ASTIGMATISMcauses, symptoms and treatments

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Last updated 9/29/2019
Dr. Assil discusses astigmatisms: causes, symptoms and treatment options.

What is astigmatism of the eye? 

Astigmatism is a common eye condition in which light rays entering the eye cannot focus evenly on the retina, resulting in blurred vision.

 

Astigmatism is caused by an abnormally shaped cornea and when light rays pass through it, they become bent (refracted) and before striking the retina, causing blurred vision. This phenomenon is known as a "refractive errors".

 

What causes astigmatism? 

Although the exact cause for abnormally shaped corneas or lenses remains unclear, heredity seems to play a big role. It can be present at birth but also can appear later in life. or develop after an eye injury or surgery.

Astigmatism: a refractive error 

Astigmatism: causes, symptoms and treatments, Assil Eye Institute Los Angeles

Refraction is the process of light being bent as it passes through an object. When light rays pass through your cornea and lens, they're bent (or refracted) before reaching the retina. Once the rays strike your retina, they're converted into signals that travel through the optic nerve to your brain for decoding into the images you see. If the light rays aren't evenly focused on the retina, blurred or distorted vision results.

 

Astigmatism is one type of refractive error, but other include myopia (nearsightedness) in which distance vision is blurred and hyperopia (farsightedness) when near vision is blurred.  In astigmatism, your vision is blurred or distorted to some degree at all distances. 

Astigmatism symptoms

Many people with astigmatism don't realize that they have it because often the symptoms come on gradually. And children born with astigmatism often go undetected until their performance in school or sports reveals a vision problem. At any age, it is important to monitor eye health with an annual eye exam and to inform your eye doctor of any changes that you notice in your vision. 

 

Astigmatism symptoms include:

  • Headaches
  • Eye strain
  • Squinting in order to see clearly
  • Distorted or blurred vision at all distances
  • Difficulty seeing at night

 

If you experience any of these symptoms, please contact your eye doctor.

Types of astigmatism

Corneal astigmatism

In a normal eye, the cornea is round like a baseball and fairly symmetric, so light rays bend the same way no matter what part of the cornea they enter. With corneal astigmatism, the cornea is football shaped, which means that light rays can bend in different directions based on where they enter the cornea, causing images to appear blurry or distorted.

 

There are two subtypes of corneal astigmatism:

Regular astigmatism 

Regular astigmatism is the most common type, where the front surface of the eye has an oval shape

 

Irregular astigmatism 

Irregular astigmatism is caused by corneal scarring from injury or surgery, or from keratoconus – a disease causing gradual thinning of the cornea

 

Lenticular astigmatism

Sometimes astigmatism is not caused by a deformed cornea, but rather by a distorted lens shape that causes light rays to bend abnormally and scatter before reaching the retina. Vision correction for lenticular astigmatism usually involves prescription eye glasses with corrective lenses that compensate for the degree of astigmatism present.

 

Astigmatism risk factors

Your risk of developing astigmatism may be higher if you have:

  • A family history of astigmatism or other eye conditions, like keratoconus
  • Scarring or thinning of your cornea
  • Extreme nearsightedness
  • Extreme farsightedness
  • Prior eye surgery

 

How is astigmatism diagnosed?

Astigmatism is diagnosed by a detailed eye examination. At AEI we use state-of-the-art technology as well as time proven traditional tools to assess your vision. Your eye exam can include:

  • Visual acuity test: your doctor may start by asking you to read letters from a chart at a distance to determine how well you can see with each eye.
  • Refraction test: your doctor asks you to look through a machine (optical refractor) while inserting different strength glass lenses to arrive at the precise prescription that corrects your vision. This test is usually performed to fit you for glasses.
  • Autorefractor: to determine your prescription by sending a beam of light into your eye and measuring how the light wave changes as it bounces off the back of the eye.
  • Keratometry: measure the slope and curvature of your cornea, in other words, it's topography.

 

Non-surgical astigmatism treatments 

Basically, the only non-surgical way to treat Astigmatism are glasses and contact lenses. Contact lenses come in two forms, rigid gas permeable and soft lens options.

 

Rigid gas permeable (RGP) contact lenses

Rigid gas permeable lenses are made of a special plastic that doesn't mold to your eye but rather provides a corrective lens through which light rays are bent correctly as they enter your eye. Unfortunately, due to their greater stiffness and thickness than soft lenses, some people can have difficulty getting used to RGP lenses.

 

Toric soft lenses 

Toric soft lenses are by far the most popular contact lens solution for astigmatism. They are formed to adjust to the shape of your eye and provide balanced and clear vision to the various prescription zones within your eye. At AEI we offer several toric soft lens options.

 

Surgical astigmatism treatments

Refractive surgery

Refractive Surgery is any surgery designed to improve your ability to focus light correctly on the retina, decreasing your dependence on glasses or contact lenses. This can take the form of laser procedures or artificial lens implantation.

 

LASIK / PRK

Traditionally, refractive laser surgery has been done using LASIK (laser assisted in situ keratomileusis) for mild astigmatism or PRK (photorefractive keratectomy) for more severe astigmatism.

 

At AEI, we offer EagleVIsion, a step beyond iDesign and Contoura Vision.  Utilizing the latest LASIK technology, EagleVIsion takes a detailed map of your entire eye (cornea and additional layers) to customize your laser treatment, frequently providing better vision than you ever had with glasses or contacts. In fact, on average, EagleVIsion surpasses the best eye glasses prescription.

 

Lens Implantation (IOL)

This surgery places a permanent prescription optical lens (IOL) inside your eye in front of your natural lens in order to correct your astigmatism. This is an option for folks with severe astigmatism who wish to be free of glasses or contact lenses and who have been told that they are not good candidates for LASIK surgery.

 

Toric intraocular lenses (IOLs for short) have different powers in different zones of the lens that enable them to correct the asymmetric power in an astigmatic eye. If you need cataract surgery and have astigmatism, you have the option of replacing your natural lens with a toric IOL that will correct your astigmatism.

 

Limbal Relaxing Incisions (LRI) 

Limbal Relaxing Incisions are partial thickness incisions made at the outer edge of an astigmatic cornea in order to flatten its steep curvature into a rounder shape. This yields clearer vision and reduces or even eliminates the need for distance glasses.

 

LRI is sometimes performed on folks with mild to moderate astigmatism during surgery for cataracts or implantation of intraocular lenses. At AEI, we perform this procedure using a Femtosecond laser to ensure that the relaxing incisions have the precise depth and length needed to safely correct your astigmatism.

 

What surgical astigmatism treatment is best for me? 

The selection of the surgical approach depends on a number of variables, such as the health of your eye, your prescription, eye shape, lifestyle and preferences. All of the above procedures are safe and achieve clear vision for many of our patients.

 

There are no “one size fits all” options at AEI. It depends upon your eyes, your lifestyle and your goals. And if we believe a surgical option is not the best approach for you, we will tell you. That’s what we would want a surgeon to tell us before we underwent any procedure. And treating our patients the way we would want to be treated is one of the core tenets of our practice. Period.

 

The AEI care difference

Assil Eye Institute’s dedication to providing the best eye care available is what motivates us to strive for the highest standards of excellence when it comes to your eye health.

 

AEI utilizes the most advanced surgical techniques and technology available today to offer our patients the best possible vision outcomes in the safest manner.

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