Myopia: The Medical Term for Near-Sightedness
Myopia is the medical term for near-sightedness, a refractive error where parallel light rays focus at a point anterior to the retina, causing blurry distance vision while near vision remains clear. 1
Understanding Myopia
Myopia occurs when:
- Light rays from distant objects converge at a focal point in front of the retina rather than directly on it
- This creates blurry distance vision
- Near objects can be seen clearly because the image forms closer to the retina when objects are brought nearer to the eyes
Pathophysiology
The refractive error in myopia results from one or more of these factors:
- Excessive axial length (most common cause)
- Increased corneal curvature
- Increased lens power
- Abnormal position of the lens
Clinical Presentation
Patients with myopia typically experience:
- Clear vision for near objects
- Blurry vision for distant objects
- Tendency to bring objects closer to see them clearly
- Possible eye strain or headaches when trying to focus on distant objects
- Squinting to improve distance vision
Epidemiology
- Typically appears between 6-12 years of age
- Progresses at approximately 0.50 D per year (median rate)
- Higher progression rates in children of Chinese origin
- Increasing global prevalence, particularly in East Asia 1, 2
Classification
According to current consensus standards 3:
- Myopia: Spherical equivalent refractive error ≤ -0.50 diopters (D)
- Low Myopia: Mild to moderate myopic refractive error
- High Myopia: Spherical equivalent refractive error ≤ -6.00 D
- Pathologic Myopia: Presence of structural complications in the fundus (posterior staphyloma or myopic maculopathy equal to or more serious than diffuse choroidal atrophy)
Complications
High myopia increases the risk of serious ocular conditions 1, 4:
- Progressive thinning of the retina and choroid
- Peripheral retinal degeneration
- Retinal detachment
- Cataracts
- Glaucoma
- Myopic choroidal neovascularization
- Myopic macular degeneration
- Posterior staphyloma
- Myopic traction maculopathy
Management Considerations
- Mild myopia may not require correction except for distance activities like driving or schoolwork 1
- Avoid overcorrection as it can cause excessive accommodation and associated symptoms
- Some patients experience increased myopia in low light conditions (nocturnal myopia)
- Interventions to slow progression include:
- Low-dose antimuscarinic agents (e.g., atropine)
- Multifocal lenses (glasses or contact lenses)
- Orthokeratology
Public Health Impact
Myopia represents a significant global health challenge 5:
- Leading cause of distance vision impairment worldwide
- Increasing prevalence creating an "epidemic" with economic consequences
- Earlier onset leads to higher final myopia and increased lifetime risk of complications
- Projected to cause visual disability in 55.7 million people by 2050 if no new control strategies are implemented
Clinical Pearl
The earlier the onset of myopia, the more myopic the individual is likely to become, with correspondingly higher risks of sight-threatening complications 5. This underscores the importance of early detection and management strategies to slow progression.