Myopia (Nearsightedness): Causes & Treatment
Myopia (nearsightedness) is a common refractive error where distant objects appear blurry. It is usually caused by an elongated eyeball or an overly curved cornea.
Things worth knowing about "Myopia"
Myopia (nearsightedness) is a common refractive error where distant objects appear blurry. It is usually caused by an elongated eyeball or an overly curved cornea.
What is Myopia?
Myopia, commonly known as nearsightedness or short-sightedness, is one of the most prevalent refractive errors of the eye worldwide. People with myopia can see nearby objects clearly but struggle to focus on objects at a distance. It affects both children and adults and its prevalence is increasing globally.
Causes
Myopia occurs when light entering the eye focuses in front of the retina rather than directly on it. This can result from:
- Axial myopia: The eyeball is too long from front to back, so the focal point falls short of the retina. This is the most common cause.
- Refractive myopia: The cornea or lens has too much curvature, creating excessive focusing power.
Genetics play a significant role: having one or both parents with myopia substantially increases the risk for children. Environmental factors such as prolonged near work (reading, screen use) and limited time spent outdoors are also known to contribute to myopia development, especially during childhood and adolescence.
Symptoms
Common signs and symptoms of myopia include:
- Blurred vision when looking at distant objects (e.g., road signs, whiteboards)
- Clear vision for close-up tasks such as reading
- Squinting to see distant objects more clearly
- Headaches caused by eyestrain
- Eye fatigue, particularly after extended screen use
In children, undetected myopia can affect school performance, as they may be unable to read content on the classroom board clearly.
Diagnosis
Myopia is diagnosed during a comprehensive eye examination by an optometrist or ophthalmologist. Common diagnostic methods include:
- Visual acuity test: Assessing how well a person sees using standardized eye charts (e.g., Snellen chart).
- Refraction assessment: Determining the exact degree of refractive error using an autorefractor or a subjective lens trial.
- Retinoscopy: An objective method for measuring refractive error using light reflection.
- Slit-lamp examination: Assessing the anterior and posterior segments of the eye.
The severity of myopia is measured in diopters (D). Values up to -3.00 D are considered mild, -3.00 to -6.00 D moderate, and above -6.00 D high myopia.
Treatment
Optical Correction
The most common approach to managing myopia involves optical correction:
- Eyeglasses: Concave (minus) lenses shift the focal point back onto the retina, correcting distance vision.
- Contact lenses: Soft or rigid gas-permeable lenses offer an alternative to glasses and provide a wider field of view.
Surgical Correction
For adults with stable myopia, permanent correction can be achieved through refractive surgery:
- LASIK (Laser-Assisted In Situ Keratomileusis): A laser reshapes the cornea to reduce refractive error.
- PRK (Photorefractive Keratectomy): The outer layer of the cornea is removed, and an excimer laser reshapes the surface.
- Phakic intraocular lens (pIOL): An artificial lens is implanted inside the eye, particularly suitable for high myopia.
Myopia Control in Children
To slow the progression of myopia in children, several interventions are available:
- Orthokeratology (Ortho-K): Specially designed rigid contact lenses worn overnight to temporarily reshape the cornea.
- Low-dose atropine eye drops: Have been shown to significantly slow myopia progression in clinical studies.
- Myopia-controlling spectacle lenses: Specially designed lenses (e.g., DIMS technology) aim to reduce the stimulus for eye elongation.
- Spending more time outdoors (at least 2 hours per day) is considered a protective factor against myopia progression.
Risks and Complications
High myopia (above -6.00 D) significantly increases the risk of serious eye conditions, including:
- Retinal detachment
- Glaucoma (increased intraocular pressure)
- Cataract (lens clouding at an earlier age)
- Myopic macular degeneration
Regular eye examinations are especially important for individuals with high myopia to detect and manage these complications early.
References
- World Health Organization (WHO): World Report on Vision. WHO, Geneva, 2019. Available at: https://www.who.int/publications/i/item/9789241516570
- Wolffsohn JS et al.: IMI - Industry Guidelines and Ethical Considerations for Myopia Control Report. Investigative Ophthalmology & Visual Science, 2019;60(3):M161-M183.
- Flitcroft DI et al.: IMI - Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies. Investigative Ophthalmology & Visual Science, 2019;60(3):M20-M30.
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