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Comparison of four different orthokeratology lenses in controlling myopia progression
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
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Comparison of four different orthokeratology lenses in controlling myopia progression Ruru Chena,b,1, Jinjin Yua,1, Michael Lipsonc, Abdullah A. Cheemad, Yan Chena,b, Hengli Liana,b, Jinhai Huanga,b,*, Colm McAlindene a
School of Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, China Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China c Department of Ophthalmology and Visual Science, University of Michigan, Northville, USA d Imperial College School of Medicine, London, United Kingdom e Department of Ophthalmology, Princess of Wales Hospital, Bridgend, United Kingdom b
A R T I C LE I N FO
A B S T R A C T
Keywords: Orthokeratology OrthoK lens Axial length Myopia progression
Purpose: To compare axial length (AL) elongation in myopic children with four Orthokeratology (OrthoK) lenses and spectacles. Methods: The medical records of 266 patients (532 eyes) who were fitted with OrthoK lenses or spectacles (control group) were reviewed. Data collection included baseline age, gender, baseline objective sphere and cylinder, baseline flat and steep corneal meridian power, corneal asphericity coefficient (Q value), AL at baseline and after 1-year, and 2-years of OrthoK or spectacle wear analyzed using analysis of repeated measures data ANOVA. Stepwise linear regressions between the changes in AL after 2 years relative to baseline parameters were calculated for the OrthoK and control groups separately. Results: The baseline subject parameters for each of the four OrthoK lenses were not statistically different. Statistically significant differences between time points were found between 12- and 24- months (all P < 0.05). AL growth was slower in all OrthoK groups than in the control group (all P < 0.05). AL grew 0.081 ± 0.034 mm per year slightly less than average with Essence compared to the Mouldway OrthoK group (P = 0.019). The coefficient of regression weakly expressed between the increases in AL over 2-years study period and baseline spherical equivalent refraction was 0.065 in Essence, 0.079 in Euclid and 0.087 in Mouldway. The coefficient of regression was also weakly between age and the increases AL over 2-years study period and baseline age in all groups. Conclusion: Different OrthoK lenses differ minimally in slowing axial elongation effectively in myopic children during 2-years lens wear.
1. Introduction Myopia is the most common form of ametropia and one of the leading causes of vision impairment in the world [1]. Estimates show that in the early 21st century, myopia affected almost 30 % of the world’s population [2]. This trend is projected to increase significantly, affecting nearly 50 % of the world’s population by 2050 [3]. Currently, numerous studies have confirmed that orthokeratology (OrthoK) is effective in slowing AL elongation and improves the quality of life in children with myopia [4–6]. OrthoK is now increasingly used as a non-pharmacological management option to slow AL elongation in myopia with specially-designed contact lenses worn while sleeping
[4,5,7,8]. Myopic OrthoK lenses incorporate a reverse geometry lens design where the central base curve is flatter than the central cornea. A single or multiple series of curves surrounding the central base curve are referred to as the reverse curve. The reverse curve is usually significantly steeper than the central base curve. Peripheral to this is a series of curves to align with the cornea. Combined, these lens parameters induce central corneal flattening and mid-peripheral corneal steepening. The resulting topographical changes temporarily correct mild - moderate degrees of myopic refractive error, providing patients with clear unaided distance vision [9–12]. It has been proposed that changes in peripheral retinal defocus induced by OrthoK may be one of the mechanisms for the deceleration of
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Corresponding author at: Eye Hospital of Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China. E-mail address: [email protected] (J. Huang). 1 They contributed equally as first authors. https://doi.org/10.1016/j.clae.2019.11.012 Received 9 July 2019; Received in revised form 15 November 2019; Accepted 26 November 2019 1367-0484/ © 2019 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Ruru Chen, et al., Contact Lens and Anterior Eye, https://doi.org/10.1016/j.clae.2019.11.012
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Table 1 Inclusion criteria for data collection. Inclusion criteria Age Subjective sphere Subjective cylinder Anisometropia Visual acuity Ocular health
Systemic health Others
8 to 13 years old −0.50 diopters (D) to −5.00 D in both eyes No more than −1.50 D in both eyes ≤1.50 D (non-cycloplegic autorefraction) Monocular corrected distance visual acuity no worse than 20/20 Intraocular pressure (IOP) < 21 mmHg No other ocular disease aside from refractive error including no keratoconus (confirmed by pre-treatment corneal topography) No binocular vision conditions such as strabismus No systemic or neurodevelopmental deviations that might affect refractive development Birth weight ≥1500 g No history of parental high myopia No history of contact lens wear, bifocal or progressive addition spectacles in the past 12 months, or atropine treatment for myopia control Maintained regular scheduled visits and completed the 2-year follow-up Unaided visual acuity of 20/20 or better at the last scheduled review appointment (criteria only for OrthoK group) Discontinued lens wear for a total of 30 days or less during the 2 years (criteria only for OrthoK group)
2.2. Data collection
myopia progression [13–15]. Paracentral retinal myopic defocus induced by OrthoK lenses is due to their reverse curve design. However, different OrthoK lenses may have varying reverse curve parameters. Furthermore, the various materials and OrthoK designs may also have different oxygen transmissibility and optic zone diameters. These factors may influence the degree of myopia control for each lens. To our knowledge there are no long-term studies on the efficacy of different OrthoK lenses to slow AL elongation in children. Therefore, the purpose of this study was to analyze AL elongation in Chinese children over two years of OrthoK lens wear with four different OrthoK lenses, relative to spectacle wear (control group).
Data was retrospectively collected from the clinical records of 266 subjects, with both eyes from each subject (total 532 eyes) being used for the statistical analysis. Data collected included: OrthoK brand or spectacles, age (in years) at the initial OrthoK lens fitting or spectacle wear, gender, baseline sphere and cylinder, initial flat and steep keratometry (Kf and Ks), corneal asphericity coefficient (Q value) (generated by a corneal topographer), and AL at initial, 1-year, and 2-years of OrthoK or spectacle wear. All OrthoK subjects used the same OrthoK lens type with comparison of the different lenses during the 2-year study period. The control group wore single-vision spectacles with the full distance best-corrected monocular visual acuity equal to or better than 20/20.
2. Materials and methods 2.1. Subjects
2.3. Materials
The clinical records of OrthoK contact lens wearers and spectacle wearers who presented to the Eye Hospital of Wenzhou Medical University from initial inspection to the time of review (August 2017) were analyzed. Children with myopia were selected for this study and inclusion and exclusion criteria are detailed in Tables 1 and 2. This study was approved by the Office of Research Ethics, Eye Hospital of Wenzhou Medical University. It was conducted in accordance with the Tenets of the Declaration of Helsinki. Written informed consent was obtained from guardians on behalf of the children. Parents were allowed to choose between two treatment options (spectacles or OrthoK lenses) for their children, taking into account factors such as parents’ opinion in controlling progression of myopia, concerns about the safety of lens wear, lens care and economic cost. As for what kind of OrthoK lens to be chosen, parents may consider the expenses of different OrthoK lenses. However, doctors provided a qualitative recommendation to the parents, taking into consideration the acceptability of various lenses suited to the needs of each individual child. Single vision spectacles are the optical means to correct vision for most myopic children and considered to be ineffective for myopia control [16], which was why we chose spectacles for the control group. Data was collected from the hospital records and no patient involvement was required.
In the OrthoK group, four different lenses were used: Essence (C&E GP Specialists Inc., San Diego, California, USA), Euclid (Euclid Systems Corporation, Herndon, Virginia, USA), Lucid (Lucid Korea Co. Ltd, Korea), Mouldway (Autek China Inc.,Sino-American Joint Venture). The detailed information about each of the four lenses is provided by the manufacturer and is listed in Table 3. All patients underwent a standard anterior eye and refractive status assessment prior to commencing OrthoK wear. This assessment included measurement of baseline corneal topography using a corneal topographer (Medmont E6.0; Medmont Pty Ltd, Brisbane, Australia). The Kf, Ks and Q value were generated by the corneal topographer over an 8 mm chord length. Cycloplegic autorefraction was performed in each group before enrollment. Cycloplegia was induced 40 min before refraction measurements with 1 % cyclopentolate hydrochloride eye drops (single dose bottle; Alcon, Puurs, Belgium). AL was measured five times using partial coherence interferometry (IOLMaster; Carl Zeiss, Germany) and the data was automatically averaged. Table 3 Nominal OrthoK lens characteristics and parameters.
Table 2 Exclusion criteria for data collection.
Lens
Material
Dk
OZD
RCW
ACW
PCW
CT
Essence
Paragon HDS100 Boston Equalens II Boston XO Boston XO
100
6.0
0.6
1.2
0.5
0.22–0.25
127
6.2
0.5
1.2
0.5
0.22
100 100
6.2 6.0
0.9 0.4–1.0
0.8 0.4–1.5
0.5 0.2–0.5
0.23 0.24
Euclid
Exclusion criteria Binocular vision conditions such as strabismus Systemic or neurodevelopmental deviations that might affect refractive development History of parental high myopia (more than −6.00 D) History of contact lens wear, bifocal or progressive addition spectacles in the past 12 months, atropine treatment for myopia control
Lucid Mouldway
Dk, oxygen permeability (10−11 cm2×mLO2)/(s × mL × mm Hg); OZD, optic zone diameter (mm); RCW, reverse curve width (mm); ACW, alignment curve width (mm); PCW, peripheral curve width (mm); CT, central thickness (mm). 2
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analysis, statistically significant changes were not found in AL between right and left eyes (F=1.014, P > 0.05).
2.4. Schedule of visits All patients were followed-up according to the standard protocol of the Eye Hospital of Wenzhou Medical University. Patients were typically evaluated at 1 day, 1 week and 1 month following OrthoK wear. Follow-up appointments were thereafter scheduled every 3 months both in OrthoK and control group. At each visit, measurements of noncycloplegic visual acuity and slit-lamp examinations assessing ocular health and OrthoK lens integrity were performed. AL was measured at 6-month intervals in the OrthoK subgroups and control group. AL at the baseline, 12-months and 24-month were collected. All patients had no more than 30 days of lens cessation during the study period from the patient follow-up files. In the control group, doctors generally suggested that the prescription of spectacles should be changed when the patients’ sphere dropped less than -0.50 D by noncycloplegic subjective refraction. After the OrthoK lenses were dispensed, the parents were instructed to help with the daily lens insertion, removal, cleaning (including daily care and one-two weekly deproteinized care according to Menicon cleaning protocol) and wearing procedures. OrthoK lenses were changed to optimize visual acuity and refractive target endpoints or decentration.
3.2. AL change in OrthoK and control groups Statistically significant differences were found in AL over time, between groups and for time*group interaction (all P < 0.01). Statistically significant differences between time points were found between 12- and 24-months (P = 0.002). Statistically significant changes were found between groups at different visit time points. The increases in AL during the 2-year study period were 0.317 ± 0.247 mm, 0.387 ± 0.273 mm, 0.358 ± 0.208 mm, 0.431 ± 0.229 mm and 0.524 ± 0.288 mm in the Essence, Lucid, Euclid, Mouldway OrthoK groups and the control group, respectively. AL elongation was slower in all OrthoK groups compared to the control group (all P < 0.05). In addition, mean AL increases were 0.081 ± 0.034 mm per year less in the Essence group than the Mouldway OrthoK group (P = 0.019). No statistically significant differences in AL elongation were seen in the other OrthoK intergroups (Fig. 1 and Table 5). 3.3. Baseline factors and AL growth In all five (Essence, Lucid, Euclid, Mouldway and control) groups, at 2 years, AL elongation had a statistically significant yet weak correlation with baseline age (Fig. 2 and Table 6). The Essence, Euclid and Mouldway OrthoK groups had a statistically significant yet weak correlation between AL elongation and SER (Fig. 3 and Table 6). None of the five groups found a statistically significant relationship between AL elongation with baseline AL or mean P-value (Table 6).
2.5. Statistical analysis Chi-squared test was used to compare gender and eyes among groups. The data of age, objective sphere and cylinder did not have a normal distribution according to the Kolmogorov-Smirnov test. The Kruskal-Wallis test was used to compare age, objective sphere and cylinder analysis among groups. After confirming normality (ShapiroWilk), baseline AL, Kf, Ks and Q value were compared via a general linear model (GLM) nested-design analysis of variance (ANOVA). GLM Nested Design ANOVA was used to correctly account for eyes to be nested within participants’ baseline parameters and AL followed over time. The data of AL at 12 and 24 months was analyzed via a mixedmodel nested-design ANOVA. Variance analysis was used to compare the differences between groups. Time was treated as the repeated factor, with lens type as a between-subject factor. The multivariate output indicated that the overall test was significant at the 95 % confidence level. Additionally, stepwise linear regressions between the change in AL after two years relative to baseline and baseline age, SER (spherical equivalent refraction = sphere + 1/2 cylinder) and mean K (mean keratometry = Kf + Ks) were calculated for the OrthoK and control groups separately. Statistical analyses were performed using the SPSS software (ver. 21.0; SPSS Inc., Chicago, Illinoi, USA) and graphing with GraphPad Prism 5 (GraphPad Software Inc., La Jolla, California, USA). The level of statistical significance was set at 0.05.
4. Discussion With the availability of many different OrthoK lenses, there is a greater need to better understand the relationship between different types of OrthoK lenses and their myopic control effect. To our knowledge, this is the first 2-year study reporting on the efficacy on myopic control with four different types of OrthoK lenses in a large number of subjects. Our results confirmed that all four OrthoK lenses tested are effective in slowing the increase in AL compared with spectacles. In this study, the increase in AL of Chinese children over two years was 0.317 ± 0.247 mm with the Essence lens, 0.358 ± 0.208 mm with the Euclid, 0.387 ± 0.273 mm with the Lucid and 0.431 ± 0.229 mm with the Mouldway. Santodomingo-Rubido et al. reported that the change in the AL for their OrthoK group following 24 months was approximately 0.4 mm in white European subjects using a different OrthoK brand, Menicon Z Night OrthoK lens [17]. In spite of differences in race and sample size, the myopia control effect of Mouldway OrthoK group in our study was nearly identical to that of the Menicon Z Night OrthoK lens. Tetsubiko et al. found AL elongation was 0.39 ± 0.27 mm after two years using the Euclid OrthoK lens manufactured with the Boston XO material [18]. Zhu et al. reported that the AL elongation was 0.34 ± 0.29 mm after two years using the Euclid OrthoK lens manufactured with the Boston Equalens II material [19]. A similar result was also found in our study (0.358 ± 0.208 mm). We could speculate that the oxygen permeability of an OrthoK lens of the same design is unlikely to affect the degree of slowing myopia progression. In a study by Lum et al. it was found that within 2 weeks, the ability of OrthoK lenses to correct refraction was improved if the oxygen transmissibility of lenses was increased. It was thought that with more oxygen reaching the epithelial cells, boosting their metabolism would lead to a faster central epithelial thinning and, potentially, midperipheral epithelial thickening. However, this difference disappeared beyond 2 weeks of lens wear [20]. Hence, the possibility that this might then somehow affect AL elongation over a 2-year period is quite unlikely. Lu et al. found low and high oxygen transmissibility lenses affect the curvature gradient of the corneal mid-periphery. After
3. Results 3.1. Patients and treatment characteristics No severe adverse events (e.g. microbial keratitis) were reported in the any of the groups. With the Chi-square test, there were no significant differences in eyes and gender between 5 groups (Table 4). Of the 266 subjects, there were 152 females and 114 males. There were 51 subjects in the Essence OrthoK group, 51 subjects in the Euclid OrthoK group, 46 subjects in the Lucid OrthoK group, 53 subjects in the Mouldway OrthoK group and 64 subjects in the control (spectacle lens) group. With the Kruskal-Wallis test, there were no statistically significant differences at baseline for age, objective sphere and cylinder (Table 4). With GLM nested-design ANOVA, there were no statistically significant differences at baseline for Kf and Ks, Q value or initial AL between five groups (Table 4). With GLM nested-design ANOVA analysis, objective sphere, cylinder, baseline Kf, Ks and Q value were not statistically different between right and left eyes (P > 0.05). With linear mixed models 3
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Table 4 Biometric data of subjects at baseline. Design
Eyes Right:Left
Gender Female:Male
Median age (years)
Median subjective sphere (DS)
Median subjective cylinder (DC)
Mean ( ± SD) initial AL (mm)
Mean ( ± SD) Kf (D)
Mean ( ± SD) Ks (D)
Mean ( ± SD) Q value
Essence
51:51
28:23
10 (9, 12)
Euclid
51:51
28:23
10 (9, 12)
Lucid
47:47
25:22
9 (9, 12)
Mouldway
53:53
32:21
9 (8, 12)
Control
64:64
39:25
10 (9, 12)
Statistics
χ2= 0.000 1.000
χ2= 1.284 0.864
K-W= 4.292 0.368
−3.25 (−4.25, −2.00) −3.25 (−3.75, −2.50) −3.00 (−4.00, −2.00) −3.00 (−4.00, −2.00) −3.125 (−4.375, −2.375) K-W = 3.003
−0.75 (−1.00, −0.50) −0.50 (−1.00, −0.50) −0.75 (−1.00, −0.50) −0.50 (−0.75, −0.50) −0.75 (−1.25, −0.50) K-W = 8.917
25.00 ± 0.80 25.05 ± 0.64 25.01 ± 0.72 24.93 ± 0.75 25.04 ± 0.63 F = 0.483
42.52 ± 1.41 42.48 ± 1.05 42.37 ± 1.08 42.60 ± 1.21 42.61 ± 1.22 F = 0.698
43.77 ± 1.38 43.76 ± 1.29 43.64 ± 1.41 43.78 ± 1.39 43.88 ± 1.34 F = 0.412
−0.39 ± 0.13 −0.38 ± 0.11 −0.39 ± 0.13 −0.39 ± 0.11 −0.39 ± 0.13 F = 0.603
0.557
0.063
0.748
0.594
0.800
0.661
P-value
Abbreviations: χ2 Chi-square, K-WKruskal-Wallis test; FF-statistic (one-WayANOVA)..
Fig. 1. Group mean and standard deviation for axial length (mm) at baseline, 6, 12, 18and 24 months of OrthoK lens or spectacle wear.
one night of wear, a steeper corneal mid-periphery was found in a low transmissibility OrthoK lens when compared with a high transmissibility lens. Although these lenses had different designs, the changes in corneal gradient resolved three hours after removing the lenses [21]. Thus, we speculate that long-term corneal shape changes are unlikely to be different so the myopia control is not affected, with lenses of different materials. In our study, Lucid and Mouldway OrthoK lenses are of different design, but made by the same material. We found no differences between these two OrthoK groups in slowing the increase in AL over two years. However, no studies have directly examined the effects of material of OrthoK lenses on AL elongation in children with myopia. Four different types of OrthoK lenses were compared by Tahhan et al. They found that even with different fitting methods, all four types of OrthoK lenses studied were comparable to each other in reducing myopic refractive error [22]. Kang et al. compared three OrthoK lens designs, finding a nominal difference in relative peripheral refraction between them, indicating they have analogous myopia control effects
Fig. 2. The relationship between the axial length elongation (mm) after 2 years and baseline age.
[23]. These previous results also support the conclusion of this study. In a different study, Kang et al. investigated the effect of changing orthokeratology lens parameters on peripheral refraction. They concluded both peripheral refraction and corneal topography profile were not affected by changes in optic zone diameter or peripheral tangent [24]. Our study strongly confirms the above speculation. In the present study, we investigated the relationship between different baseline patient factors and AL change after OrthoK lens wear. It was found that the AL elongation is related to the baseline age and studies have shown that myopic progression slows with increasing age [25–27]. In the current study, a weak negative correlation was found between AL elongation and baseline age. In addition it is possible that
Table 5 Comparison of mean AL elongation during 2 years in different groups (ANOVA analysis). Difference between groups
Difference (mm)
Standard error
P-value of difference
95 % Confidence interval
Essence - Lucid Essence - Euclid Essence - Mouldway Essence - Control Lucid - Euclid Lucid - Mouldway Lucid - Control Euclid - Mouldway Euclid - Control Mouldway - Control
−0.063 −0.033 −0.081 −0.155 0.030 −0.018 −0.092 −0.048 −0.122 −0.074
0.036 0.035 0.034 0.033 0.036 0.035 0.034 0.035 0.033 0.033
0.075 0.337 0.019* 0.000* 0.399 0.611 0.007* 0.166 0.000* 0.025*
−0.133, −0.102, −0.149, −0.220, −0.040, −0.087, −0.158, −0.116, −0.186, −0.138,
* P < 0.05. 4
0.006 0.035 −0.014 −0.090 0.100 0.051 −0.025 0.020 −0.057 −0.009
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Table 6 Correlation with AL elongation.
Baseline Age SER Baseline AL Mean P
Essence
Lucid
Euclid
Mouldway
Control
ß = −0.043, P = 0.039 ß = 0.065, P < 0.05 P > 0.05 P > 0.05
ß = −0.046, P = 0.047 P > 0.05 P > 0.05 P > 0.05
ß = −0.070, P < 0.01 ß = 0.079, P < 0.05 P > 0.05 P > 0.05
ß = −0.097, P < 0.05 ß = 0.087, P < 0.05 P > 0.05 P > 0.05
ß = −0.080, P < 0.05 P > 0.05 P > 0.05 P > 0.05
unlikely to be pertinent factors in influencing the degree of myopia control. Funding This work was supported in part by the Zhejiang Provincial Highlevel Talents Program (2017-102); Foundation of Wenzhou City Science & Technology Bureau (Y20180174); Medical and Health Science and Technology Program of Zhejiang Province (Y20170194, 2019KY111); Zhejiang Provincial Key Research and Development Program (2018C03012); Science Foundation of the Affiliated Eye Hospital of Wenzhou Medical University (YNZD1201903). Declaration of Competing Interest None. References [1] R.R. Bourne, G.A. Stevens, R.A. White, J.L. Smith, S.R. Flaxman, H. Price, et al., Causes of vision loss worldwide, 1990-2010: a systematic analysis, Lancet Glob Health 1 (2013) e339–e349. [2] B. Gilmartin, Myopia: precedents for research in the twenty-first century, Clin Exp Ophthalmol 32 (2004) 305–324. [3] B.A. Holden, T.R. Fricke, D.A. Wilson, M. Jong, K.S. Naidoo, P. Sankaridurg, et al., Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050, Ophthalmology (123) (2016) 1036–1042. [4] P. Cho, S.W. Cheung, Retardation of myopia in Orthokeratology (ROMIO) study: a 2-year randomized clinical trial, Invest Ophthalmol Vis Sci 53 (2012) 7077–7085. [5] T. Hiraoka, T. Kakita, F. Okamoto, H. Takahashi, T. Oshika, Long-term effect of overnight orthokeratology on axial length elongation in childhood myopia: a 5-year follow-up study, Invest Ophthalmol Vis Sci 53 (2012) 3913–3919. [6] C. McAlinden, M. Lipson, Orthokeratology and contact lens quality of life questionnaire (OCL-QoL), Eye Contact Lens 44 (2018) 279–285. [7] J.J. Walline, L.A. Jones, L.T. Sinnott, Corneal reshaping and myopia progression, Br J Ophthalmol 93 (2009) 1181–1185. [8] J. Charm, P. Cho, High myopia-partial reduction ortho-k: a 2-year randomized study, Optom Vis Sci 90 (2013) 530–539. [9] R. Sridharan, H. Swarbrick, Corneal response to short-term orthokeratology lens wear, Optom Vis Sci 80 (2003) 200–206. [10] H.A. Swarbrick, G. Wong, D.J. O’Leary, Corneal response to orthokeratology, Optom Vis Sci 75 (1998) 791–799. [11] A. Queiros, J.M. Gonzalez-Meijome, C. Villa-Collar, A.R. Gutierrez, J. Jorge, Local steepening in peripheral corneal curvature after corneal refractive therapy and LASIK, Optom Vis Sci 87 (2010) 432–439. [12] A. Queiros, C. Villa-Collar, A.R. Gutierrez, J. Jorge, M.S. Ribeiro-Queiros, S.C. Peixoto-de-Matos, et al., Anterior and posterior corneal elevation after orthokeratology and standard and customized LASIK surgery, Eye Contact Lens 37 (2011) 354–358. [13] W.N. Charman, J. Mountford, D.A. Atchison, E.L. Markwell, Peripheral refraction in orthokeratology patients, Optom Vis Sci 83 (2006) 641–648. [14] P. Kang, H. Swarbrick, Peripheral refraction in myopic children wearing orthokeratology and gas-permeable lenses, Optom Vis Sci 88 (2011) 476–482. [15] A. Queiros, A. Amorim-de-Sousa, D. Lopes-Ferreira, C. Villa-Collar, A.R. Gutierrez, J.M. Gonzalez-Meijome, Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery, Eye Vis (Lond) 5 (12) (2018). [16] J. Huang, D. Wen, Q. Wang, C. McAlinden, I. Flitcroft, H. Chen, et al., Efficacy comparison of 16 interventions for myopia control in children: a network metaanalysis, Ophthalmology 123 (2016) 697–708. [17] J. Santodomingo-Rubido, C. Villa-Collar, B. Gilmartin, R. Gutierrez-Ortega, K. Sugimoto, Long-term efficacy of orthokeratology contact lens wear in controlling the progression of childhood myopia, Curr Eye Res 42 (2017) 713–720. [18] T. Kakita, T. Hiraoka, T. Oshika, Influence of overnight orthokeratology on axial elongation in childhood myopia, Invest Ophthalmol Vis Sci 52 (2011) 2170–2174. [19] M.J. Zhu, H.Y. Feng, X.G. He, H.D. Zou, J.F. Zhu, The control effect of orthokeratology on axial length elongation in Chinese children with myopia, BMC Ophthalmol 14 (141) (2014). [20] E. Lum, H.A. Swarbrick, Lens Dk/t influences the clinical response in overnight
Fig. 3. The relationship between the axial length elongation (mm) after 2 years and baseline SER.
for various reasons, in older children with late onset myopia, the rate of axial elongation is already declining [5,28,29]. From the perspective of myopia control, we considered that age is not a significant factor when choosing an OrthoK lens design. Lin et al. reported that increases in AL in relation to baseline myopia showed a significantly weak correlation with OrthoK groups (Pearson correlation coefficient, r = 0.259) [30]. Hiraoka et al. plotted AL elongation against SER and the slope of linear regression line was -0.174 for the OrthoK group [5]. Similarly, in our study, the coefficient of regression was also weakly expressed between the increases in AL and SER over the 2-year period: 0.065 with the Essence lens, 0.079 with the Euclid and 0.087 with the Mouldway with an except for the Lucid OrthoK. This is unlikely to be clinically significant. Recently, the results of more studies showed that AL elongation was not significantly correlated with initial myopia [8,31]. The degree of myopia increases with age and our data appears to indicate a slightly lower efficacy of OrthoK lenses in patients with high initial myopia. This apparent reduction in efficacy was due to the gradual decline of myopic progression with age in the control group. There were several limitations to our study. First, a number of parameters, including pupil size, the effective optical zone of cornea, accommodative lag, retinal image quality and peripheral refractive status may influence myopic control with OrthoK which was not accounted for. Second, only four lens brands were explored; currently, there are many different OrthoK lens designs available to clinicians. However, because OrthoK lenses incorporate the same fundamental reverse geometry lens design, results from this study strongly suggests that different OrthoK lens designs will have a similar impact in slowing myopic AL elongation. Third, this study was a retrospective chart review and not a prospective randomized controlled trial in design. In conclusion, this study provides evidence that different OrthoK lenses differ minimally and are all effective in slowing AL elongation during two years of OrthoK lens wear. When choosing an OrthoK lens for a patient, the spherical equivalent refraction and age at baseline are 5
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[27] M.H. Edwards, The development of myopia in Hong Kong children between the ages of 7 and 12 years: a five-year longitudinal study, Ophthalmic Physiol Opt 19 (1999) 286–294. [28] L. Hyman, J. Gwiazda, M. Hussein, T.T. Norton, Y. Wang, W. Marsh-Tootle, et al., Relationship of age, sex, and ethnicity with myopia progression and axial elongation in the correction of myopia evaluation trial, Arch Ophthalmol 123 (2005) 977–987. [29] S.M. Saw, F.J. Nieto, J. Katz, O.D. Schein, B. Levy, S.J. Chew, Factors related to the progression of myopia in Singaporean children, Optom Vis Sci 77 (2000) 549–554. [30] H.J. Lin, L. Wan, F.J. Tsai, Y.Y. Tsai, L.A. Chen, A.L. Tsai, et al., Overnight orthokeratology is comparable with atropine in controlling myopia, BMC Ophthalmol (2014) 14. [31] J. Santodomingo-Rubido, C. Villa-Collar, B. Gilmartin, R. Gutierrez-Ortega, Myopia control with orthokeratology contact lenses in Spain: refractive and biometric changes, Invest Ophthalmol Vis Sci 53 (2012) 5060–5065.
orthokeratology, Optom Vis Sci 88 (2011) 469–475. [21] F. Lu, T. Simpson, L. Sorbara, D. Fonn, Corneal refractive therapy with different lens materials, part 2: effect of oxygen transmissibility on corneal shape and optical characteristics, Optom Vis Sci 84 (2007) 349–356. [22] N. Tahhan, R. Du Toit, E. Papas, H. Chung, D. La Hood, A.B. Holden, Comparison of reverse-geometry lens designs for overnight orthokeratology, Optom Vis Sci 80 (2003) 796–804. [23] P. Kang, H. Swarbrick, The influence of different OK Lens designs on peripheral refraction, Optom Vis Sci 93 (2016) 1112–1119. [24] P. Kang, P. Gifford, H. Swarbrick, Can manipulation of orthokeratology lens parameters modify peripheral refraction? Optom Vis Sci 90 (2013) 1237–1248. [25] B. Wang, R.K. Naidu, X. Qu, Factors related to axial length elongation and myopia progression in orthokeratology practice, PLoS One 12 (2017) e0175913. [26] M. He, Y. Du, Q. Liu, C. Ren, J. Liu, Q. Wang, et al., Effects of orthokeratology on the progression of low to moderate myopia in Chinese children, BMC Ophthalmol 16 (126) (2016).
6
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Contact Lens and Anterior Eye journal homepage: www.elsevier.com/locate/clae
Comparison of four different orthokeratology lenses in controlling myopia progression Ruru Chena,b,1, Jinjin Yua,1, Michael Lipsonc, Abdullah A. Cheemad, Yan Chena,b, Hengli Liana,b, Jinhai Huanga,b,*, Colm McAlindene a
School of Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, China Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China c Department of Ophthalmology and Visual Science, University of Michigan, Northville, USA d Imperial College School of Medicine, London, United Kingdom e Department of Ophthalmology, Princess of Wales Hospital, Bridgend, United Kingdom b
A R T I C LE I N FO
A B S T R A C T
Keywords: Orthokeratology OrthoK lens Axial length Myopia progression
Purpose: To compare axial length (AL) elongation in myopic children with four Orthokeratology (OrthoK) lenses and spectacles. Methods: The medical records of 266 patients (532 eyes) who were fitted with OrthoK lenses or spectacles (control group) were reviewed. Data collection included baseline age, gender, baseline objective sphere and cylinder, baseline flat and steep corneal meridian power, corneal asphericity coefficient (Q value), AL at baseline and after 1-year, and 2-years of OrthoK or spectacle wear analyzed using analysis of repeated measures data ANOVA. Stepwise linear regressions between the changes in AL after 2 years relative to baseline parameters were calculated for the OrthoK and control groups separately. Results: The baseline subject parameters for each of the four OrthoK lenses were not statistically different. Statistically significant differences between time points were found between 12- and 24- months (all P < 0.05). AL growth was slower in all OrthoK groups than in the control group (all P < 0.05). AL grew 0.081 ± 0.034 mm per year slightly less than average with Essence compared to the Mouldway OrthoK group (P = 0.019). The coefficient of regression weakly expressed between the increases in AL over 2-years study period and baseline spherical equivalent refraction was 0.065 in Essence, 0.079 in Euclid and 0.087 in Mouldway. The coefficient of regression was also weakly between age and the increases AL over 2-years study period and baseline age in all groups. Conclusion: Different OrthoK lenses differ minimally in slowing axial elongation effectively in myopic children during 2-years lens wear.
1. Introduction Myopia is the most common form of ametropia and one of the leading causes of vision impairment in the world [1]. Estimates show that in the early 21st century, myopia affected almost 30 % of the world’s population [2]. This trend is projected to increase significantly, affecting nearly 50 % of the world’s population by 2050 [3]. Currently, numerous studies have confirmed that orthokeratology (OrthoK) is effective in slowing AL elongation and improves the quality of life in children with myopia [4–6]. OrthoK is now increasingly used as a non-pharmacological management option to slow AL elongation in myopia with specially-designed contact lenses worn while sleeping
[4,5,7,8]. Myopic OrthoK lenses incorporate a reverse geometry lens design where the central base curve is flatter than the central cornea. A single or multiple series of curves surrounding the central base curve are referred to as the reverse curve. The reverse curve is usually significantly steeper than the central base curve. Peripheral to this is a series of curves to align with the cornea. Combined, these lens parameters induce central corneal flattening and mid-peripheral corneal steepening. The resulting topographical changes temporarily correct mild - moderate degrees of myopic refractive error, providing patients with clear unaided distance vision [9–12]. It has been proposed that changes in peripheral retinal defocus induced by OrthoK may be one of the mechanisms for the deceleration of
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Corresponding author at: Eye Hospital of Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China. E-mail address: [email protected] (J. Huang). 1 They contributed equally as first authors. https://doi.org/10.1016/j.clae.2019.11.012 Received 9 July 2019; Received in revised form 15 November 2019; Accepted 26 November 2019 1367-0484/ © 2019 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Ruru Chen, et al., Contact Lens and Anterior Eye, https://doi.org/10.1016/j.clae.2019.11.012
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Table 1 Inclusion criteria for data collection. Inclusion criteria Age Subjective sphere Subjective cylinder Anisometropia Visual acuity Ocular health
Systemic health Others
8 to 13 years old −0.50 diopters (D) to −5.00 D in both eyes No more than −1.50 D in both eyes ≤1.50 D (non-cycloplegic autorefraction) Monocular corrected distance visual acuity no worse than 20/20 Intraocular pressure (IOP) < 21 mmHg No other ocular disease aside from refractive error including no keratoconus (confirmed by pre-treatment corneal topography) No binocular vision conditions such as strabismus No systemic or neurodevelopmental deviations that might affect refractive development Birth weight ≥1500 g No history of parental high myopia No history of contact lens wear, bifocal or progressive addition spectacles in the past 12 months, or atropine treatment for myopia control Maintained regular scheduled visits and completed the 2-year follow-up Unaided visual acuity of 20/20 or better at the last scheduled review appointment (criteria only for OrthoK group) Discontinued lens wear for a total of 30 days or less during the 2 years (criteria only for OrthoK group)
2.2. Data collection
myopia progression [13–15]. Paracentral retinal myopic defocus induced by OrthoK lenses is due to their reverse curve design. However, different OrthoK lenses may have varying reverse curve parameters. Furthermore, the various materials and OrthoK designs may also have different oxygen transmissibility and optic zone diameters. These factors may influence the degree of myopia control for each lens. To our knowledge there are no long-term studies on the efficacy of different OrthoK lenses to slow AL elongation in children. Therefore, the purpose of this study was to analyze AL elongation in Chinese children over two years of OrthoK lens wear with four different OrthoK lenses, relative to spectacle wear (control group).
Data was retrospectively collected from the clinical records of 266 subjects, with both eyes from each subject (total 532 eyes) being used for the statistical analysis. Data collected included: OrthoK brand or spectacles, age (in years) at the initial OrthoK lens fitting or spectacle wear, gender, baseline sphere and cylinder, initial flat and steep keratometry (Kf and Ks), corneal asphericity coefficient (Q value) (generated by a corneal topographer), and AL at initial, 1-year, and 2-years of OrthoK or spectacle wear. All OrthoK subjects used the same OrthoK lens type with comparison of the different lenses during the 2-year study period. The control group wore single-vision spectacles with the full distance best-corrected monocular visual acuity equal to or better than 20/20.
2. Materials and methods 2.1. Subjects
2.3. Materials
The clinical records of OrthoK contact lens wearers and spectacle wearers who presented to the Eye Hospital of Wenzhou Medical University from initial inspection to the time of review (August 2017) were analyzed. Children with myopia were selected for this study and inclusion and exclusion criteria are detailed in Tables 1 and 2. This study was approved by the Office of Research Ethics, Eye Hospital of Wenzhou Medical University. It was conducted in accordance with the Tenets of the Declaration of Helsinki. Written informed consent was obtained from guardians on behalf of the children. Parents were allowed to choose between two treatment options (spectacles or OrthoK lenses) for their children, taking into account factors such as parents’ opinion in controlling progression of myopia, concerns about the safety of lens wear, lens care and economic cost. As for what kind of OrthoK lens to be chosen, parents may consider the expenses of different OrthoK lenses. However, doctors provided a qualitative recommendation to the parents, taking into consideration the acceptability of various lenses suited to the needs of each individual child. Single vision spectacles are the optical means to correct vision for most myopic children and considered to be ineffective for myopia control [16], which was why we chose spectacles for the control group. Data was collected from the hospital records and no patient involvement was required.
In the OrthoK group, four different lenses were used: Essence (C&E GP Specialists Inc., San Diego, California, USA), Euclid (Euclid Systems Corporation, Herndon, Virginia, USA), Lucid (Lucid Korea Co. Ltd, Korea), Mouldway (Autek China Inc.,Sino-American Joint Venture). The detailed information about each of the four lenses is provided by the manufacturer and is listed in Table 3. All patients underwent a standard anterior eye and refractive status assessment prior to commencing OrthoK wear. This assessment included measurement of baseline corneal topography using a corneal topographer (Medmont E6.0; Medmont Pty Ltd, Brisbane, Australia). The Kf, Ks and Q value were generated by the corneal topographer over an 8 mm chord length. Cycloplegic autorefraction was performed in each group before enrollment. Cycloplegia was induced 40 min before refraction measurements with 1 % cyclopentolate hydrochloride eye drops (single dose bottle; Alcon, Puurs, Belgium). AL was measured five times using partial coherence interferometry (IOLMaster; Carl Zeiss, Germany) and the data was automatically averaged. Table 3 Nominal OrthoK lens characteristics and parameters.
Table 2 Exclusion criteria for data collection.
Lens
Material
Dk
OZD
RCW
ACW
PCW
CT
Essence
Paragon HDS100 Boston Equalens II Boston XO Boston XO
100
6.0
0.6
1.2
0.5
0.22–0.25
127
6.2
0.5
1.2
0.5
0.22
100 100
6.2 6.0
0.9 0.4–1.0
0.8 0.4–1.5
0.5 0.2–0.5
0.23 0.24
Euclid
Exclusion criteria Binocular vision conditions such as strabismus Systemic or neurodevelopmental deviations that might affect refractive development History of parental high myopia (more than −6.00 D) History of contact lens wear, bifocal or progressive addition spectacles in the past 12 months, atropine treatment for myopia control
Lucid Mouldway
Dk, oxygen permeability (10−11 cm2×mLO2)/(s × mL × mm Hg); OZD, optic zone diameter (mm); RCW, reverse curve width (mm); ACW, alignment curve width (mm); PCW, peripheral curve width (mm); CT, central thickness (mm). 2
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analysis, statistically significant changes were not found in AL between right and left eyes (F=1.014, P > 0.05).
2.4. Schedule of visits All patients were followed-up according to the standard protocol of the Eye Hospital of Wenzhou Medical University. Patients were typically evaluated at 1 day, 1 week and 1 month following OrthoK wear. Follow-up appointments were thereafter scheduled every 3 months both in OrthoK and control group. At each visit, measurements of noncycloplegic visual acuity and slit-lamp examinations assessing ocular health and OrthoK lens integrity were performed. AL was measured at 6-month intervals in the OrthoK subgroups and control group. AL at the baseline, 12-months and 24-month were collected. All patients had no more than 30 days of lens cessation during the study period from the patient follow-up files. In the control group, doctors generally suggested that the prescription of spectacles should be changed when the patients’ sphere dropped less than -0.50 D by noncycloplegic subjective refraction. After the OrthoK lenses were dispensed, the parents were instructed to help with the daily lens insertion, removal, cleaning (including daily care and one-two weekly deproteinized care according to Menicon cleaning protocol) and wearing procedures. OrthoK lenses were changed to optimize visual acuity and refractive target endpoints or decentration.
3.2. AL change in OrthoK and control groups Statistically significant differences were found in AL over time, between groups and for time*group interaction (all P < 0.01). Statistically significant differences between time points were found between 12- and 24-months (P = 0.002). Statistically significant changes were found between groups at different visit time points. The increases in AL during the 2-year study period were 0.317 ± 0.247 mm, 0.387 ± 0.273 mm, 0.358 ± 0.208 mm, 0.431 ± 0.229 mm and 0.524 ± 0.288 mm in the Essence, Lucid, Euclid, Mouldway OrthoK groups and the control group, respectively. AL elongation was slower in all OrthoK groups compared to the control group (all P < 0.05). In addition, mean AL increases were 0.081 ± 0.034 mm per year less in the Essence group than the Mouldway OrthoK group (P = 0.019). No statistically significant differences in AL elongation were seen in the other OrthoK intergroups (Fig. 1 and Table 5). 3.3. Baseline factors and AL growth In all five (Essence, Lucid, Euclid, Mouldway and control) groups, at 2 years, AL elongation had a statistically significant yet weak correlation with baseline age (Fig. 2 and Table 6). The Essence, Euclid and Mouldway OrthoK groups had a statistically significant yet weak correlation between AL elongation and SER (Fig. 3 and Table 6). None of the five groups found a statistically significant relationship between AL elongation with baseline AL or mean P-value (Table 6).
2.5. Statistical analysis Chi-squared test was used to compare gender and eyes among groups. The data of age, objective sphere and cylinder did not have a normal distribution according to the Kolmogorov-Smirnov test. The Kruskal-Wallis test was used to compare age, objective sphere and cylinder analysis among groups. After confirming normality (ShapiroWilk), baseline AL, Kf, Ks and Q value were compared via a general linear model (GLM) nested-design analysis of variance (ANOVA). GLM Nested Design ANOVA was used to correctly account for eyes to be nested within participants’ baseline parameters and AL followed over time. The data of AL at 12 and 24 months was analyzed via a mixedmodel nested-design ANOVA. Variance analysis was used to compare the differences between groups. Time was treated as the repeated factor, with lens type as a between-subject factor. The multivariate output indicated that the overall test was significant at the 95 % confidence level. Additionally, stepwise linear regressions between the change in AL after two years relative to baseline and baseline age, SER (spherical equivalent refraction = sphere + 1/2 cylinder) and mean K (mean keratometry = Kf + Ks) were calculated for the OrthoK and control groups separately. Statistical analyses were performed using the SPSS software (ver. 21.0; SPSS Inc., Chicago, Illinoi, USA) and graphing with GraphPad Prism 5 (GraphPad Software Inc., La Jolla, California, USA). The level of statistical significance was set at 0.05.
4. Discussion With the availability of many different OrthoK lenses, there is a greater need to better understand the relationship between different types of OrthoK lenses and their myopic control effect. To our knowledge, this is the first 2-year study reporting on the efficacy on myopic control with four different types of OrthoK lenses in a large number of subjects. Our results confirmed that all four OrthoK lenses tested are effective in slowing the increase in AL compared with spectacles. In this study, the increase in AL of Chinese children over two years was 0.317 ± 0.247 mm with the Essence lens, 0.358 ± 0.208 mm with the Euclid, 0.387 ± 0.273 mm with the Lucid and 0.431 ± 0.229 mm with the Mouldway. Santodomingo-Rubido et al. reported that the change in the AL for their OrthoK group following 24 months was approximately 0.4 mm in white European subjects using a different OrthoK brand, Menicon Z Night OrthoK lens [17]. In spite of differences in race and sample size, the myopia control effect of Mouldway OrthoK group in our study was nearly identical to that of the Menicon Z Night OrthoK lens. Tetsubiko et al. found AL elongation was 0.39 ± 0.27 mm after two years using the Euclid OrthoK lens manufactured with the Boston XO material [18]. Zhu et al. reported that the AL elongation was 0.34 ± 0.29 mm after two years using the Euclid OrthoK lens manufactured with the Boston Equalens II material [19]. A similar result was also found in our study (0.358 ± 0.208 mm). We could speculate that the oxygen permeability of an OrthoK lens of the same design is unlikely to affect the degree of slowing myopia progression. In a study by Lum et al. it was found that within 2 weeks, the ability of OrthoK lenses to correct refraction was improved if the oxygen transmissibility of lenses was increased. It was thought that with more oxygen reaching the epithelial cells, boosting their metabolism would lead to a faster central epithelial thinning and, potentially, midperipheral epithelial thickening. However, this difference disappeared beyond 2 weeks of lens wear [20]. Hence, the possibility that this might then somehow affect AL elongation over a 2-year period is quite unlikely. Lu et al. found low and high oxygen transmissibility lenses affect the curvature gradient of the corneal mid-periphery. After
3. Results 3.1. Patients and treatment characteristics No severe adverse events (e.g. microbial keratitis) were reported in the any of the groups. With the Chi-square test, there were no significant differences in eyes and gender between 5 groups (Table 4). Of the 266 subjects, there were 152 females and 114 males. There were 51 subjects in the Essence OrthoK group, 51 subjects in the Euclid OrthoK group, 46 subjects in the Lucid OrthoK group, 53 subjects in the Mouldway OrthoK group and 64 subjects in the control (spectacle lens) group. With the Kruskal-Wallis test, there were no statistically significant differences at baseline for age, objective sphere and cylinder (Table 4). With GLM nested-design ANOVA, there were no statistically significant differences at baseline for Kf and Ks, Q value or initial AL between five groups (Table 4). With GLM nested-design ANOVA analysis, objective sphere, cylinder, baseline Kf, Ks and Q value were not statistically different between right and left eyes (P > 0.05). With linear mixed models 3
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Table 4 Biometric data of subjects at baseline. Design
Eyes Right:Left
Gender Female:Male
Median age (years)
Median subjective sphere (DS)
Median subjective cylinder (DC)
Mean ( ± SD) initial AL (mm)
Mean ( ± SD) Kf (D)
Mean ( ± SD) Ks (D)
Mean ( ± SD) Q value
Essence
51:51
28:23
10 (9, 12)
Euclid
51:51
28:23
10 (9, 12)
Lucid
47:47
25:22
9 (9, 12)
Mouldway
53:53
32:21
9 (8, 12)
Control
64:64
39:25
10 (9, 12)
Statistics
χ2= 0.000 1.000
χ2= 1.284 0.864
K-W= 4.292 0.368
−3.25 (−4.25, −2.00) −3.25 (−3.75, −2.50) −3.00 (−4.00, −2.00) −3.00 (−4.00, −2.00) −3.125 (−4.375, −2.375) K-W = 3.003
−0.75 (−1.00, −0.50) −0.50 (−1.00, −0.50) −0.75 (−1.00, −0.50) −0.50 (−0.75, −0.50) −0.75 (−1.25, −0.50) K-W = 8.917
25.00 ± 0.80 25.05 ± 0.64 25.01 ± 0.72 24.93 ± 0.75 25.04 ± 0.63 F = 0.483
42.52 ± 1.41 42.48 ± 1.05 42.37 ± 1.08 42.60 ± 1.21 42.61 ± 1.22 F = 0.698
43.77 ± 1.38 43.76 ± 1.29 43.64 ± 1.41 43.78 ± 1.39 43.88 ± 1.34 F = 0.412
−0.39 ± 0.13 −0.38 ± 0.11 −0.39 ± 0.13 −0.39 ± 0.11 −0.39 ± 0.13 F = 0.603
0.557
0.063
0.748
0.594
0.800
0.661
P-value
Abbreviations: χ2 Chi-square, K-WKruskal-Wallis test; FF-statistic (one-WayANOVA)..
Fig. 1. Group mean and standard deviation for axial length (mm) at baseline, 6, 12, 18and 24 months of OrthoK lens or spectacle wear.
one night of wear, a steeper corneal mid-periphery was found in a low transmissibility OrthoK lens when compared with a high transmissibility lens. Although these lenses had different designs, the changes in corneal gradient resolved three hours after removing the lenses [21]. Thus, we speculate that long-term corneal shape changes are unlikely to be different so the myopia control is not affected, with lenses of different materials. In our study, Lucid and Mouldway OrthoK lenses are of different design, but made by the same material. We found no differences between these two OrthoK groups in slowing the increase in AL over two years. However, no studies have directly examined the effects of material of OrthoK lenses on AL elongation in children with myopia. Four different types of OrthoK lenses were compared by Tahhan et al. They found that even with different fitting methods, all four types of OrthoK lenses studied were comparable to each other in reducing myopic refractive error [22]. Kang et al. compared three OrthoK lens designs, finding a nominal difference in relative peripheral refraction between them, indicating they have analogous myopia control effects
Fig. 2. The relationship between the axial length elongation (mm) after 2 years and baseline age.
[23]. These previous results also support the conclusion of this study. In a different study, Kang et al. investigated the effect of changing orthokeratology lens parameters on peripheral refraction. They concluded both peripheral refraction and corneal topography profile were not affected by changes in optic zone diameter or peripheral tangent [24]. Our study strongly confirms the above speculation. In the present study, we investigated the relationship between different baseline patient factors and AL change after OrthoK lens wear. It was found that the AL elongation is related to the baseline age and studies have shown that myopic progression slows with increasing age [25–27]. In the current study, a weak negative correlation was found between AL elongation and baseline age. In addition it is possible that
Table 5 Comparison of mean AL elongation during 2 years in different groups (ANOVA analysis). Difference between groups
Difference (mm)
Standard error
P-value of difference
95 % Confidence interval
Essence - Lucid Essence - Euclid Essence - Mouldway Essence - Control Lucid - Euclid Lucid - Mouldway Lucid - Control Euclid - Mouldway Euclid - Control Mouldway - Control
−0.063 −0.033 −0.081 −0.155 0.030 −0.018 −0.092 −0.048 −0.122 −0.074
0.036 0.035 0.034 0.033 0.036 0.035 0.034 0.035 0.033 0.033
0.075 0.337 0.019* 0.000* 0.399 0.611 0.007* 0.166 0.000* 0.025*
−0.133, −0.102, −0.149, −0.220, −0.040, −0.087, −0.158, −0.116, −0.186, −0.138,
* P < 0.05. 4
0.006 0.035 −0.014 −0.090 0.100 0.051 −0.025 0.020 −0.057 −0.009
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Table 6 Correlation with AL elongation.
Baseline Age SER Baseline AL Mean P
Essence
Lucid
Euclid
Mouldway
Control
ß = −0.043, P = 0.039 ß = 0.065, P < 0.05 P > 0.05 P > 0.05
ß = −0.046, P = 0.047 P > 0.05 P > 0.05 P > 0.05
ß = −0.070, P < 0.01 ß = 0.079, P < 0.05 P > 0.05 P > 0.05
ß = −0.097, P < 0.05 ß = 0.087, P < 0.05 P > 0.05 P > 0.05
ß = −0.080, P < 0.05 P > 0.05 P > 0.05 P > 0.05
unlikely to be pertinent factors in influencing the degree of myopia control. Funding This work was supported in part by the Zhejiang Provincial Highlevel Talents Program (2017-102); Foundation of Wenzhou City Science & Technology Bureau (Y20180174); Medical and Health Science and Technology Program of Zhejiang Province (Y20170194, 2019KY111); Zhejiang Provincial Key Research and Development Program (2018C03012); Science Foundation of the Affiliated Eye Hospital of Wenzhou Medical University (YNZD1201903). Declaration of Competing Interest None. References [1] R.R. Bourne, G.A. Stevens, R.A. White, J.L. Smith, S.R. Flaxman, H. Price, et al., Causes of vision loss worldwide, 1990-2010: a systematic analysis, Lancet Glob Health 1 (2013) e339–e349. [2] B. Gilmartin, Myopia: precedents for research in the twenty-first century, Clin Exp Ophthalmol 32 (2004) 305–324. [3] B.A. Holden, T.R. Fricke, D.A. Wilson, M. Jong, K.S. Naidoo, P. Sankaridurg, et al., Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050, Ophthalmology (123) (2016) 1036–1042. [4] P. Cho, S.W. Cheung, Retardation of myopia in Orthokeratology (ROMIO) study: a 2-year randomized clinical trial, Invest Ophthalmol Vis Sci 53 (2012) 7077–7085. [5] T. Hiraoka, T. Kakita, F. Okamoto, H. Takahashi, T. Oshika, Long-term effect of overnight orthokeratology on axial length elongation in childhood myopia: a 5-year follow-up study, Invest Ophthalmol Vis Sci 53 (2012) 3913–3919. [6] C. McAlinden, M. Lipson, Orthokeratology and contact lens quality of life questionnaire (OCL-QoL), Eye Contact Lens 44 (2018) 279–285. [7] J.J. Walline, L.A. Jones, L.T. Sinnott, Corneal reshaping and myopia progression, Br J Ophthalmol 93 (2009) 1181–1185. [8] J. Charm, P. Cho, High myopia-partial reduction ortho-k: a 2-year randomized study, Optom Vis Sci 90 (2013) 530–539. [9] R. Sridharan, H. Swarbrick, Corneal response to short-term orthokeratology lens wear, Optom Vis Sci 80 (2003) 200–206. [10] H.A. Swarbrick, G. Wong, D.J. O’Leary, Corneal response to orthokeratology, Optom Vis Sci 75 (1998) 791–799. [11] A. Queiros, J.M. Gonzalez-Meijome, C. Villa-Collar, A.R. Gutierrez, J. Jorge, Local steepening in peripheral corneal curvature after corneal refractive therapy and LASIK, Optom Vis Sci 87 (2010) 432–439. [12] A. Queiros, C. Villa-Collar, A.R. Gutierrez, J. Jorge, M.S. Ribeiro-Queiros, S.C. Peixoto-de-Matos, et al., Anterior and posterior corneal elevation after orthokeratology and standard and customized LASIK surgery, Eye Contact Lens 37 (2011) 354–358. [13] W.N. Charman, J. Mountford, D.A. Atchison, E.L. Markwell, Peripheral refraction in orthokeratology patients, Optom Vis Sci 83 (2006) 641–648. [14] P. Kang, H. Swarbrick, Peripheral refraction in myopic children wearing orthokeratology and gas-permeable lenses, Optom Vis Sci 88 (2011) 476–482. [15] A. Queiros, A. Amorim-de-Sousa, D. Lopes-Ferreira, C. Villa-Collar, A.R. Gutierrez, J.M. Gonzalez-Meijome, Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery, Eye Vis (Lond) 5 (12) (2018). [16] J. Huang, D. Wen, Q. Wang, C. McAlinden, I. Flitcroft, H. Chen, et al., Efficacy comparison of 16 interventions for myopia control in children: a network metaanalysis, Ophthalmology 123 (2016) 697–708. [17] J. Santodomingo-Rubido, C. Villa-Collar, B. Gilmartin, R. Gutierrez-Ortega, K. Sugimoto, Long-term efficacy of orthokeratology contact lens wear in controlling the progression of childhood myopia, Curr Eye Res 42 (2017) 713–720. [18] T. Kakita, T. Hiraoka, T. Oshika, Influence of overnight orthokeratology on axial elongation in childhood myopia, Invest Ophthalmol Vis Sci 52 (2011) 2170–2174. [19] M.J. Zhu, H.Y. Feng, X.G. He, H.D. Zou, J.F. Zhu, The control effect of orthokeratology on axial length elongation in Chinese children with myopia, BMC Ophthalmol 14 (141) (2014). [20] E. Lum, H.A. Swarbrick, Lens Dk/t influences the clinical response in overnight
Fig. 3. The relationship between the axial length elongation (mm) after 2 years and baseline SER.
for various reasons, in older children with late onset myopia, the rate of axial elongation is already declining [5,28,29]. From the perspective of myopia control, we considered that age is not a significant factor when choosing an OrthoK lens design. Lin et al. reported that increases in AL in relation to baseline myopia showed a significantly weak correlation with OrthoK groups (Pearson correlation coefficient, r = 0.259) [30]. Hiraoka et al. plotted AL elongation against SER and the slope of linear regression line was -0.174 for the OrthoK group [5]. Similarly, in our study, the coefficient of regression was also weakly expressed between the increases in AL and SER over the 2-year period: 0.065 with the Essence lens, 0.079 with the Euclid and 0.087 with the Mouldway with an except for the Lucid OrthoK. This is unlikely to be clinically significant. Recently, the results of more studies showed that AL elongation was not significantly correlated with initial myopia [8,31]. The degree of myopia increases with age and our data appears to indicate a slightly lower efficacy of OrthoK lenses in patients with high initial myopia. This apparent reduction in efficacy was due to the gradual decline of myopic progression with age in the control group. There were several limitations to our study. First, a number of parameters, including pupil size, the effective optical zone of cornea, accommodative lag, retinal image quality and peripheral refractive status may influence myopic control with OrthoK which was not accounted for. Second, only four lens brands were explored; currently, there are many different OrthoK lens designs available to clinicians. However, because OrthoK lenses incorporate the same fundamental reverse geometry lens design, results from this study strongly suggests that different OrthoK lens designs will have a similar impact in slowing myopic AL elongation. Third, this study was a retrospective chart review and not a prospective randomized controlled trial in design. In conclusion, this study provides evidence that different OrthoK lenses differ minimally and are all effective in slowing AL elongation during two years of OrthoK lens wear. When choosing an OrthoK lens for a patient, the spherical equivalent refraction and age at baseline are 5
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orthokeratology, Optom Vis Sci 88 (2011) 469–475. [21] F. Lu, T. Simpson, L. Sorbara, D. Fonn, Corneal refractive therapy with different lens materials, part 2: effect of oxygen transmissibility on corneal shape and optical characteristics, Optom Vis Sci 84 (2007) 349–356. [22] N. Tahhan, R. Du Toit, E. Papas, H. Chung, D. La Hood, A.B. Holden, Comparison of reverse-geometry lens designs for overnight orthokeratology, Optom Vis Sci 80 (2003) 796–804. [23] P. Kang, H. Swarbrick, The influence of different OK Lens designs on peripheral refraction, Optom Vis Sci 93 (2016) 1112–1119. [24] P. Kang, P. Gifford, H. Swarbrick, Can manipulation of orthokeratology lens parameters modify peripheral refraction? Optom Vis Sci 90 (2013) 1237–1248. [25] B. Wang, R.K. Naidu, X. Qu, Factors related to axial length elongation and myopia progression in orthokeratology practice, PLoS One 12 (2017) e0175913. [26] M. He, Y. Du, Q. Liu, C. Ren, J. Liu, Q. Wang, et al., Effects of orthokeratology on the progression of low to moderate myopia in Chinese children, BMC Ophthalmol 16 (126) (2016).
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