What is astigmatism?

Astigmatism is a vision problem that results due to abnormal curvature of the eye's cornea or lens.
Astigmatism is a vision problem that results due to abnormal curvature of the eye's cornea or lens.

Astigmatism is a type of vision problem due to imperfection in the curvature of the eye's cornea or lens. Hence, the cornea is unable to evenly focus light on the retina (the inner light-sensitive layer of the eye). Those with astigmatism typically have blurred or distorted vision, eye strain and headachesAstigmatism can coexist in combination with other refractive errors, such as myopia (nearsightedness) and hypermetropia (farsightedness).

What are the signs and symptoms of astigmatism?

Signs and symptoms of astigmatism may include

  • Blurred or distorted vision
  • Eyestrain
  • Squinting
  • Headaches
  • Decreased vision at night

Children and adolescents

Young children may not realize their vision is blurry, so a regular eye test is required. School-aged children may have difficulty reading, writing or seeing the blackboard/whiteboard.

What causes astigmatism?

The eye has two curved structures, the cornea and the lens. The cornea is the clear layer on the outer surface of the eye. The lens is a clear structure inside the eye that helps focus light for clear vision. The cornea and lens bend (refract) and focus light on the retina, which makes the images required for vision. In a normal eye, these curved structures are smooth so they can create sharp vision. In astigmatism, the surface of the cornea or lens is not smooth. If either the cornea (corneal astigmatism) or the lens (lenticular astigmatism) is shaped differently, then these mismatched curves bend the light rays at different angles, forming two different images. This results in distorted or blurred vision. Astigmatism is a type of refractive error. The blurred vision may occur in different directions - vertically, horizontally or diagonally.

Astigmatism is usually present from birth, which could be due to genetic predisposition. It can also develop after any eye trauma, disease or surgery. Astigmatism is not caused or worsened by reading in the dark, watching TV for too long or squinting.

How is astigmatism diagnosed?

An eye doctor (ophthalmologist) diagnoses astigmatism by performing a complete eye examination with the help of various kinds of diagnostic equipment.

What is the best way to correct astigmatism?

The goal of treating astigmatism is to improve vision and eye comfort. Treatments options are corrective lenses or refractive surgery.

Corrective lenses

Wearing corrective lenses is the simplest way to treat astigmatism by counteracting uneven curvatures of the cornea or lens. Corrective lenses may be worn as eyeglasses or contact lenses.

Refractive surgery

Refractive surgery improves vision and replaces the need to wear eyeglasses or contact lenses. Types of refractive surgery for astigmatism include

  • Laser-assisted in situ keratomileusis (LASIK): The eye surgeon creates a thin flap in the cornea. An excimer laser is then used to change the shape of the cornea. The flap is then repositioned.
  • Laser-assisted subepithelial keratectomy (LASEK): Instead of creating a flap, the cornea is loosened using alcohol. A laser is then used to alter the curvature of the cornea and then the loosened epithelium is repositioned.
  • Photorefractive keratectomy (PRK): The epithelium is removed and allowed to grow back naturally, according to the cornea's new shape.
  • Epi-LASIK: This is similar to LASEK, but this uses a mechanized blunt blade instead of the alcohol to loosen the cornea.
  • Small incision lenticule extraction (SMILE): This is a newer type of refractive surgery that reshapes the cornea by using a laser.

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What are the complications of surgery for astigmatism?

The surgeries are relatively safe. Some of the possible complications that may occur after refractive surgery are

  • Under correction or overcorrection of the initial refractive error
  • Appearance of halos or starbursts around lights
  • Dry eyes
  • Eye infection
  • Scarring
  • Vision loss

Can astigmatism be prevented?

Astigmatism is usually present from birth, which could be genetic or may develop after any eye trauma, disease or surgery. Astigmatism is not caused or worsened by reading in the dark or poor lighting; watching TV or other screens for too long; sitting too close to the screen or squinting.

Maintaining a healthy, nutritious diet, avoiding excessive screen time or straining the eyes and protecting the eyes from pollution and injuries can maintain overall eye health. However, there are no specific preventive measures for astigmatism.

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Medically Reviewed on 9/25/2020
References
Medscape Medical Reference

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