Astigmatism is a vision disorder that affects the cornea. Normally, this transparent part of the eyeball that transmits light to the lens – the transparent lens in the middle of the eye – is spherical, like a ball. But in people with astigmatism, this part presents what is called a “toric” curvature, that is to say comparable to a rugby ball. The pathology can also result from a deformation of the lens. In France, 15% of the population is affected by this pathology, according to a report from the National Union of Ophthalmologists from 2006.
Blurry, distorted or duplicated images
Astigmatism manifests itself in imperfect vision, both far and near. Due to the spherical shape of the cornea or lens, light rays converge at different points on the retina, the membrane located at the back of the eye. The images are perceived as blurry, distorted or duplicated. The affected person thus does not clearly perceive the contrasts between the horizontal, vertical or oblique lines. She can confuse the letter H with the letter M, the N and the E, the B and the 8 or the 0.
Beyond visual disturbances, the efforts required by the deformation of the cornea, the lens or both can cause squinting of the eyes, discomfort in bright light, headaches or eyestrain. Astigmatism can also prove to be an unrecognized handicap in learning to read.
How is she diagnosed?
Usually congenital, that is to say present since birth, this visual disorder does not change or very little during life. Weak astigmatism that is consistent with good vision and does not cause symptoms is common. It does not require correction.
But often astigmatism is blamed on fatigue. Vision problems can only manifest themselves at the periphery of the images, which on some occasions appear distorted. It is when it causes these signs of poor vision or eye strain that it should be treated. It is especially important to screen for it in young children, at the risk if it only affects one eye causing amblyopia: the diseased eye works less and less and ultimately no longer works at all.
A visual examination at the ophthalmologist makes it possible to define the orientation of the astigmatism, that is to say the axis of the “rugby ball” which will define the correction to be made. This defect can also be associated with myopia, hyperopia or with aging of the eyes over the years, especially from the forties, to presbyopia. Solutions exist to treat several disorders at the same time.
What correction for astigmatism?
There are three solutions for the correction of astigmatism:
- First, the ophthalmologist may advise wearing glasses with toric corrective lenses;
- He may also prescribe contact lenses;
- Finally, people with astigmatism also suffering from myopia or hyperopia can benefit from refractive corneal surgery, where a laser “corrects” the eye and the two disorders at the same time.
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