Astigmatism

Astigmatism

Astigmatism is visual impairment due to abnormalities in the curvature of the cornea or lens of the eye. This condition causes blurred or distorted vision, both at close and far distances.

Astigmatism or astigmatism can occur together with farsightedness (hyperopia) or farsightedness (myopia). Generally, abnormalities in the curvature of the eye that cause astigmatism have occurred since birth. However, injury or surgery to the eye can also cause this disorder.

Based on the location of the abnormality, astigmatism is divided into two types, namely:

  • Corneal astigmatism, which is astigmatism due to abnormalities in the curvature of the cornea
  • Lenticular astigmatism, which is astigmatism due to abnormalities in the curvature of the eye lens

Causes and Risk Factors of Astigmatism

Astigmatism is caused by an abnormality in the curvature of the cornea or lens of the eye. It is not known what triggers the disorder, but this condition is thought to be related to heredity.

Cornea and lens are parts of the eye that function to refract and transmit light to the retina. In an eye that has astigmatism, the incoming light is not completely refracted so that the resulting image is out of focus or tilted.

Astigmatism can happen to anyone. However, there are several other conditions that can increase the risk of astigmatism, namely:

  • Nearsightedness or severe farsightedness
  • Family history of astigmatism or other eye disorders, such as keratoconus (corneal degeneration).
  • History of eye injury or eye surgery, such as cataract surgery
  • Thinning of the lining of the cornea or the formation of scar tissue on the cornea

Astigmatism Symptoms

In some cases, astigmatism causes no symptoms at all. If there are symptoms, the complaints experienced by sufferers can vary, including:

  • Distortion of vision, for example straight lines become oblique
  • Blurred vision (faint) or out of focus
  • Difficult to see at night
  • Eyes get tired easily and feel uncomfortable
  • Often squint when looking at something
  • Irritation to the eyes
  • Headache

When to see a doctor

Check with your eye doctor if you or your child experience the above complaints, especially if these complaints interfere with daily activities, such as reading or driving.

Astigmatism Diagnosis

To diagnose astigmatism and determine its size, an ophthalmologist will need to perform a thorough eye exam and a cylindrical eye test , including:

Visual acuity test

In a visual acuity test, the doctor will ask the patient to read a series of letters in various sizes from a distance of 6 meters.

Refraction test

This examination consists of several series of tests. The doctor will examine the form of light that enters and receives the retina to determine whether the patient has refractive errors nearsightedness, farsightedness, astigmatism, or a combination of these.

The refraction test can be done with a simple instrument called a retinoscope or with an automatic machine. If a refractive error is found, the doctor will determine the size of the refractive error.

Astigmatism is measured on the diopter scale. A healthy eye without astigmatism has an astigmatism diopter of 0. However, in most people, an astigmatism diopter number between 0.5–0.75 causes no complaints.

Diopter measurements are performed by asking the patient to read a series of letters through a lensed device called a phoroptor . If the patient cannot see the letters clearly, the lens size will be changed until the letters can be read perfectly.

Keratometry

Keratometry is a procedure to measure the curvature of the cornea of ​​the eye using a tool called a keratometer. In addition to determining the diagnosis, this examination tool can also be used to determine the right contact lens size.

Corneal topography

This examination functions the same as keratometry, but is carried out with more sophisticated and precise tools. Usually, this examination is done if the doctor plans surgery to treat astigmatism.

Astigmatism Treatment

Handling of astigmatism or cylindrical eyes depends on the patient's diopter scale. Patients with mild astigmatism and no visual impairment may not require any treatment.

In patients with diopters above 1.5, doctors will generally recommend using glasses or contact lenses. The size of the glasses or contact lenses is determined from the results of the refraction test.

However, if the patient wants other treatment methods, refractive surgery may be an option. Several surgical methods that can be used to treat astigmatism are:

Laser-assisted in situ keratomileusis (LASIK)

LASIK is a procedure to reshape the cornea using a laser. The goal is to correct the focus of light onto the retina.

Laser-assisted subepithelial keratectomy (LASEK)

In the LASEK procedure, the surgeon loosens the outer layer of the cornea (epithelium) with special alcohol and then reshapes the cornea using a laser. After that, the epithelium will be tightened again as before.

Photorefractive keratectomy (PRK)

The PRK procedure is the same as LASEK. The difference is, during the PRK procedure, the epithelium will be removed. The epithelium will re-form naturally following the new corneal curvature.

Small-incision lenticule extraction (SMILE)

In astigmatism accompanied by mild nearsightedness, the doctor can run a SMILE to correct the shape of the cornea. This procedure is performed by using a laser to make a disc-shaped cut ( lenticule ) under the surface of the cornea and remove it through a small incision.

Astigmatism complications

Astigmatism that occurs in only one eye from birth can trigger amblyopia or what is commonly known as lazy eye . This condition occurs because the brain is used to ignoring the signals sent by the eye.

Amblyopia can be treated with an eye patch if it is detected before the visual pathways in the brain are fully developed.

Another complication that can occur due to astigmatism is keratoconus, which is a condition when the cornea thins and protrudes like a cone. Keratoconus can cause blurred vision. In fact, this condition can cause blindness if left unchecked.

Astigmatism Prevention

As explained above, astigmatism can cause blurred vision. In adult patients, this complaint may be easily recognized, but not in patients with infants and children. Therefore, eye examinations need to be carried out on newborns and continued periodically. The recommended schedule is:

  • Age 65 years: every 2 years
  • Age 65 years: once a year
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