Playing it safe: integrating UV safety with myopia control

With growing attention on outdoor time as a preventive measure for myopia control in children, a nuanced challenge emerges: balancing exposure to natural light with protection from harmful ultraviolet radiation. The authors offer guidance for eyecare professionals navigating this quandary.

With the rising concern of the myopic epidemic, there is an increased global awareness and push to encourage children to spend 14 to 17 hours a week in high-lux, UV-free outdoor light. This has been shown to offer a protective effect against axial length growth, and it’s a message that has quickly become a staple of our discussions with patients.

In this article, however, we’ll discuss the flipside of this simple message. The sight-threatening complications of ultraviolet radiation (UVR) on the eye and adnexal structures, including: periorbital skin cancers, pterygia, pingueculae, ocular surface neoplasia, cataracts and macular degeneration.

While it has been established that axial length growth occurs predominately in childhood, UV fluorescence photography has helped the scientific community to recognise that significant UV eye damage also occurs in these formative years.¹ And just as frequently-sunburned skin can have serious consequences later in life, UVR-related eye diseases can result later in life for those who “sunburn” their eyes in childhood.

UV fluorescence photography (UVFP), which can objectively quantify the degree of UV damage in childhood,^1-3 has been used to demonstrate an inverse relationship between childhood UV exposure and myopia.⁴

UVFP analysis has shown that 30% of children aged 9-11 have UV damage to their eyes. By 12-15 years of age, 81% of children had UV damage detected, and most alarmingly, 29% had clinically-evident pingueculae or pterygium.¹ It has been shown that pterygium is an indicator of UV exposure; patients with pterygium should, in fact, be screened for cutaneous melanoma as they have a 24% increased risk.⁵

Children have the least-naturally developed protection against UVR; 80% of UV eye exposure occurs before a child turns 18 years old.¹ As eyecare professionals, we need to educate our

patients about the importance of protecting their eyes from the complications of axial myopia as well as UV-related eye diseases. To do so, we need to understand how UVR reaches the eye and ensure that the sunglasses we are advocating our patients to wear provide maximum protection from UV radiation, while allowing in high lux light to protect from myopia.

UV-related eye diseases

Australia has some of the highest rates of UV-associated

diseases in the world, in part due to our outdoor lifestyles and our climate. As our understanding of UV-related eye diseases has evolved over the last 50 years, we have learned how UV light damages the eye as well as the periorbital skin. Periorbital skin cancers account for 10%⁶ of all skin cancers of which more than half occur on the lower lid.⁷

Pingueculae and pterygia have an earlier onset than other UV-related eye diseases, with a peak prevalence between 20-40 years of age. To determine a person’s degree of UVR exposure simply considering where they live is inaccurate, as UVR levels depending on the latitude, altitude, sun elevation, cloud cover and ground reflection⁷ and can be skewed based on their occupation, participation in outdoor hobbies, activities and habitual use of UV protection, such as sunglasses and hats.

For example: pinguecula, the precursor to pterygia, varies from 11% in Southern India⁸ to 56% in Greenland.¹¹ The wide variation of pterygium and pingueculae prevalence cannot be accounted for by the variations in latitude or altitude alone, just as the prevalence of skin cancer cannot be entirely explained by latitude or altitude.⁹¹

The prevalence of myopia has been tabulated against the prevalence of pterygium and pinguecula. In several populations with a low prevalence of myopia, a high prevalence of pterygium was noted (Table 1). Similarly, this inverse relationship was evident when tabulating the prevalence of myopia against pinguecula (Table 2). 

For example, in Shanghai, a high prevalence of pinguecula and low rates of myopia were documented. The very high myopia rate in South Korea at 70.6%¹⁰ inversely correlates with the 3.8% rate of pterygia.¹¹ In Greenland, myopia prevalence was 14.1%,¹² higher than expected compared to the pterygium prevalence of 8.6%.¹³ However, the high rate of myopia could be explained by the change in education policy, which made it compulsory for all Inuit children to start formal schooling. This policy would increase the rates of myopia prior to causing a reduction in the prevalence of pterygium, which has a later onset. Data from Zhang et al.,¹⁴ summarised in Table 3, shows the correlation of axial lengths against pterygium.

The dangers of UVR

UVR penetrates the eye and is a risk factor for the development of anterior cortical and posterior subcapsular cataract.¹⁵ Studies suggest UVR is a risk factor for macular degeneration.^16,17 Despite the UV protection afforded to the macula by UV absorption of an adult natural lens (REF), adults who worked outdoors have higher incidence of AMD and soft drusen.¹⁸ Furthermore, the amount of leisure time spent outdoors in summer was significantly associated with wet macular degeneration.²⁵

Less well known is that an immature child’s lens only absorbs 90-95% of UVR, thus allowing significant amount of UVR to reach the macula. We suggest this as the pathogenesis for the inversely reducing rate of any age-related macular degeneration for each dioptre of increasing spherical equivalent of myopia noted in a Korean study.¹⁹

Disease prevention

Studies confirm Australia’s high incidence of skin cancers from UVR exposure, particularly during childhood and adolescence,^20,21 which has spurred numerous skin cancer prevention programs, promoting the use of sunblock, rashies and hats to protect the skin.^22,23 But the eye and periorbital skin is still left unprotected. By age 70, two-thirds of Aussies have had treatment for at least one non-melanoma skin cancer.²⁴ About 10% of all skin cancers occur in the periocular area. Furthermore, UVR eye diseases impact millions of Australians. Despite the large number of Aussies affected, the message about the importance of protecting the eye and periorbital skin with protective sunglasses is still not well known or understood, even though the need for UV skin protection is well understood.

Is prevention of eye diseases less important than the prevention of skin diseases?

Parents avoid applying sunblock to the periocular skin on their writhing children for fear of getting sunblock in their eyes, and they don’t insist on protective sunglasses, leaving both the periocular and ocular areas unprotected. The comment ‘my child won’t wear sunglasses or she doesn’t like them’ justifies why the eyes are unprotected. However, most children also dislike sunblock – which is essentially a thick paste smeared over their body, but their parents/teachers/adults insist that it is worn to reduce skin diseases. Furthermore, the different levels of UV skin protection offered by the various SPFs of sunblocks is understood. However, the UVR protection is less well classified or understood for the eye. Even in adults, the periorbital skin is most frequently left uncovered with sunblock in 14% of cases.²⁵

When should we start protecting children?

As early as possible. It is known that exposure to UVR is cumulative and even short duration exposure can lead to long term eye health problems, many of which begin symptom free. Children receive approximately three times the annual adult dose of UVR, as they spend more time outside.

Eyecare professionals need to encourage our patients to understand the need to protect the eye from harmful UV rays. The message is clear: when a child is outside during daylight hours, their eyes should be protected from exposure to UVR. Eighty per cent of UV exposure occurs before a child turns 18 years old.²⁶ The signs of UV damage to the anterior segment of the eye can be detected as early as nine years of age.¹

impact of poorly-designed sunglasses

The tint of sunglass lenses reduce glare for the wearer and relax the squint reflex. This causes the palpebral aperture to widen, the brow to relax and the pupils to dilate.⁷ This widening paradoxically allows more UVR onto the periorbital skin, ocular surface and into the eye. Furthermore, as the sunglass lens is a smooth surface, the reflected UVR reaching the back surface of the lens from around the poor-fitting frame is reflected off the lens into the dilated pupil of the eye.^7,27 UVR damages the skin due to the effects of direct rays of light. The eye, however, is damaged from direct, overhead and reflected rays of UVR. So it’s important to consider frame design in addition to lens quality when advocating the use of sunglasses. Unfortunately, as noted in Sliney et al,⁷ some sunglasses can actually increase UVR exposure to the eye.

Sunglasses with best protection

In a child’s eye, which normally has a larger pupil diameter than an adult eye, the UVR not only damages the anterior segment and periocular skin, but also can penetrate through the pupil and immature lens and onto the retina, and particular the macula.²⁸ In addition to this, UVR is reflected from the ground, and surfaces around the wearer, and reflected off the back surface of the lenses and into the child’s anterior segment and through the pupil.²⁹ The proportion of the direct, overhead and reflected light varies due to altitude, time of day, season and surfaces surrounding the child.

All sunglasses are not the same, and price is not an indication of the level of eye protection offered by a pair of sunglasses. Sunglasses designed to offer maximum protection should block all three pathways: direct, overhead and reflected UVR from reaching the eye and periodical skin. They should block reflected side light entering the eye from below and around the temporal and nasal sides of the lenses, with antireflective coating on the back/inner side only (Figure 1).³⁰ This prevents UVR reflected from the inner surface of the lens entering the eye. The further a lens sits in front of the eye the greater the irradiation to the eye and periorbital skin.^31,32

Lens polarisation reduces reflected UVR reaching the eye through the lens. To maximally protect the eye and periorbital skin from UVR, polarisation should occur in the presence of wrap-around frame design.¹¹ In addition to wraparound frame design, polarisation and anti-reflective properties, the lens material should block direct UV light and have absorption of up to 400 nanometres for maximum protection. Children’s sunglasses should be protective, comfortable to wear and meet the international safety standards.

Protection should be worn whenever the child is outside, from sunrise to sunset, 365 days of the year. Children need to be protected from an early age, as UV penetration into the eye is maximal in the first 10 years of life, when the eye has the least developed natural defences. This habit of eye protection needs to be encouraged throughout life. Wearing protective sunglasses should be part of the sun-protection campaign worldwide, as long-term eye and skin health are both essential, and in particular in Australia with our high rates of UVR diseases.

This push for UV protection is even more important as children are being encouraged to spend more time outside to reduce myopia progression. Myopia prevention and UV protection can occur simultaneously.

It is also important as eyecare professionals that in the future our patients don’t feel that their child’s UVR eye disease is due to our advice to keep their children playing outdoors. The exposure for UVR eye diseases commonly occurs in childhood, but the diseases frequently manifest in adulthood, after cumulative damage has already occurred. In order to reduce the prevalence of these UVR related eye diseases, childhood UV exposure should be minimised.

Eyecare professionals are in the ideal position to lead the change in understanding and minimising the long-term impact of both myopia and UVR eye diseases, by educating patients, and encouraging the use of maximally protective sunglasses for children. We need to take a holistic approach to eyecare and diseases prevention, it is important to reduce the rates of axial myopia but equally we need to ensure that we don’t inadvertently increase the rates of UV related eye diseases. 

NOTE: Dr Shanel Sharma, Dr Alina Zeldovich and Dr Daya Sharma founded Beamers, which produces and sells sunglasses with Optoshield technology to address all three pathways of UVR reaching the eye and periorbital skin: www.beamers.com.au.

More reading

Combining myopia treatment with UV protection

optometry beyond myopia

Glaucoma: Integrating OSD management with peri-operative optometric care

References 

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