Astigmatism – Causes, Symptoms & Treatment
Astigmatism is a common refractive error caused by an irregularly shaped cornea or lens, leading to blurred or distorted vision at all distances.
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Astigmatism is a common refractive error caused by an irregularly shaped cornea or lens, leading to blurred or distorted vision at all distances.
What Is Astigmatism?
Astigmatism is one of the most common refractive errors of the eye. It occurs when the cornea or, less commonly, the lens inside the eye has an irregular curvature. Instead of being perfectly spherical, the surface resembles the shape of a rugby ball, with different curvature radii along different axes. As a result, light rays entering the eye are not focused at a single point on the retina but are spread across multiple focal points, causing blurred or distorted vision at all distances.
Causes
Astigmatism can be present from birth or develop over time. Common causes include:
- Irregular corneal shape: The most frequent cause is a cornea that is not perfectly round from birth.
- Keratoconus: A progressive eye condition in which the cornea thins and bulges into a cone shape.
- Eye injuries or scarring: Trauma to the cornea can lead to irregular astigmatism.
- Eye surgery: Certain surgical procedures can alter the shape of the cornea.
- Genetic predisposition: Astigmatism tends to run in families.
Symptoms
The severity of symptoms varies depending on the degree of astigmatism. Common symptoms include:
- Blurred or distorted vision at all distances
- Headaches, especially after prolonged reading or screen use
- Eye strain and fatigue
- Sensitivity to light, particularly at night
- Double vision or ghost images around objects
- Squinting in an attempt to see more clearly
Diagnosis
An eye care professional diagnoses astigmatism using several methods:
- Visual acuity test: Measures how clearly a person sees using an eye chart.
- Refraction test: Precisely measures the refractive error using a phoropter or autorefractor.
- Keratometry: Measures the curvature of the cornea.
- Corneal topography: Provides a detailed map of the corneal surface, especially important for surgical planning.
Treatment
Astigmatism is highly treatable. The best approach depends on its severity and the individual needs of the patient:
Eyeglasses
Cylindrical or sphero-cylindrical lenses in eyeglasses correct the uneven corneal curvature and are the most common and straightforward solution.
Contact Lenses
Toric contact lenses are specifically designed to correct astigmatism by compensating for the irregular curvature directly on the eye. Rigid gas-permeable (hard) contact lenses can also be very effective as they create a smooth optical surface over the cornea.
Laser Eye Surgery
Refractive laser procedures such as LASIK (Laser-Assisted In Situ Keratomileusis) and PRK (Photorefractive Keratectomy) can permanently correct astigmatism by reshaping the cornea. For suitable candidates, these offer a long-term solution.
Toric Intraocular Lenses
For patients undergoing cataract surgery, toric intraocular lenses can be implanted to simultaneously correct astigmatism alongside the removal of the clouded natural lens.
References
- World Health Organization (WHO) - Refractive errors and low vision: https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment (2023)
- Kanski, J. J. & Bowling, B. - Clinical Ophthalmology: A Systematic Approach. Elsevier, 8th edition (2015)
- American Academy of Ophthalmology - Astigmatism: Preferred Practice Pattern. AAO (2022)
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Related search terms: Astigmatism + Astigmatismus + Corneal astigmatism + Irregular astigmatism