Thursday, October 18, 2018

Astigmatism

If you experience a distortion or blurring of images at all distances -- nearby as well as far -- you may have astigmatism. Even if your vision is fairly sharp, headache, fatigue, squinting and eye discomfort or irritation may indicate a slight degree of astigmatism. A thorough eye examination, including tests of near vision, distant vision and vision clarity, can determine if astigmatism is present.
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What is Astigmatism?
Astigmatism is a common refractive error that results from an imperfection in the eye’s curvature. In normal eyes, the cornea (the front part of the eye’s surface) and the lens are smooth and evenly shaped in all directions. With astigmatism, the cornea or lens is irregularly shaped in some areas, causing blurred vision. Astigmatism is not an eye disease; it is simply a variation in the way the eye is shaped. A person can experience moderate to severe astigmatism depending on how many corneal or lens disturbances are present.
 
 
Because the astigmatic cornea is curved more (steeper) in one direction than the other, light entering the eye is refracted differently as it passes through these different areas. This causes light to come into focus at several different points on the back of the eye, rather than ideally coming into focus at just one point. Depending on the direction and the amount of astigmatism, vision through an astigmatic cornea will be affected in various ways. The illustration (below) gives a broad example of the visual effects, depending on the overall direction of the curve.
 
 
Many experts believe that all people are born with a degree of astigmatism that may worsen or stay the same throughout their lifetime. For most people, the degree of astigmatism experienced is so mild that it does not require corrective lenses. However, for those with moderate to severe astigmatism, eyeglasses or contact lenses must be worn unless their vision is corrected with refractive surgery.
What are the symptoms?
These symptoms are not exclusive to astigmatism and will vary depending on whether the patient has mild, moderate, or severe astigmatism. If you experience any of these symptoms, you should contact a qualified ophthalmologist for a comprehensive eye examination.
  Blurred vision at any distance
  Distortions of vertical, horizontal, or diagonal lines
  Frequent headaches and fatigue
  Squinting in order to see better
  Eye discomfort or irritation
What causes Astigmatism?
In the human eye, the cornea focuses images by refracting incoming light onto the retina (back of the eye). In the ideally-shaped eye, the cornea has a smooth, even curvature and is shaped like a round ball. With astigmatism, the cornea is shaped more like an oval, or football, causing light to scatter as it passes through. The result is a blurred image on the retina, making it difficult for people with astigmatism to see clearly at any distance.
 
 
Contrary to common belief, reading in poor light, squinting, or sitting too close to the television are not causes of astigmatism. Astigmatism is usually present from birth and can either stay the same or worsen over time. Eye injury, disease, or surgery can also be causes of astigmatism.
Detection
Astigmatism is usually diagnosed during routine eye exams, wherein your ophthalmologist will check your eye’s refraction (ability to properly focus light rays on the retina) and visual acuity using a standard eye chart. The eye’s refraction can be measured in a number of ways; some doctors will simply ask a series of questions about your current vision and conduct a visual acuity test, while others will use a keratometer or keratoscope to assess the curvature of your cornea and determine the presence of moderate or severe astigmatism.
Treatment
There are a number of options for patients seeking effective astigmatism treatment, from time-tested eyeglasses to the latest in laser technology. Choosing the right treatment for you will depend on a number of factors, including your lifestyle, medical history, and degree of refractive error.
 
Eyeglasses and Contact Lenses. Before the advent of refractive surgery, eyeglasses and contact lenses were the only way to correct astigmatism, and many people still prefer them. Eyeglasses and contacts are a reliable astigmatism treatment, for low to moderate astigmatism, that comfortably correct for the cornea’s irregular curve.
 
Limbal Relaxing Incisions. LRI’s are incisions that are placed on the far outer edge of the cornea (the limbus) resulting in a cornea that is more round, resulting in corrected vision. LRI's are a reliable treatment for low to moderate astigmatism.
 
Laser Vision Correction. Laser vision correction, as the name implies, uses lasers to reshape the cornea of the eye and correct the astigmatism. Laser vision correction is a widely accepted treatment for moderate to severe astigmatism. LASIK and PRK are both types of laser vision correction.
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  Limbal Relaxing Incisions (LRI)
  LASIK
  PRK
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