Myopia: Causes, Correction, and Prevention

Myopia is the most common refractive error worldwide, with prevalence rising rapidly — particularly among children. In Canada, approximately 30% of adults are nearsighted, and the rate is significantly higher among young urban populations.

How myopia develops

In a myopic eye, the eyeball grows slightly too long axially, or the cornea curves too steeply. Instead of focusing light precisely on the retina, the focal point falls in front of it — causing clear near vision and blurry distance vision.

Myopia typically develops in childhood (ages 6–14), progresses through the teenage years, and stabilizes in the early-to-mid twenties as eye growth slows.

Symptoms

Squinting to see distant objects
Difficulty reading the board at school or road signs while driving
Sitting close to screens or the front of classrooms
Eye strain and headaches after looking at distance

Correction options

Glasses

The simplest correction. Single-vision lenses are most common. For children with rapid myopia progression, certain lens designs (e.g., DIMS lenses) may have a mild myopia-control effect, though evidence is weaker than other interventions.

Standard contact lenses

Daily or monthly soft lenses provide full distance correction and are suitable for most myopic patients from adolescence onward. Standard contacts correct vision but do not slow progression.

Refractive surgery (adults)

LASIK and PRK reshape the cornea to reduce or eliminate the refractive error. These are appropriate for adults whose prescription has been stable for at least 1–2 years, typically in their mid-20s or older.

Myopia control (for children and adolescents)

Slowing progression reduces the lifetime risk of high-myopia complications. The most evidence-supported interventions:

Low-dose atropine eye drops

Nightly atropine (0.01–0.05%) slows eye elongation. The mechanism is not fully understood. Meta-analyses show 30–77% reduction in progression rate depending on concentration. Requires a prescription from an optometrist or ophthalmologist.

Orthokeratology (OrthoK)

Rigid gas-permeable contact lenses worn overnight reshape the cornea while sleeping, providing clear vision during the day without glasses or contacts. Studies show approximately 30–55% reduction in axial elongation. Popular with school-aged children.

Multifocal soft contact lenses

Soft daily lenses with a specific optical design (e.g., MiSight) have been FDA and Health Canada approved for myopia control, showing approximately 50% reduction in progression in clinical trials.

Outdoor time and prevention

Consistent evidence shows that 2+ hours of outdoor time daily significantly reduces the risk of myopia onset in children. The protective effect is thought to come from bright light stimulating dopamine release in the retina, which inhibits eye elongation. Screen time itself is a less significant factor than lack of outdoor time.

Risks of high myopia

A prescription of -6.00D or stronger is associated with meaningfully elevated risk of:

Retinal detachment — the elongated eye places mechanical stress on the retina
Glaucoma — optic nerve susceptibility increases
Myopic maculopathy — stretching of the macula causes central vision loss in severe cases
Early cataracts

Annual dilated exams are essential for anyone with high myopia.

Frequently Asked Questions

What is myopia?

Myopia (nearsightedness) is a refractive error in which the eye is slightly too long or the cornea is too curved, causing light to focus in front of the retina rather than on it. The result is clear vision up close and blurry vision at distance. It is measured in dioptres — a prescription of -1.00 or stronger indicates myopia.

Is myopia hereditary?

Yes, genetics play a significant role. If one parent is myopic, a child has roughly a 3x higher risk; if both parents are myopic, the risk is about 6x higher. However, environmental factors — particularly limited outdoor time and prolonged near work — strongly influence onset and progression, meaning genetics alone does not determine outcome.

Can myopia be reversed or cured?

Myopia cannot be reversed without surgery. Glasses, contact lenses, and refractive surgery (LASIK, PRK) correct the vision but do not change the underlying eye length. Myopia control treatments (orthokeratology, atropine drops, multifocal contact lenses) can slow progression in children but do not eliminate existing myopia.

What is myopia control and who needs it?

Myopia control refers to interventions that slow the rate at which a child's myopia worsens. It is recommended for children whose prescription is increasing rapidly (0.75D or more per year), who became myopic at a young age (under 8), or who have high myopia risk factors. Options include low-dose atropine eye drops, orthokeratology (overnight contact lenses), and multifocal soft contact lenses.

What level of myopia is considered high myopia?

High myopia is generally defined as -6.00 dioptres or stronger. High myopia significantly increases the lifetime risk of retinal detachment, glaucoma, myopic maculopathy, and early cataracts. People with high myopia need annual dilated eye exams to monitor for these complications.

Myopia (Nearsightedness): Causes, Correction, and Slowing Progression