Astigmatism is a condition of the eye where the cornea, which is the front surface of the eye, is uneven leading to the patient having blurry vision. It is a refractive error which means that light that is received by the retina is refracted instead of being reflected as is supposed to be. The cornea's curve is what is uneven so that one side may be flatter than the other or it may be steeper than the other side leading to blurry vision. This is known as corneal astigmatism. It occurs as a result of a birth defect or as a result of an eye injury or a surgery that went wrong and caused damage to the cornea.
The cornea is a layer of tissue that is positioned at the front of it and protects the eye from damage and infections. This tissue is what the eye uses to transmit and focus light into the eye. The cornea's natural shape is spherical and if one side is either flatter or steeper than the other side then the light that is being transmitted to the retina will be irregular and the light rays will focus on two spots as opposed to just one spot as it is supposed to. This is what causes blurry vision.
Astigmatism can also be caused by the lens that is behind the cornea being irregular in shape. This is known as lenticular astigmatism. This type of astigmatism is the same as corneal astigmatism but in this case the curve of the lens is irregular. The problem with the curvature causes the light to be refracted and this blurry vision. Astigmatism can occur in one eye and not the other.
The symptoms of astigmatism are blurred vision which is the most common symptom. The patient may also have distorted vision, eye strain and as a result of this, headaches, squinting and closing the eyes to relieve some of the strain caused by distorted vision.
If the patient suspects that they may be suffering from astigmatism, the following tests are used to diagnose. The patient will read a chart with letters that become smaller. Or they may study a chart that has lines that make a semicircle. Astigmatism causes some lines to be blurry. Another method of diagnosing astigmatism is using a keratometer which measures the curve of the cornea. Another instrument that can be used is the keratoscope which also measures the curve of the cornea.
The two ways in which astigmatism can be corrected is by using corrective lenses or undergoing surgery to correct the abnormality in the cornea or lens. For corrective lenses, the patient has the option of wearing glasses or contact lenses. The lenses in the glasses or contact lenses will bend the light rays that are being transmitted into the eye so as to compensate for the abnormal curve of the cornea or lens. The light will then hit the retina in just one spot. If the patient has just one eye affected by astigmatism, then the other lens will be plain. For contact lenses, then they can wear just one for the faulty eye.
There is a type of rigid contact lenses that are used to correct the curvature of the cornea. This treatment is known as orthokeratology. The contact lenses are not worn for a long period of time, just for a number of hours. However, they don't fix the abnormal curvature of the cornea permanently. If the patient stops wearing them, the abnormal curve re-occurs. This treatment is mostly used by people with a mild form of astigmatism.
Laser eye surgery is done where part of the cornea is removed and the curve is redone so that the cornea regains its spherical shape. This procedure is painful and recovery and for your eyesight to resume perfectly it takes up to a month. This procedure is known as Photorefractive keratectomy.
Another surgical procedure is LASEK where a much thinner layer of the cornea is removed using alcohol. The curve is fixed using a laser. The recovery time and sight regaining time is one week. LASIK surgery is the least painful and has no recovery time. The cornea is cut using a laser beam and then it is reshaped.