Understanding Myopia (Short-Sightedness)

What Is Myopia?

In a myopic eye, the eyeball has grown slightly too long from front to back, or the cornea is too steeply curved. Either way, parallel rays of light from a distant object are brought to a focus in front of the retina rather than precisely on it. By the time the light reaches the photoreceptors at the back of the eye, it has already diverged again, producing blur.

Near objects, which naturally produce diverging rays, require less convergence and focus closer to the retina — which is why near vision remains clear in myopia.

Myopia is classified by degree:

• • Mild myopia: up to −3.00 dioptres
• • Moderate myopia: −3.00 to −6.00 dioptres
• • High myopia: greater than −6.00 dioptres

A Growing Problem

Myopia prevalence is rising rapidly, driven primarily by environmental and lifestyle changes in contemporary life. The shift is particularly pronounced in East Asian countries, where prevalence among urban young adults now exceeds 80–90% in some populations. In Australia, current prevalence among adults is approximately 30% and climbing, with higher rates in younger generations.

High myopia (>−6.00D) carries substantially elevated risks of serious complications beyond needing strong glasses. This is why myopia control — interventions that slow progression in children — has become a clinical priority.

Causes

Myopia results from an interplay of genetic and environmental factors:

• Genetics— family history is the strongest individual risk factor. A child with two myopic parents has approximately a 50% chance of developing myopia. Dozens of genetic variants associated with eye length have been identified, though genetics alone does not account for the rapid rise in prevalence over recent decades.
• Reduced outdoor time— the most important modifiable risk factor identified by population studies. Bright outdoor light (typically >10,000 lux) stimulates retinal dopamine release, which signals the eye to slow its axial elongation. Children spending less than 90 minutes per day outdoors are at significantly higher risk of both developing and progressing myopia.
• Prolonged near work and screen use— a contributing factor, though researchers believe its primary effect is via the associated reduction in outdoor time, rather than near work directly causing eye elongation. The debate continues, but both factors likely contribute.

Risks of High Myopia

For most people with mild to moderate myopia, the main consequence is needing glasses or contact lenses. High myopia, however, is associated with structural changes to the eye — a result of the elongated eyeball mechanically stretching its internal structures — that carry independent risks:

• • Retinal detachment — the stretched, thinned peripheral retina is prone to tears and detachment; risk is approximately 10 times higher than in non-myopic eyes at >−6.00D
• • Myopic maculopathy — stretching of the central retina can cause thinning, foveoschisis, and eventually permanent central vision loss
• • Glaucoma — elevated intraocular pressure risk; the optic nerve is also more vulnerable to pressure-related damage in myopic eyes
• • Earlier cataract formation — nuclear cataracts tend to develop at a younger age in highly myopic eyes

These risks accumulate with degree of myopia. Preventing a child from progressing from −3.00D to −6.00D through control measures meaningfully reduces their lifetime risk of these complications.

Correction Options

Myopia is corrected with minus (diverging) lenses in spectacles or contact lenses, which shift the focal point back onto the retina. For those seeking glasses independence, several surgical options are available:

• Spectacles— the simplest, safest, and most universally available correction. Single-vision lenses for distance; reading may not require correction.
• Soft contact lenses— daily disposables are the most hygienic option; monthly lenses a cost-effective alternative. Provide a wider visual field than spectacles.
• Rigid gas-permeable (RGP) lenses— provide sharper vision for myopes with co-existing irregular astigmatism or keratoconus.
• Orthokeratology (Ortho-K)— rigid lenses worn overnight that temporarily reshape the cornea to correct myopia during waking hours. No daytime lens required; also a myopia control strategy.
• LASIK / PRK / SMILE— laser refractive surgery permanently reshapes the cornea. Suitable for stable myopia up to approximately −8.00 to −10.00D, depending on corneal thickness. Requires pre-operative assessment for suitability.
• Implantable collamer lens (ICL)— a phakic IOL inserted behind the iris without removing the natural lens. Suitable for higher myopia or thin corneas that preclude laser surgery. Excellent visual quality.

Myopia Control in Children

Myopia control refers to treatments that reduce the rate at which a child’s myopia progresses — slowing axial elongation and limiting the final prescription reached. Control does not cure myopia; it reduces how much worse it gets.

• Low-dose atropine drops— concentrations of 0.01% to 0.05% atropine instilled nightly reduce progression by approximately 50–60% in studies, with minimal side effects at low doses. Mechanism not fully elucidated but thought to involve retinal signalling pathways.
• Orthokeratology— as well as providing daytime vision correction, overnight corneal reshaping reduces peripheral defocus signals thought to drive axial elongation. Reduces progression by approximately 40–50%.
• Multifocal soft contact lenses— specially designed peripheral defocus lenses (such as MiSight) reduce myopia progression; clinical trial data shows approximately 50% reduction in axial growth.
• Outdoor time— not a treatment per se but a critical protective factor; at least 90 minutes daily in outdoor light is recommended alongside any optical or pharmacological control strategy.

Frequently Asked Questions