The safety of orthokeratology in myopic children and analysis of related factors

Impact of in vitro lens deposition and removal on bacterial adhesion to orthokeratology contact lenses

PURPOSE

The purpose of this study was to explore the impact of several contact lens (CL) care solutions on the removal of proteins and lipids, and how deposit removal impacts bacterial adhesion and solution disinfection.

METHODS

Lysozyme and lipid deposition on three ortho-k (rigid) and two soft CL materials were evaluated using an ELISA kit and gas chromatography respectively. Bacterial adhesion to a fluorosilicone acrylate material using Pseudomonas aeruginosa with various compositions of artificial tear solutions (ATS), including with denatured proteins, was also investigated. The impact of deposition of the different formulations of ATS on biofilm formation was explored using cover slips. Finally, the lysozyme and lipid cleaning efficacy and disinfection efficacy against P. aeruginosa and Staphylococcus aureus of four different contact lens care solutions were studied using qualitative analysis.

RESULTS

While maximum lysozyme deposition was observed with the fluorosilicone acrylate material (327.25 ± 54.25 µg/lens), the highest amount of lipid deposition was recorded with a fluoro-siloxanyl styrene material (134.71 ± 19.87 µg/lens). Adhesion of P. aeruginosa to fluorosilicone acrylate lenses and biofilm formation on cover slips were significantly greater with the addition of denatured proteins and lipids. Of the four contact lens care solutions investigated, the solution based on povidone-iodine removed both denatured lysozyme and lipid deposits and could effectively disinfect against P. aeruginosa and S. aureus when contaminated with denatured proteins and lipids. In contrast, the peroxide-based solution was able to inhibit P. aeruginosa growth only, while the two multipurpose solutions were unable to disinfect lenses contaminated with denatured proteins and lipids.

CONCLUSION

Bacterial adhesion and biofilm formation is influenced by components within artificial tear solutions depositing on lenses, including denatured proteins and lipids, which also affects disinfection. The ability of different solutions to remove these deposits should be considered when selecting systems to clean and disinfect ortho-k lenses.

Comparison of the clinical efficacy of orthokeratology and 0.01% atropine for retardation of myopia progression in myopic children

OBJECTIVE

To compare the clinical efficacy of orthokeratology (ortho-k) and 0.01% atropine for retardation of myopia progression in myopic children.

METHODS

This was a retrospective cohort study. A total of 282 patients, aged 8-17 years, were enrolled, including 100 children treated with ortho-k, 84 with 0.01% atropine, and 98 with single-vision spectacles. During the follow-up of 1 year, ortho-k wearers were examined at 1 day, 1 week, 1 month, 3 months after treatment, and thereafter every 3 months, while the others were examined every 3 months by measurements of uncorrected vision, intraocular pressure, refractive power, slit-lamp microscopy, corneal topography, and the lens fitting when necessary. The axial length was measured every 6 months.

RESULTS

Patients with ortho-k had stable uncorrected vision after 1 month of lens wear, all reaching 0 logMAR. The annual axial elongation was 0.23 ± 0.19 mm, 0.22 ± 0.20 mm, and 0.39 ± 0.27 mm in the ortho-k, atropine, and spectacle groups, respectively, with significant difference (F = 23.251, P = 0.000). The axial length was delayed to increase by 41.03% and 43.59% within a year in patients with ortho-k and atropine, respectively, as compared to patients with spectacles (F = 0.006, P = 0.936). The elongation was ≤ 0.3 mm in 69.0% and 66.7% of patients in the two groups, respectively, versus 38.8% in the spectacle group (χ2 = 17.251, P = 0.000). During the follow-up, the rate of corneal staining was 11.0% and 2.0% in the ortho-k and spectacle groups, respectively (χ2 = 8.076, P = 0.003). The use of atropine did not increase corneal staining, but the incidence of related photophobia was 4.8%. No other serious complications were observed.

CONCLUSION

Ortho-k lenses and 0.01% atropine can achieve similar efficacy of myopia retardation, which was significantly better than that obtained with single-vision spectacles, in myopic children. The risk of corneal staining after ortho-k wear may be slightly higher than that with spectacles, but could be well controlled.

Advances in myopia prevention strategies for school-aged children: a comprehensive review

Myopia has significantly risen in East and Southeast Asia, and the pathological outcomes of this condition, such as myopic maculopathy and optic neuropathy linked to high myopia, have emerged as leading causes of irreversible vision loss. Addressing this issue requires strategies to reduce myopia prevalence and prevent progression to high myopia. Encouraging outdoor activities for schoolchildren and reducing near-work and screen time can effectively prevent myopia development, offering a safe intervention that promotes healthier habits. Several clinical approaches can be employed to decelerate myopia progression, such as administering low-dose atropine eye drops (0.05%), utilizing orthokeratology lenses, implementing soft contact lenses equipped with myopia control features, and incorporating spectacle lenses with aspherical lenslets. When choosing an appropriate strategy, factors such as age, ethnicity, and the rate of myopia progression should be considered. However, some treatments may encounter obstacles such as adverse side effects, high costs, complex procedures, or limited effectiveness. Presently, low-dose atropine (0.05%), soft contact lenses with myopia control features, and orthokeratology lenses appear as promising options for managing myopia. The measures mentioned above are not necessarily mutually exclusive, and researchers are increasingly exploring their combined effects. By advocating for a personalized approach based on individual risk factors and the unique needs of each child, this review aims to contribute to the development of targeted and effective myopia prevention strategies, thereby minimizing the impact of myopia and its related complications among school-aged children in affected regions.

Is Orthokeratology Treatment Zone Decentration Effective and Safe in Controlling Myopic Progression?

OBJECTIVE

To compare the myopia control efficacy and safety of decentered versus centered positioning of orthokeratology.

METHODS

This is a retrospective intrasubject study, including 46 children with myopia (25 boys, 21 girls; age 11.12±0.33 years) treated for 1 year with OK decentration in one eye (group D) and central location in the other (Group C). Axial length was measured before and at 6 months and 12 months after the initial lens wear, respectively. Corneal topography was measured at baseline and at 1-month after lens wear. The corneal topography obtained from the 1-month visit was used to quantify treatment zone decentration (TZD) for each subject. Cycloplegic refraction was required for all children before fitting the orthokeratology lenses.

RESULTS

No differences were found between the groups in the biological ocular parameters ( P ≥0.05 for all). The axial elongation in group D and group C differed after 6 and 12 months ( P <0.001 for all). Similar corneal staining rates ( P =0.06) were noted during follow-up in groups D (n=20; 7.24%) and C (n=10; 3.62%), all of grade I. The uncorrected visual acuity (UCVA) in group D and C differed after 1, 6, and 12 months ( P =0.002, 0.010, 0.044), except 3 months ( P =0.146). Group D (n=32; 17.39%) was more likely to have glare or ghosting (chi-squared test, P <0.001) than group C (n=12; 6.52%) during follow-up visits. Axial elongation was significantly associated with baseline spherical equivalent (SE) in group C ( P =0.019). In group D, axial elongation was significantly associated with SE and TZD ( P <0.05 for all).

CONCLUSIONS

This intrasubject study showed that when the UCVA was acceptable and there were no apparent complications, orthokeratology decentration may be beneficial in controlling the progression of myopia. Axial elongation became slower in children with a higher SE and a larger TZD, because TZD ranged from 0.5 mm to 1.5 mm.

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.

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.

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.

Efficacy, predictability and safety of long-term orthokeratology: An 18-year follow-up study

PURPOSE

To determine the efficacy, predictability and safety of long-term orthokeratology in children and adults.

METHODS

Case histories of 300 orthokeratology patients (596 eyes; 34.3% children; 65.7% adults) were reviewed to collect information on demographics, corneal and refractive parameters, visual acuity, residual refraction and adverse effects. Predictability was defined as the percentage of eyes with absolute values of spherical equivalent refraction ≤ 0.5 D of emmetropia, and efficacy as the ratio of post-orthokeratology uncorrected and pre-orthokeratology corrected distance visual acuity.

RESULTS

Median duration of treatment was 37 and 28.5 months in children and adults, respectively (p = 0.022). During the first year, 17.2% of children and 33% of adults ceased lens wear (p < 0.001). For children and adults with a successful ortho-k treatment of at least one year of duration, 88.7% and 95.9% of eyes had a predictable refractive outcome, and efficacy was 0.98 and 1.01, respectively. A larger percentage of children (65.7%) were free of complications than of adults (55.4%) (p = 0.015). One event of microbial keratitis occurred in adults (6.8 cases per 10,000 patient-years) and none in children. Corneal staining was the most frequent complication, with a higher incidence in adults (p = 0.007) and in higher myopia (p < 0.001), higher anterior corneal eccentricity (p = 0.019) and smaller anterior horizontal radius (p = 0.027).

CONCLUSION

Orthokeratology is a safe and predictable long-term procedure in children and adults, with a low incidence of serious adverse effects. Corneal staining episodes are relatively frequent throughout the course of the treatment, thus highlighting the relevance of education of experienced users.

The Biomechanical Response of the Cornea in Orthokeratology

Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using orthokeratology lenses via the finite element method, numerical models with different corneal curvatures, corneal thicknesses, and myopia reduction degrees had been developed and validated to simulate the corneal response and quantify the changes in maximum stress in the central and peripheral corneal areas during orthokeratology. The influence of the factors on corneal response had been analyzed by using median quantile regression. A partial eta squared value in analysis of variance models was established to compare the effect size of these factors. The results showed central and peripheral corneal stress responses changed significantly with increased myopia reduction, corneal curvature, and corneal thickness. The target myopia reduction had the greatest effect on the central corneal stress value (partial eta square = 0.9382), followed by corneal curvature (partial eta square = 0.5650) and corneal thickness (partial eta square = 0.1975). The corneal curvature had the greatest effect on the peripheral corneal stress value (partial eta square = 0.5220), followed by myopia reduction (partial eta square = 0.2375) and corneal thickness (partial eta square = 0.1972). In summary, the biomechanical response of the cornea varies significantly with the change in corneal conditions and lens designs. Therefore, the orthokeratology lens design and the lens fitting process should be taken into consideration in clinical practice, especially for patients with high myopia and steep corneas.

A novel quantitative evaluation of deposits adhered to worn orthokeratology contact lenses

PURPOSE

Total deposition and deposition along the reverse curve of heavily deposited worn orthokeratology (OK) lenses were quantitatively evaluated using two novel imaging methods. In addition, the cleaning efficacies of a contact lens cleaning solution for daily use and an intensive cleaner and protein remover solution were evaluated using the same two methods.

STUDY DESIGN

Experimental study.

METHODS

Twenty-six worn reverse-geometry OK lenses (MY Emerald, Technopia) were photographed for use in three experiments: (1) total deposition was assessed before and after cleaning with two cleaning solutions; (2) in addition to assessing total lens deposition, the feasibility of measuring the thickness of lens deposits along the reverse curve was assessed; and (3) after confirming it was possible to assess the thickness of lens deposits, the thickness of deposits was assessed before and after cleaning with a daily contact lens cleaning solution (O₂ Care^®, Menicon Co., Ltd.) and an intensive cleaner and protein remover (Progent^®, Menicon Co., Ltd.). Total lens deposition was assessed as the total volume of cloudiness over the lens surface in terms of volume per unit pixel. Cross-sectional images were taken from worn OK lenses to assess the thickness of lens deposits on the reverse curve as the area of deposits/horizontal length.

RESULTS

Significant differences in total deposition were found between the three cleaning conditions for the twenty worn OK lenses (mean total deposition ± SD for pre-cleaning = 0.209 ± 0.076; post-daily cleaning = 0.124 ± 0.078; and post-intensive cleaning = 0.045 ± 0.046) (p < 0.001). Mean total deposition and thickness of the deposits along the reverse curve for the three lenses from the second experiment were 0.310 and 6.0 mm, respectively. The mean thicknesses of lens deposits found in the third experiment under the 3 conditions were as follows: pre-cleaning = 3.4 µm; post-daily cleaning = 2.3 µm; and post-intensive cleaning = 0.0 µm.

CONCLUSION

The two novel imaging methods used in this study detected significant amounts of deposits attached to worn OK lenses and were sensitive enough to detect a reduction in deposition following the use of the two cleaning solutions tested. Furthermore, these methods could visualize and quantify the thickness of lens deposits along the reverse curve.

One-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial

Purpose

To present the 1‐year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study, which aims to investigate the myopia control effect of orthokeratology (ortho‐k) lenses with different back optic zone diameters (BOZD).

Method

Children, aged 6 to <11 years, having myopia −4.00 D to −0.75 D, were randomly assigned to wear ortho‐k lenses with 6 mm (6‐MM group) or 5 mm (5‐MM group) BOZD. Data collection included changes in refraction, vision, lens performance and binding, ocular health conditions, axial length and characteristics of the treatment zone (TZ) area.

Results

The 1‐year results of 34 and 36 subjects (right eye only) in the 6‐MM and 5‐MM groups, respectively, are presented. No significant differences in baseline demographics were found between the groups (p > 0.05). The first‐fit success rates, based on satisfactory centration at the 1‐month visit, were 100% and 94% respectively. Horizontal TZ size was 0.92 mm and 0.72 mm smaller in the 5‐MM group at the 6‐month and 12‐month visits, respectively (p < 0.05). At the 12‐month visit, no significant between‐group differences were found in the incidence of corneal staining (low grade only), lens binding and visual performance (all p > 0.05). Axial elongation was slower in the 5‐MM group (0.04 ± 0.15 mm) than the 6‐MM group (0.17 ± 0.13 mm) (p = 0.001). A significant positive correlation was observed between the horizontal TZ size and axial elongation (r = 0.36, p = 0.006).

Conclusion

Clinical performance of the two ortho‐k lenses was similar, indicating that a smaller BOZD (5 mm) did not affect lens performance or ocular integrity. However, a smaller BOZD led to a reduced TZ, with retardation of axial elongation by 0.13 mm compared to conventional 6 mm BOZD ortho‐k lenses after one year of lens wear.