What is astigmatism?
Astigmatism is a refractive defect that causes images to focus on the retina in a distorted way, affecting near and far vision.
Astigmatism can occur by itself or in association with myopia or hyperopia, and is usually stable throughout life.
What causes it?
Astigmatism is usually caused by a problem in the curvature of the cornea that impedes clear focusing on near and far objects. The cornea loses its spherical shape, becoming elliptical.
The cause of this irregularity is often genetically determined, but may also occur as a result of trauma, disease or after surgical procedures (such as corneal transplantation).
How can it be prevented?
Astigmatism cannot be prevented but can be diagnosed through an ophthalmological examination that includes a refraction test and/or corneal topography. Certain special or complex cases may require other types of test.
Symptoms can vary depending on age and type and degree of astigmatism. If the astigmatism is low, it may not affect vision.
The most common symptoms are:
- Perception of distorted images (most common symptom).
- Poor visual acuity in far vision.
- Problems in switching between near and far vision.
- Difficulties in seeing fine detail, either near or distant.
- Headaches, eye pain or dizziness, as a result of the eye’s muscular effort in trying to compensate for the defect with the accommodation of the crystalline lens (the eye’s natural lens whose elasticity enables the eye to focus). This is especially true in cases of astigmatism associated with hyperopia.
Astigmatism can be corrected by glasses or toric contact lens.
If the patient prefers not to wear glasses or contact lenses, surgical solutions are available. Refractive surgery includes several treatments depending on the diagnosis:
- Excimer laser: applied to the thickness of the cornea, used to correct moderate astigmatism
- Incisional technique. (Arcuate keratotomy): consisting of making incisions on the corneal surface, indicated for high astigmatism.
- Toric intraocular lenses: phakic (implanted between the cornea and crystalline lens) and pseudophakic (replacing the crystalline lens). It is commonly used to correct high astigmatism
The ophthalmologist will determine the most appropriate technique for each case.
About 80% of success in surgery depends on proper diagnosis and selection of the type of surgery to use.