Normally, the eye, cornea, and lens can easily focus light rays on the retina. The disease known as
astigmatism is an imperfection in the curvature of the cornea, and it can produce a clear, round dome covering the iris and pupil.
The cornea and lens remain smooth and are always curved equally in all directions. The focus of light rays is on the retina at the back of the eye. If the cornea or lens is not smooth or evenly curved, the light rays are not refracted properly. This is type of disorder is called a refractive error.
Near-Sightedness and Far-Sightedness
When the cornea has an irregular shape, it is a condition called corneal astigmatism. As the shape of the lens becomes distorted, it can develop into lenticular astigmatism. The result of either type of astigmatism causes objects that are near or far to become blurry or distorted. The overall look is similar to a fun house mirror where the person either looks tall, fat, or wide.
With astigmatism, the images that are focused either in front of or beyond the retina cause both close and distant objects to appear unclear and dim.
Some people are born with astigmatism, but most people develop a small degree of astigmatism at some point, and it generally leads to refractive errors, namely, near-sightedness and far-sightedness.
Adults tend to have a higher degree of astigmatism and are able to recognize its effect on their vision. Children suffering from astigmatism may not have any idea there are problems with their vision; most children never complain about having blurry vision. However, astigmatism can seriously impact a child's ability to achieve in school and sports. Astigmatism can be a sign of keratoconus, which is a cone-like bulge of the cornea that can distort vision. This is why children need to have their eyes tested regularly.
Astigmatism is one of the most common vision conditions that causes blurred vision. It also affects the cornea, the clear front cover of the eye. It remains irregularly shaped and even, due to the curvature of the lens inside the eye.
The erratically-shaped cornea or lens stops the light focusing properly on the retina. The area at the back of eye is highly sensitive. It makes the vision blurred at any distance and causes uneasiness and headaches for longer periods of time.
Most people have either a slight or more severe degree of astigmatism, which can change without having any treatment. Astigmatism induces other optic diseases, such as myopia (near-sightedness) and hyperopia (farsightedness). These vision conditions affect the eyes when retracting light.
Causes of Astigmatism
The reasons behind astigmatism remain unknown. Sometimes, it is a hereditary disease, present from birth. The severity of the condition can increase or decrease over time. According to the comprehensive optometric examination, eye tests can be done to detect astigmatism. According to the diagnosis, the optometrist may suggest eyeglasses or contact lenses, which are useful in overcoming the disease and correcting vision over time. The patient has to wear the glasses or lenses regularly to correct the astigmatism and adjust the light when it enters the eyes.
Another way of treating astigmatism is to have a corneal procedure called orthokeratology. The procedure is painless and non-aggressive. Specially designed, highly rigid contact lenses can aid the patient. Theses lenses help shape the curvature of the cornea effectively and gradually reduce the astigmatism.
Laser surgery is also an advanced technique that is highly popular today and preferred by doctors. The surgery minimizes the corneal problems within a short period of time. The laser technique changes the shape of the cornea either by removing a small amount of eye tissue or by rectifying the problem area.
Use of Phoropter
The optometrist diagnoses astigmatism by testing the eye through a comprehensive eye examination. The test checks for the focus of light in the eyes as well as the power of the optical lenses required to overcome the vision problem. Various techniques used are:
- Visual acuity: Reading a chart placed on the wall measures visual acuity. Visual acuity is measured in terms of fraction, and it indicates the power required for the eyes to have clear vision.
- Refraction: Use of an instrument called a phoropter helps the optometrist by placing a set of lenses over the eyes and measuring the required focus for clarity.