What is Myopia?
Myopia, commonly known as nearsightedness or short-sightedness, is a refractive error in which light entering the eye focuses in front of the retina rather than directly on it. This occurs because the eyeball is too long (axial myopia) or, less commonly, because the cornea or lens has too much refractive power. As a result, distant objects appear blurred while close objects can be seen clearly. Myopia is typically measured in diopters (D), with mild myopia defined as up to -3.00 D, moderate myopia as -3.00 to -6.00 D, and high myopia as greater than -6.00 D. The global prevalence of myopia has been rising dramatically, with estimates suggesting that nearly 50% of the world's population could be myopic by 2050. High myopia is of particular concern because it is associated with an increased risk of sight-threatening complications including retinal detachment, myopic macular degeneration, glaucoma, and cataracts.
Symptoms
- Blurred vision when looking at distant objects
- Squinting to see clearly at a distance
- Eye strain and headaches, especially after prolonged distance viewing
- Difficulty seeing the board at school or road signs while driving
- Fatigue when driving or playing sports
- Needing to sit closer to the television or screen
In children, myopia often becomes apparent between the ages of 6 and 14 and may progressively worsen until early adulthood when the eye stops growing. Parents should watch for signs such as squinting, sitting too close to screens, and complaints of headaches.
Causes and Risk Factors
Myopia develops due to a combination of genetic and environmental factors. When the eyeball grows too long relative to the focusing power of the cornea and lens, the focal point falls short of the retina. Key risk factors include:
- Family history — children with two myopic parents have a significantly higher risk
- Excessive near work — prolonged reading, studying, or screen time
- Insufficient time spent outdoors — outdoor light exposure appears to have a protective effect against myopia development
- Early onset of myopia in childhood, which predicts higher final refractive error
- Urbanization and higher educational demands
- Ethnicity — higher prevalence in East Asian populations
Diagnosis
Myopia is diagnosed during a standard eye examination. Visual acuity is measured using a Snellen chart or equivalent. Refraction, either subjective (using a phoropter with patient responses) or objective (using an autorefractor or retinoscopy), determines the precise degree of refractive error. Cycloplegic refraction (using drops to temporarily paralyze the focusing muscle) is particularly important in children to obtain an accurate measurement. Axial length measurement using optical biometry helps monitor eye growth over time, which is crucial for myopia management in children. A comprehensive dilated eye exam is essential in high myopia to check for retinal thinning, lattice degeneration, or retinal tears.
Treatment
Treatment aims to correct the refractive error and, in children, to slow myopia progression:
- Corrective eyeglasses — the simplest and most common method of correction
- Contact lenses — soft, rigid gas permeable (RGP), or specialty lenses
- Myopia control strategies in children — atropine eye drops (low-dose, 0.01%–0.05%), orthokeratology (overnight corneal reshaping lenses), and specially designed peripheral defocus soft contact lenses or spectacle lenses (e.g., DIMS, HALT technology)
- Refractive surgery for adults with stable myopia — LASIK, PRK, SMILE, or implantable collamer lenses (ICL) for higher degrees of myopia
Prevention and Recommendations
- Encourage children to spend at least 90 to 120 minutes outdoors each day
- Follow the 20-20-20 rule to reduce near work strain
- Maintain a proper working distance of at least 30 cm when reading
- Ensure adequate lighting for all near-work tasks
- Schedule regular eye examinations for children, starting from school age
- Discuss myopia control options with your ophthalmologist if your child's myopia is progressing
- Adults with high myopia should have annual dilated retinal examinations to monitor for complications
- Report any sudden flashes, floaters, or curtain-like vision loss immediately, as these may indicate retinal detachment