Definition

Astigmatism, also known as cylindrical vision, is an imperfection in the curvature of the cornea or lens of the eye that causes vision to be blurred or distorted at any distance. This condition is part of refractive or light-bending errors in the eye, grouped with nearsightedness (myopia) and farsightedness (hypermetropia). Generally, astigmatism can be managed effectively.

Globally, the highest prevalence of astigmatism is found in adults in Southeast Asia. A study found that approximately 14.9% of all children and 40.4% of all adults worldwide have astigmatism. In Southeast Asia, around 9.8% of all children and 44.8% of all adults have astigmatism.

Causes

A normal eye has a cornea and lens that can be likened to a glass ball with an even curvature, allowing light to be refracted properly to form a clear image on the retina. However, in astigmatism, one of the cornea or lens is shaped more like an egg, creating different curvatures. This difference in curvature causes uneven light refraction, forming two images on the retina. These two images overlap, causing vision to become blurred. This blurred vision can occur in horizontal, vertical, or diagonal directions.

Risk factor

Astigmatism can occur from birth or develop later in childhood or adulthood. This condition can also develop after injury, disease, or eye surgery. Additionally, astigmatism can be inherited from parents to their children. This shows that everyone has unique shapes and curvatures of their corneas and lenses, and some people have curvature differences that cause astigmatism. However, myths such as astigmatism caused by reading in the dark or watching TV too closely are untrue.

Symptoms

Children with astigmatism may not realize their symptoms. Therefore, regularly checking children's eyes is important to detect any refractive errors early. This checkup should start early to be corrected with glasses as soon as possible.

Meanwhile, older children or adults typically report blurred or distorted vision. The distortion can appear like a curved mirror making you look fatter or thinner, too tall or too short. Other complaints may include eye strain, headaches, difficulty seeing at night, and squinting to see more clearly.

However, these symptoms do not confirm the presence of astigmatism. If you or your child experience these symptoms, it is recommended that you see an eye doctor.

Diagnosis

Astigmatism can be diagnosed by an ophthalmologist or a general doctor. The doctor will first test your visual acuity using a Snellen chart, asking you to read letters at a specific distance. This test determines your visual acuity. Next, the doctor will ask you to look at lines arranged like a clock and determine at which hour or degree your vision is most blurred.

This test can be done using trial lenses to determine the strength of glasses you need. Besides trial lenses, the following tools can also be used:

• Phoropter: Helps determine the shape of corrective lenses by asking you to look through several lenses and choose the clearest one.
• Autorefractor: Measures the lens strength needed by shining light into your eye and measuring changes in the reflected light.
• Keratometer or Corneal Topography: Measures the curvature of your cornea to see the surface shape.

Management

Astigmatism can be treated with corrective lenses or surgery. Corrective lenses for astigmatism can be glasses or contact lenses. For glasses, cylindrical lenses are used. Contact lenses can be an alternative, including rigid contact lenses in orthokeratology. These are worn during sleep to reshape the eye's curvature temporarily. To maintain the shape, these lenses need to be worn periodically. However, the eye's curvature will return if not worn, causing astigmatism again. It is also important to note the risk of infection from prolonged contact lens use, requiring regular cleaning.

Another alternative is surgery. LASIK (laser-assisted in-situ keratomileusis) involves creating a small flap in the cornea to reshape it with a laser. Other procedures include LASEK (laser-assisted subepithelial keratectomy), which loosens the corneal epithelial cells with alcohol before reshaping with a laser, and PRK (photorefractive keratectomy), which removes the epithelial layer to reshape the cornea. After PRK, the epithelial layer will naturally regrow following the new corneal shape. Special contact lenses are needed after PRK.

All treatment options should be discussed with your eye doctor.

Complications

Complications of astigmatism, like other refractive errors, include amblyopia or "lazy eye." Amblyopia is characterized by blurred vision in an eye that is physically normal or has been corrected. This issue arises from the lack or inadequate transmission of visual images to the brain for a long period during early life. One risk factor for amblyopia is uncorrected childhood astigmatism. If you have amblyopia, you should always wear glasses to see clearly.

Prevention

Astigmatism cannot be prevented but can be detected early. Screening for astigmatism can be done for children, especially at the following times:

• Newborn to the first year of life: Astigmatism above 1 diopter occurs in 50% of cases, requiring regular checkups to ensure normal vision development by ages 3-9 months.
• During growth and development checkups: Approximately every 3-6 months.
• Before starting school
• If already in school: Every 1-2 years or following the school's examination schedule.

When to see a doctor?

If you experience blurred vision that interferes with daily activities, you should visit a general doctor or ophthalmologist. The doctor will check your vision; if you have astigmatism, they will determine its degree. You can then discuss treatment options suitable for you.

Children often do not complain of blurred vision, but other signs may include:

• Frequent headaches
• Eye strain, especially after reading
• Squinting or tilting the head to see better
• Closing one eye when reading, watching TV, or looking at objects
• Frequently closing eyes due to glare in well-lit areas

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