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C-41029

Contact lenses for children

In this article Professor Bruce Evans discusses the potential for fitting young people with contact lenses

Introduction 

GOS statistics indicate that about 1.5 million children in the UK wear a refractive correction and yet only around 8% of contact lens fits in the UK are to teenagers and 2% to children. This large international survey reveals that the proportion of young people who are fitted with contact lenses in the UK is lower than in most other countries and raises the question: are we under-prescribing contact lenses to children and teenagers? To address this question we will first look at why we fit adults with contact lenses and then ask whether these reasons apply more or less strongly to young people. 

Why do we fit adults with contact lenses?

Research has established that cosmesis is the major reason why adults are motivated to wear contact lenses.2 This is supported by another study, which reveals that the major two motivations are concerns about appearance and convenience, with sports and better vision also rating highly.3 Many people spend more time involved in sporting activities during their school years than in later life, so this reason would seem to apply to young people at least as much as to older people. Since cosmesis is the major reason why adults consider contact lenses, the importance of cosmesis for children will now be considered. 

Cosmesis: an understatement for changing some children’s lives

When we think about young people and cosmesis we probably think about the teenage years, but it seems likely that children are more self-conscious than teenagers. Even today, 16–40% of children in UK schools experience bullying4 and the effects persist into adult life.5 A large study of 8.5 year-olds shows that spectacle wearers are 35% more likely to be victims of bullying.6 Research has shown that fitting children aged 8–11 years with contact lenses improves their physical appearance, athletic competence, and most importantly their social acceptance.

Figure 1Anisometropia 

In high refractive errors there are clear advantages to contact lenses over spectacles, such as larger retinal image sizes in myopia and a more normal field of view in hypermetropia. However, perhaps the most important indication for contact lenses is anisometropia, which affects 13.5% of the European population. The potential advantages of contact lenses in anisometropia were highlighted by Keith Edwards in 1979,9 and the optical benefits were demonstrated experimentally by subsequent authors.10-13 Specifically, the research indicates that for both refractive and axial anisometropia, contact lenses minimise aniseikonia and, therefore, maximise the potential for normal binocular vision. This is important not just to optimise binocularity in anisometropia but also because of the need to encourage cortical use of the monocular input from each eye. The importance of optical correction in treating amblyopia has been known for over years14 and recently it has been shown that amblyopic children improve on average by 2.5 lines just from wearing spectacles and 22% of cases need no patching, just spectacles.15 If this much improvement can be brought about with spectacles then the reduced aniseikonia and potential for better fusion with contact lenses means that a more marked treatment effect is likely with contact lenses. 

The benefit of using contact lenses in anisometropia does not just relate to the acuity now, but also to the potential for life-long best- corrected acuity improvements. The notion of a sensitive period for the treatment of amblyopia is an oversimplification. For orthotropic anisometropic amblyopia a literature review indicates that the condition can be treated, at any age.16 So, for patients with orthotropic anisometropic amblyopia, especially if they are not wearing an appropriate refractive correction for their amblyopic eye, there is a real possibility that contact lenses will bring about an improvement over time in the best-corrected acuity in the affected eye. In other words, contact lenses may do more than just correct the refractive error; they may reduce the amblyopia. Although such effects might be seen at any age, generally speaking, the younger that correction is prescribed, the better – assuming that the criteria for safe contact lens wear are met. 

There is a pressing need for randomised controlled trials to investigate the effect of contact lenses on visual acuity in anisometropia. However, what we know about aniseikonia and the effect of refractive correction on amblyopia mean that contact lenses are the preferred mode of optical correction for patients with this condition. This is quite an easy discussion to have since patients can readily visualise that it is not natural to correct their refractive error with spectacles where the two lenses are so very different. 


Myopia control

Optometrists have for many years been involved in the treatment of amblyopia, but their role in myopia has, until recently, largely been confined to correction rather than treatment. Recent research has improved our understanding of myopia and led to contact lens based interventions for slowing myopia progression. There have been several excellent reviews of this topic and it will only be briefly summarised here.17–19 Myopia is the commonest ocular abnormality and its prevalence is increasing markedly.18 Myopia increases the risk of several ocular pathologies and interventions that reduce the ultimate level of myopia will reduce the risk of these pathologies.18 Brennan has shown that reducing the rate of myopia progression by 50% would lead to a reduction in the frequency of high myopia by over 90%.20 Figure 2

The determination of refractive error during an eye exam is driven by a consideration of the situation at the fovea. For most emmetropic patients this is not an issue because when the image shell is in focus at the fovea then it is also likely to be in focus, or close to in focus, in the peripheral retina (Figure 1: Schematic diagram illustrating the possible role of relative peripheral hyperopic defocus (RPHD) in the aetiology). For myopic children the situation is different and the image shell in the periphery typically has relative hyperopic defocus (the image shell is behind the retina). This seems to occur even before the child becomes myopic the peripheral retina has hyperopic defocus and yet the fovea is in focus so no significant refractive error would be detected during a refraction (see second panel of Figure 1). It is believed that the peripheral retina dominates in the signals that drive eye growth.19 This relative peripheral hyperopic defocus (RPHD) drives eye growth and axial length elongates to bring the peripheral retina in focus, leading to myopic defocus at the fovea (third panel of Figure 1). The optometrist’s duty is to help the child see distant objects clearly so we prescribe a concave lens that will bring the image shell at the fovea into focus, but this restores the RPHD, possibly driving further myopic changes. 

This raises the possibility that optical interventions that correct RPHD may reduce myopia progression. Several research groups and manufacturers have developed or are developing special designs of soft contact lenses and the initial results show a promising ability to slow myopia progression.21–24 These designs are not yet commercially available in the UK, but there are two currently available modalities that seem to correct RPHD and show encouraging signs of slowing myopia. Orthokeratology is one of these modalities.25,26 Several studies (see Figure 2: Graph illustrating the percentage reduction in axial length growth in myopia (compared with control group in each study) Pink bars illustrate predominantly Caucasian population; blue bars indicate predominantly Asian population. CCS, case control series; RCT, randomised controlled trial) show a reduction in axial length elongation (a proxy for myopia progression) with orthokeratology.27–32 Many patients wear orthokeratology safely, but there have been concerns over the risk of microbial keratitis,33 which probably has a similar prevalence to that in other overnight contact lens modalities.34 

Figure 3Multifocal (MF) contact lenses of a centre- distance design also reduce RPHD35-37 and slow myopia progression.38,39 In Figure 3 the effects of MF contact lenses on slowing myopia progression are compared with three studies of special designs of myopia control (MC) soft contact lenses.21-23 The treatment effect seems greatest in cases where there is an esophoria (SOP) at near, indicating that the mechanism may be more complex than just RPHD.40 Figure 3: Graph illustrating the percentage reduction in myopia progression (compared with control group in each study). In the Lam et al study an improved treatment effect was found in participants who wore the lenses for more than five hours a day, as illustrated with the arrow. Pink bars illustrate predominantly Caucasian population; blue bars indicate predominantly Asian population. CCS, case control series; RCT, randomised controlled trial; MF, multifocal; SCL, soft contact lenses; SOP, esophoria; MC, myopia control)

Some caveats need to be stressed about these new and exciting interventions. First, only a summary has been possible in this article and the reader is referred to the full papers for further details such as the baseline myopia, study duration, and participant age. Although the results to date are promising they should be considered as preliminary until larger multi- centre double-masked randomised controlled trials (RCTs) have been completed. However, for children who are becoming myopic now, these RCTs may come too late and many eye care practitioners (ECPs) feel justified to act based on the data available at this time. Some other very effective methods of myopia control, for example atropine, can show a rebound effect; when the atropine is discontinued the myopia to some extent catches up, although a new low dosage is promising in this respect.41 It is possible that a rebound effect may also occur with contact lenses, although this would seem to be less of a concern than with atropine. This is because normal doses of atropine cause side effects whereas complications are rare with contact lenses so they could be worn until the patient is at an age where a rebound effect is unlikely. 

Parents and children who are considering myopia control need to know that the promising average results data to date hide individual trends. If a study shows a mean myopia slowing of 45% then within these data there will be individuals where there is a much better result than this but other individuals where the myopia does not slow at all. Patients also need to know that this use of orthokeratology and MF contact lenses is ‘off label’ (as indeed are most drugs prescribed to children) and, therefore, informed consent is particularly important. Crucially, only motivated children should be fitted and compliance is important for safe wear, as discussed later in this article. Some tips for fitting multifocal contact lenses for myopia control are:
  • Centre-distance lenses should be used. The two lens types that seem to be used most often are the CooperVision Biofinity Multifocal (centre-distance lens to each eye) and Acuvue Oasys for Presbyopia 
  • Test the patient for near esophoria (with myopic correction; for example, using the Maddox wing test). If present then try to use an add that eliminates the esophoria 
  • With the Biofinity lens, a +2.00D add seems to be used most often, although a higher add might be more effective if it does not adversely affect the distance vision 
  • The lenses are usually very well tolerated and children do not report any distance blurring, but this should be checked and the add adjusted if necessary 
  • The procedure is remarkably straightforward for most children
All-day wear may maximise the treatment effect for myopia control, if there are no physiological contraindications to this. There is also evidence that increasing time spent outdoors will reduce myopia progression and this means that UV blocking contact lenses should be recommended whenever possible.42,43 

Other reasons for fitting children with contact lenses 

In addition to the factors discussed above, there are other less common indications to fit children with contact lenses. Some patients with dyslexia or migraine benefit from precision tinted lenses44 and the cosmetic issues associated with these mean that some cases prefer precision tinted contact lenses. Some orthoptic conditions can be managed with contact lenses.45 

Maximising safety and success when fitting children with contact lenses

This article has outlined several good reasons for fitting children with contact lenses and yet international statistics show that the UK fits fewer children than many other countries.1 What is preventing optometrists from discussing contact lenses with young patients? For many parents, contact lenses are not expensive compared with other costs incurred with having children and modern contact lenses are easy to adapt to and comfortable. 

Figure 4
The Contact Lenses in Pediatrics (CLIP) study by Walline and colleagues shows that children, aged eight to 12 years, and teenagers, can wear contact lenses safely, with normal chair time from the ECP, and are associated with an improved quality of life.46,47 Another study of contact lenses versus spectacles over three years in children aged eight to 11 years, demonstrated 91% success rate and improved measures of physical appearance, athletic competence, and social acceptance with contact lenses.7 Over 90% were fitted with daily disposable contact lenses, which are often recommended for children. Perhaps the fear of microbial keratitis (MK) is a barrier for some ECPs and certainly the risk of this should be discussed with parents and children who are contemplating contact lenses. The risk with daily wear is about one in 5,000 per annum.48 All parents accept that their children will take risks, for example riding a bike, swimming, climbing trees, and so on, and ECPs need to allow parents to weigh the benefits against the risks. For myopia control, Johnson has shown statistically that the small threat of MK is more than offset for even a modest degree of myopia control by the decreased risk of myopia-associated pathology in later life.49 Children are afraid of the unknown and ECPs can introduce children to contact lenses in a way that addresses their fears: 
  • When children need glasses, explain that contact lenses are a viable option 
  • Tell the child that they are not going to wear a lens today but they can have a look at one 
  • Place a trial lens on the child’s finger and let them touch it
  • Ask the child what it is mostly made of. They might guess plastic or rubber. Eventually, tell them that it is mostly made of water
  • Ask the child if they have ever had a drop of rain go in their eye. Highlight that it would not have hurt but would have felt cold and wet and made them blink 
  • Explain that the contact lens, which is mostly water, will feel cold, wet, make them blink but should never hurt 
  • Educate the child and parent that if a lens hurts it is a warning sign and requires the lens to be removed and if the problem persists the ECP should be consulted 
  • Tell the child that since you have handled the trial lens without washing your hands then it must not be worn and should be thrown away. Let them watch you throw it away
The best way of maximising success in fitting children with contact lenses is to only fit cases where both the child and the parent are motivated. Compliance is a major challenge in contact lens wear and so it is important to ensure that children and parents are fully engaged with the importance of and requirements for safe wear.50 A quiz is helpful for enhancing compliance.51 The present author gives every child the quiz and answers in Figure 4, and tells them that they will be asked some of these questions in a ‘test’ at every aftercare visit. It is also helpful to observe the child at aftercare to check, for example, that they wash hands prior to contact lens removal. 

For all contact lens patients, the concern is that no matter how well they behave in our consulting room they may have unsafe habits at home. Here, the situation with children and teenagers is potentially better than with older patients if ECPs can engage parents in monitoring for compliance at home. 

Conclusion 

It has been demonstrated in this article that the main reasons why ECPs fit adults with contact lenses apply more strongly to children. Children, typically, aged eight to 12 years, can benefit just as much from contact lenses as teenagers and can be fitted with high success rates. ECPs should discuss contact lenses as an option in any person needing a refractive correction and they should be recommended as the optimum mode of correction for people with anisometropia. Myopia control is likely to become a major part of clinical practice in the near future52 and today currently available centre distance multifocal contact lenses can slow progression by significant amounts. ECPs need to take an active role in encouraging compliance and should enlist the help of parents in this endeavour. 

About the author

Professor Bruce Evans is director of research at the Institute of Optometry and a visiting professor to City University London and London South Bank University. He spends most of his week working as a community optometrist where he has a special interest in children's vision and contact lenses. 

References

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