Astigmatism

 

Astigmastism

Definition

Astigmatism is a vision disorder, not a disease.

Astigmatism is a common type of refractive error. It is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye.

Source : National Eye Institute

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Symptoms

Astigmatism makes it difficult to see fine details, either close up or from a distance.

Source : Medline Plus 

 

Frequency

Astigmatism can affect both children and adults. Some patients with slight astigmatism will not notice much change in their vision. It is important to have eye examinations at regular intervals in order to detect any astigmatism early on for children.

Source : National Eye Institute 

Astigmatism often occurs early in life, so it is important to schedule an eye exam for your child to avoid vision problems in school from uncorrected astigmatism.

In a recent study of 2,523 American children ages 5 to 17 years, more than 28 percent had astigmatism of 1.0 diopter (D) or greater.

Also, there were significant differences in astigmatism prevalence based on ethnicity. Asian and Hispanic children had the highest prevalences (33.6 and 36.9 percent, respectively), followed by whites (26.4 percent) and African-Americans (20.0 percent).

In another study of more than 11,000 eyeglass wearers in the UK (both children and adults), 47.4 percent had astigmatism of 0.75 D or greater in at least one eye, and 24.1 percent had this amount of astigmatism in both eyes. The prevalence of myopic astigmatism (31.7 percent) was approximately double that of hyperopic astigmatism (15.7 percent).

Source : All About Vision

 

Causes

Astigmatism is usually caused by an irregularly shaped cornea. Instead of the cornea having a symmetrically round shape (like a baseball), it is shaped more like a football, with one meridian being significantly more curved than the meridian perpendicular to it.

(To understand what meridians are, think of the front of the eye like the face of a clock. A line connecting the 12 and 6 is one meridian; a line connecting the 3 and 9 is another.)

The steepest and flattest meridians of an eye with astigmatism are called the principal meridians

In some cases, astigmatism is caused by the shape of the lens inside the eye. This is called lenticular astigmatism, to differentiate it from the more common corneal astigmatism.

Source : All About Vision

 

Evolution

Astigmatism may change with time, requiring new glasses or contact lenses. Laser vision correction can usually eliminate, or greatly reduce, astigmatism.

Source : Medline Plus 

 

Diagnosis

Astigmatism is usually found during a comprehensive dilated eye exam. Being aware of any changes in your vision is important. It can help in detecting any common vision problems. If you notice any changes in your vision, visit your eye care professional for a comprehensive eye dilated examination.

Source : National Eye Institute 

 

Treatment

Astigmatism can be corrected with eyeglasses, contact lenses, or surgery. Individual lifestyles affect the way astigmatism is treated.

Eyeglasses are the simplest and safest way to correct astigmatism. Your eye care professional will prescribe appropriate lenses to help you see as clearly as possible.

Contact Lenses work by becoming the first refractive surface for light rays entering the eye, causing a more precise refraction or focus. In many cases, contact lenses provide clearer vision, a wider field of vision, and greater comfort. They are a safe and effective option if fitted and used properly. However, contact lenses are not right for everyone. Discuss this with your eye care professional.

Refractive Surgery aims to change the shape of the cornea permanently. This change in eye shape restores the focusing power of the eye by allowing the light rays to focus precisely on the retina for improved vision. There are many types of refractive surgeries. Your eye care professional can help you decide if surgery is an option for you.

Source : National Eye Institute

 

Images

Blur from astigmatic lens at different distances

Astigmatism text blur

Source : Tallfred at English Wikipedia Português: , via Wikimedia Commons  

 

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