Astigmatism is one of the most common vision problems. In fact, the American Academy of Ophthalmology® states that one in three people in the United States has some level of astigmatism. Despite its prevalence, many are unaware of the basics of the condition. We’ve compiled our expertise to explain everything you need to know about astigmatism.
What is Astigmatism?
Astigmatism is an eye condition caused by an imperfect curvature of the cornea or lens. Typically, the lens and cornea create a perfect, smooth curvature around the eye. When the cornea and lens are smooth, light rays are sharply focused onto the retina in the back of the eye. In the case of astigmatism, the fault in the curve causes a refractive error resulting in blurred vision. The causal location of this error determines the type of astigmatism.
There are two types of astigmatism: corneal and lenticular. The most common type of astigmatism, corneal astigmatism, is caused by an irregularly shaped cornea. Lenticular astigmatism, on the other hand, is caused by crystalline lens distortion.
Astigmatism is typically diagnosed with myopia (nearsightedness), hyperopia (farsightedness), or mixed myopia and hyperopia.
The primary symptoms of astigmatism are blurred or distorted vision at any distance. In many cases, symptoms can also include eye strain, such as squinting, and headaches – most commonly occurring after reading, driving at night, or lengthy exposure to screens.
How is Astigmatism Diagnosed?
Currently, there is no known cause of astigmatism. It is often hereditary and can increase or decrease over time, beginning at birth. Annual eye exams are a simple way to monitor vision changes, including astigmatism.
Annual comprehensive optometric exams include tests for astigmatism. This exam can include a visual acuity test to determine the clarity and sharpness of your vision, a keratometry and topography test to measure the shape of the cornea, and a refraction test to determine how the eyes focus light. These tests use letters and light beams to see how the eyes function and to determine the corrective lens that will adjust for the clearest vision.
These tests will measure a variety of factors including the eye’s sphere, cylinder, and axis. The sphere measurement shows the degree of nearsightedness or farsightedness. Positive numbers indicate farsightedness while negative numbers specify nearsightedness. Higher numbers indicate stronger corrective prescriptions.
Cylinder measurements indicate the degree of astigmatism, or the shape of the cornea or lens, and are measured in diopters. A perfect eye measures at zero diopters. Most people have some level of astigmatism, measured between 0.5 to 0.75 diopters, although they may not require treatment. Measurements greater than 0.75 diopters may require vision correction through contacts, glasses, or laser treatment.
The axis measurement determines the location of the imperfection on the cornea or lens. It is measured in degrees from 0 to 180.
How is it Treated?
Astigmatism can be treated in a variety of ways ranging from topical to surgical.
1. Eyeglasses – Eyeglasses are the simplest corrective tool as the appropriate lens will be prescribed to correct the specific level of astigmatism.
2. Contact lenses – Astigmatic-correcting contact lenses, known as toric lenses, are a common solution for low-grade astigmatism. Contacts sit on top of the eye, becoming the first surface that light hits. This allows the light to be refracted in a more focused beam onto the retina.
3. LASIK – During a LASIK procedure, astigmatism can be corrected by using lasers to reshape the cornea to correct the irregular curve. This allows the light to refract more precisely on the retina.
4. Limbal relaxing incisions (IRL) – During a refractive lens exchange (RLE) or cataract surgery, astigmatism can be corrected with limbal relaxing incisions. In this procedure, the surgeon uses a laser or hand to reshape the cornea and correct the irregular curve through the implementation of one or more arc-shaped incisions on the cornea.
5. Toric intraocular lens implant – During cataract surgery, our surgeons can replace the clouded lens with a toric intraocular lens (IOL) implant. The implant is securely positioned inside the eye, eliminating the mobility that a regular contact has on the eye. This improves distance vision while reducing the need for eyeglasses or contacts after cataract surgery.
There are multiple treatment options for astigmatism, and our staff is dedicated to finding the perfect vision solution to fit your lifestyle. For more information, contact our office at (716) 564-2020 or register to attend one of our monthly Evening Vision Solutions Open House events.