Pauline Cho’s research while affiliated with Sichuan University and other places

Purpose To investigate the change in subfoveal choroidal thickness (SFChT) in bilateral anisomyopic children undergoing orthokeratology (ortho‐k) over 2 years and the association with axial elongation (AE). Methods SFChT, axial length and refractive data from 26 bilateral anisomyopic subjects (aged 7–12 years) who participated in a 2‐year prospective orthokeratology study were analysed using generalised estimating equations and linear mixed models. Results SFChT in the more myopic eyes (MME) (at least 1.50 D more myopia than the fellow eye) became thicker (mean ± standard deviation change, 25 ± 20 μm) after 6 months of ortho‐k lens wear (p < 0.001) and remained stable thereafter (p ≥ 0.13), but no such change was observed in the less myopic eyes (LME) (p ≥ 0.07). Combining data from both eyes, the baseline SFChT and SFChT change after 2 years of ortho‐k treatment were associated with 2‐year AE [generalised estimating equation (accounting for the inclusion of both eyes): β = 0.002, p = 0.03 and β = −0.005, p < 0.001, respectively]. Conclusions After 2 years of ortho‐k treatment, the increase in the SFChT occurred exclusively in the MME. Considering both eyes, greater SFChT thickening was associated with less eye growth.

Purpose To explore the associations between myopia defocus dosage (MDD), aberration coefficients (primary spherical aberration and coma), and axial elongation in children undergoing orthokeratology (ortho-k) with back optic zone diameters (BOZD) of 5 mm and 6 mm over 2 years. Methods Data from 80 participants from two ortho-k studies were analyzed: 22 and 58 children wore lenses with 5-mm and 6-mm BOZD, respectively. Four MDD metrics were calculated from corneal topography data over a 5-mm pupil for the 1-month and 24-month visits: the circumferential, flat, steep, and volumetric MDD. Corneal primary spherical aberration and comatic aberrations were also extracted from topography data over a 5-mm pupil. Linear mixed modelling was performed to explore the associations between the MDD, corneal aberrations, and axial elongation over 2 years, while controlling for confounding factors (e.g., baseline age and sex). Results Participants in the 5-mm BOZD group displayed less axial elongation than the 6-mm BOZD group over 2 years (0.15 ± 0.21 mm vs. 0.35 ± 0.21 mm, P < 0.001). A greater volumetric MDD was observed in the 5-mm BOZD group compared with the 6-mm BOZD group at the 1- and 24-month visits (both P < 0.001). No significant differences were observed between the two groups for the other MDD metrics or corneal aberration coefficients (all P > 0.05). Less axial elongation was associated with a greater volumetric MDD at the 1- and 24-month visits (both β = –0.01, P < 0.001 and P = 0.001), but not with any other MDD metrics or corneal aberrations (all P > 0.05). Conclusions The volumetric MDD over a 5-mm pupil after 1 month of ortho-k lens wear was associated with axial elongation after 24 months, and may be a useful predictor of future axial elongation in children undergoing ortho-k.

Purpose To investigate axial elongation (AE) and changes in relative peripheral refraction (RPR) in anisomyopic children undergoing orthokeratology (ortho‐k). Methods Bilateral anisomyopic children, 7–12 years of age, were treated with ortho‐k. Axial length (AL) and RPR, from 30° nasal (N30°) to 30° temporal (T30°), were measured at baseline and every 6 months over the study period. AE, changes in RPR and changes in the interocular AL difference were determined over time. Results Twenty‐six of the 33 subjects completed the 2‐year study. The AE of the higher myopic (HM) eyes (at least 1.50 D more myopia than the other eye) (0.26 ± 0.29 mm) was significantly smaller than for the less myopic (LM) eyes (0.50 ± 0.27 mm; p = 0.003), leading to a reduction in the interocular difference in AL (p = 0.001). Baseline RPR measurements in the HM eyes were relatively more hyperopic at T30°, N20° and N30° (p ≤ 0.02) and greater myopic shifts were observed at T20° (p < 0.001), T30° (p < 0.001), N20° (p = 0.02) and N30° (p = 0.01) after lens wear. After 2 years of ortho‐k lens wear, temporal–nasal asymmetry increased significantly, being more myopic at the temporal locations in both eyes (p < 0.001), while AE was associated with the change in RPR at N20° (β = 0.134, p = 0.01). The interocular difference in AE was also positively associated with the interocular difference in RPR change at N30° (β = 0.111, p = 0.02). Conclusions Ortho‐k slowed AE in bilateral anisomyopia, with slower growth in the HM eyes leading to a reduction in interocular AL differences. After ortho‐k, RPR changed from hyperopia to myopia, with greater changes induced in the HM eyes, and slower AE was associated with a more myopic shift in RPR, especially in the nasal field of both eyes.

Purpose: To report the characteristics (prevalence, severity, and location) of corneal epithelial microcysts and investigate associated risk factors in children wearing orthokeratology (ortho-k) lenses. Method: Ninety-five myopic children wearing ortho-k lenses (examined by one of three independent investigators from March to September 2020) were included in this retrospective cross-sectional study. Pertinent data at baseline before ortho-k treatment and at the aftercare visits (the first visit when the microcysts were observed for children with microcysts, and the last visit before October 2020 for children without microcysts) were retrieved and analysed. Results: A microcystic response was observed in 52.6% of children wearing ortho-k lenses. Children with high myopia (≥ 5.00 D) had a higher prevalence (100.0%, 23/23) and severity (69.5% (16/23) > grade 2 Efron scale) compared to children with low myopia (≤ 4.00 D) (prevalence of 37.5% (27/72) and 7.0% (5/72) > grade 2, p < 0.001). Microcysts were predominantly (86.0%) observed in the region of the inferior pigmented arc, typically originating in the inferior mid-peripheral cornea, and expanding over time into a semi- or whole annulus. Baseline myopia and topographical change at the treatment zone centre were significantly greater (p < 0.05) in low myopic children with microcysts (univariate analyses). Conclusions: During the COVID-19 pandemic, probably due to lifestyle changes, microcysts were frequently observed in children wearing ortho-k lenses and were associated with higher baseline myopia. Practitioners should examine ortho-k wearers with caution using a slit lamp with high magnification and illumination, especially the mid-peripheral cornea. The use of highly oxygen permeable lenses and frequent aftercare are necessary for ortho-k wearers, especially those with higher myopia.

Purpose To compare axial elongation (AE) and treatment zone (TZ) characteristics in children wearing 6 mm or 5 mm back optic zone diameter (BOZD) orthokeratology (ortho‐k) lenses over 2 years. Methods Forty‐five (6 to <11 years of age) myopic (−4.00 to −0.75 D) children of Chinese ethnicity were randomly assigned to use the two different lens designs (23 and 22 wore the 6 and 5 mm lenses, respectively). Data collection was performed at baseline and every 6‐months after commencing lens wear. Results After 24 months, subjects wearing lenses with a 5 mm BOZD achieved smaller TZ diameter (horizontal: 2.69 ± 0.28 vs. 3.84 ± 0.39 mm; vertical: 2.65 ± 0.22 vs. 3.42 ± 0.34 mm, p < 0.001) and less AE (0.15 ± 0.21 vs. 0.35 ± 0.23, p = 0.005) compared to those using the 6 mm design, with no difference in choroidal thickness (ChT) changes (p = 0.93). A significant increase in ChT, using pooled data analysis, was noted at the 6‐month (11.8 ± 19.77 μm, p < 0.001) and 12‐month (12.0 ± 23.7 μm, p = 0.004) visits, compared to baseline, indicating a transient change in ChT. Significant associations were noted, using linear mixed models, between AE and the TZ diameters (p < 0.003) after adjusting for baseline data. A very weak association was found between ChT changes and AE, with the effect size close to zero. Conclusions Smaller BOZD ortho‐k lenses resulted in a smaller TZ diameter, which was associated with less AE after 2 years of treatment. The changes in ChT played a very weak role, suggesting that other factors may contribute more to the reduced AE in subjects wearing lenses having a smaller BOZD.