Astigmatism is one of those words that gets thrown around the eye doctor’s office like it’s common knowledge. With its strange name, it’s sometimes incorrectly referred to as astigma eyes or stigmatism. But what exactly is astigmatism? This article will review the astigmatism definition and much more.
What Is Astigmatism?
Refractive errors are a group of conditions that affect how light refracts when entering the eye. Astigmatism is a common type of refractive error, like hyperopia, myopia, and presbyopia. Emmetropia is a term used to describe the absence of refractive error. Astigmatism distorts vision at both distance and near. It is often present in combination with myopia (nearsightedness) or hyperopia (farsightedness). Presbyopia develops later in life, generally in one’s 40s, and causes difficulties with near vision. An eye can only be myopic or hyperopic, not both. However, presbyopia occurs with myopia, hyperopia, or astigmatism.
Astigmatism can cause blurry vision all-around, regardless of how far or close the target object is. Therefore, bringing an object closer or further from the eyes usually won’t help to clear things up. Objects might look shadowed or distorted. Night vision may be difficult. Squinting may help to clear things temporarily but can lead to eyestrain and headaches.
What Do People With Astigmatism See?
People with sufficient uncorrected astigmatism will have blurry, fuzzy, or distorted vision. However, many people have low amounts of astigmatism where they won’t even have symptoms. It takes at least 0.75-1.00 diopters of astigmatism to be noticeable, though this can vary depending on the individual. Astigmatism can also cause shadowing of images. This can make letters appear as if they’re double. Astigmatism at night can make vision particularly challenging, causing debilitating glare and halos around lights.
When children have astigmatism, they may not be able to verbalize it. Parents should look out for the symptoms described, in addition to eye rubbing or closing one eye.
What Causes Astigmatism?
Astigmatism is usually present at birth, as a result of the shape of the eye. However, it can change through life. The source of astigmatism is most commonly the cornea, the clear tissue at the front of the eye. This is called corneal astigmatism. Astigmatism can also come from the crystalline lens inside the eye. This is called lenticular astigmatism.
In corneal astigmatism, the curvature of the cornea is uneven, instead of being shaped like a perfect sphere. The corneal contour in astigmatism is comparable to a football, rather than a basketball or soccer ball.
When the cornea is uneven in shape, the light that enters the eye doesn’t focus exactly where it should. Rather than landing on the retina, the light-sensitive tissue at the back of the eye, it lands in front or behind it. When light doesn’t focus where it should, vision is blurry. Thankfully, astigmatism is not a blinding condition.
Similarly, when the lens is uneven in shape, it can cause astigmatism and therefore fuzzy vision. So far, we have discussed the most common type of astigmatism, termed regular astigmatism. Irregular astigmatism is a rare subtype that results from trauma to the eye or certain corneal conditions such as keratoconus, pellucid marginal degeneration, epithelial basement membrane dystrophy, and others.
There are many options for treating astigmatism, the most common being glasses. Astigmatism glasses look just like any other glasses, though they can get quite thick at the edges in very high amounts of astigmatism. Glasses are only able to correct regular astigmatism, not irregular. Contacts for astigmatism are another option. Most people use the soft type, which can only correct regular astigmatism, not irregular. The term toric is used to describe contact lenses that provide the astigmatic correction. Sometimes, rigid gas-permeable lenses may be a better option than soft lenses, particularly in the rare case of irregular astigmatism. Traditional gas-permeable contact lenses are used during the day and taken out at night. Some people may be candidates for orthokeratology, specially fitted rigid gas-permeable contact lenses that are worn overnight. These lenses change the shape of the cornea during the night to minimize the need for glasses during the day. Orthokeratology only works for corneal astigmatism, not the lenticular type. It’s a way to treat astigmatism naturally, though it’s only temporary.
If you’re looking to permanently treat your eye astigmatism, then you’ll need refractive surgery. There are a few procedures available to cure astigmatism. They are only able to correct astigmatism that comes from the cornea, not the lens, so part of your initial screening will involve checking the source of your astigmatism.
Laser-assisted in situ keratomileusis (LASIK) is the most common refractive surgery procedure, followed by photorefractive keratectomy (PRK). LASIK for astigmatism is a technique that offers a quick recovery. In LASIK, the surgeon creates a thin flap of tissue in the cornea, lifts it, and applies a laser to the cornea. The flap is then replaced and smoothed out. The recovery process is very quick after LASIK, as the flap helps to protect the eye as it heals. Because of the quick and predictable healing after LASIK, both eyes are usually done at the same time.
After their initial screening, some people may be found to be better candidates for PRK. This is commonly due to the cornea being too thin for LASIK, though there are other reasons. In PRK, the outermost corneal epithelial cells are removed. Then, a laser is applied to the cornea. A bandage contact lens is then placed to protect the cornea as it mends. PRK takes a little longer to heal, so generally, one eye is done at a time. With both LASIK and PRK, here at the Kraff Eye Institute, we utilize iDesign 2.0. This is the most advanced, highest definition way, of mapping and screening your cornea. This technology allows us to treat patients who have high levels of astigmatism safely.
Occasionally, some people may have a procedure called intrastromal ring segments, or intacs, to correct their astigmatism. Intacs are plastic inserts strategically placed in the cornea to change its curvature. These compensate for astigmatism, improving vision. This technique is not nearly as common as LASIK and PRK. In addition, if a patient is found not to be a good candidate for LASER eye surgery, a doctor may recommend an Implantable Collamer Lens procedure. In this type of procedure, a surgeon is implanting a lens, which is calculated for your specific vision needs, into the eye. The lens sits behind the colored part of the eye and your natural crystalline lens.
Although astigmatism can certainly be a nuisance, there is no reason to suffer from it. As you can see, there are plenty of options to clear up your vision. Interested in getting rid of your astigmatism for good? Call us to schedule your complimentary consultation today.