For an image to be seen sharply, the horizontal and vertical rays of light that reach the eye's optical system must form a focal point on the retina.
An astigmatism implies an imperfection along the curvature of the cornea or crystalline lens, leading the vertical and horizontal rays of light to have different focal points on the retina, which is called a refractive error. It can be associated with both short-sightedness and long-sightedness.
An eye with astigmatism sees distorted images as it cannot focus properly close-up or far away. Objects may seem longer or wider, sometimes letters and numbers get confused, and on some occasions shadows may even appear.
The most common symptoms of astigmatism are:
- Blurred or distorted vision
- Tired eyes
- Eye strain
Astigmatism cannot be prevented but it can be detected with a full eye examination.
If you have a significant astigmatism in adulthood, your eyesight may not be as good as it should be. However, it's harder for a child to realise that they have poor eyesight. In childhood, an uncorrected astigmatism may cause lazy eye (amblyopia). This situation can be avoided by using glasses to correct it before the age of 8. This is why an eye check-up is essential, even in the absence of symptoms.
There are currently different treatment options for the correction of astigmatism.
► Glasses or contact lenses. This is the simplest way of correcting long-sightedness.
► Corneal laser surgery. LASIK, PRK and SMILE techniques are the most commonly used in astigmatism procedures for their proven safety and efficacy.
► Intraocular lenses. In selected cases, there are other surgical techniques, such as toric intraocular lens implants, either phakic (conserving the crystalline lens) or pseudophakic (following crystalline lens or cataract removal).