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PURPOSE. This retrospective longitudinal study aimed to examine the relationship between ocular higher-order aberrations (HOA) and axial eye growth in young myopic children undergoing orthokeratology (ortho-k) treatment. METHODS. Axial length and ocular HOA, measured under cycloplegia annually over a 2-year period from the right eyes of myopic children, who previously completed ortho-k clinical trials, were retrieved. Linear mixed model analyses were applied to determine the association between ocular HOA, other known confounding variables (age, sex, and refractive error), and axial eye growth. RESULTS. Data from 103 subjects were analyzed. The root-mean square (RMS) values of total ocular HOA (third to sixth orders combined), spherical (Z0 4 and Z0 6 combined), and comatic (Z− 3 1, Z1 3, Z− 5 1, and Z1 5 combined) aberrations increased by approximately 3, 9, and 2 times, respectively, after 2 years of ortho-k treatment. After adjusting for age, sex, and refractive error, higher RMS values of total HOA and spherical aberrations were associated with both longer axial length and slower axial elongation (all P < 0.01). For individual Zernike term coefficients, a higher level of positive spherical aberration (Z0 4) was also associated with longer axial length and slower axial elongation (both P < 0.01), after adjusting for baseline HOA. CONCLUSIONS. Ortho-k for myopia control significantly increases the Zernike coefficients and therefore the RMS values for a range of total ocular HOA terms or metrics in children. These findings suggest the potential role of HOA, particularly spherical aberration, as the possible mechanism of slowing axial elongation in ortho-k treatment.

Background: To investigate the influence of compression factor upon changes in ocular higher-order aberrations (HOAs) in young myopic children undergoing orthokeratology treatment. Methods: Subjects aged between six and < 11 years, with low myopia (0.50–4.00 D inclusive), low astigmatism (≤ 1.25 D), and anisometropia (≤ 1.00 D), were randomly assigned to wear orthokeratology lenses of different compression factors in each eye (one eye 0.75 D and the fellow eye 1.75 D). HOAs were measured weekly over one month of lens wear. Wavefront analysis was conducted over a 5-mm pupil using a sixth order Zernike polynomial expansion. Linear mixed models were used to examine the individual Zernike co-efficients and specific root-mean-square (RMS) error (spherical, comatic, total HOAs) metrics and their changes between the two eyes during the study period. Results: Twenty-eight myopic (mean manifest spherical equivalent refraction: −2.10 ± 0.58 D) children (median [range] age: 9.3 [7.8–11.0] years) were analysed. Significant interocular differences in HOAs at baseline were observed for (Z6 -6) and ((Z6 -4) only (both p < 0.05). During the lens wear period, eyes fitted with the increased compression factor showed greater changes in primary spherical aberration (Z4 0, p = 0.04) and RMS values for spherical and total HOAs (both p < 0.01). Considering data from both eyes together, after adjusting for the paired nature of the data, some other Zernike terms (Z3 1) and (Z6 0), both p < 0.01) and the RMS value of comatic aberrations (p < 0.001) significantly increased after one month of orthokeratology treatment. The increase in primary spherical aberration (Z4 0) was positively correlated with the reduction in spherical equivalent refractive error, but only in eyes fitted with the increased compression factor (r = 0.69, p < 0.001). Conclusions: Increasin

Objective: To investigate the repeatability of choroidal thickness measurements determined from enhanced depth imaging optical coherence tomography (EDI-OCT) images of eyes after wearing single-vision spectacles (SV) and orthokeratology (ortho-k) lenses. Methods and analysis Two EDI-OCT images of 40 children (SV: 20, ortho-k: 20) taken at a single visit were analysed twice. Subjects in the ortho-k group had been wearing ortho-k for 1–4 weeks. The choroidal thickness was determined from each image using a graph theory-based software and, where appropriate, manual correction of choroidal boundaries was undertaken by an experienced examiner. Results The mean (±SD) choroidal thickness was 227.3±42.2 µm for the SV subjects and 251.1±54.4 µm for the ortho-k subjects. The interimage differences in choroidal thickness were −0.99±3.54 and −1.14±5.03 µm for the SV and ortho-k subjects, respectively, and the limits of agreement were +5.96 to −7.93 and +8.72 to −11.00 µm, respectively. Conclusion: The coefficients of repeatability of choroidal thickness measurements from two EDI-OCT images taken at a single visit were 7.08 µm (SV) and 10.06 µm (ortho-k), suggesting that a change in choroidal thickness of less than 10 µm may not indicate a real change resulting from ortho-k lens wear.

Purpose: To determine the influence of compression factor upon changes in axial length and choroidal thickness during and following orthokeratology treatment. Methods: Orthokeratology lenses of different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to 28 subjects (median [range] age: 9.3 [7.8–11.0] years). Ocular biometrics were measured weekly for 1 month of lens wear and after lens cessation until the refraction stabilized (mean duration: 2.8 ± 0.4 weeks). Changes between eyes, and the associations between axial shortening and choroidal thickening with other ocular biometrics were analyzed. Results: There were no significant between-eye differences in the changes of ocular biometrics (all P > 0.05). After adjusting for paired-eye data, axial length initially decreased by 26 ± 41 µm (P = 0.03) at week 1, then gradually returned to its original length. An approximate antiphase relationship of choroidal thickness (mean change: 9 ± 12 µm, P < 0.001) with axial length was observed. A significant rebound in axial length, but not choroidal thickness, occurred during the cessation period. Central corneal thinning and choroidal thickening accounted for 70% of initial axial shortening. Conclusions: Increasing the compression factor by 1.00 D did not affect changes in ocular biometrics in short-term orthokeratology. Significant axial shortening and choroidal thickening were observed during early treatment period. Axial shortening could not be entirely explained by central corneal thinning and choroidal thickening, which warrants further investigation. Translational Relevance: Initial axial shortening in orthokeratology is transient and therefore axial length remains useful for long-term monitoring of axial elongation in children.

This retrospective longitudinal analysis aimed to investigate the association between ocular higher-order aberrations (HOAs) and axial eye growth in Hong Kong children. Measures of axial length and ocular HOAs under cycloplegia were obtained annually over a two-year period from 137 subjects aged 8.8 ± 1.4 years with mean spherical equivalent refraction of -2.04 ± 2.38 D. A significant negative association was observed between the RMS of total HOAs and axial eye growth (P = 0.03), after adjusting for other significant predictors of axial length including age, sex and refractive error. Similar negative associations with axial elongation were found for the RMS of spherical aberrations (Z[4,0] and Z[6,0] combined) (P = 0.037). Another linear mixed model also showed that greater levels of vertical trefoil (Z[3,-3]), primary spherical aberration (Z[4,0]) and negative oblique trefoil (Z[3,3]) were associated with slower axial elongation and longer axial length (all P < 0.05). These findings support the potential role of HOAs, image quality and a vision-dependent mechanism in childhood eye growth.