Changes in choroidal and retinal thickness 6 months before and during 18 months of orthokeratology lens treatment in myopic children.

purposeTo investigate changes in choroidal and retinal thickness before and during myopia control treatment with orthokeratology lenses (OKL) in myopic children.

methodsThis was a sub-study of CONTROL and CONTROL2 studies. The present study was a 2-year, prospective, single-group interventional study consisting of a 6-month pre-treatment observation period followed by 18-month OKL treatment. Choroidal and retinal thicknesses were measured using a 3D macula scan with swept-source optical coherence tomography. All thickness measures were corrected for magnification using the Imagenet6 software. Axial length was measured using Lenstar LS900 and corrected for change in central corneal thickness. Data were collected at three pre-treatment visits and seven post-treatment visits (from Day 3 up to 18 months).

resultsThe 20 study participants had a mean age of 11.2 ± 1.9 years, median cycloplegic spherical equivalent refractive error of -2.58 diopters (range - 4.75 to -1.00) and mean axial length of 24.56 ± 0.63 mm. During the pre-treatment period, there was a statistically significant decrease in retinal thickness of -1.44 μm (p = 0.038, SE 0.70, 95% CI -2.82 to -0.08), but a significant increase was seen after initiation of OKL treatment. Thickness peaked at 2.54 μm (p < 0.001, SE 0.72, 95% CI 1.13 to 3.95) at the 6-month follow-up. We observed a tendency for the choroidal thickness to decrease during the pre-treatment period (-5.96 μm, p = 0.12, SE 3.78, 95% CI -13.37 to 1.46) and then a statistically significant increase after treatment initiation with a peak of 11.95 μm after 1 month of treatment (p = 0.003, SE 4.08, 95% CI 3.94 to 19.96). Short-term change in choroidal thickness after treatment initiation did not correlate with change in overall eye length defined as subfoveal choroidal thickness plus axial length adjusted for post-treatment change in central corneal thickness. For each individual participant, the choroidal thickness and retinal thickness were highly positively correlated at each visit throughout the study (p < 0.001, 95% CI 0.69 to 2.09, linear mixed model).

conclusionTreatment with OKL increased both retinal and choroidal thickness in myopic children. Short-term change in choroidal thickness was not a predictor for growth of the overall eye length. Further studies of the presumed structural changes in the choroid and the retina are warranted.