to −4.00D and astigmatism ≤1.00D who underwent OK therapy. They collected data on refractive changes and axial length at baseline and then at three and 24 months after initiating OK treatment.

They found axial length increased by 0.48 ±0.18mm, which corresponded to an increase of 1.94±0.74%. But when they compared the axial length changes to corneal power changes, they realized the two were not correlated for any of the corneal regions they studied (nasal, temporal, inferior and superior) relative to baseline. Inhibition of axial length growth in OK patients “is not a consequence of a relative myopic shift in the peripheral retinal image induced by changes in corneal power,” the authors conclude.

“The reduction in central corneal power and relative increase in paracentral and pericentral power induced by OK over two years were not significantly correlated with concurrent changes in axial length of white European children,” the study concludes.