Myopia Control with Contact Lenses: A Practitioner Toolkit

Myopia is a common condition and is the single most important cause of distance vision impairment. With its rapidly rising prevalence and association with co-morbidities and vision impairment at higher levels, the burden imposed by the condition is significant.1 Therefore in recent years, there has been a substantial effort to develop strategies and solutions to stem the rising burden.

As the central care provider for an individual with myopia, eye care practitioners (ECPs) play an important role in evaluating the needs of the individual, assessing the risk of future progression and risk of complications, and deciding on appropriate interventions.

individuals should be advised to wear myopia control contact lenses for all waking hours

Once a decision is made, ECPs play a critical role in informing, educating, and managing the affected individual. The goal of management is to rectify distance vision impairment and reduce the risk of future progression, if any. In this respect, a range of behavioural, therapeutic, and optical options are now available in the practitioner’s tool kit to manage myopia. The options include improved outdoor time, atropine including low dose atropine,^2,3 spectacles (progressive addition, peripheral defocus management and executive bifocals),^4-10 contact lenses (lenses that impose myopic defocus across sections of the retina),^11-16 and or orthokeratology.^17-19

Of the various interventions available for myopia control, contact lenses fare reasonably well on the risk-benefit assessment. In addition to the lens power that corrects the distance vision impairment, myopia control contact lenses also incorporate design features that slow myopia, thus obviating the need to have a two pronged approach for myopia control, i.e. a first device/strategy to correct the distance refractive error and a second method/treatment for myopia control. Furthermore, with the advent of newer and better materials and wear modalities that minimise the risk of complications (e.g. daily disposables), contact lens wear is generally safe and comfortable. Importantly, children and teenagers who wear contact lenses report an improved quality of life with respect to appearance and satisfaction with correction.₂₀ 

Table 1

However, it is well recognised that contact lens wear may not suit every individual, and children younger than eight years of age may not be able to independently care for their lenses. Additionally, although generally safe, lens wear carries a risk of developing sight threatening complications and requires the wearer and their carers to be vigilant and compliant with lens care and wear procedures.

As the evidence on myopia control is evolving and rapidly accumulating, the practitioner is faced with the need to synthesise the vast and rapidly accumulating information on myopia control, then translate and incorporate these into specific recommendations for care in clinical practice. The objective of this article is to provide practical information to help make informed decisions in managing myopia with contact lenses.

WHEN TO INTERVENE

Annual progression of myopia is greater in younger, compared to older, children and therefore early intervention reduces the risk of the eye reaching high myopia.²¹ From approximately eight years of age, children are able to successfully manage independent wear and care of lenses and achieve the required duration of lens wear.^{11,13,14,16,22,23} If contact lens wear is contemplated for children younger than eight years, substantial carer involvement will be needed to manage contact lens wear.

Conditions such as allergic or vernal conjunctivitis have an onset in childhood and in some instances, contact lens wear may aggravate or increase the risk of flare up of these conditions. Thus, due consideration should be given to any previous history of episodes of allergic or vernal conjunctivitis, and examination should include an eversion of the tarsal conjunctiva.

WHICH LENS TO CHOOSE

Over recent years, a number of contact lens options have emerged for myopia control and practitioners are now able to choose from one of these lenses. Evidence from published clinical trials show that myopia control soft contact lenses appear to be as efficient as orthokeratology in slowing myopia.^{11,12,16-19,24} However, there is no product yet for myopia control that is approved by the United States Food and Drug Administration. Table 1 lists the products that are available or soon to be available in Australia. In addition to the lenses listed in Table 1, the defocus incorporated soft contact lens, referred to as the DISC lens, is being distributed by VST in Hong Kong. The DISC lens uses the principle of simultaneous defocus and was found to slow the progression of myopia by 25 per cent on average, and up to 46 per cent in those that wore the lenses for five or more hours per day.¹³

LENS POWER AND FIT ASSESSMENTS

As per standard practice, the practitioner simply selects the lens power based on the distance refractive error. Where applicable and available, the manufacturer’s guidelines for lens selection should be adopted. An exception is the multifocal contact lens, where the practitioner will have to select the distance lens power and the ‘relative positive’ or ‘add power’. Based on evidence, a centre distance lens design with a +2.00D add power may be an appropriate starting point. Lens power should preferably be based on cycloplegic spherical equivalent refractive error (non cycloplegic refractive error leads to a more myopic refractive error) and appropriately adjusted for vertex distance.

Lens assessment on eye i.e. centration, movement, will need to be performed using standard techniques. Wearers generally find the first few minutes of lens wear unsettling but tend to adapt rapidly. In clinical evaluations, visual acuity, and subjective visual performance of these lenses was acceptable, however, since the lenses have more than one power incorporated in the lens design, depending on the design, the visual performance of these lenses may be not be fully optimal.^25,28 Reduced or poor visual performance, if found, may be related to a number of factors including lens related issues such as lens decentration, excessive lens movement, power profile of the lens (for example, concentric rings of plus power versus gradient increase in plus power) as well as pupil size, ambient illumination, and contrast. A higher add power with multifocal contact lenses may also affect visual performance. A thorough evaluation, taking into account the above factors, may determine if the situation requires a change in lens fit, lens design or a simple reassurance to the individual. To minimise errors related to head tilt and movement behind the phoropter, over refraction should be conducted using a trial frame rather than a phoropter.

LENS WEARING TIME AND REPLACEMENT MODALITY

Compliance to lens wear resulted in a better efficacy outcome and therefore, individuals should be advised to wear myopia control contact lenses for all waking hours.¹³ To reduce the risk of complications associated with lens wear, practitioners should:

1. a) Prescribe a wearing regime that minimises lens handling and therefore the risk of microbial contamination of the lenses,
2. b) Educate patients on risks associated with overnight lens wear and napping in lenses, and
3. c) Train patients in appropriate lens care and handling techniques.

A daily wear, daily disposable, or frequent replacement schedule minimises the aforementioned risk factors and should be the preferred prescribed approach, especially for young individuals. Additionally, with young children, although it is common practice to train both the child and the parent, the practitioner should ensure that the child is fully adept at managing all aspects of lens wear such as insertion and removal, and lens disinfection, as well as steps to take during adverse events.

FOLLOW-UP AND MONITORING PROGRESSION

A three to six monthly follow up schedule is recommended, especially in young myopes, as progression is rapid during childhood and any progression will result in under correction and blurred vision. If progression is ≥0.50D over six months, it is advisable to review the wearing schedule and compliance and if required, make appropriate adjustments. Additionally, the practitioner may need to contemplate one or more factors including switching lens design or type of myopia control strategy, and possibly even combining one or more myopia control strategies.

CONCLUSIONS

Considerable evidence exists for slowing myopia with contact lenses. For an individual deemed to be at risk of myopia progression, practitioners should consider myopia control contact lenses after taking into consideration the expectations of the individual and their ability to manage lens wear.

Professor Padmaja Sankaridurg is the Head of myopia program and Head of Intellectual property at Brien Holden Vision Institute. One of the world’s leading myopia researchers, she is also Conjoint professor at the University of New South Wales, School of Optometry and Vision Science. Dr. Ravi Bakaraju is head of research and development at Brien Holden Vision Institute. He is a lead inventor on a number of granted patents and several other pending patent applications around lens designs and concepts spanning myopia control technology, novel presbyopia corrections, astigmatism correction and other innovative vision correction platforms. The Brien Holden Vision Institute receives royalties on the sale of certain contact lens and myopia control products.

References 

Available at www.mivision.com.au