Astigmatism — Know It All!

Editorial

All you need to know about Astigmatism.

Know your ailment well, so you can manage it better!!

Here we come with Astigmatism today!

What is Astigmatism?

Astigmatism is a condition in which your eye isn’t completely round.

Ideally, an eyeball is shaped like a perfectly round ball. Light comes into it and bends evenly, which gives you a clear view. But if your eye is shaped more like a football, light gets bent more in one direction than another. That means only part of an object is in focus. Things at a distance may look blurry and wavy.

It’s common to have astigmatism along with nearsightedness (myopia) or farsightedness (hyperopia). These three conditions are called refractive errors because they involve how your eyes bend (refract) light.Astigmatism is fairly easy for an eye doctor to fix with glasses, contacts, or surgery.

What causes Astigmatism?

Your eye has two curved surface structures that bend (refract) light onto the retina, which produces the images:

The cornea, your eye’s clear front surface, along with the tear film

The lens, a clear structure that changes shape inside your eye to help concentrate on near objects

Each of these elements has a round curvature within a perfectly shaped eye, like the surface of a smooth ball. To make a sharply focused image directly on the retina at the back of your eye, a cornea and lens with such curvature bend (refract) all incoming light equally.

A refractive error

If either your cornea or lens has two mismatched curves in the shape of an egg, light rays aren’t bent the same, forming two different images. Both of these images overlap or combine and lead to blurred vision. A type of refractive error is astigmatism.

When your cornea or lens is curved more steeply in one direction than in another, astigmatism occurs. If the cornea has mismatched curves, you have corneal astigmatism. When your lens has mismatched curves, you have lenticular astigmatism.

Blurred vision can be caused by either type of astigmatism. Blurred vision, horizontally, vertically or diagonally, can occur in more than one direction.

Astigmatism can be present from birth, or after an eye injury, illness, or surgery, it can develop. Astigmatism isn’t caused or made worse by reading in poor light, sitting too close to the television or squinting.

Other refractive errors

Astigmatism may occur in combination with other refractive errors, which include:

Near-sightedness (myopia).

This occurs when too much of your cornea is curved or the eye is longer than normal. Light is focused in front of your retina instead of being concentrated precisely on your retina, making distant objects seem blurry. Light is focused in front of your retina instead of being concentrated precisely on your retina, making distant objects seem blurry.

Light is focused in front of your retina instead of being concentrated precisely on your retina, making distant objects seem blurry.

Farsightedness (hyperopia).

This happens when too little of the cornea is curved or your eye is shorter than normal. The result is the reverse of nearsightedness. Light never concentrates on the back of your eye when your eye is in a relaxed state, making nearby objects seem blurry.

What are the symptoms of Astigmatism?

Blurred vision is the most common symptom of astigmatism. It is described as double vision by some people, but in only one eye. Eyestrain, squinting and headaches are developed by some individuals with astigmatism from working to focus on near or distant objects. People are born with astigmatism, but until a child starts attending school or learns to read, it may not be noticed.

How is Astigmatism diagnosed?

The symptoms of astigmatism occur slowly. When you notice changes in your vision, go to an eye doctor. You’ll need a full eye examination. Using a standard eye exam, an ophthalmologist or an optometrist can diagnose astigmatism.

By asking you to read an eye chart, your doctor will test the sharpness of your eyesight. To measure your vision, they will also use instruments, including:

Phoropter.

To find the ones that give you the clearest vision, you look through a series of lenses.

Topographer/keratometer.

To measure the curve of your cornea, this machine uses a circle of light.

Autorefractor.

As it bounces off the back, this device shines light into your eye and measures how it changes. This provides your doctor with an understanding of which lenses you need.

What is the treatment for Astigmatism?

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

Corrective lenses

Wearing corrective lenses treats astigmatism by counteracting uneven curvatures of your cornea and lens.

Types of corrective lenses include:

  • Eyeglasses. Eyeglasses are made with lenses that help compensate for the uneven shape of your eye. The lenses make the light bend into your eye properly. Eyeglasses can also correct for other refractive errors, such as nearsightedness or farsightedness.
  • Contact lenses. Like eyeglasses, contact lenses can correct most astigmatism. They are available in a variety of types and styles, including disposable soft; extended wear; rigid, gas permeable; and bifocal.
    Contact lenses are also used in a procedure called orthokeratology. In orthokeratology, you wear rigid contact lenses during the night while sleeping until the curvature of your eye evens out. Then you wear the lenses less frequently to maintain the new shape. If you discontinue this treatment, your eyes return to their former shape and refractive error.
    Wearing contact lenses for extended periods of time increases the risk of infection in the eye.
  • Ask your eye doctor about the pros and cons and risks of contact lenses and what might be best for you.

Refractive surgery

Refractive surgery improves vision and reduces the need for eyeglasses or contact lenses. Your eye surgeon uses a laser beam to reshape the curves of the cornea, which corrects the refractive error. Before surgery, doctors will evaluate you and determine if you’re a candidate for refractive surgery.

Types of refractive surgery for astigmatism include:

  • Laser-assisted in-situ keratomileusis (LASIK). With this procedure, your eye surgeon makes a thin, hinged flap in your cornea. He or she uses an excimer laser to sculpt the shape of the cornea and then repositions the flap.
  • Laser-assisted subepithelial keratectomy (LASEK). Instead of creating a flap in the cornea, the surgeon loosens the cornea’s thin protective cover (epithelium) with special alcohol. He or she uses an excimer laser to change the curvature of the cornea and then repositions the loosened epithelium.
  • Photorefractive keratectomy (PRK). This procedure is similar to LASEK, except the surgeon removes the epithelium. It will grow back naturally, conforming to your cornea’s new shape. You may need to wear a bandage contact lens for a few days after surgery.
  • Epi-LASIK. This is a variation of LASEK. Your doctor uses a special mechanized blunt blade — instead of the alcohol — to separate a very thin sheet of the epithelium. He or she then uses an excimer laser to reshape the cornea and repositions the epithelium.
  • Small-incision lenticule extraction (SMILE). This newer type of refractive surgery reshapes the cornea by using a laser to make a lens-shaped bit of tissue (lenticule) below the cornea surface. The lenticule is then removed through a very small incision. For now, the SMILE procedure is only approved for treating mild nearsightedness.

Other types of refractive surgeries include clear lens extraction and implantable contact lenses. There is no one best method for refractive surgery, and the decision should only be made after a complete evaluation and thorough discussion with your surgeon.

Some of the possible complications that can occur after refractive surgery include:

  • undercorrection or overcorrection of your initial problem
  • Visual side effects, such as a halo or starburst appearing around lights
  • Dry eye
  • Infection
  • Corneal scarring
  • Rarely, vision loss

Discuss the potential risks and benefits of these procedures with your eye doctor.

References:

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https://www.health.harvard.edu/a_to_z/astigmatism-a-to-z

https://www.mayoclinic.org/diseases-conditions/astigmatism/diagnosis-treatment/drc-20353838

https://www.webmd.com/eye-health/astigmatism-eyes

https://www.aao.org/eye-health/diseases/what-is-astigmatism

https://www.medicalnewstoday.com/articles/158810#causes