Astigmatism
How does astigmatism affect vision? Learn about its causes, symptoms, and the most effective treatments for correction.
Symptoms and Causes
Astigmatism is an imperfection in the curvature of the cornea or the lens of the eye that causes a refractive error, leading to blurred vision at any distance. This visual impairment is very common among the population, but it is usually mild and often does not require any correction.
Astigmatism is classified into different types depending on the part of the eye affected. When the irregularity involves the meridians of the cornea, it is categorized as:
- Regular astigmatism: The two meridians form a 90-degree angle but have different refractive powers.
- Irregular astigmatism: The meridians are not perpendicular to each other.
- With-the-rule astigmatism: The vertical meridian is more curved than the horizontal one.
- Against-the-rule astigmatism: The horizontal meridian is more curved than the vertical one.
If the refractive error is due to changes in the structure of the retina, it is classified as:
- Myopic astigmatism: One focal point is located in front of the retina.
- Hyperopic astigmatism: Objects are focused behind the retina.
- Mixed astigmatism: One meridian focuses light in front of the retina, while the other focuses it behind.
Symptoms
The most common symptoms of astigmatism include:
- Blurred vision at both near and far distances.
- Distorted perception of objects.
- Headache.
- Eye strain.
- Decreased visual acuity, especially at night.
Causes
Astigmatism typically occurs when the cornea is oval-shaped rather than round. As a result, light rays entering the eye horizontally do not focus on the same point on the retina as those entering vertically, leading to the formation of two superimposed images.
Risk Factors
Some risk factors for astigmatism include:
- Having a family history of the condition.
- Undergoing eye surgery, as post-surgical scars may alter the shape of the eye.
- Suffering trauma or a disease that modifies the shape of the cornea or the lens.
Complications
Astigmatism does not usually cause severe complications, but it may result in poor vision or general discomfort, such as eye irritation, light sensitivity, or headaches.
Prevention
Astigmatism cannot be prevented. However, adopting healthy habits may help avoid its progression:
- Reading with adequate lighting.
- Avoiding rubbing or touching the eyes with the hands.
- Using contact lenses for the recommended duration as prescribed by an ophthalmologist.
Which Doctor Treats Astigmatism?
Astigmatism is diagnosed and treated by an ophthalmologist.
Diagnosis
Astigmatism is diagnosed through an eye examination, which typically includes visual acuity and refraction tests, such as the clock dial test. This test involves observing the radii of a circular figure with each eye separately and then together. If some lines appear clearer than others, there is a high likelihood of astigmatism.
Treatment
Astigmatism often corrects itself, particularly when diagnosed in young children. In other cases, vision correction may be required. The available options include:
- Prescription glasses with cylindrical lenses: These have different optical power and focal lengths in each axis to compensate for the eye’s shape.
- Toric contact lenses: These correct the eye’s refractive power to allow clear vision.
- Surgery: Laser techniques can correct up to four diopters, while intraocular lenses can address up to six diopters.
