Astigmatism is a defect in the shape of your eye’s lens or cornea, which is the transparent dome that sits atop your iris and pupil. In healthy eyes, both your cornea and lens possess a smooth and equal curvature, like a ping pong ball. This condition, which fosters normal eyesight, is referred to as astigmatism.
By contrast, a distorted astigmatic eye resembles an egg. Eyes with astigmatism twist and bend light coming through it towards the light-sensitive tissue in the back of your eye called the retina. This uneven distribution of light results in refractive errors, causing poor eyesight.
If you are having any abnormal visual symptoms, you should always be evaluated with a thorough consultation and examination by a physician for an accurate diagnosis and treatment plan as it may be a symptom or sign of a serious illness or condition.
Astigmatism can be present at birth or develop over a long period of time. While astigmatism leads to overall poor eyesight both at a distance and up close, nearsightedness (myopia) is a condition where your eye’s lens or the cornea has become elongated. This condition focuses the light in front of your retina. Farsightedness (hyperopia) is the opposite condition, where your eye or cornea has become shortened and thus the light is focused past your retina. Both myopia and hyperopia are correctable with eyeglasses.
When the defect resides in the cornea, it is called corneal astigmatism. Lenticular astigmatism refers to the lens. In either case, your vision becomes blurred and warped in a manner similar to an individual wearing the wrong prescription eyeglasses. These conditions can exist independently or concurrently.
- Blurred vision at all distances
- Persistent squinting
- Poor night vision
- Overly sensitive to light (photophobia)
If any these symptoms become apparent, visit your eye doctor, who can to test for astigmatism. If you are having any abnormal visual symptoms, you should always be evaluated with a thorough consultation and examination by a physician for an accurate diagnosis and treatment plan as it may be a symptom or sign of a serious illness or condition. And whether you have symptoms or not, you should visit your eye doctor to be tested for astigmatism every two years once you hit age 40 and every year after the age of 55.
What Causes Astigmatism
The immediate cause of astigmatism is the distorted shape of the eye lens or the cornea. People are generally believed to be born with astigmatism. You may have the condition immediately, or it can develop later in life. Though no definite link has been proven, it appears most likely to be a hereditary trait.
Astigmatism also can develop as the result of a disease, injury, or surgery to the eye. Eye diseases include keratoconus and
keratoglobus. These are conditions that cause the cornea to bulge, thin, or just deform. It’s a myth, however, that astigmatism is caused by reading in low light, watching too much TV, or sitting too close to a computer monitor.
How Astigmatism Is Diagnosed
Your eye doctor diagnoses stigmatism through a comprehensive
eye exam. The testing process analyzes how well your eye focuses light by testing through a series of magnification lenses on the eyes. These tests may include any or all of the following:
- Visual Acuity: The results of this eye exam determine the smallest letters you can distinguish on a chart from 20 feet away. This visual acuity is represented as a fraction, such as 20/30. The top number (20) represents the distance at which you are viewing the chart. The bottom number represents the smallest readable number at that distance. In this case, the test result indicates that you can only see at 20 feet what a person with normal vision (20/20) could see at 30 feet.
- Keratometry: This is a topographical test conducted with a keratometer to determine the curvature of the cornea. The instrument focuses light on the cornea and measures the reflection to determine if there are any defects to the shape.
- Refraction: This is usually the final test. It uses a phoropter, a machine that’s placed in front of your face and has a multitude of lenses available for your eye doctor to try until he determines which one offers the best results for your specific vision needs.
You can have an
astigmatism correction procedure or you can try other corrective procedures, as recommended by your ophthalmologist, such as:
- Orthokeratology is a therapy that involves wearing a rigid contact lens at night to temporarily reshape the cornea for moderate astigmatism. It improves vision temporarily, but it doesn’t last if the treatment is stopped.
- Surgery includes various surgical techniques available to correct astigmatism. ALK, RK, PRK, and LASIK surgery are all techniques where lasers are employed to remove excess tissue from the cornea.
- Eyeglasses are still the safest and easiest way to correct astigmatism. Both optometrists and ophthalmologists can prescribe the appropriate lens for your condition.
- Hard contact Lenses may be the right solution for you. Check with your eye doctor. The appropriate lens refocuses the refracted light onto your retina, resulting in a clearer image with a wider field of view than eyeglasses provide. Rigid contact lenses are made of a composite material of glass and plastic. These lenses are non-permeable, however, so they prevent oxygen from reaching the eye. For this reason, they can be uncomfortable.
- Soft contact Lenses were developed after hard lenses. More people claim to enjoy these new contact lenses that much more. A few examples of the newest contact lenses include:
- One Day Acuvue Moist, made especially for astigmatism patients, are a single use disposable lens that provides comfort and convenience. Offering Class 2 UV protection, it also allows 88 percent of available oxygen to your open eye. Its patented technology provides your eyes with a smooth wet feeling that mimics real tears.
- Acuvue Oasys, also designed for astigmatism, is a longer-wear lens. You can wear it daily for up to two weeks or continuously for six days. It allows 98 percent of available oxygen to pass through to your open eye, and its Class 1 UV protection is the highest industry standard. Its state-of-the-art technology promises to be so comfortable that you forget you have contacts on at all.
- Air Optix is another contact lens designed especially for astigmatism. This brand employs its own technology to increase the smooth and moist feeling important to you. Air Optix is also specifically designed for stability. It has two locking points on your eye and thus maintains its position during an active day.