Astigmatism 101

WHAT IS ASTIGMATISM?

Astigmatism is a visual problem that is characterized by unequal curvature of the cornea and lens of the eye. The lens and cornea are located on the front surface of the eye. This unequal curving alters the way light passes to the retina, the inner surface of the eye. The resultant effect is visual blurring, fuzziness, or distorted vision. Other problems that affect the way by which light passes to the retina are myopia and hypermetropia. Myopia is shortsightedness while hypermetropia is long-sightedness.

TYPES OF ASTIGMATISM

This condition can either be corneal astigmatism or lenticular astigmatism. When the irregular shape is on the cornea, it is called corneal astigmatism and lenticular astigmatism when the lens is abnormally curved.

CAUSES OF ASTIGMATISM

The exact cause of astigmatism remains unknown but genetic factors have been known to play a role. It is sometimes present at birth (congenital) and other times, develops later in life. It can also occur following trauma to the eye or after eye surgery. This condition often occurs in combination with either shortsightedness or long-sightedness.

RISK FACTORS FOR ASTIGMATISM

Astigmatism occurs in both children and adults but the chances of it occurring are more if you have any of the following:

  • Family history of astigmatism or other eye conditions such as corneal degeneration
  • Corneal scarring or thinning
  • Excessive shortsightedness which leads to blurry far vision
  • Excessive long-sightedness which leads to blurry near vision
  • Past history of eye surgery such as cataract surgery

SYMPTOMS OF ASTIGMATISM

The symptoms of astigmatism are not the same for everyone. Some people may even be asymptomatic. The symptoms that can be seen in this condition include:

  • Blurry or fuzzy vision whether far or close
  • Impaired night vision
  • Straining of the eye to see
  • Squinting
  • Eye irritation
  • Headaches

If you have any of these symptoms, see a doctor. Some of these symptoms may be for other eye conditions and not necessarily astigmatism.

DIAGNOSIS OF ASTIGMATISM

A comprehensive eye examination is carried out by an optometrist or ophthalmologist before a diagnosis can be made. An optometrist is an eye doctor that makes a diagnosis of eye problems and diseases while an ophthalmologist is a medical doctor that specializes in the medical and surgical treatment of visual conditions and eye problems. There are many tests that are employed by optometrists and ophthalmologists during an eye examination to diagnose astigmatism and they include:

Visual acuity assessment test

Here, a chart is placed ideally at 6 meters distance and you are asked to read letters from it. This is to determine how well you can visualize the letters.

Refraction test

Here, an optical refractor is used and it has numerous corrective glass lenses of different powers. The doctor will ask you to read through a chart with different lenses on the optical refractor to determine which one is clearer. The clearer one is that which will adequately correct your vision.

Keratometry

This is a measurement of the curvature of the cornea using a keratometer.

TREATMENT OF ASTIGMATISM

Less severe cases may not need treatment. When this condition causes visual problems, the following modalities of treatment can be instituted:

Corrective lenses

The doctor can prescribe corrective lenses or contact lenses for use. These are the commonest and least invasive modalities of treatment.

Orthokeratology

This method makes use of rigid contact lenses which are worn for limited periods of time. It only corrects the unequal curvature temporarily. You may put them on during sleep and remove them during the day. Some people have clearer vision during the day when undergoing orthokeratology even without putting on corrective lenses. As it is temporary, the benefits of using this method are only seen when using it and it stops after you stop orthokeratology.

Surgery

If your case of astigmatism is very severe, the doctor may recommend refractive surgery. Refractive surgery makes use of lasers or tiny knives to reshape the cornea. It is a permanent correction for this condition. The 3 common surgeries for this condition are:

  • Laser in situ keratomileuses (LASIK)
  • Photorefractive keratectomy (PRK)
  • Radial keratotomy (RK)

All of these surgeries are associated with risks. Your doctor will talk to you about the risks and benefits before undergoing surgery for this condition.

COMPLICATIONS OF ASTIGMATISM

 Lazy eye results when astigmatism in one eye is left uncorrected. The medical term for lazy eye is amblyopia.

LONG TERM OUTLOOK

Vision can be restored to normal using corrective lenses or surgery. There is no known prevention of this condition for now.  

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