ASTIGMATISM is one of the three most common vision disorders. It is a sign of poor functioning of the lens or cornea, which are not symmetrical with respect to the axis of the eye. If the eye has a greater width than height the cornea and lens rather than focusing the light in the circular area of the retina will form a blurred image in one of the directions. Images seen by patients with astigmatism will be out of focus in certain areas of their field of view.
The direct cause of astigmatism is the incorrect structure or extension of the cornea of the eye, which may also be related to the construction of the lens of the eye.
Incorrect focus of the light on the retina is associated with these disorders, and this in turn leads to a distorted and “smeared” view.
The main cause of astigmatism is the incorrect construction of the cornea – the first structure of the eye, which is responsible for transmitting and focusing light into the eye. An astigmatic cornea has two different radii of curvature. This can be visualized by comparing a normal cornea to a slice of an ideal sphere, while the abnormal cornea is a segment of an egg-shaped geometric figure. This causes the light rays to split in the eye, never achieving a singular point of focus.
Specific reasons for astigmatism are not exactly known, but it is believed that in most cases the defect is inherited and usually is present from childhood and can change as it develops.
Onset and treatment
Patients with astigmatism have difficulties in focusing seen objects (blurred vision from near and far), frontal headaches, squinting and rubbing, general eye strain. With a slight astigmatism the only symptom may be more frequent blinking, because people with this type of visual impairment are trying to get a sharp image by sudden changes in focal length.
A complete eye exam; retinoscopy or an automatic refraction test will diagnose astigmatism. Treatment options for astigmatism include eyeglasses or contact lenses. Orthokeratology is another treatment that involves wearing lenses overnight that reshape the cornea so you can see clearly after you remove the lenses the following day.
Advanced treatment for astigmatism includes:
-Laser eye surgery – A surgical procedure where vision is adjusted by eliminating a small part of the eye with a laser. A specialist removes a fragment of the eye tissue, smoothing the cornea and correcting the focus.
-Astigmatic keratotomy – A surgical procedure preferred for high levels of astigmatism, where a specialist makes microscopic cuts in the steepest curves of the cornea, refocusing the light that enters into the eye.