Paediatric Contact Lenses

Introduction

Fitting contact lenses to children of different ages requires varying skill sets to achieve the best results for the patients. Lenses fall into two main categories: refractive and pathological. Refractive fittings are similar with all ages and, in the main, are fitted by general contact lens practitioners, while significant ophthalmic problems requiring specialist contact lenses are more likely to be fitted in conjunction with an ophthalmologist. High prescriptions, orthokeratology and myopia control are covered in other chapters and are therefore only touched on in this chapter.

General Points When Fitting Young People

Every contact lens patient, whatever their age, needs a full eye and slit-lamp examination prior to commencing fitting. As well as assessing the eyes, this can also show how cooperative they are likely to be. Most of the relevant points are covered in Chapter 6, Chapter 15 , but a few extra points are covered here. Bear in mind that if lenses are fitted to a child who cannot be examined adequately, it may prove impossible to carry out a thorough aftercare examination. However, if a child refuses to wear spectacles and is likely to develop amblyopia, contact lenses may be preferable, even if a full examination proves difficult.

Fitting and teaching young people to wear and care for lenses may take slightly longer than adults, but the outcome is usually just as good, if not better ( ).

Age to fit lenses

In practice, there is no particular age at which lenses should be first attempted. Some 5-year-olds are excellent candidates for lens wear, and some 15-year-olds are definitely not. The decisions about whether to fit lenses should be made on an individual basis.

Many children who initially appear keen to try lenses may not understand, on closer questioning, what contact lenses are or that they have to be inserted into the eye! Discuss with the child why they want to wear lenses, and try to stop the parent from answering for them.

Peer pressure or bullying, even in young children, can be the reason. found that 37% of spectacle wearers aged 8.5 years were likely to have been the victims of bullying. However, it may be that changing to a cosmetically more acceptable spectacle frame is preferable to being fitted with contact lenses. Conversely, the psychological effects of having to wear spectacles should be considered ( ), and where there are no obvious contraindications, contact lens fitting can be initiated.

If a child is keen to wear lenses but the parent is against the idea, as long as the practitioner thinks the child is suitable, the advantages of lens wear should be explained to the parent. Similarly, parents can bring pressure to bear on both child and practitioner either to fit lenses initially or to maintain the child in lenses when the practitioner advises otherwise; this rarely works. A child may be coerced into trying lenses, but day-to-day wear becomes less regular as the novelty wears off. By the time the child returns for follow-up, they have often reverted to spectacles.

Lens fitting

No one type of lens suits all. Discuss the different types of lenses available and the advantages and disadvantages of each. Always give reasons for the decisions. If the reason not to fit is because of reluctance on the part of the child, leave the way open to trying again at a later date.

Stress lens hygiene: Children over the age of 5 are often enthusiastic and are prepared to clean their own lenses. Parental supervision is advisable initially, but after a time children should be capable of caring for their own lenses. Allow both child and parent time to ask questions. Remember that when dealing with children, they may be young, but they can be very astute, and they need to understand what is going on.

As with all dealings with children, several short appointments are usually better than one lengthy one. Be patient and positive. If the patient finds lens insertion difficult, the following may help:

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Ask the parents to instil artificial tears for a few weeks.
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Encourage the child to touch their conjunctiva with a clean finger.
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Use an eye bath filled with normal saline while keeping the eye open.

By the subsequent appointment, they are usually more relaxed and keen to show off their achievements.

It can help with cooperation, especially if rigid gas-permeable (RGP) lenses are to be fitted, to instil local anaesthetic drops first. Ask the patient whether they prefer to have drops. If anaesthetic drops are instilled and the lenses left to settle for more than 15 minutes, the drops will have worn off by the time the patient returns. If at that stage the lenses are comfortable, explain that is how they will feel when they are worn regularly.

Sometimes it is advisable to start with a lens that is not optimal; for example, fitting a slightly thicker soft lens can help train a child to insert their own lenses, and the lens type can be changed later.

Teenagers

In general, children in primary school are the responsibility of their parents, both in the money spent on their lenses and on the care taken to ensure safe lens management. By the time they are at secondary school, patients should be taking more responsibility for their own eyes and lens care.

Teenagers' reasons for wanting lenses are the same as adults', but the emphasis varies depending on the age of the patient ( ). These reasons include:

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physical appearance
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hobbies
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social aspects
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comfort
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confidence
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vision.

Some of these are discussed here in more detail.

Physical Appearance

Using a quality of life survey, assessed the satisfaction of young spectacle wearers when they had worn contact lenses for 3 months. They found that teenagers felt that their appearance was greatly improved and that they were better able to participate in activities.

Make-up (see Chapter 5 , Chapter 16 )

Poor habits with make-up can result in eye infections. Blepharitis and herpes simplex keratitis can be passed on by sharing make-up or using old contaminated make-up.

Acne is a common problem in teenagers and young adults (see also Chapter 6 ). It is associated with hypersecretory meibomian gland dysfunction ( ) and can result in blepharitis, chalazia, styes or corneal infections. If these occur, contact lenses should not be worn, but teenagers are often averse to stopping lens wear.

Coloured Contact Lenses

Teenagers will frequently experiment with ways to alter their appearance, including changing the colour of their eyes. It is essential that they are taught the importance of obtaining their coloured lenses from a registered practitioner and maintaining safe hygiene. Contact lens jewellery ( Chapter 27 ) and eyebrow piercings can also be a source of hygiene problems.

Hobbies

Sport as a hobby is carried out by many people of all ages and has been found to help teenagers develop both physically and socially ( ). The need for safety sports goggles worn over lenses must be emphasised as 90% of sports-related eye injuries have been shown to be preventable ( ). Swimming in contact lenses should always be avoided.

Sports teams and drama and dance groups often do not allow their members to wear spectacles, so young people may request lenses for these activities for short periods of wear. However, the wearing time usually increases once they are used to the lenses.

Computers and small screens – Messaging friends, doing homework or playing games all involve concentration that can lead to ocular discomfort ( ) and headaches. The problems are compounded if contact lenses are worn as the blink reflex is suppressed especially when playing fast-paced games ( ), and the number of incomplete blinks increases ( ).

Taking regular breaks or using rewetting or comfort drops helps, but such advice is frequently ignored.

Confidence

Self-concepts in pre-teens increase when fitted with lenses ( ), as do social acceptance, self-perceptions and quality of life ( ). This becomes more evident in adolescents.

Information and instructions

Most information is still provided in paper form, which does not work well for teenagers; they are more likely to respond if it is received electronically. YouTube has several videos on lens handling and hygiene. One such example from Acuvue is http://www.acuvue.com/wearing-apply-remove , or practitioners can produce their own, preferably with an adolescent demonstrating the procedures. Mobile apps are available to download, alerting the patient when a new pair of lenses should be started or when the next batch of disposable lenses is ready to collect.

Liability (see Chapter 31 )

Contact lenses are medical devices and as such need a certain level of understanding on their fitting and care. Those patients under the age of 16 years are considered children in law, and families of children in this age group should be involved in decisions about their care unless there is a valid reason for not doing so ( ). As long as patients are competent to understand, they must be included in any discussion, and advice must be given at a level that they can understand ( http://patient.info/doctor/consent-to-treatment-in-children-mental-capacity-and-mental-health-legislation ). The patient, as well as the parent or guardian, is expected to sign any documents relating to what they have been told.

For children seen in the NHS in England, all types of records should be retained for 10 years after they were last seen or until their 25th birthday (or 26 if they are 17 when treatment ends) or 10 years after their death. If a child’s illness or death could be relevant to an adult condition or have genetic implications for their family, records may be kept for longer (Records Management Code of Practice for Health and Social Care 2016).

For a more detailed review of lens fitting for teenagers, see .

Corneal Topography and Physiology in Young Infants

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The infant has a large eye/head ratio.
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The length of the eyeball is approximately 17 mm, compared with 20 mm at 2 years, 21 mm at 4 years and 24 mm in the adult ( , , ).
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The average corneal diameter at birth is 10.0–10.5 mm; by the age of 1 year, it has grown to 11.7 mm, which is almost adult size ( ).
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The corneal radius is around 7.1 mm, which gradually flattens to an adult average of 7.86 mm ( ). Other authors have suggested that the infant corneal radius may be somewhat flatter ( ) or steeper and that the corneal radius changes little after the first few months ( ).
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Many figures have been quoted for the refractive error in babies, ranging from slightly myopic in the premature infant to moderately hypermetropic and astigmatic in many normal neonates ( , , , , table by Grounds in ).
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Corneal physiology differs little from that of the adult, except that the number of endothelial cells per unit area is greater ( ). This may account for the apparent ability of the infant cornea to recover rapidly from hypoxia. Infants' corneas are less sensitive than those of older children and adults ( ), and young infants can usually tolerate RGP lenses without a local anaesthetic.
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Blink rate is lower in infants than in adults; the mean rate of spontaneous blinking is less than 2 per minute in early infancy, increasing steadily during childhood up to 14–20 per minute by the mid teens ( ).

Fitting Contact Lenses to Young Children

Infants wearing contact lenses

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Explain the risks of overnight wear and encourage daily removal and disinfection from the outset.
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If daily removal is not possible, lenses should be removed at least once a week initially and frequency increased to every day. The parents should check the eyes carefully every morning.
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Stress the importance of removing the lens if there is any sign of infection or redness.

Refractive conditions

High Myopia (see Chapter 21 )

Although visual acuity is better with contact lenses due to the enlarged retinal image size, visual development is likely to be just as good with either form of correction. It is, therefore, not always advisable to fit lenses with all their inherent problems to the very young child. Associated conditions such as Marfan syndrome or Stickler syndrome should be considered when a child presents with high myopia (see p. 458 ).

Choice of Lens Type.

Lens fitting is very similar to that in adults (see Chapter 21 ).

The myopic-retarding effect of contact lens wear (see Chapter 28 ) should be considered on a case-by-case basis. Other treatment, such as 0.01% atropine, may prove to be a better option ( ), which the practitioner may also consider.

High hypermetropia

Parents and patients should be warned that they will not see as well when fitted with contact lenses compared with spectacles due to the magnifying effect of the spectacle lenses and the effect on accommodation (see Chapter 7 ).

Anisometropia or unilateral ametropia

Myopia in children is thought to be only axial ( ), and aniseikonia is less for both axial and refractive anisometropia when contact lenses are employed ( ). Visual development in unilateral myopes is better than in unilateral hypermetropes ( ), so better stereopsis should develop if lenses can be prescribed early. However, unilateral myopia of more than −9.00 D does not respond well to patching ( ).

Unilateral ametropes, be they myopes or hypermetropes, are often reluctant to wear spectacles; they rarely derive any visual benefit from them, as the ametropic eye is usually amblyopic. Contact lenses, together with any amblyopia treatment, are a better option but where there is resistance to lens wear, spectacles and patching can still work well, especially if there is no binocular vision as aniseikonia does not appear to be a problem in children.

Strabismus

Spectacles and contact lenses are interchangeable, although the squint angle may differ.

Coloured lenses (see ‘ Photophobic Conditions ’ Below)

It is up to the individual practitioner, together with the parents, to decide whether it is appropriate to fit children with lenses to change their eye colour. Tinted lenses for mild photophobia should not usually be recommended, as the tint is then worn indoors and out. A pair of sunglasses worn over the lenses on bright days is more beneficial. Photophobia from contact lens wear usually indicates a problem from the lenses themselves, and the fitting should be reassessed.

Congenital and Pathological Conditions

Most infants and young children with congenital and pathological conditions are seen in hospital clinics and in conjunction with an ophthalmologist. The ability to cope with both the patient and their parents remains the lynchpin around which successful fitting is based. Other than some therapeutic lenses (TCLs; see below), it is advisable that all lenses are removed daily to reduce the risk of infection and hypoxia.

Aphakia

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Cataracts can occur sporadically or as part of a syndrome, for example trisomy 21 (Down's syndrome) and congenital rubella.
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Aphakia comprises the largest group of infants with pathology fitted with contact lenses.
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The number of aphakes is reducing in older children as more intraocular lenses (IOLs) are used. It has been found that aphakia and contact lenses may be preferable for infant congenital cataracts, as intraocular implant surgery results in more adverse events and repeat surgery ( ).
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The most common surgical procedures are lensectomy and aspiration, both of which produce small scars near the limbus which induce a minimal degree of astigmatism (see Fig. 24.4 below). Topography is only slightly altered by surgery.

In infants born with congenital cataracts obscuring the visual axis ( Figs 24.1 and 24.2 ), persistent foetal vasculature (PFV) (previously termed persistent hyperplastic primary vitreous), and posterior lenticonus, surgery should be carried out not earlier than six weeks of age in order to reduce the risk of glaucoma ( ), but preferably before three months of age to reduce the amblyogenic effect ( ). Incomplete cataracts need to be carefully monitored to ensure that surgery can be performed before amblyopia affects the visual development.

Fig. 24.1, Congenital cataracts in an infant.

Fig. 24.2, Congenital cataracts do not always show as white pupils, as in (a). As with adults, it may be easier to recognise them with a retinoscope or ophthalmoscope held away from the eye, as in (b).

Corneal diameters and radii can be measured at the time of surgery. If a hand-held keratometer is not available, use a conventional keratometer and, laying the child on his or her side, interchange the horizontal and vertical measurements. Temporary aphakic spectacles should be loaned for use after surgery and once any inflammation has settled, usually at least 1 week postoperatively, contact lenses can be fitted. Lenses provide a more normal visual environment, besides overcoming the mechanical difficulties of spectacles ( Figs 24.3 and 24.4 ), but acuity can develop equally well with either modality, and this should be stressed to parents. To ensure continuous visual stimulation, back-up spectacles should also be prescribed for periods when the contact lenses cannot be worn.

Fig. 24.3, Infant in aphakic spectacles. Note the right esotropia, which results in poor centration of a spectacle lens in front of that eye; a contact lens would provide much better centration.

Fig. 24.4, Bilateral aphake wearing contact lenses. The right lens is not well centred, but the pupil is covered by the lenticular part of the lens all the time. Note the scars from surgery at the 2 and 9 o'clock positions on the cornea.

Lens Power

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Carry out retinoscopy, taking care to refract on axis.
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There is no active accommodation, so cycloplegia is not needed and dilation only necessary if the pupil is very small.
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No trial frame is used, as it is impractical on a baby's small features.
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The spectacle prescription is usually more than +20.00 D. Hold the lens close to the eye, as a small increase in back vertex distance (BVD) induces a large increase in effective power; +20 D at 12 mm BVD requires a +26.3 D contact lens on the eye (see Chapter 7 and Further Information available at: https://expertconsult.inkling.com/ ).
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Infants are motivated and attracted by objects that are close to them: faces, food, toys, etc., and as they are unable to accommodate, the lenses should be focused at one-half to one-third of a metre; that is an overcorrection of 2–3 D, reducing to distance prescription once reading or bifocal spectacles can be managed.

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High-power trial lenses are essential (see ‘ Inventory ’ below and Table 24.1 ), and the first trial lens is of the order of +30.00 D (although there is a wide range of powers).

Table 24.1

Back Vertex Powers (D) and Appropriate BOZR and TD Values for an Infant Aphakic Soft Lens Fitting Set

	TD (mm)
BOZR (mm)	12.00	12.50	13.00	13.50	14.00
7.00	+34.00	+32.00	+30.00
	+30.00	+28.00
7.20	+32.00	+30.00	+28.00	+22.00
		+26.00	+24.00
7.40		+28.00	+26.00	+24.00	+22.00
			+22.00	+20.00
7.60			+24.00	+22.00	+18.00
7.80				+20.00	+16.00

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Astigmatism is not corrected until the child is older (except where spherical RGP lenses are fitted to a toric cornea), but it is usually only of a small degree induced by lensectomy or aspiration. It is not practical to fit toric lenses, and many emmetropic adults start life with varying degrees of astigmatism ( ).

Ultraviolet Inhibitor.

Because of the potential danger to the retina caused by ultraviolet light in an aphakic eye, where possible, lenses with an ultraviolet inhibitor should be prescribed.

Soft Lenses

Silicone hydrogel lenses are not necessarily a first option as they tend to be more difficult to insert and remove and to deposit more than hydrogel lenses. Both modalities of lens can be slept in for a few hours whilst the child naps during the day.

Manufacture of small high power lenses is difficult.

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The refractive index of the xerogel is 1.52, giving very high powers in the dry state which are difficult to measure; hence the back vertex power (BVP) may be less accurate and more difficult to check on the focimeter.
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Lens parameters are likely to steepen more than lower powers as the lenses hydrate.
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The carrier lens and junction need to be thicker than in an adult's lens to make for reasonable handling.
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Lenses are thick: 1 mm centre thickness is not uncommon in soft lenses, and hence overnight wear can result in corneal hypoxia, even with silicone hydrogel materials. This is less likely if RGP lenses are fitted.

Advantages

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wide range of custom made parameters
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available in different water contents
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UV-inhibitor available in most materials

Disadvantages.

Lenses are:

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liable to break
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easily rubbed out
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dry out, resulting in lens displacing or falling out
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can cause corneal desiccation
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difficult to handle with small, deep-set eyes
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silicone hydrogel lenses tend to be more difficult to remove.

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