ASTIGMATISM - Watsons Health

ASTIGMATISM

Astigmatism is a common eye condition causing blurring or distorted vision.

It occurs when the cornea or lens isn’t perfectly curved. Many people who wear glasses have some degree of astigmatism.

Astigmatism belongs to a group of related eye conditions known as refractive errors. Other common refractive errors include:

  • short-sightedness (myopia)
  • long-sightedness (hypermetropia)

Astigmatism usually occurs in combination with the previously mentioned conditions.

Astigmatism may cause headaches, eye strain and fatigue (tiredness), particularly after doing tasks that require focusing for long periods, such as reading or using a computer.

What causes astigmatism?

Astigmatism is usually the result of an irregular-shaped cornea or lens. The cornea is the transparent layer of tissue at the front of the eye, while the lens is a biconcave structure behind the iris. The cornea and the lens are responsible for refracting light entering the eye. Light is bent to be focused on the retina or the back of the eye.

The cornea should be regularly curved like the surface of a football, but in cases of astigmatism it has an irregular curve, more like the shape of a rugby ball. This means that light rays entering the eye aren’t focused properly, creating a blurred image.

In most cases, astigmatism is present at birth. However, it sometimes develops after an eye injury or as a complication of an eye operation.

Types of astigmatism

There are two types of astigmatism – regular and irregular.

Regular astigmatism is where the cornea is curved more in one direction than the other. It’s more common than irregular astigmatism and can be corrected with glasses or contact lenses.

Irregular astigmatism is where the curvature of the cornea isn’t even across the surface of the eye. Instead of being curved mostly in one direction, it could be curved in multiple directions, or the curve could be steeper towards the bottom.

Irregular astigmatism is often the result of an eye injury that causes a scar to develop on the cornea. It can’t be corrected with glasses, but it can be corrected with contact lenses.

Diagnosing astigmatism

The diagnosis of astigmatism can be done after a routine eye examination wherein a series of test will be performed, such as the visual acuity test, refraction and even keratometry.

It’s very important to have regular eye tests because astigmatism sometimes goes undiagnosed for years, and it can affect the ability to read and concentrate.

 

Treating astigmatism 

In many cases, the symptoms of astigmatism are so mild that treatment to correct vision isn’t required.

Treatment, when necessary, will depend  on the type of astigmatism you have (regular or irregular). Options usually include corrective lenses (glasses or contact lenses) or laser eye surgery.

Corrective lenses

Corrective lenses work by compensating for the irregular curve of the cornea so incoming light passing through the corrective lens is properly focused on to the retina. The retina is the light-sensitive layer of tissue at the back of the eye.

Glasses and contact lenses are usually equally effective at treating astigmatism. The type of corrective lenses used will depend on personal preference and the advise from the optometrist.

There’s no medical reason why children can’t wear contact lenses, although the opinion of your optometrist will be important in deciding if they’re suitable. Most children over 12 years of age will be able to wear them.

However, the importance of the correct use of lenses should be emphasized. Instructions related to its use, such as the length of time they can be kept in and care should be strictly followed.

If contact lenses are used, it’s important to ensure good lens hygiene to prevent eye infections.

Laser eye surgery

Laser surgery involves using lasers (narrow beams of light) to remould the tissue of the cornea to change its curve.

Medical consult with an ophthalmologist is done for evaluation and preparation for the procedure.

During laser surgery, the outer layer of cells of the corneal surface is removed. A laser is then used to remove tissue and reshape the cornea. The treatment usually takes 20 to 30 minutes.

There are a number of different techniques used for laser surgery. The pros and cons of each technique will be discussed, including any risks involved. The risks of complications associated with eye surgery are low.

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