Pediatric patients who experience axial length (AL) reduction following orthokeratology (ortho-k) treatment may undergo ocular biometric parameter changes, which include crystalline lens thickening, decreased anterior chamber depth (ACD), and vitreous chamber depth thinning, according to a study published in Eye and Vision. These changes may be indicators for better myopia control effects, the report suggests.
Researchers retrospectively reviewed data from 75 children who completed 1 year of ortho-k treatment and stratified them into groups based on AL change. Group 1 participants experienced AL reduction during treatment (mean AL change, -0.18 mm; n=37; 20 girls; mean age, 11.49 years) while group 2 participants experienced AL elongation (mean AL change, 0.28 mm; n=38; 18 girls; mean age, 10.92 years). Participants underwent refraction and ocular biometry measurements including AL, central corneal thickness (CCT), ACD, and crystalline lens thickness. All participants were fit with the same 4-zone ortho-k lens, and follow-up was performed at 1-day, 7-day, and 1-, 6-, and 12-month visits.
After 1 year of treatment, children in group 1 had a decreased ACD (P <.001), thickened crystalline lens thickness (P =.002), thinned vitreous chamber depth (P <.001), and smaller treatment zone (P =.03) compared with group 2 participants. There were no significant differences for CCT or pupil diameter.
The report shows that AL reduction was negatively associated with baseline age (β, -0.048; 95% CI, -0.083 to-0.013; P =.009) and positively associated with the treatment zone (β, 0.024; 95% CI, 0.009-0.040; P =.003).
A total of 16.22% of study participants had an AL reduction of more than 0.25 mm, which researchers speculate is the result of choroidal changes.
“The choroid has a crucial role in relaying signals derived from the retina to the sclera, further altering the synthesis of scleral extracellular matrix molecules and changing the size of the eye,” according to researchers. “Therefore, we hypothesized that choroidal thickening after wearing Ortho-K lenses might modulate the sclera and thus further affect AL.”
Study limitations include failure to measure spherical equivalent refraction after ortho-k treatment, a short study duration, and small sample size.
Tang T, Li X, Chen S, et al. Long-term follow-up of changes in ocular biometric parameters in orthokeratology lens wearers with relatively large-scale axial length reduction. Eye Vis. Published online February 2, 2023. doi:10.1186/s40662-022-00324-z