Researchers evaluated how long-term orthokeratology affects corneal biomechanical properties and assessed whether early biomechanical changes can predict axial elongation in pediatric patients with myopia in a 25-month prospective study.
The researchers followed 37 pediatric patients aged 8 to 16 years with low to moderate myopia over a 24-month period of nightly orthokeratology (ortho-k) lens wear, followed by a 1-month discontinuation period. Corneal biomechanical assessments were conducted using the Corvis ST device at multiple time points, including baseline, during treatment, and following discontinuation. Axial length (AL) was measured at baseline, at 1 month, and then every 6 months.
Significant early changes in corneal biomechanical properties (CBP) were observed within 2 weeks of treatment initiation. Specifically, central corneal thickness, biomechanically corrected intraocular pressure (bIOP), integrated inverse concave radius (Integr Radius), and Ambrósio’s relational thickness horizontal (ARTh) all decreased significantly. Long-term trends included progressive decreases in stiffness parameter at first applanation (SP-A1), bIOP, and ARTh.
After ceasing ortho-k lens wear for 1 month, most CBPs returned to baseline values except for SP-A1 and bIOP, which remained significantly altered compared with pretreatment levels. “This suggests the responsiveness of the cornea to external stresses induced by ortho-k and subsequent restoration to its original state and affirms the reversibility of the effects of prolonged ortho-k use,” wrote lead study author Hou-Ren Tsai, of the Department of Ophthalmology at the Hualien Tzu Chi Hospital at the Buddhist Tzu Chi Medical Foundation in Hualien, Taiwan, and colleagues.
The researchers also described the potential “clamping effect” of ortho-k lenses—a phenomenon that inhibits overnight central corneal swelling and results in gradual residual thickening in the stromal midperiphery.
Multiple linear regression identified early changes in CBPs as predictive of axial elongation at 1 and 2 years; specifically, decreases in deformation amplitude (DA) ratio and SP-A1 at 2 weeks. “A smaller reduction in the DA ratio at 2 weeks appears to be linked to better axial elongation control,” the study authors wrote. Comparatively, a greater decrease in SP-A1 at 2 weeks was associated with increased axial elongation. The predictive model using baseline and 2-week values yielded R² = 0.549 (1 year) and R² = 0.579 (2 years) for AL increment.
Study limitations included a relatively small, ethnically homogeneous sample (Chinese children), and subgroup analyses were limited because of the sample size. The 1-month discontinuation period may not have captured longer-term rebound effects or complete biomechanical recovery.
“These results may guide clinicians to optimize ortho-k treatment, as CBPs assessed with the Corvis ST can play a pivotal role in predicting AL progression,” the study authors concluded.
No conflicts of interest were reported.
