Astigmatism

Astigmatism

An optical defect in which the vision gets blurred is known as astigmatism. Here, the person who suffers from this condition is unable to focus due to the irregular curvature of the cornea. It is a kind of refractive error.

According to the experts, astigmatism is a very common eye condition. In fact, they say that each one of us is born with a degree of astigmatism. However, children may not realise this defect until there is a problem is reading or seeing distant objects. Hence, doctors recommend regular eye-tests or eye-check-ups from a very young age.  

According to a recent study in Bangladesh, nearly 30-35% of adults over the age of 30 years suffer from astigmatism. And according to an American study around 28% of children in the age group of 5 to 17 years have astigmatism. A number of medical studies have shown that astigmatism only increases with the age.

Types of astigmatism:
There are two types of astigmatism:
Regular astigmatism: It arises from either the cornea of the eye or the crystalline lens. It can be corrected with the help of a toric lens.
Irregular astigmatism: It causes due by corneal scar or scattering in the crystalline lens. It cannot be corrected with the help of a standard spectacle lenses. However, wearing contact lenses can correct the condition.

Signs and symptoms:
Mild astigmatism may hardly show any symptoms. If you are suffering from astigmatism which is slightly on the severe/higher side, you may experience following symptoms:

  • Headache
  • Sensitivity to light
  • Blurred vision or distorted vision at all distances
  • Problem in focusing for long periods
  • Constant blinking of eyes
  • Squinting

Causes:
The causes that lead to astigmatism are:

  • Astigmatism can be hereditary, and can be congenital (right from the birth)
  • Incorrect posture
  • Incorrect reading habits
  • Pressure from eyelids to cornea
  • Excessive use of eyes or strenuous use of eyes due to work.

Diagnosis:
If you are suffering from the symptoms mentioned above, you need to consult an eye-specialist, ophthalmologist or optometrist. Your eye-specialist may diagnose your condition after examining your eyes through these tests:

Astigmatic dial: In this test, the patient will be shown a chart wherein a series of lines form a semi-circle. Those who have perfect/ normal vision will see all the lines clearly. But, those suffering from astigmatism may see few line clearly, while few of them will appear blurred or hazy.

Visual acuity test: Here, patient will have to read out the letters mentioned on the chart. The condition is, that the size of the letter will get smaller with each passing line. The test is how clearly visible is it to the patient.

Keratometer: This testing device also known as opthalmometre is used to measure the amount of light reflected from the surface of the cornea. It measures the radius of the curvature of the cornea and can assess the degree of abnormal curvature of the cornea.

Keratoscope: This device is marked with circles and lines, and observes the reflex of the cornea. It calculates the variations of curvature, by measuring the spacing between the rings. This in turn, calculates the degree of astigmatism. This device is also known as Placido’s disk. A videokeratoscope is a keratoscope fitted with a video.

Treatment:
The doctors may provide contact lenses to the patient to rectify the eyesight. There are various types of contact lenses, and hence, it is important for the doctor to examine the eyes and condition, and suggest the right kind of lenses. However, if the patient is not comfortable with the lenses, he/she may undergo laser eye surgery for a better eyesight. However, laser eye surgery cannot be done under the following circumstances:

  • If the vision is still changing
  • If the patient suffers from diabetes
  • If the patient is under the age of 21 years
  • Pregnant women of breast-feeding mothers

On an average, a person blinks about 25,000 times a day. If we total up the blinking of eyes per day, it comes up to 30 minutes with closed eyes. It is more in case of women, as they have a tendency to blink twice as much as men do.