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ISSN : 1229-6457(Print)
ISSN : 2466-040X(Online)
The Korean Journal of Vision Science Vol.26 No.4 pp.217-223
DOI : https://doi.org/10.17337/JMBI.2024.26.4.217

The Efficacy in the Short-Term Treatment of Orthokeratology about Low to Moderate Myopia in Adolescents

Zhao Weiying1,2), Geun-Chang Ryu3), Eun-Sun Seo3)
1)Dept. of Optometry, Graduate School, Dongshin University, Student, Naju
2)Dept. of Optometry, Nanjing Normal University Zhongbel College, Professor, Danyang
3)Dept. of Optometry, Dongshin University, Professor, Naju
* Address reprint requests to Eun-Sun Seo (https://orcid.org/0000-0002-4574-2310) Dept. of Optometry, Dongshin University, Naju TEL: +82-61-330-3555, E-mail: eunsun111@hanmail.net
August 19, 2024 December 13, 2024 December 13, 2024

Abstract


Purpose : This study investigated whether orthokeratology lenses have an inhibitory effect on short-term myopia progression in adolescents with low and moderate myopia who visited a Chinese eye hospital.



Methods : Among myopic patients who visited Visit J Eye Clinic, 40 patients, 20 in the low myopia group (40 eyes) and 20 in the moderate myopia group (40 eyes), were prescribed orthokeratology lenses and followed up for 6 months. The visual acuity, axial length, keratometry, intraocular pressure, and central corneal thickness after wearing the corneal refractive correction lenses were examined, analyzed, and compared after 1 month, 3 months, and 6 months, respectively. Statistical analysis was performed using SPSS27.0 software.



Results : The corrected visual acuity increased in both low and moderate myopia groups, and data differences were statistical significance . The axial length of the eye increased less in the moderate myopia group, and data differences have statistical significance. The decrease in corneal curvature was greater in the moderate myopia group, and data differences have statistical significance. Patients wearing orthokeratology lenses showed no significant change from reference values in terms of intraocular pressure and central corneal thickness.



Conclusion : Orthokeratology lenses effectively corrects myopia in adolescents and are one of the methods to inhibit the progression of myopia, which varies according to the degree of myopia. In addition, it is more effective in controlling myopia in patients with moderate myopia than in patients with low myopia.


Myopia control , Orthokeratology

청소년 중저도 근시에 대한 각막굴절교정 렌즈의 단기 치료 효과

자오웨이잉1,2), 유근창3), 서은선3)
1)동신대학교 일반대학원 옵토메트리학과, 학생, 나주
2)난징사범대학교 중북대학 안경광학과, 교수, 단양
3)동신대학교 안경광학과, 교수, 나주

    Ⅰ. Introduction

    Myopia is the most common eye disease that causes vision loss in the world. It is a condition in which light enters the eye through the pupil in a relaxed state of adjustment and converges before the retina in the macula, resulting in the formation of a diffuse circle of light on the retina. The prevalence of myopia is highest in East and Southeast Asia, with a prevalence rate of 80% to 90% among young people.1) According to relevant data, the myopia rate among Chinese children and adolescents has ranked first in the world, and with the gradual occurrence of myopia at an early age, the prevalence rate of myopia has reached 98%.2,3) It can be seen that adolescence is a period of high incidence of myopia. If myopia is not prevented and controlled in a timely manner, myopia will continue to deepen and become high myopia, which will increase and cause the incidence of ocular and endophthalmic diseases. As the degree of myopia increases, the risk of eye complications significantly increases, and it has been proven to lead to permanent visual impairment and blindness.4)

    In recent years there are many measures to control myopia divided into surgical and non-surgical corrections. Non-surgical corrective methods: (1) Commonly used pharmacological interventions are mainly atropine,5) pirenzepine.6) Of these, low concentrations of atropine are more widely used.7) (2) Wear optical frames (frames are further divided into monofocal, bifocal8) and multifocal glasses9)), corneal contact lenses of various designs.10) (orthokeratology lens, rigid gas permeable contact lenses, soft contact lenses, etc.). (3) Participating in outdoor sports can also prevent myopia to a certain extent, and can slow down the growth rate of myopia.

    The orthokeratology lens is a rigid gas-permeable contact lens with an inverse geometric design.11) The principle of the orthokeratology lens is to mechanically compress the cornea, causing the lens to move and the hydraulic pressure caused by tears to change the shape and reshape the cornea, making the central curvature of the cornea smaller and the peripheral curvature larger, thereby changing the refractive state of the human eye and reducing paracenter defocus, so wearing orthokeratology lenses can slow down the growth of the axial length of the eye and inhibit it. Improve uncorrected visual acuity and control the development of myopia.

    However, because orthokeratology lens still have different effects and differences on individuals with different degrees, this article collects and organizes parameters such as naked eye vision, axial length, intraocular pressure, and corneal curvature of adolescents with low and moderate myopia who have been wearing orthokeratology lens for six months, and further observes the control effect of orthokeratology lens on adolescents with different degrees. It also provides an effective basis for our hospital’s subsequent fitting of orthokeratology lenses.

    Ⅱ. Subjects and Methods

    1. Study Subjects

    40 cases (80 eyes) of adolescent myopia patients with orthokeratology lenses attending the Visit J Eye Clinic, from January 2023 to July 2023 were selected and divided into two groups: low myopia group and moderate myopia group, 20 cases (40 eyes) in each group. All patients have signed an informed consent form for orthokeratology lens trials. Examinations of all patients were performed by the same permanent staff.

    The selection criteria for patients wearing orthokeratology lenses are shown in Table 1 and detailed below(Table 1).

    The orthokeratology lens uses the XO series high oxygen permeability material produced by BOSTON Company in the United States, which adds polymer materials of silicon and fluorine. Orthokeratology lenses are blue or green in color. BC: 7.50~9.93 mm, optical zone diameter: 5.50~7.00 mm; The total lens diameter is 10~11.5 mm; center thickness: 0.15~0.30 mm. The DK value is 100x10~11(cm2·mlO2)/(s.ml.mmHg). And the test lens diameter is 10.60 mm. Innovative tear balance four zone multi arc design, fast and stable effect(Table 2).

    2. Items to be checked when wearing orthokeratology lenses

    The inspection process is shown in the figure (Fig. 1).

    3. Research methods

    Selection of study subjects. A total of 40 patients were selected for the study.

    The patients were divided into low myopia and moderate myopia groups and their naked eye visual acuity, eye axis, corneal curvature, intraocular pressure and central corneal thickness were examined.

    4. Statistical methods and analysis

    Statistical analysis was conducted using SPSS 27.0 software. Repeated measures analysis of variance was used to compare various indicators at different time points between the two groups. Quantitative data were expressed as mean (±) standard deviation. T-tests were used to compare the differences in various indicators between the two groups before and 6 months after wearing orthokeratology lens, and p<0.001 was used to indicate statistical significance.

    Ⅲ. Results

    The low myopia group consisted of 20 patients, 10 males and 10 females, aged between 9 and 14 years with a mean age of (11.47±1.46) years. The moderate myopia group consisted of 20 patients, 12 males and 8 females, aged between 9 and 17 years, with a mean age of (12.80±2.34) years. The patients in both groups wore orthokeratology lens for 8-10 hours per night while sleeping.

    Before wearing orthokeratology lens, there was no significant difference in the comparison of data between the low myopia group and the moderate myopia group, indicating comparability between the two groups (p>0.050, Table 3).

    After 6 months of wearing orthokeratology lenses, the corrected visual acuity of patients in both groups gradually improved. The difference in data between the low myopia group and the moderate myopia group is significant (p<0.001, Table 4). The results of the axial length showed an increase in the axial length of both groups after wearing orthokeratology lens, but the increase was less in patients with moderate myopia compared to those with low myopia. The difference in data between the low myopia group and the moderate myopia group is significant (p<0.001, Table 4). The corneal curvature results showed a significant decrease in corneal curvature (horizontal and vertical curvature) in both groups of patients with orthokeratology lens, but the decrease was greater in patients with moderate myopia compared to those with low myopia. The difference in data between the low myopia group and the moderate myopia group is significant (p<0.001, Table 4).

    There was no significant change in intraocular pressure and central corneal thickness in both groups and the difference was not statistically significant (p>0.050, Table 4).

    Ⅳ. Discussion and Conclusion

    1. Effectiveness of OK lens

    1) Corrected visual acuity(CVA)

    The difference between the low myopia group and the moderate myopia group is not significant before wearing lenses (p>0.050, Table 3). CVA increased more in the moderate myopia group compared to the low myopia group after 6 months. Low myopia group: 1.06±0.09; moderate myopia group: 0.13±0.08 (p<0.001, Table 4).

    2) Axial length(AL)

    The difference between the low myopia group and the moderate myopia group is not significant before wearing lenses(p>0.050, Table 3). After 6 months the AL of the moderate myopia group increased less compared to the low myopia group. Low myopia group: 0.11±0.07, moderate myopia group: 0.05±0.07 (p<0.001, Table 4).

    3) Corneal curvature (Flat-K ,Steep-K)

    The difference between the low myopia group and the moderate myopia group is not significant before wearing lenses (p>0.050, Table 3). After 6 months, the corneal curvature(Flat-K ,Steep-K) was reduced more in the moderate myopia group compared to the low myopia group. Low myopia group Flat-K:-0.42±0.55, Steep-K:-0.37±0.67; moderate myopia group Flat-K:-0.82±0.93, Steep-K:-1.01±0.98 (p<0.001, Table 4).

    2. Safty of OK lens

    There were no statistically significant changes in intraocular pressure or corneal thickness in either group before or after orthokeratology lenses were fitted(Table 3,Table 4, p>0.050).

    In this study, patients with moderate myopia had better results in both groups of patients who wore orthokeratology lenses for a short period of time. Because the curvature of the BC decreases the corrected myopia diopter, the curvature of the RC increases, resulting in myopic defocus,The RC forms a positive lens. The higher the degree of myopia, the higher the degree of the positive lens, the more obvious the myopic defocus will be, and the better the effect of controlling myopia will be. Compared with patients with low myopia, the eyeball shape of patients with moderate myopia is more oblate and oval, and the peripheral hyperopic defocus is more obvious. The peripheral hyperopic defocus produced after the orthokeratology lens completes the shaping of the cornea is more significant. It slows down the stimulation to the eye axis and has a relatively strong effect on inhibiting the development of myopia.

    The safety of orthokeratology lens is also demonstrated by the fact that there were no significant changes in intraocular pressure or corneal thickness before or after lens wear. Therefore, it can be seen that orthokeratology lens can safely and effectively control the growth rate of myopia in a short period of time and the effect is more obvious for patients with moderate myopia.

    Figure

    KJVS-26-4-217_F1.gif

    Orthokeratology lens Fitting Flow Chart.

    Table

    Inclusion criteria and exclusion criteria

    Orthokeratology lens parameters

    Comparison of parameters between the two groups of patients before wearing orthokeratology lenses

    Comparison of the difference in changes between two groups after wearing orthokeratology lens

    *Indicating p<0.001

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