Astigmatism
Astigmatism – sometimes mispronounced as “a stigmatism” – is blurred vision resulting from a misshaped cornea. Astigmatism, unlike normal vision, occurs when the cornea is shaped like a football or like the back of a spoon (more curved in one direction than the other). This causes light to be unfocused in more than one point on the retina, resulting in blurry and distorted vision at all distances.
Symptoms of Astigmatism
Blurry, distorted vision at all distances.
Causes of Astigmatism
Heredity, Corneal scars, Keratoconus
Diagnosing Astigmatism
Your eye doctor can conduct a refractive evaluation to determine whether your eyes focus light rays exactly on the retina at distance and near. A visual acuity test will determine your ability to see sharply and clearly at all distances.
Treatment of Astigmatism
Glasses and contact lenses are used by many for the temporary treatment of astigmatism. However, there are a number of vision correction procedures that can surgically reduce or eliminate astigmatism.
Astigmatic Keratotomy
ASTIGMATIC KERATOTOMY (AK) is an incisional procedure popularized in the 1970s by Fyodorov. Dr. Mark Sibley was trained by Dr. Fyodorov in the 1980's. This procedure is performed by making precise, superficial incisions in the periphery of the cornea with a microscopic blade. The effect of these incisions is to cause changes in the shape of the central cornea from egg shaped to round again.
Factors that affect surgical outcome include the patient age and amount of astigmatism the patient age and amount of astigmatism. The results of AK are best in patients with low to moderate astigmatism (up to +6.0 D).
Complications
Intraoperative complications of AK are possible and may include perforation of the cornea.
Postoperative complications include epithelial in growth or endothelial cell loss, glare or induced astigmatism, difficulty with contact lens fitting ,under- and over-correction, endophthalmitis , diurnal fluctuation in vision ,infectious and noninfectious keratitis, late traumatic ruptured incisions , fluctuation in vision
AK has some distinct advantages over modern forms of refractive surgery, including can have immediate visual improvement and results, more long-term data on this procedure than on any other refractive surgical options , equipment that is less expensive than that used in laser surgery ,conveniently done in the office , can be safely repeated for additional effect.
Limbal relaxing incisions (LRI)
Limbal relaxing incisions (LRI) are truly a modification of astigmatic keratotomy (AK), which is a procedure to treat astigmatism. Astigmatism is present when the cornea is not spherical, i.e., it is steeper in one meridian than the opposite meridian 180 degrees away. The cornea with astigmatism may be thought of as being more football shaped rather than basketball shaped. LRI’s are incisions that are placed on the far peripheral aspect of the cornea (the limbus) resulting in a cornea that is more round. The astigmatism is thus reduced and uncorrected vision is improved.
The procedure can be completed in a few seconds after numbing the eye with anesthetic drops. There is usually little if any post-operative discomfort. The procedure is extraordinarily safe and is not associated with glare or starburst, as often occurs with true corneal incisions (RK and AK).
Limbal relaxing incisions have gained widespread acceptance amongst cataract surgeons where it is often combined with the cataract operation to reduce pre-existing astigmatism. This results in better post-operative vision without glasses.
The procedure can also be used in individuals whose primary refractive error is astigmatism.
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