The Safety of Orthokeratology--A Systematic Review

Diurnal variation of visual functions for driving with and without orthokeratology: A multicenter study

PURPOSE

To investigate orthokeratology-related diurnal variations in visual acuity, contrast sensitivity, mesopic (twilight) vision, and glare sensitivity, and to verify compliance with requirements for driver licensing.

METHODS

In this prospective, multicenter, controlled study, fifty myopic (range, -1.00 to -4.50 D) and non-presbyopic glasses or soft contact lens wearers (age range, 16-39 years) were fitted with orthokeratology (OK) contact lenses. Before and after completion of OK lens fitting, measurements of visual acuity, contrast sensitivity, mesopic vision and glare sensitivity were performed at three times of the day, morning, afternoon and evening using a standardized binocular vision testing device (Oculus Binoptometer 4P). Monocular and binocular visual acuity were tested according to ISO 8596 and compared to requirements of cars and motorcycles drivers in different countries.

RESULTS

Compared to the prior correction, binocular visual acuity (logMAR) with orthokeratology was statistically significant better in the morning (0.04 ± 0.12; p < 0.05) and afternoon (0.04 ± 0.10; p < 0.05), while the difference was not statistically significant in the evening (p = 0.512). Furthermore, there was no statistically significant difference in contrast sensitivity in the morning (p = 0.813), afternoon (p = 0.742) or evening (p = 0.945). For both mesopic vision and glare sensitivity, there was no statistically significant difference between the contrast levels achieved with orthokeratology compared to the prior correction in the morning (p = 0.083; p = 1.000), afternoon (p = 0.054; p = 0.125) or evening (p = 0.195; p = 0.635). With orthokeratology, no statistically significant diurnal variation was found for binocular visual acuity, contrast sensitivity, mesopic vision or glare sensitivity (p > 0.05).

CONCLUSIONS

These results provide evidence, that visual functions of OK lens wearers are stable throughout the day and comparable to the prior correction. Although the visual standards for driving are not uniform within countries, the requirements for visual acuity are met in all of the countries. Mesopic vision and glare sensitivity, which are suggested as other aspects to influence driving performance, also appear to be constant over the course of the day.

Clinical Safety and Efficacy of Orthokeratology Contact Lenses With Toric Peripheral Curves: A Review of the Literature

OBJECTIVE

To assess the clinical safety and efficacy of orthokeratology (OK) lenses with toric peripheral curves (TPCs), based on a review of published literature.

METHODS

A literature search on OK lenses with TPCs using 11 relevant search term combinations was conducted. Databases included PubMed, Cochrane Online Library, Prospero International Prospective Register of Systematic Reviews, and Embase. The period covered was January 1, 2012, to May 1, 2024.

RESULTS

In total, 600 publications were identified in the search databases using the search criteria. Based on titles and abstracts, 52 distinct articles were identified for further review; of these, 16 were determined related to clinical evaluation of OK lenses with TPCs. The published studies involved five different lens models from five different manufacturers: Menicon Z Night Toric (Menicon Co, Ltd, Nagoya, Japan), Euclid Emerald Toric (Euclid Systems Corporation, Herndon, VA), Lucid Night Ortho-K Toric (Lucid Korea, Seoul, Korea), Dual Axis Corneal Refractive Therapy (Paragon Vision Sciences, Gilbert, AZ), and Eyebright Base Curve Aspheric Ortho-K (Eyebright Medical Technology Co, Ltd, Beijing, China).

CONCLUSIONS

Published literature suggests that OK lenses with TPCs are effective in treating patients with both myopia and astigmatism, with favorable safety profiles.

Evaluation of large language models for providing educational information in orthokeratology care

BACKGROUND

Large language models (LLMs) are gaining popularity in solving ophthalmic problems. However, their efficacy in patient education regarding orthokeratology, one of the main myopia control strategies, has yet to be determined.

METHODS

This cross-sectional study established a question bank consisting of 24 orthokeratology-related questions used as queries for GTP-4, Qwen-72B, and Yi-34B to prompt responses in Chinese. Objective evaluations were conducted using an online platform. Subjective evaluations including correctness, relevance, readability, applicability, safety, clarity, helpfulness, and satisfaction were performed by experienced ophthalmologists and parents of myopic children using a 5-point Likert scale. The overall standardized scores were also calculated.

RESULTS

The word count of the responses from Qwen-72B (199.42 ± 76.82) was the lowest (P < 0.001), with no significant differences in recommended age among the LLMs. GPT-4 (3.79 ± 1.03) scored lower in readability than Yi-34B (4.65 ± 0.51) and Qwen-72B (4.65 ± 0.61) (P < 0.001). No significant differences in safety, relevance, correctness, and applicability were observed across the three LLMs. Parental evaluations rated all LLMs an average score exceeding 4.7 points, with GPT-4 outperforming the others in helpfulness (P = 0.004) and satisfaction (P = 0.016). Qwen-72B's overall standardized scores surpassed those of the other two LLMs (P = 0.048).

CONCLUSIONS

GPT-4 and the Chinese LLM Qwen-72B produced accurate and beneficial responses to inquiries on orthokeratology. Further enhancement to bolster precision is essential, particularly within diverse linguistic contexts.

Corneal elevation asymmetry vector: Viable predictor of severe one-year-averaged orthokeratology lens decentration

BACKGROUND

To assess the predictive value of pretreatment corneal elevation asymmetry vector (CEAV) for severe orthokeratology (Ortho-k) lens decentration (LD) in Chinese myopic adolescents.

METHODS

A retrospective analysis of 247 myopic participants over one year employed a novel MATLAB algorithm to calculate CEAV and precise LD vector. Subjects were categorized into mild (<1 mm) and severe (≥1 mm) yearly averaged LD (YALD) groups. Logistic regression and ROC analysis evaluated the relationship between corneal parameters and severe YALD.

RESULTS

LD reached stability within the first month, with severe YALD compromising visual quality and corneal health. Notably, univariate linear regression revealed a paradoxical correlation between axial length elongation (ALE) and YALD: ALE negatively correlated with YALD in the mild group (standardised β = -0.546, P < 0.05), contrasting with a positive correlation in the severe group (standardised β = 0.599, P < 0.05). Horizontal CEAV (standardised β =  - 0.237, < 0.05) and curvature differences between nasal and temporal quadrants at 8 mm (KTN) (standardised β = 0.227, P < 0.01) significantly correlated with horizontal YALD, while vertical CEAV vector associated with vertical YALD (standardised β =  - 0.237, < 0.05). Multivariate analysis identified CEAV as an independent predictor of severe YALD (OR = 3.145, 95 % CI: 1.334 ∼ 4.607, P < 0.01). Other risk factors included larger horizontal visible iris diameter (HVID) (OR = 2.430, 95 % CI:0.6136 ∼ 10.07, P < 0.05), corneal astigmatism (CA) (OR = 1.506, 95 % CI: 1.017 ∼ 2.244, P < 0.05), and KTN (OR = 1.864, 95 % CI: 0.934 ∼ 3.864, P < 0.05). CEAV magnitude alone predicted severe YALD with AUC = 0.698 (95 %CI: 0.615-0.783, P < 0.001), improving to AUC = 0.732 (95 % CI: 0.660-0.805, P < 0.001) when combined with other risk factors.

CONCLUSIONS

Pretreatment CEAV may emerge as a viable predictor of severe Ortho-k YALD, warranting its consideration in further tailored lens fitting to improve outcomes.

Development and psychometric evaluation of beliefs about the orthokeratology lens compliance scale (BOLCS): Based on the theory of planned behavior

PURPOSE

Non-adherence to standard wear, care, and follow-up procedures is a major risk factor for contact lens-related complications. The effectiveness of orthokeratology largely depends on the wearer's adherence. However, a deficiency in scales capturing adherence beliefs pertinent to orthokeratology exacerbates the lack of guidance for effective intervention strategies. The purpose of this study is to develop and evaluate the psychometric properties of a new scale based on the Theory of Planned Behavior that assesses the level of adherence among ortho-k wearers.

METHODS

This study involved three stages following the STROBE checklist: (1) developing initial scale items based on the Theory of Planned Behavior, a literature review, and a qualitative study; (2) evaluation of content and face validity; (3) psychometric testing on 296 participants. Item analysis, based on Classical Test Theory, assessed the overall consistency, reliability, and validity of the scale.

RESULTS

The final 37-item Beliefs about the Orthokeratology Lens Compliance Scale (BOLCS) comprises 11 dimensions. The Cronbach's alpha coefficients for each dimension ranged from 0.560 to 0.798. The folded half reliabilities were 0.845, and the combined reliabilities ranged from 0.676 to 0.793, indicating strong reliability. Item-level CVI (I-CVI) and scale-level CVI/average (S-CVI/Ave) values, assessed by the panel, ranged from 0.71 to 1 and 0.954, respectively. Exploratory and confirmatory factor analyses supported a factor structure consistent with the theoretical model.

CONCLUSIONS

The scale's construction adhered to a standardized process, yielding preliminary validation results with satisfactory reliability and validity.

Comparison of trial lens-fitting and software-fitting in orthokeratology for myopia control in children with high corneal eccentric value

PURPOSE

To compare the safety and efficacy of the trial lens-fitting and software-fitting in orthokeratology for myopia control in children with high corneal eccentric value.

METHODS

Myopic children with high corneal eccentric value (≥0.65) receiving treatment for orthokeratology from July 2020 to January 2022 were included in this retrospective study. Only the right eyes were included. The participants were allocated into two groups: the trial lens-fitting group (n = 41) and the software-fitting group (n = 48). The uncorrected visual acuity (UCVA), corneal topography, and ocular health (Efron grading scales) were recorded at baseline, one week, two weeks, one, three, six, and 12 months afterthe initiation of lens wear. The axial length and endothelial cell density were assessed at baseline and after 12 months of lens wear.

RESULTS

The success rate of the first fit in the software-fitting group and trial lens-fitting group reached 98 % and 95 %, respectively. The difference in UCVA and corneal staining were statistically insignificant between the two groups during all visits. The software-fitting group exhibited a smaller treatment zone size (radius 1.69 ± 0.21 mm vs 1.81 ± 0.16 mm, p = 0.004; area 9.13 ± 2.15 mm2 vs 10.36 ± 1.82 mm2, p = 0.005) and less decentration (0.58 ± 0.31 mm vs 0.74 ± 0.39 mm, p = 0.036) compared with the trial lens-fitting group. There were no significant differences in axial elongation (0.15 ± 0.12 mm vs. 0.17 ± 0.14 mm, p = 0.534) or changes in endothelial cell density (-36.63 ± 99.37/mm2 vs - 13.71 ± 87.72/mm2, p = 0.256) between the software-fitting group and the trial lens-fitting group at one-year follow-up visit.

CONCLUSION

Both fitting methods were effective and safe. However, the software-fitting method resulted in a smaller treatment zone size and less decentration.

Corneal astigmatism after temporary discontinuation from long-term spherical and toric orthokeratology

OBJECTIVE

To investigate changes in corneal astigmatism (curvatures and corneal sagittal height difference (C-sagDiff) at 8-mm chord) after temporary discontinuation from long-term spherical and toric orthokeratology (ortho-k) lens wear in a Chinese population.

METHODS

Relevant data were retrieved from 110 patients (55 wearing spherical ortho-k lenses, 55 wearing toric ortho-k lenses) who have been undergoing ortho-k treatment for at least one year and stopped lens wear temporarily for scheduled lens replacement. The topographic and refraction data at baseline and post-discontinuation was collected for all the patients. Only data from the right eye was used for analysis. Corneal curvature changes and C-sagDiff at 8-mm chord in the two principal meridians within each group and the corneal astigmatism changes between the two groups were analyzed.

RESULTS

No significant differences in age, gender, baseline flat K (FK) and steep K (SK), myopia, refractive astigmatism, and duration of lens wear were noted between the two groups (P > 0.05). Baseline corneal astigmatism and C-sagDiff in toric ortho-k group was higher than spherical ortho-k group (P < 0.001). For both ortho-k groups, after treatment discontinuation of about 1-month (30-37 days), FK became flatter, SK remained unchanged, corneal astigmatism and C-sagDiff increased. Changes in corneal astigmatism for spherical and toric groups were 0.24 ± 0.33 and 0.32 ± 0.32 D, respectively. C-sagDiff increased from 22.85 ± 8.41 to 31.37 ± 12.98 μm and from 32.35 ± 12.39 to 45.40 ± 15.01 μm in the spherical and toric ortho-k groups, respectively. No significant between-group difference in corneal astigmatism change was found (P = 0.214). Corneal astigmatism change was affected by wearers' age and duration of ortho-k lens wear. The younger the subject and the longer the duration of ortho-k lens wear, the more significant the corneal astigmatism change after discontinuation of the treatment.

CONCLUSION

After 1-month discontinuation from long-term ortho-k lens wear, corneal flat K became flatter, steep K remained unchanged, the C-sagDiff and the corneal astigmatism increased, irrespective of whether spherical or toric lenses were used. The change of corneal astigmatism was about 0.25D on average, which was not clinically significant. There was no significant difference of corneal and refractive astigmatism change between spherical and toric ortho-k groups.

Guidelines for preventing and slowing myopia progression in Brazilian children

This document on myopia control is derived from a compilation of medical literature and the collective clinical expertise of an expert committee comprising members from the Brazilian Society of Pediatric Ophthalmology and the Brazilian Society of Contact Lenses and Cornea. To manage myopia in children, the committee recommends corneal topography and biannual visits with cycloplegic refraction, along with annual optical biometry. For fast-progressing myopia, biannual biometry should be considered. Myopic progression is defined as an annual increase in spherical equivalent greater than 0.50 D/year or in axial length greater than 0.3 mm (until 10 years old) or 0.2 mm (above 11 years). The proposed treatments for myopia progression include environmental control, low concentration atropine, defocus glasses, contact lenses, or Ortho-K lenses, and combinations of these methods may be necessary for uncontrolled cases. Treatment should be sustained for at least 2 years. This document serves as a comprehensive guideline for diagnosing, treating, and monitoring pre-myopic and myopic children in Brazil.

Effectiveness of orthokeratology and myopia control spectacles in a real-world setting in China

OBJECTIVE

To compare the effectiveness of myopia control in Chinese children, who had been wearing either orthokeratology (ortho-k) lenses or myopia control spectacles (MCS) for one year.

METHODS

Relevant data were retrieved from 212 patients, with baseline myopia of -5.00 to -0.75 D, astigmatism ≤ 1.50 D, who had been undergoing myopia control treatment with either ortho-k (Euclid (OK1) or CRT (OK2)) or MCS (Stellest (MCS1) or DIMS (MCS2)) for at least one year. Myopia control effectiveness among the four groups was compared based on the change in spherical equivalent refraction (SER) (for the spectacle groups) and axial length (AL) (for all groups). Data retrieved, from the right eye only, included best corrected visual acuity (BCVA), SER, and AL at both the initial clinic visit (baseline) and the one-year visit was analysed.

RESULTS

Although no significant differences in gender, cylindrical power, or BCVA were observed at the baseline visit (P > 0.05), there were significant differences in baseline age, myopia, and AL among the four groups (P < 0.05). No significant difference in axial elongation (AE) was found among the four groups after one year of treatment (P = 0.49). AE, adjusted for baseline age and spherical power, were 0.19 ± 0.15, 0.18 ± 0.14, 0.19 ± 0.19, 0.20 ± 0.18 mm for OK1, OK2, MCS1, MCS2, respectively. Only age was a significantly factor associated with AE and SER increase (P < 0.05), with negative associations between AE and age in all groups and positive association between SER increase and baseline age in the spectacle groups observed.

CONCLUSION

Both brands of ortho-k lenses and MCS had similar myopia control effectiveness for mild to moderate myopic children treated in a real-world setting in China. Average AE in one year ranged from 0.18 to 0.20 mm, comparable to previous reports on myopia control using ortho-k.

Daily Low-Level Red Light for Spherical Equivalent Error and Axial Length in Children With Myopia: A Randomized Clinical Trial

Importance

Treatments are needed to slow progression of or reduce incidence of myopia.

Objective

To evaluate the efficacy and safety of daily 650-nm low-level red light (LLRL) for myopia treatment.

Design, Setting, and Participants

Single-masked, randomized clinical trial at 1 site in China. Baseline measurements were completed from August to September 2021. Participants were children aged 6 to 12 years with spherical equivalent error (SER) of -6 diopters (D) to 3 D. Data were analyzed from March to July 2023.

Interventions

Irradiation daily with 650-nm LLRL for 3 minutes twice daily 4 or more hours apart or no intervention.

Main Outcomes and Measures

Primary outcomes were changes in cycloplegia SER and axial length (AL) at 6- and 12-month follow-up visits. Safety was assessed on masked fundus photograph evaluations.

Results

A total of 336 children were randomly allocated into the LLRL group or control group in a 1:1 ratio. The control group contained 86 female patients (51.2%), and the treatment group contained 90 female patients (53.6%). The mean (SD) age, SER, and AL were 9.0 (1.9) years, -1.3 (1.5) D, and 23.8 (1.0) mm for all patients. A total of 161 (95.8%) in the LLRL group and 159 (94.6%) in the control group returned for the 6-month follow-up. A total of 157 (93.5%) in the LLRL group and 152 (90.5%) in the control group returned for the 12-month follow-up. Mean (SD) changes in SER were 0.15 (0.16) D and -0.26 (0.21) D for the LLRL group and the control group, respectively (difference, -0.41 D; 95% CI, -0.48 to -0.34 D; P < .001), at 6 months and 0.24 (0.27) D and -0.65 (0.33) D for the LLRL group and the control group, respectively (difference, -0.89 D; 95% CI, -0.95 to -0.83 D; P < .001), at 12 months. Mean (SD) changes in AL were -0.06 (0.08) mm and 0.13 (0.12) mm for the LLRL group and control group, respectively (difference, 0.19 mm; 95% CI, 0.16 to 0.22 mm; P < .001), at 6 months and -0.11 (0.10) mm and 0.26 (0.16) mm for the LLRL group and control group, respectively (difference, 0.37 mm; 95% CI, 0.34 to 0.40 mm; P < .001). Masked fundus photograph review did not identify retinal changes in either group.

Conclusions and relevance

These findings suggest daily use of 650-nm LLRL for 1 year can slow progression of SER and AL without safety concerns identified. Confirmation of these findings at independent sites seems warranted, as well as determining whether these effects can be sustained with or without continued treatment and whether LLRL has any effect on pathological myopia.

Trial Registration

ChiCTR2200058963.

Myopia Control: Are We Ready for an Evidence Based Approach?

INTRODUCTION

Myopia and its vision-threatening complications present a significant public health problem. This review aims to provide an updated overview of the multitude of known and emerging interventions to control myopia, including their potential effect, safety, and costs.

METHODS

A systematic literature search of three databases was conducted. Interventions were grouped into four categories: environmental/behavioral (outdoor time, near work), pharmacological (e.g., atropine), optical interventions (spectacles and contact lenses), and novel approaches such as red-light (RLRL) therapies. Review articles and original articles on randomized controlled trials (RCT) were selected.

RESULTS

From the initial 3224 retrieved records, 18 reviews and 41 original articles reporting results from RCTs were included. While there is more evidence supporting the efficacy of low-dose atropine and certain myopia-controlling contact lenses in slowing myopia progression, the evidence about the efficacy of the newer interventions, such as spectacle lenses (e.g., defocus incorporated multiple segments and highly aspheric lenslets) is more limited. Behavioral interventions, i.e., increased outdoor time, seem effective for preventing the onset of myopia if implemented successfully in schools and homes. While environmental interventions and spectacles are regarded as generally safe, pharmacological interventions, contact lenses, and RLRL may be associated with adverse effects. All interventions, except for behavioral change, are tied to moderate to high expenditures.

CONCLUSION

Our review suggests that myopia control interventions are recommended and prescribed on the basis of accessibility and clinical practice patterns, which vary widely around the world. Clinical trials indicate short- to medium-term efficacy in reducing myopia progression for various interventions, but none have demonstrated long-term effectiveness in preventing high myopia and potential complications in adulthood. There is an unmet need for a unified consensus for strategies that balance risk and effectiveness for these methods for personalized myopia management.

Factors influencing myopia stabilisation in young myopic adult Singaporeans

PURPOSE

To evaluate factors influencing stabilisation of myopia in the Singapore Cohort of Risk factors for Myopia.

METHODS

We evaluated the longitudinal natural history of 424 myopic participants from 1999 to 2022. The outcome was the change in myopia from the adolescence follow-up visit (aged 12-19 years) to the adulthood follow-up visit (aged 26-33 years). Association of predictive factors, including baseline spherical error, gender, ethnicity, parental myopia, time outdoor, near work and age at adolescence, was examined with the dichotomous outcome of adult myopia progression (≤ -1.00 dioptres (D) over 10 years) using multiple logistic regression and progression in linear regression models.

RESULTS

For the primary outcome, the mean rate of progression of the outcome was found to be -0.04±0.09 D per year from the adolescent to the adulthood follow-up visits. 82.3% (95% CI 78.3% to 85.8%) had myopia stabilisation, with progression of less than 1.00 D over 10 years while 61.3% (95% CI 56.5% to 66.0%) of the subjects had progression of less than 0.50 D. In logistic regression models, both male gender (p=0.035) and non-Chinese ethnicity (p=0.032) were more likely to achieve myopia stabilisation while in linear multivariate regression models, males had a significantly slower degree of myopia progression (p=0.021).

CONCLUSION

5 in 6 Singaporean young adults had myopia stabilisation. Male gender is 2 times and non-Chinese ethnicities are 2.5 times more likely to achieve myopia stabilisation. However, a proportion of myopes continue to exhibit a clinically significant degree of progression in adulthood.

The efficacy of a device-based approach to microorganism disinfection and protein removal for orthokeratology lenses in varied clinical circumstances

PURPOSE

RigidCare is an electrolysis-based device that recently obtained approval from the US's FDA to sterilise microorganisms and remove proteins for orthokeratology (O-K) lenses. The study was conducted to investigate the device's performance in varied clinical circumstances.

METHODS

Trial lenses and private lenses were employed by O-K lens wearers from five hospitals for an evaluation of disinfection and sterilisation and an assessment of protein removal, respectively. Menicon multipurpose solution and protein remover were selected for use with the control group. Following the instructions, pre-cleaning lens samples, post-cleaning lens samples and residual solution samples of trial lenses of the experimental and control groups were collected for microorganism examinations by an experienced third-party testing organisation. The levels of protein deposition for these two approaches were rated by senior O-K experts. Categorical variables were analysed using statistical tests, such as the chi-squared test and Fisher's exact test.

RESULTS

The microbial positive rate detected from the pre-cleaning and post-cleaning lens samples and the residual solution of the trial lenses for the experimental and control group was 4/76 vs 1/74 (P = 0.37), 1/76 vs 0/74 (P = 1.00) and 0/76 vs 8/74 (P = 0.006), respectively. Following protein removal, the experimental group exhibited a significantly higher overall proportion of lenses rated as 'clean' or with a 'mild deposit' (96.4 %, 79/82) compared to the control group (85.7 %, 66/77), with a significant difference (P < 0.05).

CONCLUSION

This multi-center study demonstrated that RigidCare exhibited superior efficacy in disinfection, sterilisation and protein removal as compared to Menicon multipurpose solution and protein remover.

Myopia control: Seeing beyond efficacy

SIGNIFICANCE

The availability of a range of effective myopia control modalities enables the clinician to exercise judgment when discussing the treatment plan with the patient and their parents. This article outlines important considerations beyond efficacy.Clinically meaningful myopia control may be attained with some spectacle lenses, select soft contact lenses, some concentrations of atropine, and overnight orthokeratology. Given that satisfactory efficacy can be achieved with a range of modalities, other factors should be considered when deciding upon the best intervention for a given child. Four key factors-compliance, quality of vision, quality of life, and safety-are discussed in this review. Compliance directly impacts efficacy regardless of the modality and is the most important consideration, as it is influenced by quality of vision and comfort. Daily disposal myopia control contact lenses and overnight orthokeratology are generally associated with high compliance, provide better vision-related quality of life than spectacles, and carry a very low risk when used appropriately. A further benefit of overnight orthokeratology is the elimination of a need for optical correction during the day.

Orthokeratology combined with spectacles in moderate to high myopia adolescents

PURPOSE

Wearing ortho-k lenses overnight may not fully correct their daytime refractory errors of adolescents with moderate to high myopia. There are three common ways to deal with the daytime residual refractive error (RRE): 1) wearing spectacles to correct the RRE; 2) wear ortho-k lenses during the daytime instead of overnight.; 3) not correcting the residual refractive error. According to previous laboratory studies, myopic peripheral refraction is associated with better myopic control. This study had two aims:1) to compare relative peripheral refractive error (RPRE) among these ways after one-month stabilization; 2) to assess the axial length changes over 2 years of ortho-k lens overnight wear combined with spectacle glasses.

METHODS

This was a prospective, non-controlled, non-randomized, observational study in which a total of 27 subjects (20 females, 7 males, mean age 12.48 ± 2.23Y) with spherical equivalent refractive error from -5.00 to -8.25D were enrolled. All participants in the study wore orthokeratology (ortho-k) lenses overnight for a minimum of one month. Subsequently, their peripheral refractive error (PRE) was assessed using an open-field autorefractor. During the assessment, the participants underwent three conditions in a random order in a same morning: 1) unaided eye after orthokeratology (referred to as the Unaided-eye condition), 2) wearing glasses to correct any remaining refractive errors after orthokeratology (referred to as the Spec-RE condition), and 3) wearing ortho-k lenses during the daytime (referred to as the Continuous OK wear condition). After testing, all subjects were instructed to wear ortho-k lenses overnight and glasses during the daytime to correct their RRE for the next 2 years, during which time the progression of their axial length was followed up.

RESULTS

1) RPRE in either Unaided-eye or Spec-RE condition subjects were significantly more myopic than those in the Continuous OK wear condition. 2) No difference in RPRE was seen between Unaided-eye and Spec-RE conditions. 3) Axial length growth was 0.05 ± 0.20 mm and 0.17 ± 0.32 mm (mean ± standard deviation) at 1-year and 2-year follow-ups after the initial visit, respectively, which were comparable to mild myopia patients after orthokeratology. 4) After orthokeratology, axial length change had negative correlation with the initial age (p = 0.001, r = -0.616) and residual diopter (p = 0.022).

CONCLUSIONS

For myopes above refraction < -5.00D, wearing Ortho-k lenses overnight and glasses to correct the RRE in the daytime is recommended to ensure good visual quality and have more myopic RPRE for potential myopia control.

Safety, Efficacy, and Visual Performance of an Orthokeratology Lens with Increased Compression Factor

The aim was to evaluate the safety, efficacy, and visual performance of an orthokeratology lens with an increased compression factor (ICF) of 1.25 D in a 3-month follow-up. Thirty-six myopic patients (5 males and 31 females; 24.2 ± 5.8 years) were fitted with Alexa AR (Tiedra Farmacéutica S.L., Madrid, Spain) contact lenses (CLs) and twenty participants finished the follow-up. Visual acuity (VA), subjective refraction, primary spherical and primary coma aberrations, keratometry, central pachymetry, and ocular surface evaluation were performed at baseline and after 1 night, 1 week, 1 month, and 3 months of CL wear. The differences among visits were analyzed using a repeated-measures analysis of variance or the Friedman test. The spherical equivalent decreased (p ≤ 0.005), and the uncorrected VA improved (p < 0.001) until the first week. Corneal and ocular aberrations showed a significant increase (p ≤ 0.02). A significant decrease (p < 0.001) was found for keratometry values. No significant changes were observed in either central pachymetry or ocular surface parameters among study visits. In conclusion, an orthokeratology CL with an ICF of 1.25 D provides good safety, efficacy, and visual performance in a 3-month follow-up. Seven days of orthokeratology wear are enough to achieve the full myopic compensation, resulting in satisfactory VA.

Two Cases of Bilateral Rhegmatogenous Retinal Detachment During Orthokeratology Treatment

Orthokeratology may be effective in slowing myopic progression. However, whether orthokeratology is beneficial enough to prevent rhegmatogenous retinal detachment formation remains unclear. Two cases of bilateral rhegmatogenous retinal detachment were seen during orthokeratology treatment and corrected with scleral buckling and cryopexy under general anesthesia. This is the first report of bilateral retinal detachment found during orthokeratology treatment. Although orthokeratology is effective for myopic correction and prevents axial length elongation, patients still have a risk of rhegmatogenous retinal detachment. Careful follow-up not only of the anterior segment but also of the peripheral retina is necessary.

Prospective assessment of corneal biomechanical properties and intraocular pressure after scleral lens wear: A 12-month follow-up study

PURPOSE

To investigate the long-term influence of scleral lens (SL) wear on corneal biomechanical properties and intraocular pressure (IOP) in irregular and regular corneas. Secondary goal comprised evaluate the fluid reservoir (FR) thickness overtime and correlate it with the changes in corneal biomechanical parameters and IOP.

METHODS

Seventy (70) eyes with irregular corneas (IC Group) and 21 eyes with regular corneas (RC Group) were fitted with 16.4 mm SL and wore the lenses for 12 months. Corrected IOP (IOPcc), Goldmann equivalent IOP (IOPg) and corneal biomechanical parameters (Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF)) were measured with Ocular Response Analyzer. Slit lamp images were analyzed with ImageJ software to assess FR thickness overtime. Measurements were taken at lens dispensing visit prior lens wear (LDV1) and after 60 min of lens wear (LDV2) and at 1, 6 and 12-month follow-up visits. Measurements were done immediately after lens removal.

RESULTS

There were no statistically significant differences on IOPcc, IOPg, CRF and CH over the follow-up visits in both groups. Mean IOPcc and IOPg fluctuations overtime were clinically insignificant and below 1 mmHg in both groups. IOPg, CH and CRF were significantly lower on IC Group (p < 0.001), although no statistically significant differences were found between groups for IOPcc. Regarding FR thickness, statistically significant differences were found over the follow-up on both groups, with a mean decrease of 186.29 µm on IC Group and 175.32 µm on RC Group (p < 0.001). Statistically significant moderate to high negative correlations between FR and IOPg, CRF and CH were found only in the RC Group.

CONCLUSIONS

Long-term SL wear was not associated to changes in corneal biomechanical parameters neither on IOP as measured after lens removal. Besides IOP measurement without SL removal, more studies are needed to investigate the potential relationship with SL fitting characteristics (namely FR thickness).

Epithelial and stromal thickness profile and lens decentration in myopic orthokeratology

PURPOSE

To study topographic epithelial and total corneal thickness changes in myopic subjects undergoing successful orthokeratology treatment in connection with the objective assessment of contact lens decentration.

METHODS

A prospective-observational and non-randomized study in 32 Caucasian myopic eyes undergoing Ortho-k for 3 months. Total, epithelial, and stromal thicknesses were studied before and after Ortho-k treatment, using optical coherence tomography with anterior segment application software. Central, paracentral, and mid-peripheral values are taken along 8 semi-meridians.

RESULTS

The central average total corneal thickness was 4.72 ± 1.04 μm thinner after Ortho-K. The paracentral corneal thickness showed no significant changes (p = 0.137), while the mid-peripheral corneal thickness was increased by 3.25 ± 1.6 μm associating this increase exclusively to the epithelial plot (p<0.001). When lens centration was assessed, a lens fitting decentration less than 1.0 mm was found for the whole sample, predominantly horizontal-temporal (87.5%) and vertical-inferior (50%) decentring. Corneal topographical analysis revealed a horizontal and vertical epithelial thickness asymmetric change profile with paracentral temporal thinnest values, and mid-peripheral nasal thickest values.

CONCLUSIONS

The present study found a central corneal thinning induced by Ortho-k lenses in subjects with moderate myopia, only associated with a change in epithelial thickness, as well as mid-peripheral thickening, that seems to be mainly epithelial in origin. The authors also found a tendency of contact lens decentration toward temporal and inferior areas conditioning an asymmetric epithelial redistribution pattern.

The rate of orthokeratology lens use and associated factors in 33,280 children and adolescents with myopia: a cross-sectional study from Shanghai

OBJECTIVES

To investigate the rate of orthokeratology lens (ortho-k lens) use and its associated factors in children and adolescents with myopia.

METHODS

Cross-sectional study. Children from 104 primary and middle schools in Shanghai were enrolled by cluster sampling. Ophthalmic examinations were conducted and information was obtained using questionnaires for associated factors analysis.

RESULTS

A total of 72,920 children and adolescents were included, among which 32,259 were the potential population for ortho-k lens use. A total of 1021 participants used ortho-k lenses, equating to a use rate of 1.4% in the total population and 3.1% in the potential population. Age (OR 0.91, 95% CI: 0.88-0.95, p < 0.001), BMI (≥95th percentile: OR 0.48, 95% CI: 0.35-0.66, p < 0.001), age at initiation of refractive correction (≤12 years: OR 1.75, 95% CI: 1.31-2.33, p < 0.001), and parental myopia (either: OR 2.09, 95% CI: 1.58-2.75, p < 0.001; both: OR 3.94, 95% CI: 3.04-5.11, p < 0.001) were independently associated with ortho-k lens use. Of the ortho-k lenses users, 12.4% had a logMAR CVA of ≥0.3. A correction target (SE) of ≤-3.0 D (OR 2.05, 95% CI: 1.38-3.05, p < 0.001) and a sleeping duration of ≤6 h (OR 4.19, 95% CI: 2.03-8.64, p < 0.001) were factors independently associated with CVA ≥ 0.3.

CONCLUSIONS

A certain proportion of children and adolescents in Shanghai chose to wear ortho-k lenses, related to the situation of parents and children themselves. Health education and follow-ups should be strengthened to ensure orthokeratology application quality.

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.

Long-Term Efficacy of Orthokeratology to Control Myopia Progression

OBJECTIVES

To assess the efficacy of orthokeratology in controlling the rate of myopia progression in children and investigate the factors associated with axial length (AL) growth rate with an average of 48 months of orthokeratology lens wear.

METHODS

As a retrospective study, 84 subjects underwent relatively complete ophthalmologic examinations. After initial lens wear, AL was measured on average every 12 months. The linear mixed-effects model (LMM) was used to compare the differences in AL growth rates at each time interval. The contribution of the independent variables to AL change was assessed using multiple linear regression.

RESULTS

In the LMM, there was a significant difference in the AL growth rate ( P <0.001) at each follow-up. The growth rate of AL was associated with initial AL, spherical equivalent refractive errors (SERs) and diameter of lens ( P =0.045, 0.003 and 0.037, respectively). When the baseline age was included as a factor, the influence of initial AL and SER became insignificant in the analysis, whereas age and diameter of lens were significantly correlated with the growth rate of AL ( P< 0.001 and P< 0.001, respectively). There were significant differences in growth rates among different age groups.

CONCLUSIONS

Results of the study demonstrated that the factors associated with lower growth rate in AL were older age and longer diameter of lens.

Short- and mid-term changes in CORVIS ST parameters in successful, adult orthokeratology patients

CLINICAL RELEVANCE

The changes in various biomechanical and tomographic characteristics of the cornea associated with orthokeratology may allow us to identify potential mid- and long-term structural alterations, resulting in a better understanding of the governing mechanisms of this procedure and in its optimisation.

BACKGROUND

The study aimed at describing short and mid-term changes in CORVIS ST® parameters and indices in orthokeratology (ortho-k), and their diurnal variations.

METHODS

A prospective observational study was designed in which several CORVIS ST® parameters of 75 new adult participants successfully fitted with overnight ortho-k Seefree® (Conóptica - Hecht Contactlinsen) contact lenses were explored. Measurements were conducted in baseline (BL) conditions and in the morning and evening at the one-night (1 NM/1NT), one-week (1WM/1 WT) and 3-month (3 MM/3MT) follow-up visits.

RESULTS

Statistically significant differences were found in DARatio_2 mm, IntRad, ARTh, CBI and TBI following overnight ortho-k, when compared with BL values, with most values reaching stability at 1WM or reverting to BL values at 3 MM. The ARTh and CBI parameters showed some of the most significant temporal variations (both p < 0.001), probably reflecting the encountered differences in central corneal thickness between BL and 1WM (p = 0.010) and between BL and 3 MM (p = 0.016). In general, corneal rigidity was higher in the morning at all follow-up visits, and decreased during the day. No statistically significant changes in adjusted intraocular pressure values were found.

CONCLUSION

Ortho-k in adults may be considered a safe procedure in terms of short and mid-term changes in CORVIS ST® parameters. The observed alterations in most of the parameters provided by the Corvis ST® probably responded to the well-described changes in corneal pachymetry and tomography, rather than to actual alterations in corneal rigidity.

A machine learning-based algorithm for estimating the original corneal curvature based on corneal topography after orthokeratology

OBJECTIVE

To estimate the original corneal curvature after orthokeratology by applying a machine learning-based algorithm.

METHODS

A total of 497 right eyes of 497 patients undergoing overnight orthokeratology for myopia for more than 1 year were enrolled in this retrospective study. All patients were fitted with lenses from Paragon CRT. Corneal topography was obtained by a Sirius corneal topography system (CSO, Italy). Original flat K (K1) and original steep K (K2) were set as the targets of calculation. The importance of each variable was explored by Fisher's criterion. Two machine learning models were established to allow adaptation to more situations. Bagging Tree, Gaussian process, support vector machine (SVM), and decision tree were used for prediction.

RESULTS

K2 after one year of orthokeratology (K2after) was most important in the prediction of K1 and K2. Bagging Tree performed best in both models 1 and 2 for K1 prediction (R = 0.812, RMSE = 0.855 in model 1 and R = 0.812, RMSE = 0.858 in model 2) and K2 prediction (R = 0.831, RMSE = 0.898 in model 1 and R = 0.837, RMSE = 0.888 in model 2). In model 1, the difference was 0.006 ± 1.34 D (p = 0.93) between the predictive value of K1 and the true value of K1 (K1before) and was 0.005 ± 1.51 D(p = 0.94) between the predictive value of K2 and the true value of K2 (K2before). In model 2, the difference was -0.056 ± 1.75 D (p = 0.59) between the predictive value of K1 and K1before and was 0.017 ± 2.01 D(p = 0.88) between the predictive value of K2 and K2before.

CONCLUSION

Bagging Tree performed best in predicting K1 and K2. Machine learning can be applied to predict the corneal curvature for those who cannot provide the initial corneal parameters in the outpatient clinic, providing a relatively certain degree of reference for the refitting of the Ortho-k lenses.

The efficacy and safety of 0.01% atropine alone or combined with orthokeratology for children with myopia: A meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of 0.01% atropine alone and in combination with orthokeratology for myopia control using a meta-analysis.

METHODS

PubMed, Cochrane Library, and EMBASE were searched. We included eligible randomized controlled trials (RCTs), non-RCTs, and retrospective cohort studies, published up to August 1, 2022. We calculated the weighted mean difference (WMD) and 95% confidence interval (CI) for all outcomes and plotted them in forest plots.

RESULTS

Fourteen studies were included; 4 and 11 in the 0.01% atropine monotherapy and atropine-orthokeratology (AOK) groups, respectively. Compared with orthokeratology (OK) alone, 0.01% atropine alone had similar effects on slowing the axial elongation (WMD: -0.00 mm; 95% CI: -0.05-0.04, p<0.31), while AOK significantly lowered axial growth. Moreover, the baseline myopic degree and duration of treatment were influential for the change in axial elongation (WMD: -0.12 mm; 95% CI: -0.17--0.07, p = 0.00001 and WMD: -0.11 mm; 95% CI: -0.15--0.108, p<0.00001, respectively). Additionally, the AOK may reduce the change rate of the spherical equivalent refraction and the accommodation amplitude (WMD: -0.13 D; 95% CI: 0.07-0.19, p<0.001 and WMD: -1.08 mm; 95% CI: -1.73--0.43, p<0.0001, respectively), and cause a slight increase in the diameter of the pupil (WMD: 0.56 mm; 95% CI: 0.43-0.70, p = 0.007). No significant differences in the uncorrected distant visual acuity, best corrected visual acuity, intraocular pressure, tear film break-up time, lipid layer thickness, and corneal endothelial cell density were found between the OK and AOK groups.

CONCLUSION

In slowing the axial elongation, 0.01% atropine alone and OK alone have similar effects, while AOK is more effective than OK alone in slowing down the axial elongation. Furthermore, the baseline degree of myopia and treatment duration may affect changes in axial elongation.

Orthokeratology in adults and effect on quality of life

OBJECTIVE

To determine changes in various ocular parameters of adults wearing orthokeratology (ortho-k) lenses and their levels of satisfaction and quality of life (QoL) after commencing treatment.

METHODS

Adults aged 18-38 years, with mild to moderate myopia and astigmatism < 1.50D, were wearing ortho-k lenses for one year. Data collection, which included history taking, refraction, axial length (AL), corneal topography, corneal biomechanics, and biomicroscopy examination, was performed at baseline and every 6 months during the study period. The level of satisfaction with the treatment and QoL was determined via questionnaires.

RESULTS

Forty-four subjects completed the study. AL was shortened significantly at the 12-month visit: AL -0.03 (-0.45 to 0.13) mm compared to baseline (p < 0.05). A significant number of subjects in both groups presented with overall and central corneal staining, but the majority were mild (Grade 1). Central endothelial cell density was reduced by 40/mm² (loss rate 1.4 %) (p < 0.05). High scores were obtained in the satisfaction questionnaire, with no significant differences between visits. At the 12-month visit, NEI-RQL-42 total score, dependence on correction, activity limitation, appearance, and satisfaction with the treatment all significantly increased compared to baseline values.

CONCLUSIONS

Results suggest that ortho-k can be an effective and safe myopia correction technique for adults with low to moderate myopia, improving daytime vision without serious adverse events. Satisfaction with ortho-k lens wear was high, particularly those who were dependent on vision correction and found spectacles or contact lenses limiting specific activities or cosmetically undesirable.

Orthokeratology lenses with increased compression factor (OKIC): A 2-year longitudinal clinical trial for myopia control

PURPOSE

To investigate the effectiveness of orthokeratology (ortho-k) lenses and corneal changes with increased compression factor for myopia control over a 2-year period.

METHODS

Young participants (age: 6-<12 years), with low myopia (0.50-4.00 D) and low astigmatism (≤1.25 D), were recruited and allowed to choose to wear either single-vision spectacles or ortho-k lenses (randomly assigned to compression factor of either 0.75 or 1.75 D). Axial length and cycloplegic refraction were measured at six monthly intervals for two years by a masked examiner. The myopia control effectiveness was determined by axial elongation.

RESULTS

A significant number of control (63 %) dropped out, mainly due to concern about myopia progression (58 %). A total of 75 participants (mean age: 9.3 ± 1.0 years; control: n = 11, ortho-k [0.75 D]: n = 29, ortho-k [1.75 D]: n = 35) completed the study. Considering ortho-k groups only, the mean axial elongation of participants wearing ortho-k lenses of conventional compression factor (0.75 D) and increased compression factor (1.75 D) were 0.53 ± 0.29 and 0.35 ± 0.29 mm, respectively, over the 2-year study period. The between-group differences in corneal health were not significant at all visits.

CONCLUSION

Participants wearing ortho-k lenses of increased compression factor further slowed axial elongation by 34%, when compared with the conventional compression factor without compromising corneal health. Further investigations are warranted to confirm the potential mechanism of an increased compression factor for improved myopia control effectiveness.

Effect of overnight orthokeratology lenses on tear film stability in children

PURPOSE

To assess the tear film surface quality after orthokeratology using an automated Medmont E300 corneal topographer.

METHODS

Children who wore orthokeratology lenses for more than one year were selected in this retrospective study. Tear film disruption (TFD) and central tear film disruption (cTFD) were measured with Medmont E300 corneal topographer at initial and each follow-up visit after fitting with orthokeratology lenses, providing a nominal value from 0 (perfect) to 1 (poor). Tear film surface quality before and after ortho-k treatment was compared.

RESULTS

145 children using orthokeratology lenses were observed. TFD and cTFD significantly increased at 1-day follow up (TFD, t = -17.3, P < 0.001; cTFD, t = -10.4, P < 0.001). This change remained consistent through to 12-months visit (TFD, F = 51.1, P < 0.001; cTFD, F = 28.0, P < 0.001). A sub-group of n = 11 children were discontinued for 1-month before being refit with OrthoK lenses of a different design. Similarly, there was a significant increase in TFD compared to pre-orthoK scans (0.172 ± 0.161), but this returned to baseline levels after ceasing lens wear (0.084 ± 0.059). A sub-group of monocular OrthoK wearers (n = 23) found that TFD and cTFD values increased in eyes with monocular lens-wearing but remained stable in the lateral eyes.

CONCLUSIONS

Objective measurements of tear-film quality are reduced in children after fitting with orthokeratology lenses, but return to baseline after 1-month of lens cessation. It is of importance to ensure tear film surface quality is continuously monitored throughout use of orthoK lenses.

Long-term changes in the ocular surface during orthokeratology lens wear and their correlations with ocular discomfort symptoms

PURPOSE

To evaluate the changes in ocular surface parameters during orthokeratology lens wear and determine their correlations with ocular discomfort symptoms.

METHODS

Fifty individuals were enrolled in this prospective pilot study. Clinical evaluation of the ocular surface included the ocular surface disease index, slit-lamp examination, Keratograph 5M, optical quality analysis system, and corneal staining. After baseline examinations, clinical tests were performed at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after orthokeratology lens wear. Correlations between ocular discomfort symptoms and signs of ocular discomfort were evaluated.

RESULTS

Overall ocular surface disease index score and two subscale scores (ocular symptoms and vision-related function) significantly increased at the 3-month visit (P < 0.05), and decreased to levels close to baseline at the12-month visit (P > 0.05). The basic objective scatter index and the mean tear film objective scatter index increased, peaking at 3-month visit (P < 0.05) and gradually decreased thereafter. The modulation transfer function cut-off significantly decreased at the 3-month visit (P < 0.05). During the 12-month study period, the overall ocular surface disease index score and vision-related function score were significantly and positively correlated with the basic objective scatter index and mean tear film objective scatter index (P < 0.05). After 1 week of lens wear, Grade 1 corneal staining increased to 16.4 %, mostly involving the central and inferior cornea.

CONCLUSIONS

Orthokeratology lens wear increased ocular discomfort symptoms and decreased the function of tear film, mainly within 3 months of lens wear. Tear-related visual function parameters were correlated with ocular discomfort. A new parameter, tear film objective scatter index, measured with the optical quality analysis system, was more sensitive in detecting the quality and stability of tear film than traditional indicators.

Deep learning system to predict the 5-year risk of high myopia using fundus imaging in children

Our study aims to identify children at risk of developing high myopia for timely assessment and intervention, preventing myopia progression and complications in adulthood through the development of a deep learning system (DLS). Using a school-based cohort in Singapore comprising of 998 children (aged 6-12 years old), we train and perform primary validation of the DLS using 7456 baseline fundus images of 1878 eyes; with external validation using an independent test dataset of 821 baseline fundus images of 189 eyes together with clinical data (age, gender, race, parental myopia, and baseline spherical equivalent (SE)). We derive three distinct algorithms - image, clinical and mix (image + clinical) models to predict high myopia development (SE ≤ -6.00 diopter) during teenage years (5 years later, age 11-17). Model performance is evaluated using area under the receiver operating curve (AUC). Our image models (Primary dataset AUC 0.93-0.95; Test dataset 0.91-0.93), clinical models (Primary dataset AUC 0.90-0.97; Test dataset 0.93-0.94) and mixed (image + clinical) models (Primary dataset AUC 0.97; Test dataset 0.97-0.98) achieve clinically acceptable performance. The addition of 1 year SE progression variable has minimal impact on the DLS performance (clinical model AUC 0.98 versus 0.97 in primary dataset, 0.97 versus 0.94 in test dataset; mixed model AUC 0.99 versus 0.97 in primary dataset, 0.95 versus 0.98 in test dataset). Thus, our DLS allows prediction of the development of high myopia by teenage years amongst school-going children. This has potential utility as a clinical-decision support tool to identify "at-risk" children for early intervention.

[Effect of conventional and orthokeratological hard contact lenses on anatomical and functional characteristics of the cornea]

Contact lenses are widely used for correction of myopia due to their accessibility, effectiveness and relative safety.

PURPOSE

This study evaluated the potential effects of conventional hard contact lenses (HCL) and orthokeratological contact lenses (OKL) on anatomical and functional condition of the cornea in myopia correction.

MATERIAL AND METHODS

The study included 80 patients (159 eyes) with low, moderate and high myopia. Group 1 consisted of 40 patients (79 eyes) who used conventional HCL; group 2 included 40 patients (80 eyes) who used OKL. All patients underwent topographic keratometry, corneal pachymetry mapping (Pentacam, Oculus, Germany; Visante OCT, Carl Zeiss, Germany), high-order aberrometry (OPD Scan, Nidek, Japan), confocal microscopy (Confoscan 4, Nidek, Japan), evaluation of corneal biomechanical properties (ORA, Reichert Technologies, USA) and corneal light scattering (Pentacam, Oculus, Germany). Examinations were taken before the treatment started and after 8-12 months of contact lens wear.

RESULTS

Group 1 showed corneal thickness increase in all zones (by 0.9-1.1%), no significant changes in corneal refraction, and increase in corneal hysteresis and corneal resistance factor. OKL wear led to a significant flattening of anterior surface of the cornea and steepening of its paracentral area, decrease in central corneal thickness (by 2.8%) and increase in mid-peripheral thickness (by 2.2%). No significant changes in posterior corneal surface were observed in the study patients. More significant increase in higher-order aberrations and the degree of light scattering was observed in group 2, while changes in subepithelial nerve plexus and stromal structure were more significant in group 1.

CONCLUSION

Long-term OKL wear shows more significant morphological and functional corneal changes compared to RGP lens.

Comparison of Functional Vision and Eye-Related Quality of Life between Myopic Children Treated with Orthokeratology and Single-Vision Spectacles in Southern China

Objective

To compare eye-related quality of life between Chinese children wearing orthokeratology (OK) contact lenses and single-vision spectacles (SVS) using the Pediatric Eye Questionnaire (PedEyeQ) and to evaluate the impact of different myopia correction methods on children and their parents.

Methods

Children aged 12-17 years and their parents/legal guardians were recruited. The children's myopia ranged from -0.50 to -5.00 diopters (D), and their astigmatism was <1.50 D. They had all been wearing OK contact lenses or SVS for at least 12 months. The children completed the Child PedEyeQ. One of their parents (or a legal guardian) completed the Proxy PedEyeQ and the Parent PedEyeQ. Rasch-calibrated PedEyeQ scores were calculated for each domain and were converted to a scale from 0 to 100 for statistical analysis.

Results

A total of 50 children wearing OK contact lenses, 43 children wearing SVS, and their parents/legal guardians completed the questionnaires. The scores of all Child, Proxy, and Parent PedEyeQ domains in the OK contact lens group were higher than those in the SVS group (all P < 0.05). In the mild and moderate myopia subgroups, the Child, Proxy, and Parent PedEyeQ scores in the mild myopia OK contact lens subgroup were higher than those in the mild myopia SVS group (all P < 0.05) except functional vision and bothered by eyes/vision domains for the proxy PedEyeQ. Similarly, the Child, Proxy, and Parent PedEyeQ scores in the moderate myopia OK contact lens subgroup were higher than those in the moderate myopia SVS subgroup (all P < 0.05) except impact on parent and family domain for the parent PedEyeQ. In the subgroup analysis of glasses type, no significant score difference of any Child, Proxy, and Parent PedEyeQ domain was detected between mild and moderate myopia in either the OK contact lens group or the SVS group (all P > 0.05).

Conclusion

Compared with children wearing SVS, children wearing OK contact lenses have better functional vision and eye-related quality of life. Moreover, OK contact lens has a better correction effect, higher acceptance rates, and less impact on parents and families than SVS.

Application of orthokeratology on myopia control and its effect on ocular surface and meibomian gland function in Chinese myopic adolescents

Purpose

This study aimed to investigate the influence of orthokeratology (OK) on myopia control and ocular surface and meibomian gland function in myopic adolescents.

Methods

A prospective study was conducted over a 12-month period. The subjects were classified into two groups, namely, the OK lens group and the frame glasses control group. Axial length, corneal curvature, ocular surface, and meibomian gland parameters were measured at baseline, 1, 3, 6, and 12 months after wearing OK lenses.

Results

The axial length growth rate in the OK group was significantly slower than in the control group (P < 0.01). The naked eye vision and the ocular surface disease index (OSDI) scores recorded 1, 3, 6, and 12 months after wearing OK lenses were significantly higher than the scores recorded before wearing OK lenses. There was no significant difference in other ocular parameters at each follow-up time point compared with pre-wearing (P > 0.05). After using the OK lens for 6 months, the OSDI score and corneal fluorescein staining (CFS) score increased significantly (P < 0.001), but there were no significant differences in other parameters among the groups. No infectious keratitis occurred during the study.

Conclusion

These results provide evidence that the use of OK lenses can control the axial growth and progress rate of myopia compared with frame glasses. During the 12-month follow-up, although wearing OK lenses may have aggravated dry eye symptoms, each patient's ocular surface and meibomian gland function did not change significantly, indicating that the use of OK lenses is a relatively safe modality for the control of myopia in adolescents.

Contact Lens Safety for the Correction of Refractive Error in Healthy Eyes

ABSTRACT

Contact lenses are a safe and effective method for correction of refractive error and worn by an estimated 45 million Americans. Because of the widespread availability and commercial popularity of contact lenses, it is not well appreciated by the public that contact lenses are U.S. Food and Drug Administration (FDA)-regulated medical devices. Contact lenses are marketed in numerous hard and soft materials that have been improved over decades, worn in daily or extended wear, and replaced in range of schedules from daily to yearly or longer. Lens materials and wear and care regimens have impact on the risks of contact lens-related corneal inflammatory events and microbial keratitis. This article reviews contact lens safety, with specific focus on the correction of refractive error in healthy eyes.

Immediate Effect in the Retina and Choroid after 650 nm Low-Level Red Light Therapy in Children

INTRODUCTION

The objective of this study was to investigate the changes in the retina and choroid of children after 650 nm low-level red light therapy (LLRLT).

METHODS

In this prospective study, 25 subjects in the Shanghai Eye and ENT Hospital of Fudan University were included from August 2021 to September 2021. One eye was randomly selected to receive LLRLT for 3 min. Swept-source optical coherence tomography (OCT) and OCT angiography were used to measure retinal fovea perfusion density (RFPD), retinal fovea thickness (RFT), choroidal fovea blood flow (CFBF), and choroidal fovea thickness (CFT) before LLRLT, 5 min and 1 h after LLRLT. Baseline characteristics between LLRLT and non-LLRLT eyes were compared. Changes in the retinal and choroidal parameters were analyzed by ANCOVA models. SAS software was used for data analysis. The difference was considered statistically significant if p < 0.05.

RESULTS

There was no difference in baseline characteristics between LLRLT eyes and non-LLRLT eyes. The RFPD in LLRLT eyes significantly increased 5 min after LLRLT, and the increment was 1.70 ± 0.83% (p = 0.0389). The RFPD significantly decreased from 5 min to 1 h after LLRLT with a mean of -2.62 ± 0.86% decrement (p = 0.0031). The RFPD levels returned to baseline at 1 h after LLRLT (p = 0.8646). However, compared with insignificant RFPD changes in non-LLRLT eyes, there was no significant difference in RFPD changes at any sampling point. No significant changes in RFT, CFBF, and CFT were found in LLRLT eyes at each sampling point.

CONCLUSION

Although 3 min of LLRLT has no effect on the choroid, it may cause a short-term transient increase in RFPD. It will provide theoretical support for the role of LLRLT in myopia control.

Electroretinogram responses in myopia: a review

The stretching of a myopic eye is associated with several structural and functional changes in the retina and posterior segment of the eye. Recent research highlights the role of retinal signaling in ocular growth. Evidence from studies conducted on animal models and humans suggests that visual mechanisms regulating refractive development are primarily localized at the retina and that the visual signals from the retinal periphery are also critical for visually guided eye growth. Therefore, it is important to study the structural and functional changes in the retina in relation to refractive errors. This review will specifically focus on electroretinogram (ERG) changes in myopia and their implications in understanding the nature of retinal functioning in myopic eyes. Based on the available literature, we will discuss the fundamentals of retinal neurophysiology in the regulation of vision-dependent ocular growth, findings from various studies that investigated global and localized retinal functions in myopia using various types of ERGs.

Corneal Wound Associated With Orthokeratology Lenses

This case report describes a diagnosis of corneal epithelial defect after a patient presentation of eye pain and tearing with orthokeratology lens wear.

Analysis of the Reasons for the Discontinuation of Orthokeratology Lens Use: A 4-Year Retrospective Study

PURPOSE

Although orthokeratology has a positive effect on myopia control, some patients discontinue orthokeratology lens use. This study analyzed the data of all patients who had been fitted with an orthokeratology lens in the past 4 years and the reasons for discontinued lens use, with the aim of improving the prevention and control of myopia.

METHODS

This retrospective study analyzed the data of patients, aged 8 to 18 years, fitted with orthokeratology lenses from 2017 to 2020. The ametropic spherical lens powers ranged from -6.00 D to -0.75 D, and the cylindrical lens powers were all more than -1.50 D. The reasons for discontinuation of lens wear were analyzed and compared. The period of lens wear (median [range]) was 24 (13.5-34.5) months.

RESULTS

A total of 2,499 patients' files were retrieved. The duration of lens wear was 24 (13.5-34.5) months. A total of 50 patients discontinued lens use, including 25 patients (50.0%) who could not adhere to lens use for various reasons, nine patients (18.0%) with a short sleep time, eight patients (16.0%) with economic difficulties, and five patients (10.0%) who experienced a poor effect after wearing the lenses. Corneal infiltrates affected lens use in three patients (6.0%). In addition, 30 patients underwent surgical correction when they reached adulthood.

CONCLUSION

Although orthokeratology lenses are effective and safe, there are still a small number of patients who discontinued lens use for various reasons. Adherence and precautions should be emphasized during the process.

Assessment of Satisfaction, Compliance and Side Effects among Long-Term Orthokeratology Wearers

Purpose: This study aims to assess the satisfaction, compliance, and side effects among the long-term orthokeratology (Ortho-K) users in a tertiary hospital in Taiwan and analyze the side effects and related risk factors. Methods: Children and their guardians were assessed using a structured and validated questionnaire inquiring about background information, wear and care behaviors, daily activities, satisfaction, and related concerns. Clinical information, including refractive data and side effects, was obtained through patient medical files. Results: Three hundred and five school-aged patients were enrolled, and the average age was 13.13 ± 3.39 years, with an average wearing period of 17.1 ± 8.1 months. Over 83% of the subjects had clear daytime vision all day, around 88% felt satisfied or very satisfied with the results, and 98% exhibited a willingness to continue wearing the Ortho-K lenses. Most guardians (83%) were pleased with the controlling effect of myopic progression. Initial spherical equivalent and regular cleaning of the lens protein significantly correlated with clear day vision. Wearing >6 days/week correlated with less risk of lens binding. Based on the questionnaire, the main reasons for using Ortho-K were effectiveness, safety, and practicality, while the major concerns were discomfort, harmful to the eyes, and no effect. Conclusion: With a comprehensive care program from practitioners and good compliance of users, Ortho-K could be the most effective and satisfactory option for myopic children in Taiwan.

The Effect of Corneal Refractive Power Area Changes on Myopia Progression during Orthokeratology

Purpose

To investigate the effect of corneal refractive power area changes on myopia progression during orthokeratology.

Methods

One hundred and sixteen children who met the inclusion criteria and insisted on wearing orthokeratology lenses for two years were retrospectively assessed. Seventy-two children with the orthokeratology lens decentration distance more than 0.5 mm but less than 1.5 mm were in the decentered group, and forty-four children with the orthokeratology lens decentration distance less than 0.5 mm were in the centric group. The orthokeratology decentration via tangential difference topography was analyzed. This study calculated the different power areas in the central 4 mm pupillary area by axial-difference corneal topography, compared the differences of the different power areas between these two groups, and evaluated the relationships between corneal positive-power area, orthokeratology decentration, and AL changes.

Results

The axial length changes of the centric group presented a statistical difference with the decentered group (0.52 ± 0.37 mm vs. 0.38 ± 0.26 mm; t = 2.403, p=0.018). For all children, both the AL changes (0.43 ± 0.31 mm) and decentration distance (0.64 ± 0.33 mm) showed a significant correlation with the positive-power area (r = −0.366, p < 0.001 and r = 0.624, p < 0.001); AL changes also presented a statistical correlation with decentration distance (r = −0.343, p < 0.001), baseline age (r = −0.329, p < 0.001), and baseline spherical equivalent refractive power (r = 0.335, p < 0.001). In the centric group and decentered group, the AL changes (centric group: r = −0.319, p=0.035; decentered group: r = −0.332, p=0.04) and decentration distance (centric group: r = 0.462, p=0.002; decentered group: r = 0.524, p < 0.001) had a significant correlation with the positive-power area yet. In the multiple regression analysis, AL changes were increased with less baseline age (beta, 0.015; p < 0.001), positive-power area (beta, 0.021; p=0.002), and larger SER (beta, 0.025; p=0.018).

Conclusions

The corneal positive-power area had a positive impact on affirming AL changes during orthokeratology. This area might be formed by lens decentration to provide an additional myopia-defocusing influence on the retina to achieve better myopia control.

Comparison of compliance with care procedures performed by orthokeratology wearers and their parents and factors affecting compliance

PURPOSE

To compare the levels of compliance with care routines of orthokeratology (ortho-k) wearers and their parents and to identify factors affecting compliance in a hospital setting in Chengdu, China.

METHODS

Patients who had worn ortho-k lenses for at least one month were invited to participate in a survey on compliance. Wearers or their parents were required to complete a questionnaire to determine their compliance with hand hygiene, ortho-k lenses and accessory care procedures.

RESULTS

A total of 200 wearers, 78 male wearers and 122 female wearers, median age 12 (range 8-18) years were enrolled. Except for use of lens solution, the percentage of participants reporting total compliance with all procedures did not differ significantly between lens wearers and their parents. However, compliance for some items was significantly higher when performed by parents p < 0.001-0.01). 'Eye care practitioner provided instructions' was a significant protective factor for most procedures (p < 0.001-0.04). Age and sex were significant risk factors for some items (p < 0.001-0.04; p = 0.03-0.04, respectively), with girls having higher compliance than boys. 'Parental supervision' was a significant protective factor for some items (p = 0.02-0.04) when wearers performed the procedures themselves. When parents performed lens care procedures, only 'eye care practitioner provided instructions' was a significant variable (p = 0.001-0.04).

CONCLUSION

Some degree of non-compliance was noted in the majority of ortho-k wearers, particularly for the care of the lens case and suction holder. Compliance with care of some items was higher when performed by parents. Regular reinforcement of care procedures by practitioners is important, especially for older and male lens wearers. Parental supervision is necessary when children perform lens care procedures themselves, even for older wearers.

Fitting of Orthokeratology in the United States: A Survey of the Current State of Orthokeratology

SIGNIFICANCE

The Fitting of Orthokeratology in the United States (FOKUS) survey provides information about the United States (US) OrthoK market. This independent survey is the first to attain detailed assessment of the OrthoK market.

PURPOSE

Develop and administer a survey to eye care providers (ECP's) in the US who are managing orthokeratology patients and those who are not to determine a profile of prescribers, patients and overall market.

METHODS

The FOKUS survey was administered and distributed online. Outcome measures of the FOKUS survey involved general categories of 1) practice and practitioner profiles, 2) clinical prescribing patterns, 3) patient profile, 4) products and marketing, 5) fees and 6) market size and growth.

RESULTS

The number of ECP's who are actively fitting and managing OrthoK patients in the US is approximately 3,000. 545 responded to the survey, 283 reported they were actively fitting orthokeratology. Orthokeratology is prescribed with the intent of managing myopia by 68% of respondents, 53% monitor axial length, and 61% start OrthoK patients at age 13 years old or under. The mean number of years a patient wears OrthoK is 7.8. A commonly reported complication with orthokeratology is corneal staining. Microbial keratitis (MK) is rarely or never seen by 86% of respondents. Of those currently fitting, 56% anticipate growth of orthokeratology fitting over the next twelve months. Of those not currently fitting orthokeratology, 46% plan to start within two years.

CONCLUSIONS

Orthokeratology represents a small but growing segment of the US contact lens market. The number of practitioners actively prescribing and fitting orthokeratology in the US is approximately 3,000 with high potential for growth within the next two years. Results of the FOKUS survey are relevant to practitioners currently fitting or considering orthokeratology, manufacturers, educators and researchers as baseline for future orthokeratology market assessment.

Overview on Defocus Incorporated Multiple Segments Lenses: A Novel Perspective in Myopia Progression Management

Myopia is becoming more common across the world, affecting approximately two billion people and rising. Different kinds of therapies (optical, pharmaceutical, environmental, or behavioral) have been proposed to decrease myopia progression, but with variable results and a lack of standardization. The evidence that targeted myopic defocus inhibits eye length growth has paved the way for several contact and spectacle lense designs to induce a peripheral defocus, thus slowing myopia progression, but the perfect configuration has yet to be defined. One of the newest and more promising approaches in this field is the use of Defocus Incorporated Multiple Segments (DIMS) lenses. These lenses are built from the assumption that targeted myopic defocus, produced by 396 mid-peripheral lenslets with positive power, inhibits eye length growth. Recent studies have highlighted the effectiveness of these lenses compared to children who had worn single vision spectacle lenses, in terms of myopia control and tolerability. Despite the evidence that these lenses can help slow down the progression of myopia, the occasional mid-peripheral aberrations they can induce, as well as the overall eye strain that comes with wearing them, should not be overlooked. The aim of this review is to give attention to the advantages and the shortfalls of this new approach and to evaluate its effectiveness in clinical practice.

Comparison of Two Main Orthokeratology Lens Designs in Efficacy and Safety for Myopia Control

Purpose

This study aimed to compare the efficacy and safety of corneal refractive therapy (CRT) lenses and vision shaping treatment (VST) lenses for myopia control in children.

Methods

Medical records of 1,001 children (2,002 eyes) who had been fitted with orthokeratology lenses for over 1.5 years were retrospectively reviewed. We collected the clinical data of four types of orthokeratology (OK) lenses available: one CRT lens (brand: CRT) and three VST lenses (brands: Euclid, Alpha, and Hiline) over 1.5 years. Results were compared and analyzed using a one-way ANOVA and Pearson's chi-square test.

Results

Axial length elongation in the CRT lens group was 0.13 ± 0.02 mm faster than that in the Euclid lens, 0.1 ± 0.02 mm faster in the Alpha lens, and 0.08 ± 0.02 mm faster in the Hiline lens over the 1.5-year period (all P < 0.05). Among the subjects, 37.3% of them using the CRT lens experienced more than 1 D of refractive growth, compared with 20.2–30.8% of subjects wearing the three groups of VST lenses (all P < 0.05). A lower incidence of total adverse events was found with the CRT lenses compared with the VST lenses (P < 0.05), especially corneal staining. No difference was found in axial length elongation, refraction growth, and incidence of adverse events among the three types of VST lenses (all P > 0.05).

Conclusions

Compared with the VST lenses, CRT lenses demonstrated a weaker effect on myopia control but with a better safety profile. Different types of VST lenses had similar efficacy and safety in the context of controlling myopia progression.

Group-Based Trajectory Modeling to Identify Factors Influencing the Development of Myopia in Patients Receiving Orthokeratology

Purpose

To analyze the factors influencing the progression of myopia in adolescents receiving orthokeratology.

Methods

This prospective cohort study collected the data of 378 myopia patients receiving orthokeratology. The follow-up time was 12 months ranging from December 2015 to December 2019. The group-based trajectory modeling (GBTM) was used to identify similar developmental trajectories in the levels of uncorrected visual acuity and changes of axial length elongation. Univariate and multivariate logistic regression analyses were conducted to explore the influencing factors of myopia development in patients wearing orthokeratology.

Results

There was no factor having effect on visual acuity (left) and visual acuity (right) in different trajectories (all P>0.05). The corneal curvature K1 (left) (OR=0.382, 95% CI: 0.188–0.776), corneal curvature K2 (left) (OR=0.362, 95% CI: 0.187–0.699), degree of spherical refraction (left) (OR=0.139, 95% CI: 0.082–0.235) and spherical equivalent (left) (OR=7.276, 95% CI: 3.724–14.215) were factors associated with the changes of axial length elongation (left). The corneal curvature K1 (right) (OR=0.260, 95% CI: 0.116–0.585), corneal curvature K2 (left) (OR=0.272, 95% CI: 0.121–0.610) and degree of spherical refraction (right) (OR=0.129, 95% CI: 0.068–0.244) were correlated with the changes of axial length elongation (right). All P<0.05.

Conclusion

Orthokeratology is a promising method for controlling the progression of myopia. The corneal curvature, degree of spherical refraction and spherical equivalent were factors influencing the changes of axial length elongation in myopia patients wearing orthokeratology. The findings might give a reference for the application of orthokeratology in clinic.

Evaluation of the meibomian glands using the tear interferometer wearing orthokeratology lenses

Background

To investigate the impact of orthokeratology wear on meibomian glands in Korean pediatric population using the tear interferometer.

Methods

Fifty-three orthokeratology wearers and 79 non-lens wearers were evaluated using the LipiView® II ocular surface interferometer which shows incomplete blink rate, average lipid layer thickness, and meiboscores.

Results

No significant differences in the incomplete blink rate and meiboscores for upper eyelids, but the lipid layer thickness and meiboscores for lower eyelids were significantly higher in the Ortho-K group than in the control group (p = 0.024 and 0.007, respectively). Correlation analysis showed no significant correlation between the duration of orthokeratology wear and the parameters measured by LipiView® (p > 0.05 for all). Among subgroups based on average duration of lens wear, the longer duration (≥ 24 months) subgroup showed higher meiboscores of lower eyelids (p = 0.011), but no other significant differences.

Conclusions

Ortho-K wearers showed no significant differences in the incomplete blink rate and meiboscores of upper eyelids, but they were associated with increased LLT and higher meiboscores of lower eyelids. Thorough examination and close monitoring of orthokeratology wearers is necessary. Prospective and observational studies are needed to further elucidate the relationship between Orthokeratology and meibomian glands.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02365-3.

Overnight orthokeratology-associated Acanthamoeba keratitis at a tertiary referral hospital in Taiwan: A retrospective case-control study

BACKGROUND

Acanthamoeba keratitis (AK) is a vision-threatening disease, usually associated with contact lens (CL) wear. As overnight orthokeratology (OOK) is increasingly used to control myopia, we have found incidence of OOK-associated AK is increasing. This study aimed to investigate the clinical presentation and visual outcomes of OOK-associated AK.

METHODS

Demographic characteristics, clinical features, and treatment outcomes were collected by reviewing the medical charts of CL-associated AK patients (n = 35) diagnosed at Taipei Veterans General Hospital from 2001 to 2016. Cases were OOK-associated AK patients (n = 13), and controls were all other CL-associated AK patients (n = 22). Student t tests and chi-square tests were used to compare cases and controls. Linear regression analyses were used to identify factors associated with the final visual outcome in CL-associated AK.

RESULTS

OOK-associated AK accounted for half of all CL-associated AK after 2010. OOK-associated AK patients and other CL-associated patients had similar best-corrected logarithm of the minimum angle of resolution visual acuity (BCLVA) before treatment (1.10 ± 0.75 vs 1.13 ± 0.76, p = 0.893), but OOK-associated AK patients were younger (17.15 ± 3.21 vs 26.36 ± 12.81 years, p = 0.004), had less severe disease (ring infiltration, 0% vs 31.82%, p = 0.023), and had better post-treatment BCLVA (0.06 ± 0.15 vs 0.51 ± 0.95, p = 0.041). Multiple linear regression analysis showed that better BCLVA after treatment in CL-associated AK was associated with initial presentation without ring infiltration (p = 0.002) but not with OOK use itself (p = 0.793). Twenty-six of 35 CL-associated AK patients had final BCLVA equal to or better than 0.10 (Snellen visual acuity of 6/7.5). All 13 OOK-associated AK cases were treated with chlorhexidine 0.02% ± voriconazole 1% ± oral voriconazole, and 12 of these patients had final BCLVA equal to or better than 0.10.

CONCLUSION

Most CL-associated AK patients had satisfactory visual outcomes. Half of AK at our hospital is OOK-associated since 2010. Early diagnosis and correct treatment may be the reason why OOK-associated AK patients had better vision prognosis.

Myopia Control With Orthokeratology: A Review

ABSTRACT

A number of studies regarding the effect of orthokeratology (OK) on myopia progression have been published and shown that it can slow myopia progression in school-aged children. Recently, OK has been considered to be one of the most effective optical treatments for myopia control. This article reviewed the peer-reviewed literature on the efficacy of OK for myopia control. Although it cannot halt myopia progression completely, the inhibitory effect on axial elongation for 2 years has been reported to be from 32% to 63%, as compared with single-vision spectacles and contact lenses. In addition, the efficacy and acceptable safety have been confirmed even in several long-term studies up to 10 years. However, the possibility of a rebound phenomenon in myopia progression after OK discontinuation remains unknown. It is also unclear how long the treatment should be continued to attain the maximum benefit in each patient. In the near future, further research including assessment of rebound phenomenon should be conducted with longer follow-up periods in more diverse populations.

The effect of orthokeratology treatment zone decentration on myopia progression

Background

This study aimed to compare the changes in the axial length (AL) in myopic children that wear centered and decentered orthokeratology (Ortho-K).

Methods

This retrospective study included 217 subjects who were treated with an Ortho-K lens for >12 months. The subjects were divided into three groups based on the magnitude of the Ortho-K lens treatment zone decentration: mildly, moderately, and severely decentered groups. Distance and direction of treatment zone decentration were calculated using software that was developed in-house. The AL changes in different groups were compared.

Results

Based on the distance of the treatment zone decentration, 65 children (65 eyes) were included in the mildly decentered group, 114 children (114 eyes) in the moderately decentered group, and 38 children (38 eyes) in the severely decentered group. The mean decentration distance in the three groups was 0.35 ± 0.11 mm, 0.71 ± 0.13 mm, and 1.21 ± 0.22 mm, respectively. The mean AL increase in the three groups after 12 months of Ortho-K lens wear was 0.24 ± 0.21 mm, 0.23 ± 0.18 mm, and 0.19 ± 0.20 mm, respectively. There were no significant differences in AL changes among the three groups.

Conclusions

Ortho-K lens decentration is common in clinical practice. The AL change after Ortho-K lens wear was not significantly different in subjects with different magnitudes of Ortho-K lens decentration. Fitting the Ortho-K lens in the properly centered zone is recommended to ensure the safety of Ortho-K lens wear and to maintain visual quality.