Dr Nina Tahhan( PhD)( left) Program director for the International Myopia Institute and director of clinical research at the Brien Holden Vision Institute, Sydney, NSW.

Dr Elias Elie Kehdi( right) Paediatric, glaucoma and cataract specialist at Western Sydney Eye Doctors, Sydney, NSW.

First published online on 21 June 2024

BACKGROUND

MYOPIA, also known as short-sightedness

or near-sightedness, results in blurred vision when viewing objects in the distance. Myopia is a refractive error, that is, one where vision can be corrected with spectacles or contact lenses.

Refraction describes the bending of light rays as they pass from one transparent medium to another that has a different density. During vision, the light reflected from an object is refracted by the cornea and lens, which focus it on the retina.

Myopia is more common than the other refractive eye conditions of hyperopia( long-sightedness) and astigmatism( torical / cylindrical rather than spherical refractive error).

Myopia occurs when the eyeball length( axial length) grows slightly longer than is necessary or when the cornea is too curved / steep for images to be focused clearly on the retina, where the image is instead focused in front of the retina( see figure 1).

Myopia typically develops during childhood, more commonly

during the school-age years, and tends to progress until early adulthood when the eye’ s growth tends to stabilise.

Myopia is becoming increasingly common and researchers are citing the rising global prevalence as evidence that the condition is more environmentally than genetically driven. 1, 2 The condition is generally more concerning than other refractive eye conditions because axial elongation of the eye can increase the risk of more serious and potentially sight-threatening complications, including retinal detachment( see figures 2 and 3), glaucoma, cataract and myopic macular degeneration. Any myopia, but particularly high myopia( typically defined as greater than 5-6 dioptres of optical correction) can lead to a reduced quality of life and be financially burdensome on families because of the cost of optical appliances, frequent eye examinations and the costs associated with the treatment and management of complications. 3

Clinicians have traditionally provided optical correction( single-vision minus powered lenses) to treat the visual symptoms of

myopia; however, the level of myopia typically continues to increase with this management approach. The surge in research in recent decades has identified other management options that have been shown to slow down or stop / control the progression of myopia rather than just treat the visual symptoms. It is important for clinicians to be aware of the increasingly available options that improve patient management, prognosis, and quality of life.

This How to Treat provides up-to-date evidence on the aetiology, epidemiology, risk factors, signs and symptoms, management options and prognosis of myopia. It aims to ensure GPs can answer commonly asked questions, provide advice to those at risk or requiring management and help arrange timely referral for those requiring multidisciplinary care.

EPIDEMIOLOGY

MYOPIA is a widespread and growing problem worldwide. In 2020 it was estimated that nearly 30 % of the world’ s population was affected and this is projected to rise to 50 %

by 2050. 1 The prevalence of high myopia is also growing and is projected to rise to 10 % in 2050 from 3 % in 2020. 1

In East Asia the prevalence has been found to be more than 80 % in high school students. 4 Although the prevalence of myopia is not as high in Australia, a cross-sectional population-based study of 12-yearold children reported an increase in myopia from 11.5 % in 2006 to 18.9 % in 2011. 5 Children of East Asian ethnicity in Australia have a higher likelihood of becoming myopic than other Australian children; however, they have a lower prevalence than Asian children living in Asia, suggesting lifestyle factors may play a bigger role than genetics in aetiology. Increased educational pressures in Asia have been cited as one such contributor. 2, 6

Overall, the prevalence of myopia in Australia was estimated at 20 % in 2020 and this is projected to increase to 55 % in 2050. 1

The prevalence of high myopia in infants and children under the age of five is rare( less than 1 %). 7 Data from areas in China where there is a high prevalence of myopia