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HomemieyecareMyopia in Young Adults Is Onset and Progression Important?

Myopia in Young Adults Is Onset and Progression Important?

We used to think of myopia as a condition that only develops and progresses during childhood. Indeed, the rate of axial elongation and height growth is closely linked and is most apparent during puberty when children experience growth spurts.1,2

Here, Samantha Sze-Yee Lee reviews the literature on myopia onset and progression in young adulthood.

The Correction of Myopia Evaluation Trial reported that the mean age of myopia stabilisation was around 15–16 years old. Yet, most of us in our practices would have seen patients in their 20s or 30s who experience continued myopia progression.

This has not gone unnoticed in the literature, with several studies since the 1990s reporting an annual myopia incidence of 5–11% and progression of 0.10+ D/year.3 These studies were all conducted on university students (aged 18+ to mid-20s), which gives the impression that myopia onset/progression during early adulthood only occurs in those who attend university.

However, our 20s are also the time in life when many people, especially those of the Millennial generation or later, are likely to start their first full-time jobs. These jobs, regardless of whether one has had tertiary education, are likely to be based indoors.

Unlike during childhood, when school timetables usually have designated time outdoors, the freedom of being an adult comes with other responsibilities that might make spending time outdoors less of a priority, thus, increasing the likelihood of a new myopia onset or continued progression.

Risk Factors for Young Adults

Recently, in a young adult cohort who are generally representative of Western Australia’s population, we found that more than one-third of the sample had myopia progression of 0.50D or more in either eye between the ages of 20 and 28 years.4 More than one in five of these people had myopia progression of 0.50D or more in both eyes.

The study also highlighted that, out of every seven people who did not have myopia at 20 years old, one would develop myopia eight years later.4

Most of the risk factors for myopia onset or progression during young adulthood were not modifiable.4

Women: The rate of myopia progression and axial elongation was more than twice of that in men, with 80% higher odds of myopia onset compared to men.
Parental myopia: For each biological parent with myopia, the rate of progression and axial elongation increased by 25%, while odds of myopia onset increased by 60%.
East Asian ancestry: Compared with those of European descent, those of East Asian ancestry had a 70% faster rate of axial elongation. Yet, spherical equivalent change did not differ from the rest of the cohort. The effect of axial elongation on refractive error seems to be counteracted by a flattening of the cornea, which was not observed in those of other ethnicities. The odds of myopia onset, however, was six times higher than those of European ancestry.

No modifiable risk factors were found for myopia progression, and only one was found for myopia onset – ocular sun exposure. We noticed that individuals with a larger area of actinic changes to the bulbar conjunctiva (measured as conjunctival ultraviolet autofluorescence), an objective and natural marker of ocular sun exposure, were less likely to have myopia onset during their 20s.4

However, we failed to find any link with self-reported time outdoors,4 which suggests that this participant-reported long-term information may not be reliable, as has been found in a previous report.5

Level of education was also not a significant risk factor for myopia onset or progression,4 crushing the notion that myopigenesis during young adulthood is more likely to occur in people who pursue tertiary education.

Why Women?

It is curious that women are at higher risk of myopia onset and have faster progression than men. In children, faster rates of myopia progression in girls have been partly attributed to pubertal stage where, at the time of examination, girls were at a later stage of puberty than boys.2 This cannot explain the sex difference in young adults.

The sex differences in myopia onset and progression are also unlikely to be related to outdoor time or a societal push for education in girls and women, given that we have controlled for these factors in the analysis.4 Other possible explanations, such as biological, genetic, or lifestyle factors, should be explored in this demographic group.

Rate of Progression

On average, the rate of myopia progression and axial elongation in the third decade of life are only 0.041D and 0.02mm per year. Over a decade, these equate to less than -0.50D change in spherical equivalent and 0.2mm growth in axial length. This is not an alarming rate. However, the average is not what we should be concerned about.

Of the 700-odd participants in our young adult sample, 11.3% had a myopia progression of 1D or more, including 1.4% who progressed by more than -2D over eight years (Figure 1). Axial length increased by 0.5mm or more in 6.6% of the young adults, including 0.8% with at least 1mm elongation. This means, for every 10–15 ‘20-somethings’ we see in our practice, there will be one whose myopia will increase by at least 1D, or axial elongation by at least 0.5mm, within a decade. Of your 20-year-old patients, one out of every 70–125 will have myopia progression of at least 2D or axial elongation of 1mm or more before their 30th birthday.

Figure 1. Eight-year change in spherical equivalent and axial length in a population-based young adult sample. Myopia progressed by 1D or more in 11.3% of the sample (yellow bars; left) and by 2D or more in 1.4% (orange bars; left). Axial length elongated by 0.5mm in 6.6% of the sample (yellow bars; right) and by 1mm or more in 0.9% (orange bars; right).

Recently, at the Australia Vision Convention, I presented a real-life case of a patient whose -0.50D myopia was only detected in their early 20s. This individual’s myopia subsequently increased to -11D by their early- to mid-30s – a rate of almost 1D per year. At the age of 42, this became pathological when they lost vision in their left eye due to myopic maculopathy. Fortunately for that patient, anti-VEGF had recently been introduced as a treatment for choroidal neovascularisation at that time, and their vision was restored to 6/12.

As summarised by Bullimore and Brennan, “…a one diopter increase in myopia is associated with a 67% increase in the prevalence of myopic maculopathy” and “slowing myopia by one diopter should reduce the likelihood of a patient developing myopic maculopathy by 40%”.6

While the authors referred to children in their article, this can be applied to adults.

Myopia Control: Is it for Adults?

For the case described above, one wonders if this patient’s vision would have been preserved had myopia control been available in the 1990s when their myopia was progressing.

In the past decade, we have seen tremendous advances in myopia control – from optical methods such as the highly aspheric lenslets (H.A.L.T.) technology7-8 and Defocus Incorporated Multiple Segment (DIMS) lenses, to orthokeratology and low-concentration atropine eye drops. Myopia control for fast-progressors, even adults, should be a no-brainer and perhaps even an obligation.

There is a caveat: none of the myopia control approaches have been tested for efficacy in adults. Nonetheless, there is no evidence to suggest that myopigenic processes differ between children and adults. In fact, the continued thickening of the choroid9 and axial elongation4 during young adulthood, similar to what has been observed during childhood, suggests that ocular development may just be slowing down during young adulthood, rather than completely stopped.

Additionally, a thickening of the choroid, a potential biomarker for efficacy of myopia control, following short-term orthokeratology wear has been noted in children10 and young adults,11 suggesting that myopia control methods tested in children are likely to work the same way in young adults.

However, there is a key difference between children and adults when it comes to managing progressive myopia – their responsibilities.

In children, the onus of their eye health mostly lies with their parents or carers. Based on experience from the WA Atropine for the Treatment of Myopia (WA-ATOM) Study,12 adherence to treatment is usually dependent on parents. Parents order the treatment. They bring it along on holidays and concern themselves with their child’s eyesight. This concern is usually greater than that for their own personal eye health.

In adults, this responsibility falls on themselves. As mentioned earlier in this article, young adulthood is a busy time in life, when people are generally healthy and independent.

This, paired with myopia, a condition often perceived as harmless, could make it challenging for optometrists and ophthalmologists to convince that 20-something year old patient, who perhaps has a young child and a full-time office job, to take their myopia control seriously.

As with any other conditions and patient demographic, it is critical to educate the patient on the importance of myopia control to improve adherence to treatment and follow-up visits.

As optometrists, we should take it upon ourselves to identify the fast-progressors and simplify myopia control as much as possible for our young adult patients. Consider which method of myopia control would be easiest for the patient to use. Does the chosen method suit that patient’s lifestyle and are they likely to adhere to treatment?

Taking these considerations seriously could mean the difference between moderate myopia and permanent visual impairment.

Dr Samantha Sze-Yee Lee is a postdoctoral research fellow at the University of Western Australia and the Lions Eye Institute’s Genetics and Epidemiology group. She is involved with several international projects aimed at understanding how genes and environment interact to influence an individual’s risk of myopia and glaucoma.

References
1. Wang D., Ding X., Liu B., et al., Longitudinal changes of axial length and height are associated and concomitant in children. Investigative ophthalmology & visual science. 2011;52(11):7949-7953.
2. Yip V.C., Pan C.W., Lin X.Y., et al., The relationship between growth spurts and myopia in Singapore children. Invest Ophthalmol Vis Sci. 2012;53(13):7961-7966.
3. Lee S.S., Mackey D.A., Prevalence and risk factors of myopia in young adults: Review of findings from the Raine study. Front Public Health. 2022;10:861044.
4. Lee S.S., Lingham G., Sanfilippo P.G., et al., Incidence and progression of myopia in early adulthood. JAMA Ophthalmol. 2022;140(2):162–169.
5. Lingham G., Milne E., Yazar S., et al., Recalling our day in the sun: comparing long-term recall of childhood sun exposure with prospectively collected parent-reported data. Photochem Photobiol Sci. 2020;19(3):382–389.
6. Bullimore M.A., Brennan N.A., Myopia control: Why each diopter matters. Optometry and Vision Science: Official Publication of the American Academy of Optometry. 2019;96(6):463–465.
7. Bao J., Huang Y., Li X., et al., Spectacle lenses with aspherical lenslets for myopia control vs single-vision spectacle lenses: A randomized clinical trial. JAMA Ophthalmol. 2022;140(5):472–478.
8. Bao J., Yang A., Huang Y., et al., One-year myopia control efficacy of spectacle lenses with aspherical lenslets. The British Journal of Ophthalmology. 2022;106(8):1171–1176.
9. Lee S.S., Alonso-Caneiro D., Lingham G., et al. Choroidal thickening during young adulthood and baseline choroidal thickness predicts refractive error change. Invest Ophthalmol Vis Sci. 2022;63(5):34.
10. Chen Z., Xue F., Zhou J., et al., Effects of orthokeratology on choroidal thickness and axial length. Optometry and Vision Science: Official Publication of the American Academy of Optometry. 2016;93(9):1064–1071.
11. Lee J.H., Hong I.H., Lee T.Y., et al., Choroidal thickness changes after orthokeratology lens wearing in young adults with myopia. Ophthalmic Res. 2021;64(1):121–127.
12. Lee S.S., Lingham G., Blaszkowska M., et al., Low-concentration atropine eyedrops for myopia control in a multi-racial cohort of Australian children: a randomised clinical trial. Clin Exp Ophthalmol. 2022.