CPD Modules Available

Print this page

Myopia Control with Soft Contact Lenses

2 CPD in Australia | 0.5G in New Zealand | 2 December 2017



By Dr. Nicola Anstice, Dr. Philip Turnbull, Dr. Andrew Collins and Dr. John Phillips

The discussion around myopia management is undergoing a significant paradigm shift, from correction to control of myopia. Current research findings challenge practitioners to consider whether simply correcting the refractive error of children with progressing myopia is sufficient, or whether advice and treatment options regarding myopia control should also be provided to the patients and their caregivers from the outset.

Myopia is the most common ocular disorder and is generally the result of abnormal elongation of the eye. Although distance visual acuity can be improved with various methods, for examples spectacles, contact lenses and laser refractive surgery, these do not address the underlying abnormal enlargement of the eye. Myopia places substantial burdens both on individuals and society. It is the leading cause of correctable visual impairment and the costs related to its optical correction are significant. High myopia, often taken as a refraction greater than -6.00 D, has long been associated with sight-threatening conditions including myopic maculopathy, retinal detachment, cataract and glaucoma.1 However, this threshold is arbitrary, and it is now recognised that even low to moderate degrees of myopia can increase the risk of such comorbidities. The main determinant of visual impairment in myopic eyes appears to be axial length, with the risk of visual impairment increasing from 3.8 per cent in eyes with axial lengths less than 26 mm, to 25 per cent  in eyes with axial lengths >26 mm, and greater than 90 per cent for patients with eyes longer than 30mm.2,3

Furthermore, while high myopia has been considered more genetic than environmental in origin, the rapid increase in the prevalence of myopia in East and Southeast Asia over the last few decades has revealed a new pattern of development of high myopia.4 In this pattern, high myopia develops at around 11 years of age, due to the onset of common (or school) myopia at six to seven years of age, and is associated with a relatively high progression rate of more than -1 D per year. This form of rapidly progressing myopia appears to be associated with the adoption of an intensive and prolonged education system. While the current “epidemic” of myopia is commonly associated with Asian countries and states, the association between intensive academic education and myopia was originally noted over 150 years ago by the German ophthalmologist Hermann Cohn.5 Thus, both genetic and environmental factors are likely to play a role in development of myopia and progression of refractive error and identifying ‘at risk’ children is an important part of any myopia control strategy.

Although a few dioptres of myopic refractive error may be considered beneficial once presbyopia has developed, the aim of myopia control is to identify myopia progression early in children, and initiate an appropriate myopia control method to reduce the rate of progression and axial elongation of the eye, and hence the final degree of myopic refractive error in adulthood. Current evidence-based myopia control options can be divided into optical (orthokeratology, multifocal soft contact lenses, progressive addition spectacle lenses and executive-style bifocals) and pharmacological (atropine, usually in low-dose concentrations) methods.6

This review specifically discusses the use of soft contact lens designs for myopia control. A brief comparison with other myopia control methods is included for reference but these interventions are not the focus of this article.

Children and Soft Contact Lenses

There is growing evidence that children as young as eight years of age can successfully wear soft contact lenses.7,8 However, the proportion of children fitted with contact lenses varies considerably between countries, depending on the clinical indication, access to contact lenses, and the training and confidence of eye care practitioners, as well as parental attitudes and experiences. In countries such as New Zealand and Australia, approximately 10-15 per cent of all contact lenses are prescribed to infants, children and adolescents.9

Fitting children and adolescents with single vision contact lenses does not cause any change in myopia progression, axial elongation or steepening of corneal curvature compared with age-matched spectacle lens wearers.10,11 Nevertheless, conventional single vision soft contact lenses provide advantages beyond visual correction. Children also benefit from soft contact lens wear in terms of self-perception, particularly in the domains of physical appearance, athletic ability and social acceptance. Therefore, eye care practitioners should also consider the social benefits of early contact lens wear,12,13 in addition to the potential myopia control benefits that can be gained by certain soft contact lens designs.

Peripheral Retinal Defocus and Myopia Control

Optical interventions for myopia were traditionally based on the concept of managing accommodative demand or the lag of accommodation associated with near work. However, an alternative hypothesis whereby the reduction in myopia progression is achieved by altering retinal defocus under all viewing conditions is now more widely accepted.14 The role of peripheral retinal defocus in the control of refractive development is supported by a number of studies in animal models of myopia.15-17 In these models, manipulation of the retinal focal plane so that it lies behind the retina (hyperopic retinal defocus) promotes a compensatory axial elongation of the eye, resulting in the development of a myopic refractive error. Conversely, relative peripheral myopic defocus (image plane in front of the retina) slows axial elongation and myopia development, even when the foveal region experiences hyperopic defocus. These findings have been developed into commercial optical solutions, including novel soft contact lens designs, intended to produce relative myopic retinal defocus, with the aim of reducing myopia progression.

Evidence Base for Myopia Control

Evidence for the use of soft contact lenses for the control of myopia progression was first published in 2008 in a case report of identical twins, one of whom was fitted with single vision soft contact lenses and the other with Acuvue bifocal lenses.18 In the first year of contact lens wear, the child fitted with the single vision soft contact lens showed myopia progression of -1.32 D more than their twin, however their myopia progression halted once she switched to bifocal contact lenses.

Figure 1: Diagram to show optic zones of Dual Focus lens (A) and focal points formed in the eye (B). Green zones represent areas of distance correction and pink zones represent treatment zones of under-correction.

More recently, we have published results from a paired-eye study of ‘dual-focus’ contact lenses - a rotationally symmetrical multifocal soft contact lens constructed with a centre distance zone to correct refractive error, and surrounding treatment zones designed to produce 2.00 D of myopic retinal defocus.19 Eyes randomly assigned to dual-focus contact lenses showed less myopia progression (-0.44 ± 0.33 D) than eyes fitted with single vision contact lenses (-0.69 ± 0. 38 D). This reduction was accompanied by a corresponding reduction in eye growth (0.11 ± 0.09 mm in dual-focus versus 0.22 ± 0.10 mm in single vision lenses). This dual-focus lens design provided the basis for the CooperVision MiSight lens, and three-year clinical trial data from CooperVision has shown a sustained 59 per cent reduction in refractive error progression and a 52 per cent reduction in mean axial elongation of the eyes fitted with MiSight lenses compared to single vision controls.20 Children fitted with dual-focus lenses show normal accommodation, suggesting that the mechanism of action for the reduction in axial myopia progression was not due to a change in accommodative lag, but the presence of myopic retinal defocus.

Similar myopia control results are seen with other multifocal contact lenses. The Proclear Multifocal ‘D’ lenses, commercially available for correcting presbyopic adults, reduced refractive progression by 50 per cent and slowed axial elongation of the eye by 29 per cent in  eight to 11 year old children.21 A randomised clinical trial of Acuvue Bifocal contact lenses in an ethnically diverse group of eight to 18 year olds found greater rates of myopia reduction: 72 per cent reduction in refractive error progression and 80 per cent reduction in axial elongation of the eye.22 Although participants were originally recruited because all had a near eso-fixation disparity, there was no association between myopia progression and initial fixation disparity or associated phoria while wearing contact lenses.

Other novel, custom made soft multifocal contact lenses have also been designed and trialled in paediatric populations. In a cohort of Hong Kong school children, myopia progression was slowed by up to 46 per cent in participants wearing ‘Defocus Incorporated Soft Contact’ (DISC) lenses for five or more hours a day.23 Similarly, both refractive error and axial growth of the eye, was reduced by one-third in a cohort of Chinese children fitted with a soft contact lens designed to reduce relative peripheral hyperopia compared with spectacle lens wearing controls.24

Possible Mechanisms of Action

The most widely accepted explanation for efficacy of myopia control with multifocal soft contact lenses is the presentation of myopic defocus to the retina. Animal studies have shown that even brief episodes of myopic retinal defocus, induced with positive lenses, are sufficient to slow eye growth.25

The dual-focus/MiSight lens comprises a central correction zone surrounded by a series of alternating treatment (+2.00 D defocus) and correction zones, which are designed to produce two focal planes (Figure 1). The optical power of the correction zones corrects the patient’s refractive error, while the treatment zones simultaneously provide 2.00 D of myopic retinal defocus. Zone diameters were specifically chosen based on age-appropriate pupil sizes26,27 to ensure that accommodation was still used during near viewing in children and that good distance acuity was maintained.

Measurement of refraction along the horizontal field through the Proclear D lens shows these lenses induce myopic retinal defocus.28 However only ‘add’ powers of +3.00 D and +4.00 D produced a significant change in peripheral retinal refraction.29 Proclear D lenses with a +1.00 D add reportedly had no effect on either central or peripheral retinal defocus, while the +2.00 D add lens produced equal myopic retinal defocus at all measured points (approximately 0.87 D both centrally and peripherally). Conversely it has been noted that some single vision soft contact lenses also induce relative myopic peripheral refractions30,31 so we cannot assume that the myopia control effect is solely due to changes in peripheral retinal focus.32 Other factors such as simultaneous central myopic retinal defocus may also be important in the anti-myopiagenic effects of multifocal soft contact lenses.

Reducing Accommodative Demand

Another potential mechanism for myopia control with these lens types could be via reduced accommodative (and therefore also convergence) demand. Reducing accommodative effort was the basis for the original COMET study,33 in which myopia progression was compared between children in single vision and progressive addition glasses. After three years, there was a statistically significant, but not clinically meaningful, reduction in the amount of myopia progression in children wearing progressive addition glasses of 0.20 D over the three year period.34 Subsequent analysis suggested the myopia control effect of progressive addition lenses was higher in children who had both accommodative lag and near esophoria, which prompted a second study targeting these children. However, results of COMET2 were similar, with children in progressive addition glasses progressing just 0.28 D less over the three year study period than the single vision control group.35

While soft contact lenses with increased plus power in the periphery could be used to reduce the near accommodative demand, there is limited evidence to suggest that children use this as a near addition.19 However, there is some evidence that young adults wearing orthokeratology lenses, which have been shown to produce relative myopic retinal defocus,36 have lower lags of accommodation and more exophoria compared with age-matched soft contact lens wearers.32 Furthermore, children fitted with radial refractive gradient soft contact lenses also show reduced lags of accommodation. This reduction may be in part due to the positive spherical aberrations induced by these lenses, which would protect against the increased negative spherical aberration that occurs with accommodation.37

Quantifying accommodative responses through multifocal soft contact lenses is inherently difficult and depends on the measurement method and calculation methods used. Baka Raju et al. assessed on-eye accommodative error (lag or lead of accommodation) using on-axis wave-front aberrometry in 40 young myopic adults through single vision, bifocal and multifocal contact lenses.38 While peak accommodative response appeared to be twice as high with single vision lenses compared with bifocal/multifocal lenses, measures of accommodative error varied significantly depending on the calculation method used. Further investigation on the relative weight of these various potential anti-myopia mechanisms is needed to fully elucidate the relative contribution of these factors.

Fitting Considerations

Visual Performance in Eyes Wearing Soft Myopia Control Contact Lenses

There is reportedly no significant difference in high illumination-high contrast visual acuity between spectacle correction and myopia control soft contact lenses.39 However, in low illumination-low contrast situations, multifocal lenses show a decrease of approximately one logMAR line compared with spectacle correction at distance, intermediate and near, which is also accompanied by a slightly lower patient rating for visual quality.39 Other studies have shown a small difference between high contrast distance visual acuity in multifocal soft contact lenses compared with single vision lenses40,41 but these differences were clinically small and within test-retest variability of standard acuity charts.42

Subjective ratings of visual performance were worse with multifocal contact lenses, lenses with the greatest power variation across the lens profile (near centre lenses), and lenses that decentred inferiorly.40 Therefore, fitting well-centred lenses, performing an appropriate over-refraction and gaining subjective performance measures are all important steps in prescribing multifocal soft contact lenses for myopia control.

Pupil Size

Pupil size is also an important consideration when prescribing contact lenses for myopia control. Power analysis profiles of the MiSight lens suggests that there will be minimal myopic retinal defocus induced in pupils less than 4mm which could compromise treatment efficacy.43 Changes in pupil dynamics will also affect the performance of multifocal soft contact lenses as the size of the pupil plays a crucial role in refractive performance of these lenses.44 Therefore, when fitting soft multifocal lenses for myopia control it is important to consider both pupil size under different illumination conditions and power profile of the soft contact lens. While published studies have reported that multifocal myopia control lenses with concentric treatment zones provide adequate coverage both in terms of distance correction and treatment zone19,23 there has been little published work on the optimisation of treatment zone sizes based on the pupil size of children.

Risk of Ulcerative Keratitis

Based on retrospective chart analysis, contact lens wearers eight to 15 years of age show fewer inflammatory and infiltrative events compared to adolescents (15-25 years of age).45,46 Overall, the risk of infiltrative and inflammatory events increased with age, from 1.6 per cent of visits in children aged between eight to 13 years, to 4.8 per cent in patients between 20-27 years of age, and the youngest age group was the least likely to require time off from contact lens wear.46

Other risk factors associated with increased adverse events were number of years of soft contact lens wear, use of multi-purpose solution, silicone hydrogel lenses and extended wear. So, it appears that contact lens wearers younger than 14 years of age show few adverse events, and by fitting either daily disposable or hydrogel lenses, the risk may be further reduced.

Comparison With Other Methods for Myopia Control

While reported efficacy of soft contact lenses for myopia control varies between studies, a recent meta-analysis found myopia control rates of 30-50 per cent over two years.47 Concentric ring multifocal lenses (such as the MiSight and Acuvue Bifocal lenses) were more effective than peripheral add lenses. The mean myopia control effect of concentric ring bifocal lenses was a 0.31 D reduction in refractive error progression accompanied by a 0.12 mm slowing of axial elongation of the eye. This is compared with a 0.22 D and 0.10 mm reduction with peripheral add bifocals.

While 0.5 per cent and 1 per cent atropine eye drops essentially halt myopia progression,48-50 the associated side effects and accelerated myopia progression following cessation of use51 makes the widespread use of atropine in these concentrations problematic. Low dose atropine (typically prescribed as 0.01 per cent) has minimal effect on accommodation, near vision and pupil size, and although less efficacious than high dose atropine, still significantly reduces myopia progression compared with controls.52,53 However, the limited availability of commercially prepared atropine 0.01 per cent eye drops currently limits widespread clinical use.

Recent meta-analyses suggest that over-night corneal reshaping/orthokeratology effectively reduces axial eye growth by approximately 0.14 mm per year (45 per cent) compared with age-matched controls.54,55 This is slightly less than the efficacy of low dose atropine (59 per cent reduction) but orthokeratology does have the additional benefit of providing good ‘correction-free’ distance and near vision during the day.

Over 100 cases of microbial keratitis were associated with orthokeratology lens wear between 2004 and 2008,56 however none have been reported in studies which have specifically fitted orthokeratology lenses for myopia control. Because of the complexity of fitting orthokeratology and the potential risk of sight threatening keratitis, a recent meta-analysis has suggested that low dose atropine and focus-altering soft contact lenses are the most clinically viable options for controlling myopia progression.6

Conclusion

Recent clinical evidence suggests that soft multifocal contact lenses are as effective as orthokeratology in controlling myopia progression.57,58 Fitting soft contact lenses is much simpler than orthokeratology, requires less clinical chair time,59 and does not need any specialist equipment such as a corneal topographer. The long term efficacy of soft contact lenses for myopic control is robust and spectacle-free refractive error correction for children and teenagers also has psychosocial benefits including improved self esteem and confidence. Evidence from clinical trials clearly supports the use of myopia control strategies in children experiencing myopia progression and the role of the eye care provider is now to educate patients and their parents of the options available to them.

Assessing the Options

There are now many different options available for practitioners to control myopia. Due to the known co-morbidities of a myopic eye, which increase with each additional dioptre of myopic refractive error, even slowing the rate of progression is a worthwhile endeavour. As primary eye care providers, it could be argued that optometrists now have a duty of care to offer myopia control options to young, progressing myopes. Some myopia control options do require a certain amount of upskilling, like orthokeratology, and this may also require additional capital expenditure (a trial fitting set and topographer), or access to a compounding pharmacy to prepare low-concentration atropine eye drops. However, soft contact lenses are an equally valid treatment option, and require very little change to current practice.

Additionally, fitting children with soft daily disposable contact lenses does not carry the risks that some may think, and instead can offer the child the other freedoms that contact lenses provide. Contact lenses also require more regular reviews, ensuring that any changes to prescription are identified and vision is maximised. Parents may be willing to commit to more regular reviews as there is no longer the need to regularly upgrade their child’s spectacles.  

 

 
 

 

Dr. Nicola Anstice, BOptom (Hons) PhD CertOcPharm, is currently a Senior Lecturer at the School of Optometry and Vision Science, University of Auckland but will take up the role of Head of Discipline of the new optometry programme at the University of Canberra early in 2018. In 2009, Dr. Anstice submitted her PhD looking at a new contact lens to slow myopia progression in children, and spent a year working as a paediatric optometrist in the Department of Ophthalmology, Manukau Super Clinic before returning to take up a lecturer’s position in the Department of Optometry & Vision Science. Her current research interests include children’s vision screening, vision and visual development and binocular vision.

 

 
 

 

Dr. Philip Turnbull, BOptom (Hons) PhD, School of Optometry and Vision Science, University of Auckland. Philip has roles as both a lecturer and postdoctoral research fellow, where he focuses on how emerging technologies can improve optometric practice, and enhance our understanding of vision. This includes developing more objective measures of vision, utilising techniques such as infrared eye-tracking, virtual reality, electrophysiology, and MRI. Prior to this, he completed a PhD which demonstrated emmetropisation in cephalopods, and served as director of the Myopia Control Clinic.

 

 
 

 

Dr. Andrew Collins, BOptom MSc (Hons) PhD CertOcPharm, is the Academic Director of the School of Optometry and Vision Science, University of Auckland. His myopia research, while working as a Senior Tutor in the School of Optometry and Vision Science, developed into a PhD research project investigating the effects of light on myopia development. Andrew teaches in the areas of clinical optometry and ocular disease. He is continuing his research into the role of light and myopia.

 

 
 

 

Dr. John Phillips BSc(MechMech Eng) BSc(Optom) MSc PhD MCOptom, is a Senior Lecturer in the School of Optometry and Vision Science, University of Auckland, and Principal Investigator of the Auckland Myopia Laboratory. Research in this group includes clinical research into childhood myopia development and progression and into the physiological processes which control eye size and which normally ensure that as the eye grows it remains emmetropic.


References
1.Saw, S.-M., Gazzard, G., Shih-Yen, E. C., & Chua, W.-H. (2005). Myopia and associated pathological complications. Ophthalmic & Physiological Optics: The Journal of the British College of Ophthalmic Opticians, 25(5), 381–391.
2.Cheng, S. C. K., Lam, C. S. Y., & Yap, M. K. H. (2013). Prevalence of myopia-related retinal changes among 12-18 year old Hong Kong Chinese high myopes. Ophthalmic & Physiological Optics: The Journal of the British College of Ophthalmic Opticians , 33(6), 652–660.
3.Tideman, J. W. L., Snabel, M. C. C., Tedja, M. S., van Rijn, G. A., Wong, K. T., Kuijpers, R. W. A. M., … Klaver, C. C. W. (2016). Association of Axial Length With Risk of Uncorrectable Visual Impairment for Europeans With Myopia. JAMA Ophthalmology, 134(12), 1355–1363.
4.Holden, B. A., Fricke, T. R., Wilson, D. A., Jong, M., Naidoo, K. S., Sankaridurg, P., … Resnikoff, S. (2016). Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050. Ophthalmology, 123(5), 1036–1042.
5.Cohn, H. L. (1883). The hygiene of the eye in schools.
6.Huang, J., Wen, D., Wang, Q., McAlinden, C., Flitcroft, I., Chen, H., … Qu, J. (2016). Efficacy Comparison of 16 Interventions for Myopia Control in Children: A Network Meta-analysis. Ophthalmology, 123(4), 697–708.
7.Li, L., Moody, K., Tan, D. T. H., Yew, K. C., Ming, P. Y., & Long, Q. B. (2009). Contact lenses in pediatrics study in Singapore. Eye & Contact Lens, 35(4), 188–195.
8.Walline, J. J., Long, S., & Zadnik, K. (2004). Daily disposable contact lens wear in myopic children. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 81(4), 255–259.
9.Efron, N., Morgan, P. B., Woods, C. A., & The International Contact Lens Prescribing Survey Consortium. (2011). Survey of Contact Lens Prescribing to Infants, Children, and Teenagers. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 88(4), 461.
10.Horner, D. G., Soni, P. S., Salmon, T. O., & Swartz, T. S. (1999). Myopia progression in adolescent wearers of soft contact lenses and spectacles. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 76(7), 474–479.
11.Walline, J. J., Jones, L. A., Sinnott, L., Manny, R. E., Gaume, A., Rah, M. J., … ACHIEVE Study Group. (2008). A randomized trial of the effect of soft contact lenses on myopia progression in children. Investigative Ophthalmology & Visual Science, 49(11), 4702–4706.
12.Rah, M. J., Walline, J. J., Jones-Jordan, L. A., Sinnott, L. T., Jackson, J. M., Manny, R. E., … ACHIEVE Study Group. (2010). Vision specific quality of life of pediatric contact lens wearers. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 87(8), 560–566.
13.Walline, J. J., Jones, L. A., Sinnott, L., Chitkara, M., Coffey, B., Jackson, J. M., … ACHIEVE Study Group. (2009). Randomized trial of the effect of contact lens wear on self-perception in children. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 86(3), 222–232.
14.Berntsen, D. A., Barr, C. D., Mutti, D. O., & Zadnik, K. (2013). Peripheral defocus and myopia progression in myopic children randomly assigned to wear single vision and progressive addition lenses. Investigative Ophthalmology & Visual Science, 54(8), 5761–5770.
15.Benavente-Pérez, A., & Nour, A. (2014). … Error Development Can Be Modified by Exposing the Peripheral Retina to Relative Myopic or Hyperopic DefocusPeripheral Defocus Can Alter Central Eye …. Investigative Ophthalmology & Visual Science. Retrieved from http://iovs.arvojournals.org/article.aspx?articleid=2212598
16.Smith, E. L., 3rd, Hung, L.-F., & Huang, J. (2009). Relative peripheral hyperopic defocus alters central refractive development in infant monkeys. Vision Research, 49(19), 2386–2392.
17.Smith, E. L., 3rd, Kee, C.-S., Ramamirtham, R., Qiao-Grider, Y., & Hung, L.-F. (2005). Peripheral vision can influence eye growth and refractive development in infant monkeys. Investigative Ophthalmology & Visual Science, 46(11), 3965–3972.
18.Aller, T. A., & Wildsoet, C. (2008). Bifocal soft contact lenses as a possible myopia control treatment: a case report involving identical twins. Clinical & Experimental Optometry: Journal of the Australian Optometrical Association, 91(4), 394–399.
19.Anstice, N. S., & Phillips, J. R. (2011). Effect of dual-focus soft contact lens wear on axial myopia progression in children. Ophthalmology, 118(6), 1152–1161.
20.Pascal. (2017, June 13). Misight presented at BCLA 2017 | myopia care. Retrieved September 4, 2017, from https://www.myopiacare.com/misight-presented-bcla-2017/
21.Walline, J. J., Greiner, K. L., McVey, M. E., & Jones-Jordan, L. A. (2013). Multifocal contact lens myopia control. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 90(11), 1207–1214.
22.Aller, T. A., Liu, M., & Wildsoet, C. F. (2016). Myopia Control with Bifocal Contact Lenses: A Randomized Clinical Trial. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 93(4), 344–352.
23.Lam, C. S. Y., Tang, W. C., Tse, D. Y.-Y., Tang, Y. Y., & To, C. H. (2014). Defocus Incorporated Soft Contact (DISC) lens slows myopia progression in Hong Kong Chinese schoolchildren: a 2-year randomised clinical trial. The British Journal of Ophthalmology, 98(1), 40–45.
24.Sankaridurg, P., Holden, B., Smith, E., 3rd, Naduvilath, T., Chen, X., de la Jara, P. L., … Ge, J. (2011). Decrease in rate of myopia progression with a contact lens designed to reduce relative peripheral hyperopia: one-year results. Investigative Ophthalmology & Visual Science, 52(13), 9362–9367.
25.Park, T. W., Winawer, J., & Wallman, J. (2005). In a matter of minutes, the eye can know which way to grow. Investigative Ophthalmology & Visual Science. Retrieved from http://iovs.arvojournals.org/article.aspx?articleid=2182565
26.MacLachlan, C., & Howland, H. C. (2002). Normal values and standard deviations for pupil diameter and interpupillary distance in subjects aged 1 month to 19 years. Ophthalmic & Physiological Optics: The Journal of the British College of Ophthalmic Opticians , 22(3), 175–182.
27.Winn, B., Whitaker, D., Elliott, D. B., & Phillips, N. J. (1994). Factors affecting light-adapted pupil size in normal human subjects. Investigative Ophthalmology & Visual Science, 35(3), 1132–1137.
28.Kang, P., Fan, Y., Oh, K., Trac, K., Zhang, F., & Swarbrick, H. A. (2013). The effect of multifocal soft contact lenses on peripheral refraction. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 90(7), 658–666.
29.Lopes-Ferreira, D., Ribeiro, C., Maia, R., García-Porta, N., Queirós, A., Villa-Collar, C., & González-Méijome, J. M. (2011). Peripheral myopization using a dominant design multifocal contact lens. Journal of Optometry, 4(1), 14–21.
30.Backhouse, S., Fox, S., Ibrahim, B., & Phillips, J. R. (2012). Peripheral refraction in myopia corrected with spectacles versus contact lenses. Ophthalmic & Physiological Optics: The Journal of the British College of Ophthalmic Opticians , 32(4), 294–303.
31.Chung, J., Bakaraju, R. C., Fedtke, C., Ehrmann, K., Falk, D., Ozkan, J., … Holden, B. A. (2014). Horizontal and vertical peripheral refraction profiles with single-vision and multifocal contact lenses. Investigative Ophthalmology & Visual Science, 55(13), 4677–4677.
32.Gifford, K., Gifford, P., Hendicott, P. L., & Schmid, K. L. (2017). Near binocular visual function in young adult orthokeratology versus soft contact lens wearers. Contact Lens & Anterior Eye: The Journal of the British Contact Lens Association, 40(3), 184–189.
33.Gwiazda, J., Marsh-Tootle, W. L., Hyman, L., Hussein, M., Norton, T. T., & COMET Study Group. (2002). Baseline refractive and ocular component measures of children enrolled in the correction of myopia evaluation trial (COMET). Investigative Ophthalmology & Visual Science, 43(2), 314–321.
34.Gwiazda, J., Hyman, L., Hussein, M., Everett, D., Norton, T. T., Kurtz, D., … Scheiman, M. (2003). A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. Investigative Ophthalmology & Visual Science, 44(4), 1492–1500.
35.Correction of Myopia Evaluation Trial 2 Study Group for the Paediatric Eye Disease Investigator Group. (2011). Progressive-addition lenses versus single-vision lenses for slowing progression of myopia in children with high accommodative lag and near esophoria. Investigative Ophthalmology & Visual Science, 52(5), 2749–2757.
36.González-Méijome, J. M., Faria-Ribeiro, M. A., Lopes-Ferreira, D. P., Fernandes, P., Carracedo, G., & Queiros, A. (2016). Changes in Peripheral Refractive Profile after Orthokeratology for Different Degrees of Myopia. Current Eye Research, 41(2), 199–207.
37.Pauné, J., Thivent, S., Armengol, J., Quevedo, L., Faria-Ribeiro, M., & González-Méijome, J. M. (2016). Changes in Peripheral Refraction, Higher-Order Aberrations, and Accommodative Lag With a Radial Refractive Gradient Contact Lens in Young Myopes. Eye & Contact Lens, 42(6), 380–387.
38.Bakaraju, R. C., Fedtke, C., Ehrmann, K., Falk, D., Chung, J., Ho, A., & Holden, B. A. (2014). Accommodation error with single vision, bifocal and multifocal soft commercial contact lenses. Investigative Ophthalmology & Visual Science, 55(13), 3760–3760.
39.Kollbaum, P. S., Jansen, M. E., Tan, J., Meyer, D. M., & Rickert, M. E. (2013). Vision performance with a contact lens designed to slow myopia progression. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 90(3), 205–214.
40.Fedtke, C., Bakaraju, R. C., Ehrmann, K., Chung, J., Thomas, V., & Holden, B. A. (2016). Visual performance of single vision and multifocal contact lenses in non-presbyopic myopic eyes. Contact Lens & Anterior Eye: The Journal of the British Contact Lens Association, 39(1), 38–46.
41.Fedtke, C., Ehrmann, K., Thomas, V., & Bakaraju, R. C. (2016). Visual performance with multifocal soft contact lenses in non-presbyopic myopic eyes during an adaptation period. Clinical Optometry, 37.
42.Anstice, N. S., & Thompson, B. (2014). The measurement of visual acuity in children: an evidence-based update. Clinical & Experimental Optometry: Journal of the Australian Optometrical Association, 97(1), 3–11.
43.Ruiz-Alcocer, J. (2016). Analysis of the power profile of a new soft contact lens for myopia progression. Journal of Optometry. https://doi.org/10.1016/j.optom.2016.08.003
44.Madrid-Costa, D., Ruiz-Alcocer, J., García-Lázaro, S., Ferrer-Blasco, T., & Montés-Micó, R. (2015). Optical power distribution of refractive and aspheric multifocal contact lenses: Effect of pupil size. Contact Lens & Anterior Eye: The Journal of the British Contact Lens Association, 38(5), 317–321.
45.Chalmers, R. L., Wagner, H., & Mitchell, G. L. (2011). Age and other risk factors for corneal infiltrative and inflammatory events in young soft contact lens wearers from the Contact Lens Assessment in Youth (CLAY …. & Visual Science. Retrieved from http://iovs.arvojournals.org/article.aspx?articleid=2188092
46.Wagner, H., Chalmers, R. L., Mitchell, G. L., Jansen, M. E., Kinoshita, B. T., Lam, D. Y., … CLAY Study Group. (2011). Risk factors for interruption to soft contact lens wear in children and young adults. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 88(8), 973–980.
47.Li, S.-M., Kang, M.-T., Wu, S.-S., Meng, B., Sun, Y.-Y., Wei, S.-F., … Wang, N. (2017). Studies using concentric ring bifocal and peripheral add multifocal contact lenses to slow myopia progression in school-aged children: a meta-analysis. Ophthalmic & Physiological Optics: The Journal of the British College of Ophthalmic Opticians , 37(1), 51–59.
48.Chou, A. C., Shih, Y. F., Ho, T. C., & Lin, L. L. (1997). The effectiveness of 0.5% atropine in controlling high myopia in children. Journal of Ocular Pharmacology and Therapeutics: The Official Journal of the Association for Ocular Pharmacology and Therapeutics, 13(1), 61–67.
49.Chua, W., Balakrishnan, V., Tan, D., Chan, Y., Group, A. S., & Others. (2003). Efficacy results from the atropine in the treatment of myopia (ATOM) study. Investigative Ophthalmology & Visual Science, 44(13), 3119–3119.
50.Chua, W.-H., Balakrishnan, V., Chan, Y.-H., Tong, L., Ling, Y., Quah, B.-L., & Tan, D. (2006). Atropine for the treatment of childhood myopia. Ophthalmology, 113(12), 2285–2291.
51.Tong, L., Huang, X. L., Koh, A. L. T., Zhang, X., Tan, D. T. H., & Chua, W.-H. (2009). Atropine for the treatment of childhood myopia: effect on myopia progression after cessation of atropine. Ophthalmology, 116(3), 572–579.
52.Chia, A., Chua, W.-H., Cheung, Y.-B., Wong, W.-L., Lingham, A., Fong, A., & Tan, D. (2012). Atropine for the treatment of childhood myopia: safety and efficacy of 0.5%, 0.1%, and 0.01% doses (Atropine for the Treatment of Myopia 2). Ophthalmology, 119(2), 347–354.
53.Chia, A., Lu, Q.-S., & Tan, D. (2016). Five-Year Clinical Trial on Atropine for the Treatment of Myopia 2: Myopia Control with Atropine 0.01% Eyedrops. Ophthalmology, 123(2), 391–399.
54.Si, J.-K., Tang, K., Bi, H.-S., Guo, D.-D., Guo, J.-G., & Wang, X.-R. (2015). Orthokeratology for myopia control: a meta-analysis. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 92(3), 252–257.
55.Sun, Y., Xu, F., Zhang, T., Liu, M., Wang, D., Chen, Y., & Liu, Q. (2015). Orthokeratology to control myopia progression: a meta-analysis. PloS One, 10(4), e0124535.
56.Van Meter, W. S., Musch, D. C., Jacobs, D. S., Kaufman, S. C., Reinhart, W. J., Udell, I. J., & American Academy of Ophthalmology. (2008). Safety of overnight orthokeratology for myopia: a report by the American Academy of Ophthalmology. Ophthalmology, 115(12), 2301–2313.e1.
57.Gifford, P., & Gifford, K. L. (2016). The Future of Myopia Control Contact Lenses. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 93(4), 336–343.
58.Turnbull, P. R. K., Munro, O. J., & Phillips, J. R. (2016). Contact Lens Methods for Clinical Myopia Control. Optometry and Vision Science: Official Publication of the American Academy of Optometry, 93(9), 1120–1126.

' Fitting well-centred lenses, performing an appropriate over-refraction and gaining subjective performance measures are all important steps in prescribing multifocal soft contact lenses for myopia control '