What is Astigmatism? Symptoms, Types and Treatment

Astigmatism is a vision problem caused by an irregular curvature of the cornea or lens. Refractive defects such as myopia and hypermetropia are considered. As with the others, the light fails to focus where it should on the retina.

Depending on the type of astigmatism, light can be focused in front of or behind the retina. So, people with astigmatism cannot see clearly near or far, depending on the area where the light falls on the retina.

Astigmatism is derived from the combination of the Greek prefix "a" meaning "deprivation" and "stigma" meaning "point". The origin of the word means that there is no focal point in the Greek language. It is an eye problem characterized by blurred vision for far or near vision or both.

What are the Symptoms of Astigmatism?

• Blurred vision at near, far and medium distance, distortions in different points of the field of vision;
• A feeling of eye fatigue after reading or visual activities that require attention;
• Headache;
• Advanced double vision and strabismus;
• Difficulty driving at night;
• Desire to squint to see clearly;
• Frequent squinting in the eye

Symptoms of Astigmatism in Children

Symptoms of astigmatism in children may go undetected because your child may not be aware of the condition or may not show it. That's why routine eye exams in children are so important. However, some symptoms of astigmatism may make the family suspicious.

Symptoms of astigmatism in children can be listed as follows:

Eye strain;

Tilting the child's head to the side;

Rubbing his eyes;

Squinting or closing one eye;

Sensitivity to light;

Nausea and headaches.

Astigmatism, especially in one eye, is one of the most important causes of lazy eye in children. Therefore, children should be examined before the age of 4.

How do Those with Astigmatism See?

They see the objects and shapes they are looking at as elongated and diffusely blurred. At night, they also see light rays on the edges of illuminated objects.

What Causes Astigmatism?

It is usually congenital. However, it can also occur after various eye surgeries and due to eye injuries. Another cause may be keratoconus, a disease in which the cornea gradually thins. It is a less common refractive error compared to myopia and hypermetropia. As with myopia and hyperopia, various visual activities, such as reading in low light or watching TV closely, do not show improvement.

The normal cornea and the lens have a surface curvature proportional to each other. If the cornea is elliptical rather than round, the diameters of the crystal and the cornea are not equal. Because of this, the light entering the eye cannot be refracted properly and two different images are formed on the retina. These two different images overlap on the retina, resulting in blurred vision for both near and far objects.

Degrees of Astigmatism

Degrees of astigmatism can vary from 0.25 to 6.0 degrees. There is no need to use glasses in the case of 0.25 - 0.50 degrees of astigmatism. At this time, the symptoms are very mild.

However, people with astigmatism between 1.00 and 4.00 also have nearsightedness or farsightedness. In this case, glasses should be used. People with astigmatism above 4.00 must wear glasses. If necessary, surgery can be done.

Types of Astigmatism

There are several different types of astigmatism:

Corneal Astigmatism is the most common type and is caused by an abnormal curvature of the cornea. Curvature can occur on the front or back surface of the cornea.

In case of lenticular astigmatism, the surface of the crystal becomes uneven and bumpy. Under normal conditions, the crystal is located behind the pupil and ensures that the image is formed on the retina. However, if there is curvature in it, the image does not focus properly on the retina. As a result, the image becomes blurry.

In addition to the above, astigmatism has various subtypes such as myopic astigmatism and hyperopic astigmatism.

How is Astigmatism Detected? Astigmatism Test

It is detected during a detailed examination by an ophthalmologist. An astigmatism test is done to determine the size of optical material needed by measuring the ability of the eyes to focus light. The following tests and examinations are used during this appointment.

At the first stage of the diagnosis and treatment procedure, a visual acuity test is applied. During the test, the person is required to read certain letters and symbols from a distance of 20 feet. As the value in the table decreases, so does the visual acuity.

With the help of a phoropter, the ophthalmologist places a series of lenses in front of the patient's eyes and measures how the eyes focus on light. The measurement is done with the help of a device called a retinoscope. Various letters and symbols are shown to the patient and the degree of astigmatism is calculated according to their answers.

How is Astigmatism Treated?

Treatment may not be necessary for very mild astigmatism. However, if the astigmatism is severe, the use of glasses or contact lenses will be necessary. In some cases, laser surgery may also be required.

Common treatments for astigmatism include:

Eyeglasses: The main treatment for astigmatism is the use of glasses. The goal is to correct vision using glasses.

Contact lens: Some patients may be more comfortable wearing contact lenses. It may also be preferred by some people as it does not weigh down the face like glasses. However, contact lenses should be used more carefully than glasses. Since the lenses are in direct contact with the eyes, they must be handled with care.

Orthokeratology: This method aims to change the shape of the cornea. This is achieved by using a series of rigid contact lenses. These lenses must be worn for a certain amount of time every day, often at night. People with moderate astigmatism can easily see their surroundings without lenses, albeit temporarily. However, this is not a permanent solution. When the lens is stopped, the vision returns to its previous state.

Laser Surgery: The goal of laser surgery is to reshape the cornea. There are two methods: LASIK and PRK. The goal of both methods is to treat the eye defect. This is achieved by removing tissue from the layers of the cornea. PRK is a more complicated procedure than LASIK. It is applied to patients with a thin cornea.