What is myopia (nearsightedness)?

Myopia (Nearsightedness): Definition and Overview

Myopia is a refractive error where the eye cannot focus light properly on the retina, causing distant objects to appear blurry while near objects remain clear. It is primarily caused by an increase in the axial length of the eyeball 1.

Epidemiology and Public Health Impact

• Myopia has reached epidemic proportions globally, particularly in East Asia where prevalence rates of 80-90% are observed in young adults 2
• Approximately 20% of myopic individuals develop high myopia (≥-6 diopters), which significantly increases the risk of sight-threatening complications 2
• The condition typically begins in childhood and can progress throughout adolescence 3

Pathophysiology

Myopia occurs when:

• The eyeball is too long (axial myopia)
• The cornea is too curved
• The lens has increased refractive power

This causes light rays to focus in front of the retina rather than directly on it, resulting in blurred distance vision.

Complications and Associated Risks

High myopia significantly increases the risk of serious ocular complications:

• Each additional 1 diopter of myopia increases the risk of:

  • Myopic maculopathy by 58%
  • Open-angle glaucoma by 20%
  • Posterior subcapsular cataract by 21%
  • Retinal detachment by 30% 4

• Other complications include:

  • Early cataracts
  • Glaucoma
  • Choroidal neovascularization
  • Macular atrophy 1, 2

Risk Factors

Myopia development is influenced by both genetic and environmental factors:

• Genetic factors:

  • Polygenic risk scores can help identify children at risk of myopia development 5
  • Individuals with a polygenic risk score in the top 10% have a 6.1-fold higher risk of high myopia 5

• Environmental factors:

  • Reduced outdoor time
  • Increased near work activities (reading, screen time)
  • Earlier school age myopia onset correlates with faster progression and higher risk of severe myopia 2

Prevention and Management

Several strategies have shown effectiveness in preventing or slowing myopia progression:

• Preventive measures:

  • Increased outdoor activities
  • Decreased duration of near work 2

• Treatment interventions:

  • Low-concentration atropine eye drops
  • Defocusing corrective lenses
  • Defocusing contact lenses
  • Orthokeratology 1, 2

Benefits of Myopia Control

The benefits of myopia control significantly outweigh the risks:

• A 1-diopter reduction in myopia can reduce predicted years of visual impairment by 0.74-1.21 years 4
• The number needed to treat to prevent 5 years of visual impairment is between 4.1 and 6.8 4

Early Detection

Early detection is crucial for implementing effective myopia control strategies. Currently, cycloplegic autorefraction remains the best indicator of myopia risk (AUROC 0.87), though genetic screening approaches are improving 5.