Astigmatism is an quite common eye disease, especially among children. It can be corrected easily with contact lenses, glasses or through surgical intervention. Astigmatism occurs when the cornea, the front surface of the eye, has an irregular and abnormal curvature. Astigmatism is a refraction disorder and can be normal (when it has a value around 0.5 diopters) or pathological (if more than 1 diopter). In other words if the curvature of the cornea is very pronounced, patients have to be treated. If the diopter values are not very high and do not interfere with the patients quality of life, the treatment is not recommended.
The eye has a spherical shape and two lenses: the cornea and lens.The cornea is transparent and covers the iris, pupil and the anterior chamber of the eye. The lens is located behind the iris. It has a biconvex shape and with the cornea it refracts the light that will be focused on the retina.
The cornea and lens have together, more than two thirds of the entire optical power of the eye. Normally, when light enters the eye it reflects uniformly and forms a clear, unique image of the object.
In the eye with astigmatism that does not happen – the light is refracted in different ways, resulting in a poor focalization (only parts of the object are focused). The whole object will appear blurry and unclear. Patients with astigmatism may not perceive fine details and sometimes vertical lines appear distorted.
Causes of astigmatism
Astigmatism can be hereditary. In is can be present at birth or it can be acquired – as a result of significant pressure exerted by the eyelids on the cornea, improper posture, or prolonged use of vision at the work place (especially for observing details). Most refractive disorders tend to stabilize (in terms of dioptric) around the age of 22 to 25.
Although the exact cause of astigmatism is not fully known, there are many potentially harmful factors (considered risk factors) such as:
– Healing with scars or abrasions due to corneal perforations
– Eye-bruises or other eye injuries
– Eye-infections and shape changes of the cornea secondary to eye surgery.
Patients with astigmatism are often misdiagnosed and therefore untreated usually complain about headache, eye-fatigue, blurred vision, low perception of details, especially at distance. Although these symptoms are not specific and do not necessarily suggest an astigmatism, patients are advised to visit the doctor for a proper diagnosis and treatment if they notice this kind of symptoms
- Eye glasses with cylindrical lenses. They have a particular form, used for equilibrating the cornea pathological form (which caused the disturbances of visual acuity). The glasses are very useful for distant vision. If the patient constantly looks down for long periods of time, the images may appear distorted. Some experts believe that if the defect is small the astigmatism should remain uncorrected
- Contact lenses. Special contact lenses can correct astigmatism. The lens change their normal position when the person blinks (they rotate). Lenses for astigmatism have the ability to return to the initial position no matter how often the patient blinks.
- Surgical intervention. Astigmatism can be treated with the aid of a laser. The method reshapes the cornea so that light can focus much better forming therefore a good image on the retina. It is believed that surgical treatment is the best way to effectively correct the causes of this type defect.