Astigmatism is a common eye condition that causes blurred vision. The condition can be hereditary and is usually already present since birth. It can also increase or decrease over time. It commonly occurs together with other vision conditions such as nearsightedness (myopia) and farsightedness (hyperopia). Collectively, these conditions are known as refractive errors because they affect how light is ‘refracted’ or bent in the eye.
Many people have some form of astigmatism. However, mild astigmatism normally does not affect vision, and treatment is not necessary.The symptoms of astigmatism include blurred and distorted vision, eye strain, squinting and headaches.
Astigmatism occurs when the cornea, which is the clear front cover of the eye, is shaped irregularly. Sometimes, it is caused by the curvature of the lens inside the eye. The imperfect curvature of the cornea causes a refractive error. Consequently, the light rays are not properly reflected back onto the light-sensitive retina at the back of the eye. This results in blurred and distorted vision.
Correction of Astigmatism
There is a wide range of options available to correct astigmatism. They include eyeglasses, contact lenses, orthokeratology, laser and other refractive surgery procedures.
To correct their blurred vision, people with astigmatism commonly choose to wear eyeglasses, which contain a special cylindrical lens prescription. This compensates for the astigmatism, by providing additional power in specific parts of the lens. Usually, a single-vision lens is prescribed. This will provide clear vision at all distances. However, people who are over age 40 who have presbyopia may need a bifocal or progressive addition lens.
2. Contact Lenses
People with astigmatism may also wear contact lenses. For some people, contact lenses can provide clearer vision and a wider field of view, compared to eyeglasses. However, the contact lenses need to be cleaned regularly to safeguard eye health. Nonetheless, you must be aware that not all types can be used to correct astigmatism. Special toric soft contact lenses can be used to correct many types of astigmatism, but standard soft lenses may not be effective for this purpose.
Meanwhile, rigid gas-permeable contact lenses can compensate for the cornea’s irregular shape because they can maintain their regular shape while on the cornea. Therefore, they can be used to improve vision for people with astigmatism.
Orthokeratology (ortho-k)requires the fitting of a series of rigid contact lenses in order to reshape the cornea. The patient will be required to wear contact lenses for limited periods of time, such as overnight. After that, they are removed. Those with moderate astigmatism may temporarily have clear vision without lenses for most of their daily activities. However, if the patient stops wearing the retainer lenses, their vision may return to its prior condition.
4. Laser and Other Refractive Surgery Procedures
Laser surgery can also be used to treat some types of astigmatism. LASIK (laser in situ keratomileusis) or PRK (photorefractive keratectomy) can help to correct astigmatism by reshaping the cornea. The difference between the two is LASIK removes only tissue from the inner layer of the cornea, whereas PRK removes tissue from the superficial and inner layers of the cornea.