Astigmatism: Definition, Types and Correction Options

Astigmatism is probably the most misunderstood vision problem. For starters, it’s called “astigmatism,” not “stigmatism.” (You don’t have “a stigmatism”– you have astigmatism.)

Like nearsightedness and farsightedness, astigmatism is a refractive error, suggesting it is not an eye disease or eye health problem; it’s merely an issue with how the eye focuses light.

In an eye with astigmatism, light fails to come to a single concentrate on the retina to produce clear vision. Instead, numerous focus points occur, either in front of the retina or behind it (or both).

In Europe and Asia astigmatism affects between 30 and 60% of adults. Individuals of all ages can be affected. Astigmatism was first reported by Thomas Young in the early 1800s.

Astigmatism Symptoms

Astigmatism generally causes vision to be blurred or misshaped to some degree at all ranges.

Symptoms of uncorrected astigmatism are eye strain and headaches, especially after reading or other prolonged visual jobs.

Squinting likewise is a typical symptom.

What Causes Astigmatism?

Astigmatism generally is triggered by an irregularly shaped cornea. Instead of the cornea having a symmetrically round shape (like a baseball), it is shaped more like a football, with one meridian being substantially more curved than the meridian perpendicular to it.

To understand what meridians are, think about the front of the eye like the face of a clock. A line linking the 12 and 6 is one meridian; a line linking the 3 and 9 is another.

The steepest and flattest meridians of an eye with astigmatism are called the primary meridians.

In many cases, astigmatism is caused by the shape of the lens inside the eye. This is called lenticular astigmatism, to separate it from the more common corneal astigmatism.

Types of Astigmatism

There are 3 primary types of astigmatism:

  • Myopic astigmatism. One or both principal meridians of the eye are nearsighted. (If both meridians are nearsighted, they are myopic in differing degree.)
  • Hyperopic astigmatism. One or both primary meridians are farsighted. (If both are farsighted, they are hyperopic in varying degree.)
  • Mixed astigmatism. One prinicipal meridian is nearsighted, and the other is farsighted.

Astigmatism also is classified as regular or irregular. In routine astigmatism, the primary meridians are 90 degrees apart (perpendicular to each other). In irregular astigmatism, the primary meridians are not perpendicular. A lot of astigmatism is regular corneal astigmatism, which provides the front surface area of the eye a football shape.

Irregular astigmatism can result from an eye injury that has actually caused scarring on the cornea, from specific types of eye surgery or from keratoconus, a disease that causes a progressive thinning of the cornea.

Astigmatism Definition, Types and Correction Options

How Common Is Astigmatism?

Astigmatism often happens early in life, so it is important to set up an eye examination for your child to avoid vision issues in school from uncorrected astigmatism.

In a recent study of 2,523 American children ages 5 to 17 years, more than 28 percent had astigmatism of 1.0 diopter (D) or higher.

Likewise, there were significant distinctions in astigmatism prevalence based on ethnic culture. Asian and Hispanic children had the greatest occurrences (33.6 and 36.9 percent, respectively), followed by whites (26.4 percent) and African-Americans (20.0 percent).

In another study of more than 11,000 glasses wearers in the UK (both children and adults), 47.4 percent had astigmatism of 0.75 D or higher in a minimum of one eye, and 24.1 percent had this quantity of astigmatism in both eyes. The prevalence of myopic astigmatism (31.7 percent) was roughly double that of hyperopic astigmatism (15.7 percent).

Astigmatism Test

Astigmatism is found during a regular eye exam with the same instruments and strategies used for the detection of nearsightedness and farsightedness.

Your optometrist can estimate the quantity of astigmatism you have by shining a light into your eye while manually presenting a series of lenses between the light and your eye. This test is called retinoscopy.

Though numerous optometrist continue to perform retinoscopy, this manual procedure has been changed or supplemented in many eye care practices with automated instruments that offer a much faster initial test for astigmatism and other refractive errors.

Whether your eye examination consists of retinoscopy, an automated refraction, or both, your optometrist or ophthalmologist will carry out another test called a manual refraction to fine-tune the outcomes of these initial astigmatism tests.

In a manual refraction (also called a manifest refraction or subjective refraction), your eye doctor positions an instrument called a phoropter in front of your eyes. The phoropter contains lots of lenses that can be introduced in front of your eyes one at a time so you can compare them.

As you look through the phoropter at an eye chart at the end of the test space, your eye doctor will show you various lenses and ask you questions along the lines of, “Which of these two lenses makes the letters on the chart look clearer, lens A or lens B?” Your answers to these questions assist identify your spectacles prescription.

Astigmatism Correction Options

Astigmatism, like nearsightedness and farsightedness, normally can be corrected with spectacles, contact lenses or refractive surgery.

In addition to the round lens power used to remedy nearsightedness or farsightedness, astigmatism needs an additional “cylinder” lens power to correct the distinction in between the powers of the two principal meridians of the eye.

So a glasses prescription for the correction of myopic astigmatism, for instance, could look like this: -2.50 -1.00 x 90.

  • The first number (-2.50) is the sphere power (in diopters) for the correction of myopia in the flatter (less nearsighted) principal meridian of the eye.
  • The second number (-1.00) is the cylinder power for the additional myopia correction required for the more curved principal meridian. In this case, the total correction required for this meridian is -3.50 D (-2.50 + -1.00 = -3.50 D).
  • The 3rd number (90) is called the axis of astigmatism. This is the place (in degrees) of the flatter principal meridian, on a 180-degree rotary scale where 90 degrees designates the vertical meridian of the eye, and 180 degrees designates the horizontal meridian.

If you wear soft toric contact lenses for astigmatism correction, your contact lens prescription will likewise consist of a sphere power, cylinder power and axis classification.

Gas permeable contact lenses are also a choice. Because these lenses are rigid and optically replace the cornea as the refracting surface of the eye, a cylinder power and axis may or may not be needed, depending upon the type and severity of astigmatism correction required. The very same holds true for hybrid contact lenses.

Refractive surgery such as LASIK likewise can correct most types of astigmatism. Go over with your eye doctor which procedure is best for you.

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Comments: 6
  1. Melinda Dannon, MD

    If astigmatism progresses, a complete diagnosis, including corneal examination (keratotopography), must be performed to rule out progressive corneal pathology. If it is only detected, there is a need for correction depending on the strength of the astigmatism, age, etc.

  2. Kate

    In elementary school I started having problems with my eyesight, that is, myopia -1, not so much. I was prescribed ordinary glasses, I wore them, people laughed at me. So in high school I didn’t wear them all the time. I only put them on when I couldn’t see from the board. Gradually, my vision deteriorated, and in high school it was impossible to understand words on the blackboard without glasses. Then I started wearing lenses. I wore them until the third year of college, when I got an eye virus. For this reason I was forbidden to wear lenses during the treatment and a few months afterwards. That is, I needed glasses. I went to a free eye doctor, he checked my eyesight and gave me a prescription for glasses. I got glasses, I put them on, and everything floats. The ground seemed closer than it really was, the planes became convex, and the straight lines curved. It was impossible to walk in them, it hurt my head and eyes + you stumble all the time when walking. I started googling what the hell this is. I found out about astigmatism. I went to the doctor, they looked at my eyes with the help of different devices and took a long time to choose lenses for glasses with degrees.
    When I wore glasses at school I did not have astigmatism and my glasses were very basic.
    Now I wear glasses with lenses with degrees for my astigmatism and contact lenses. There are no requirements for contact lenses in connection with astigmatism, you can wear any. But the glasses will have to be picked up.
    I didn’t realize I had astigmatism until I wore glasses with simple lenses, it didn’t show up in any other way.
    Google what it is. It’s a curvature of something in there that causes light to focus at the wrong angles, and glasses with degrees make it focus correctly.

  3. Jane Oliversson

    I have congenital astigmatism in one eye. They didn’t prescribe eyeglasses so they wouldn’t ruin the other eye. They said I could have laser surgery after I grew out. When in my teens I developed a migraine and my eye was affected (migraine with aura), I was prescribed a treatment, which helped. At a mature age, I went for a check-up and thought about surgery, but the doctor discouraged it. She said it was a very difficult eye, it was dangerous to operate on it. So I live like this, I can see very badly in the distance and normal near. Tired eyes, sometimes migraines come back, but in general I got used to it, I prefer supermarkets, because I can’t tell the difference between yogurts in stores))))

  4. Harry Harris

    According to the report of the ophthalmologist, spasm of accommodation and astigmatism, and here it is already those strange sensations with the vision when everything seems to float and either blurred or really eyes in different directions. The optometrist said that if it suddenly happened, there is a chance that everything will recover. I think you also have something with the blood vessels, maybe there was stress?

  5. Ann Trump

    I have asthismatism in one eye and see blurred, I have glasses, I have changed glasses for the third time, through the glasses (if you close the healthy eye) the sick eye sees blurred, I do not understand is it supposed to be? I see through glasses with both eyes the same as I do without glasses. I have a doctor’s appointment, they picked the wrong glass or something.

  6. Redhair Waiter

    I am a former astigmatic in both eyes. I’ve been wearing glasses all my life, but I changed lenses a lot because that’s what makes astigmatism so tricky, because the degree changes so quickly. I had the surgery and everything is normal). It shouldn’t be blurry! But if it was fine at first and then worsens, that’s your peculiarity.

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