Peripheral refraction, relative peripheral refraction, and axial growth: 18-month data from the randomised study-Clinical study Of Near-sightedness; TReatment with Orthokeratology Lenses (CONTROL study).

PURPOSE: To investigate changes in peripheral and relative peripheral refraction (RPR) during orthokeratology lens (OKL) use in children, and predictors for myopia progression in a randomized controlled trial. METHODS: Refraction and axial length (AL) were measured at baseline, 6, 12, and 18 months for children aged 6-12 years, with myopia of 0.5 to 4.75 dioptres (D) spherical component randomized to either OKL or single-vision spectacles (SVS) at baseline. Cycloplegic spherical equivalent refractive error (SEQ) was measured on-axis and eccentric at 10°, 20°, and 30° during nasal and temporal gaze in the horizontal plane with Shin-Nippon Nvision-K 5001. RPR was computed as SEQ(eccentricity) minus SEQ(on axis) . AL was measured with Lenstar LS900. RESULTS: Twenty-one and 28 subjects from the OKL and SVS groups, respectively were available for analysis. OKL wear induced significant myopic RPR at all eccentricities (p ≤ 0.004) whereas peripheral refraction only changed in two out of six eccentric measuring points. Baseline peripheral refraction SEQ at all eccentricities, baseline on-axis SEQ, and baseline RPR at 30° nasal eccentricity were positively correlated to treatment efficacy defined as change in AL. CONCLUSION: We found no correlations between change in RPR and treatment efficacy defined as change in AL. Interestingly, our results suggest that the central emmetropisation that occurs during OKL-use accounts for most of the optical changes and to a lesser extent the mid-peripheral plus-zone of the lens.

Repeatability and inter-observer variation of choroidal thickness measurements using swept-source optical coherence tomography in myopic danish children aged 6-14 years.

PURPOSE: To estimate repeatability and inter-observer variation of choroidal thickness measurements in myopic Danish children aged 7-14 years using swept-source optical coherence tomography (SS-OCT). METHODS: Thirty-nine children were enrolled. Optical correction was single-vision spectacles (SVS) or orthokeratology lenses (OKL). Three repeated 7 × 7 mm 3-dimensional SS-OCT macula scans and three repeated 9 mm SS-OCT line scans were collected for each child using a DRI OCT Triton. Choroidal thickness was measured using three different methods: line scan method 1 (LM1), line scan method 2 (LM2) and 3D macula scan method (3DM). Segmentation was adjusted if needed. Coefficients of repeatability (CR) and limits of agreement (LoA) were calculated. RESULTS: The CRs ranged from 13.4 to 23.9 µm, 14.5 to 26.2 µm and 5.2 to 10.7 µm for LM1, LM2 and 3DM, respectively. The LoA ranged from -22.9 to +31.5 µm, -23.3 to +32.2 µm and -10.2 to +12.4 µm for LM1, LM2 and 3DM, respectively. Segmentation was adjusted in most scans (63%-92%). Mean choroidal thickness ranged from 142.2 ± 47.2 to 253.8 ± 60.9 µm and 190.1 ± 64.0 to 299.0 ± 55.8 µm for the SVS and OKL groups, respectively, measured by 3DM. CONCLUSION: The 3DM was the most repeatable method in this paediatric population. It yielded a CR of 10.7 µm, confidence interval 2.4 µm, which makes the minimal detectable difference between two measurements 13.1 µm. Most inter-observer variation could be explained by the intramethod variation. Segmentation adjustment on 3D macula scans did not increase CR on a group level.