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Study finds corneal power change predicts axial growth after ortho-K
In a study to evaluate the relationship between corneal refractive power change after orthokeratology treatment, researchers found that the measurements can predict myopia progression.
Zhong and colleagues evaluated 27 Chinese children, 9 to 14 years old, over a 24-month period. After the children underwent a corneal shaping process resulting from ortho-K treatment, researchers measured the corneal refractive powers along the nasal, temporal and inferior axes. They selected the maximum power change along each axis and divided them into two groups, level 1 and level 2, determined by whether the value was above or below average. They also measured axial length every 6 months, according to the study abstract.
The researchers reported in Optometry and Vision Science that changes in corneal refractive power significantly affected axial elongation. Results showed that patients with larger corneal power changes (level 2) experienced axial elongation by 54%; patients with smaller corneal power changes (level 1) experienced axial elongation by 69%.
"Subjects with larger magnitude of corneal relative peripheral power change along specific axes after ortho-K treatment experienced slower axial elongation by the end of 24 months," the authors concluded. "This effect might be mediated by the induction of greater amount of relative myopic defocus on the peripheral retina. Our study lends weight to potential ortho-K lens designs for myopia control in children."
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Optom Vis Sci. 2014;doi: 10.1097/OPX.0000000000000183.