Lens designers and manufacturers are continually searching for more effective ways to control myopia progression. In this article, Dominque Jorgensen sets out the options for myopia control with spectacle and contact lenses.

WRITER Dominique Jorgensen

There have been many attempts to slow down the progression of myopia over the years, including under-correcting the myopic prescription, or dispensing either executive (E-line) bifocals or short corridor progressives. While some of these methods were occasionally effective, others were never effective, and were found to increase progression.

While research in this field is continually evolving, most control options currently available are built on the idea that myopia progression results from elongated axial length due to peripheral hyperopic defocussing from myopic correction.

In other words, when an eye is corrected with a minus lens, the central vision is focussed on the retina. However, the peripheral light rays then become focussed behind the retina (hyperopically) and trigger the eye to grow bigger (or more specifically, longer) to try to bring that peripheral image into focus on the retina, thus increasing the myopia.

Currently the most common myopia control methods include specialised spectacle lenses, specific soft contact lenses, orthokeratology, and compounded atropine drops. These treatment options are provided in conjunction with discussions on the importance of time spent outside and engaging in healthy screen habits.

SPECTACLE LENSES: THE PROS AND CONS

Several manufacturers design specialised spectacle lenses for myopia control based on the principle of peripheral defocussing. They use a wide range of new technologies to shift peripheral vision from focussing behind to in front of the retina, while maintaining clear distance vision at the macula. Manufacturers are so confident in the efficacy of their lenses that some offer guarantees contingent on the success of the lens in reducing myopia progression over the first year of wear.

Clear Distance Vision

Unlike bifocals or standard progressive lenses, one of the many upsides of myopia control spectacle lenses is that they allow for clear distance vision through all parts of the lens. These lenses use different technologies to provide peripheral myopic defocussing, bringing the peripheral focus point in front of the retina.

For example, Defocus Incorporated Multiple Segments (DIMS) technology is used in HOYA’s MiyoSmart lens to create the required defocus. A honeycomb-shaped array of +3.50D lenslets is arranged around a 9.4mm clear central zone, providing a 50:50 ratio between defocus and clear distance vision.

Meanwhile, Essilor uses Highly Aspherical Lenslet Target (H.A.L.T) technology to create the required defocus in its new Stellest Lens. With 1,021 lenslets arranged in 11 concentric rings around a 9mm clear central distance zone, the Stellest also provides clear distance vision between each lenslet.

Appearance

While these myopia control lenses have different physical structures (some that can be seen when looking at the shadows cast by the lenslets) they mostly appear like normal single vision lenses, which is a benefit for children wishing to wear ‘normal’ glasses. Some lenses can also be provided with different anti-reflection multicoats, photochromic capabilities, polarisation, and blue light filters, adding to the overall visual performance and appearance.

Adaptation

Adaptation to new lenses is always a consideration when dispensing for children. Thankfully, most myopia control lenses have very high adaptation rates; ZEISS boasts a 100% adaptation rate within one day with its MyoCare and MyoCare S lenses. Rodenstock’s MyCon uses defocus in the nasal and temporal areas of the lens to provide the required defocus, while leaving the superior and inferior areas clear to aid adaptation.

Material and Indices

Adding to flexibility, myopia control lenses that were once only available in polycarbonate, are now becoming available in a wider range of materials and indices. Lenses that use polycarbonate material, such as EssilorLuxottica’s Stellest and HOYA’s MiyoSmart, add impact protection to the list of pros. Others offer high index materials, including Rodenstock’s MyCon and Opticare’s Myoease – both being available in 1.6, 1.67, and 1.74 indices.

Price Tag

As with most things, there is a small list of cons for myopia control lenses, one being the price tag. According to the Optical Distributors and Manufacturers Association’s EyeTalk Reference Guide, a pair of one brand’s myopia control lenses cost AU$650, which may be a barrier for some families. However, Elisse Higginbotham, a lecturer in the University of Western Australia’s Doctor of Optometry program said “most parents don’t like watching their child’s prescription go up every six months and are relieved that there are now options that might prevent this”.

This highlights the importance of not making assumptions about your patients’ situation, as many caregivers feel that myopia control is a worthwhile investment in their child’s future eye health.

Central Clear Vision

There may also be issues with comfortable central vision if the clear vision circle is not positioned correctly in front of the eyes. This could be because the frame has been knocked or twisted, not adjusted appropriately, or the dispensing measurements were taken incorrectly, cutting either the treatment or clear zones out of the frame.

It’s important to ensure that experienced and trained staff are responsible for dispensing these lenses, and that young patients are educated on how to care for their spectacles. Caregivers also need to be aware of the importance of consistent correction from an early age.

Discussing Spectacle Lenses with Caregivers

When discussing myopia progression spectacle treatment with caregivers, Ms Higginbotham explained, “the concern is that the eye is continuing to grow longer, which is the cause of both the prescription going up, and the reason for increased risk of eye disease in the future”.

She advises caregivers that “wearing the glasses helps to send a signal to the eye that it should stop growing. This will only be effective if the glasses are on pretty much all waking hours”. She also points out that spectacles are not a quick treatment; but rather one that needs to be undertaken full time and over several years.

Some kids love wearing their glasses; they provide clear vision, protection from wind and sometimes impact, and can be an important fashion accessory. However, at times, they can restrict a child from taking part in activities they enjoy, cause stress for children with sensory issues, or lead to bullying. This is why some practitioners will consider other options such as contact lenses before spectacles.

SOFT CONTACT LENSES: A USEFUL OPTION

For children who require flexibility that spectacles cannot provide, or who prefer not to wear glasses, there are a handful of soft contact lenses available on the Australian market that are designed specifically for myopia control.

Daily Soft Contact Lenses

CooperVision has a range of daily disposable contact lenses that have been shown to “slow the progression of short-sightedness (myopia) in children”. Its MiSight 1 Day uses a dual focus design that contains concentric rings of +2.00D.

Another option is NaturalVue Multifocal 1 Day contact lenses by Vision Technologies Inc (VTI), which uses patented neurofocus optics technology with an extended depth of focus (EDOF) centre distance design to provide peripheral defocus. Daily contact lenses are a great option for younger children, where handling, hygiene, and frequency of wear are a concern.

Mark’ennovy, in conjunction with the Brien Holden Vision Institute (BHVI), has a range of monthly disposable silicone hydrogel contact lenses that use BHVI’s patented EDOF technology to control myopia progression. These are ideal if the patient wishes to wear contacts more frequently and hygiene standards can be maintained.

Insertion, Removal, and Hygiene

Gavin Swartz, a lecturer in University of Western Australia’s Doctor of Optometry program, and Fellow of the International Academy of Orthokeratology and Myopia Control, said parents usually take responsibility for inserting and removing contact lenses for young patients, depending on their age and abilities. This does allay some caregivers’ concerns about hygiene while handling, however he does point out that “the child may be out playing in dirty environments and increasing risk of infection with poor hygiene practices”. This factor needs to be carefully considered by the practitioner when prescribing soft contact lenses for children.

ORTHOKERATOLOGY: A NIGHTTIME TREATMENT

While soft contact lenses provide significant freedom from spectacles for young myopes, when looking at efficacy and practicality, Mr Swartz suggests an ideal treatment option for myopia progression is orthokeratology (OK) – specially designed Rigid Gas Permeable (RGP) lenses.

Handling and Hygiene

Unlike soft contact lenses, which are worn during the day, OK lenses are worn overnight to help reshape the cornea and prevent axial growth. Mr Swartz said the upside of OK lenses is that “the parents are in complete control of their management and the environment [in which] the child is wearing the lenses”. The lenses are inserted just before sleep, usually by the caregiver, who can ensure proper hygiene standards are maintained.

Comfort and Adaptation

Mr Swartz also noted that adaptation to OK lenses is usually quick. This is partly due to the larger diameter of the lens when compared with standard RGP lenses, which makes OK lenses move around a lot less. Quick adaptation is also partly because the lenses are worn at night while the child is asleep and lid interaction is reduced.

Price Tag

Again, myopia treatment often comes with a significant price tag, with OK lenses ranging from around $300 to $600 each. Keeping in mind that with all being well when refraction, ocular health, and axial length are reviewed, these lenses are replaced on average around every two years and sometimes end up less expensive than soft contact lenses. In addition, some health funds may pay benefits towards OK, making this treatment option more financially accessible than it first appears.

ATROPINE EYE DROPS: A THERAPEUTIC CHOICE

If the young patient is not interested in full-time correction, OK treatment, or only has low myopia now, there are always compounded atropine eye drops. According to Ms Higginbotham “atropine eye drops are a great option and are regularly prescribed by ophthalmologists and optometrists”. With only minimal side-effects in modern therapeutic doses, and long-term data on safe use, the drops offer a low-cost, first-line treatment for families unable to afford other control options. Compounded atropine eye drops have shown to be an excellent option, especially when used in conjunction with another control method.

DISPENSING CONSIDERATIONS

As with all dispenses, the success of the optical aide and treatment is highly dependent on the practitioner’s experience and attention to detail. Excellent communication from all involved is essential to find an appropriate option for the child – the child’s temperament, hygiene, preferences, lifestyle, and the family’s budget should all be taken into consideration.

If spectacles are the most suitable choice, it’s important to account for growth patterns of children by taking new, mono-interpupillary measurements at every dispense. Diligence during the frame styling process will ensure a comfortable fit, and that standard vertex distance, wrap, and pantoscopic tilt measurements are appropriate. Heights should be taken using the centre of rotation rule, especially if using an aspheric lens design. Make sure to check with your lens supplier for any additional fitting information required.

When contact lenses are the more appropriate option, ensure the child and caregiver are confident with handling and cleaning techniques. They also need to be educated on what to expect, and more importantly, what to do if they suspect something is wrong.

During discussion on myopia progression and control options, it’s important to remember that your patient, the child, is relying on your knowledge and expertise to help them avoid significant ocular problems in the future. Whether you’re an optometrist, optical dispenser, or other eye care professional, your continued learning and recommendation of control options are crucial for these children’s development. As a high-myope, and the mother of a myopia progression patient, I’m eternally grateful for your work.

Dominique Jorgensen is an Assessor for the Australasian College of Optical Dispensing (ACOD), and Optical Dispensing Instructor and Technical Officer for the University of Western Australia’s Doctor of Optometry Program. She is a qualified optical dispenser with 10 years’ experience in practice.