Efficacy of Myopia Control and Distribution of Corneal Epithelial Thickness in Children Treated with Orthokeratology Assessed Using Optical Coherence Tomography

Relative corneal refractive power shift and inter-eye differential axial growth in children with myopic anisometropia treated with bilateral orthokeratology

PURPOSE

To investigate the relationship between relative corneal refractive power shift (RCRPS) and axial length growth (ALG) in bilateral myopic anisometropes treated with orthokeratology.

METHODS

A total of 102 children with myopic anisometropia in this prospective interventional study were randomly assigned to the spectacle group and orthokeratology group. Axial length (AL) and corneal topography was measured at baseline and the 12-month follow-up visit. ALG was defined as the difference between the two measurements, and RCRPS profiles were calculated from two axial maps obtained.

RESULTS

In the orthokeratology group, the ALG in the more myopic eye (0.06 ± 0.15 mm) was significantly smaller than that in the less myopic eye (0.15 ± 0.15 mm, p < 0.001), and the interocular difference in AL significantly decreased following 1-year treatment, from 0.47 ± 0.32 to 0.38 ± 0.28 mm (p < 0.001). However, in the spectacle group, the ALG was similar between the two eyes, and the interocular difference in AL did not change significantly over one year (all p > 0.05). The interocular difference in ALG in the orthokeratology group was significantly correlated with the interocular difference in RCRPS (dRCRPS, β=-0.003, p < 0.001) and the interocular difference in baseline AL (β=-0.1179, p < 0.001), with R2 being 0.6197.

CONCLUSION

Orthokeratology was effective in decreasing the magnitude of anisometropia. The interocular variation in RCRPS is an important factor accounting for the reduction of interocular ALG difference in anisomyopic children post-orthokeratology. These results provide insight into establishing eye-specific myopia control guidelines during orthokeratology treatment for myopic anisometropes.

Exploring the Location of Corneal Pigmented Arc and Myopia Control Efficacy in Orthokeratology-Treated Children Using Pentacam Measurements

OBJECTIVES

To determine the location and intensity of the corneal pigmented arc in orthokeratology (ortho-k)-treated children and its relationship with annual axial length (AL) change using Pentacam.

METHODS

This retrospective cohort study enrolled children aged 9 to 15 years who had been followed up for at least one year after ortho-k treatment for myopia control. A Pentacam was used to determine the location and intensity of pigmented arc after lens wear. Annual AL changes were further used as the outcome measurement to determine their relationships with the location and intensity of pigmented arc using generalized estimating equations (GEE).

RESULTS

In total, 62 eyes from 33 patients (mean age 10.9 years) were included in our final analysis. The mean follow-up time was 30.6 months. The mean annual AL changes were 0.10 mm. Age statistically correlated with annual AL change (GEE, P= 0.033). In addition, the annual AL change was negatively associated with the relative vertical distance of the lowest density of pigmented arc point based on the visual center, pupil center, and corneal thinnest point after adjustment with age ( P =0.005, P =0.004, and P< 0.001, respectively).

CONCLUSIONS

Pentacam could be a useful tool for evaluating the location and intensity of the corneal pigmented arc. In addition, there was a negative correlation between the vertical distance of the pigmented arc and annual AL change. These findings may provide important information regarding myopia control, next-generation ortho-k design, and prescription.

Corneal Epithelial Thickness Mapping: A Major Review

The corneal epithelium (CE) is the outermost layer of the cornea with constant turnover, relative stability, remarkable plasticity, and compensatory properties to mask alterations in the underlying stroma. The advent of quantitative imaging modalities capable of producing epithelial thickness mapping (ETM) has made it possible to characterize better the different patterns of epithelial remodeling. In this comprehensive synthesis, we reviewed all available data on ETM with different methods, including very high-frequency ultrasound (VHF-US) and spectral-domain optical coherence tomography (SD-OCT) in normal individuals, corneal or systemic diseases, and corneal surgical scenarios. We excluded OCT studies that manually measured the corneal epithelial thickness (CET) (e.g., by digital calipers) or the CE (e.g., by confocal scanning or handheld pachymeters). A comparison of different CET measuring technologies and devices capable of producing thickness maps is provided. Normative data on CET and the possible effects of gender, aging, diurnal changes, refraction, and intraocular pressure are discussed. We also reviewed ETM data in several corneal disorders, including keratoconus, corneal dystrophies, recurrent epithelial erosion, herpes keratitis, keratoplasty, bullous keratopathy, carcinoma in situ, pterygium, and limbal stem cell deficiency. The available data on the potential role of ETM in indicating refractive surgeries, planning the procedure, and assessing postoperative changes are reviewed. Alterations in ETM in systemic and ocular conditions such as eyelid abnormalities and dry eye disease and the effects of contact lenses, topical medications, and cataract surgery on the ETM profile are discussed.

Short-term Changes in Epithelial and Optical Redistribution Induced by Different Orthokeratology Designs

OBJECTIVES

This study aimed to investigate corneal epithelial and topographic changes caused by two commercial myopia orthokeratology (ortho-k) designs.

METHODS

Twenty-six subjects fitted with vision shape treatment (VST) lenses and 30 subjects fitted with corneal reshaping therapy (CRT) lenses were reviewed 1 day, 1 week, and 1 month after lens initiation. A spectral-domain optical coherence tomography system was used to create epithelial maps that were in turn used to determine the average epithelial thickness of each zone and the diameter of treatment zone. By measuring the topographic tangential differential map, the treatment zone diameter and the power and width of the high convex zone (HCZ) were obtained. All epithelial thicknesses and topographic corneal variations recorded were analyzed.

RESULTS

At the central zone, the epithelial thickness changes (△ET) decreased significantly after 1 day of ortho-k in two groups. At 2- to 9-mm peripheral zone, ortho-k increased △ET until 1 week in the VST group, whereas it kept increasing in the CRT group after 1 week. At 1 month, the central △ET is -9.51±2.38 mm in the VST group, which was comparable to -8.72±3.43 mm in the CRT group. The nasal HCZ power and the △ET of nasal and inferior nasal were significantly larger in the CRT group. A positive correlation was found between the HCZ power and △ET generated by VST-type lenses inferiorly and temporally. For the CRT group, a positive correlation was found between inferior HCZ power and △ET.

CONCLUSIONS

At the early stage of ortho-k, epithelial thickness and topography change quickly and simultaneously. Epithelial changes were in line with corneal topography reshaping. Epithelial and optical remodelling were affected by different lens types.

Orthokeratology in controlling myopia of children: a meta-analysis of randomized controlled trials

BACKGROUND

Delaying the development and lowering the progression of myopia in children is the focus of current ophthalmology researches. We aimed to evaluate the role of orthokeratology in controlling myopia of children, to provide insights to the clinical treatment and care of children with myopia.

METHODS

Two investigators searched the The Cochrane Library, Embase, Pubmed, China national knowledge infrastructure, China biomedical literature database, WanFang and Weipu databases for randomized controlled trials(RCTs) on the role of orthokeratology in controlling myopia of children up to November 5, 2022. Two researchers independently searched, screened and extracted the studies according to the inclusion and exclusion standards. RevMan5.3 software was used for statistical analysis.

RESULTS

A total of 14 RCTs involving 2058 children were included in this meta-analysis. Synthesized outcomes indicated that orthokeratology improved the uncorrected visual acuity(MD = 0.40, 95%CI: 0.05 ~ 0.74), reduced the diopter change(MD=-3.19, 95%CI: -4.42~-1.95), changes of corneal curvature(MD=-3.21, 95%CI: -3.64~-2.79), the length of ocular axis (MD=-0.66, 95%CI: -1.27~-0.06) and amount of ocular axis change(MD=-0.42, 95%CI: -0.64~-0.21) after 1 year of wearing orthokeratology(all P < 0.05). Besides, orthokeratology reduced the diopter change (MD=-3.22, 95%CI: -4.86~-1.58), the length of ocular axis (MD=-1.15, 95%CI: -2.25~-0.06) and the amount of ocular axis change after 2 year of wearing orthokeratology (MD=-0.53, 95%CI: -0.96~-0.11) after 2 year of wearing orthokeratology (all P < 0.05). No publication biases were found amongst the synthesized outcomes (all P > 0.05).

CONCLUSIONS

Orthokeratology delays the progression of myopia in children, the long-term effects of orthokeratology need further investigations in future studies.

Biomechanical study of cornea response under orthokeratology lens therapy: A finite element analysis

Orthokeratology (OK) is becoming a mainstream modality for myopia correction and control, but its underlying mechanism is not yet fully understood. In this study, the biomechanical response of cornea under the OK lens was investigated to further understand the mechanism of OK therapy. Numerical models of the cornea and OK lens with different corneal refractive powers and myopia degrees were established to analyze features and differences of the spatial displacement and stress distribution in different areas of the anterior corneal surface by finite element method. Displacement distributions on the anterior cornea surface with refractive powers of 39.5, 43, 46 D, and myopia degrees of -1.0, -3.0, -6.0 D demonstrate similar deformation trends and nearly rotationally symmetrical attributes of different corneal parameters. Displacement of mid-peripheral cornea was significantly high compared with that of the central and peripheral cornea, peaking at ~2.4 mm off the corneal apex. The stress increased with the increase in myopia degrees and was significantly large for the myopia degrees of -6.0 D at S1; the stress at S2 and S6 was low and stable and did not differ much at S3; the stress at S4 and S5, however, was extremely high. In summary, simulation result of orthokeratology can effectively evaluate the performance of OK lens and it properly associates with the differential map of the corneal topography. The base curve of the OK lens may also play a role in mid-peripheral corneal steepening. The design around the OK lens' alignment curve needs to be optimized.

Treatment of Myopia with Atropine 0.125% Once Every Night Compared with Atropine 0.125% Every Other Night: A Pilot Study

(1) Purpose: To investigate the efficacy of myopia treatment in children using atropine 0.125% once every two nights (QON) compared with atropine 0.125% once every night (HS). (2) Methods: This retrospective cohort study reviewed the medical records of two groups of children with myopia. Group 1 comprised children treated with atropine 0.125% QON, while group 2 included children treated with atropine 0.125% HS. The first 6 months of data of outcome measurements were subtracted as washout periods in those children undergoing both atropine QON and HS treatment. The independent t-test and Pearson's chi-square test were used to compare the baseline clinical characteristics between the two groups. A generalized estimating equations (GEE) model was used to determine the factors that influence treatment effects. (3) Results: The average baseline ages of group 1 (38 eyes from 19 patients) and group 2 (130 eyes from 65 patients) were 10.6 and 10.2 years, respectively. There were no significant differences in axial length (AL) or cycloplegic spherical equivalent (SEq) at baseline or changes of them after 16.9 months of follow-up. GEE showed that the frequency of atropine 0.125% use has no association with annual AL (QON vs. HS: 0.16 ± 0.10 vs. 0.18 ± 0.12) and SEq (QON vs. HS: -0.29 ± 0.44 vs. -0.34 ± 0.36) changes in all children with myopia. It also showed that older baseline age (B = -0.020, p < 0.001) was associated with lesser AL elongation. (4) Conclusion: The treatment effects of atropine 0.125% HS and QON were similar in this pilot study. The use of atropine 0.125% QON may be an alternative strategy for children who cannot tolerate the side effects of atropine 0.125% HS. This observation should be confirmed with further large-scale studies.

Zebrafish (Danio rerio) Is an Economical and Efficient Animal Model for Screening Potential Anti-cataract Compounds

Purpose

To develop a zebrafish cataract model for screening potential anti-cataract compounds.

Methods

Living zebrafish were anesthetized and exposed to ultraviolet-C (UV-C) irradiation at a dosage of 3250 mJ/cm2/d until they developed severe cataracts. These cataracts were graded based on photographs analyzed with ImageQuant TL version 7.0. Fish with severe cataracts were used to evaluate a range of compounds for cataract treatment, including the previously demonstrated hit compound lanosterol. For the initial evaluation, fish were divided into four groups: no treatment, balanced salt solution, β-cyclodextrin (β-CD), and lanosterol dissolved in β-CD. The treatments were performed for 10 days, and the clarity of lenses was evaluated. To assess the persistence of treatment, fish were treated with β-CD and lanosterol dissolved in β-CD for seven consecutive days followed by monitoring for three days without treatment.

Results

The average time for zebrafish to develop severe cataracts using the present UV-C irradiation protocol was 7.8 days (range 4-15 days). Both study designs required only another 10 days to determine the effect of hit compounds. The total experimental period could be completed within one month, and the entire experiment was economical.

Conclusions

We could assay a large number of hit compounds at a reasonable cost and within a short time using this newly developed zebrafish cataract model. These assays may allow development of an efficient platform for screening potential anti-cataract compounds.

Translational Relevance

The results may facilitate the development of ani-cataract medication for humans after further experiments and investigations.