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| General Info about Astigmatism |
Astigmatism is a refractive error which causes blurred or distorted vision. It is one of the most common vision problems. Astigmatism usually occurs when the front surface of the eye, the cornea, has an irregular curvature. This irregular shape prevents light from focusing properly on the back of the eye, the retina. As a result, a person's vision may be blurred at all distances. Normally the cornea is smooth and equally curved in all directions. With astigmatism, the cornea is "warped", meaning it curves more in one direction and objects appear somewhat indistinct and slanted.It can occur with or without shortsightedness or long-sightedness. |
| What are the causes of Astigmatism ? |
| Astigmatism can also occur when the cornea's shape is more oblong than spherical. Normally cornea is spherical. The oblong shape causes light rays to focus on two points at the back of your eye, rather than on just one. Many people are born with this oblong cornea, and the vision problem may get noticed over time. In some people, astigmatism may be due to pressure of the eyelids on the cornea. It can also be due to incorrect posture or an increased usage of the eyes for close work. Heredity is also a cause of astigmatism. Rarely it is caused by lid swellings in a condition called chalazia or due to corneal scars. An eye injury may cause the cornea to scar, changing the path of light as it enters the eye. It may also be due to keratoconus, a rare condition in which the cornea loses its normal shape. Some patients experience surgically induced astigmatism after eye surgery. Sutures that are tightly placed can cause a slight wrinkling of the cornea and the patient will experience astigmatism until the surgical wound is healed. |
| What are the symptoms of Astigmatism ? |
How to recognize Astigmatism?
Patients with astigmatism have blurred or distorted vision at all distances. It can also cause images to appear doubled, particularly at night. Patients have inconsistent difficulty focusing on various objects such as finely printed words and lines. Headache and fatigue are common as the person tends to strain his eyes. Squinting, eye discomfort and irritation are also frequent. |
| How can we diagnose Astigmatism ? |
| Astigmatism is diagnosed with a routine eye examination. In an eye with a refractive error, the light rays do not bend properly to achieve a single focus point on the retina. Instead, light rays either focus in front of the retina, or do not focus at a single point. A process called refraction is used to measure the refractive error of the eye. A visual acuity test is performed to determine the focusing power of the eye at different distances. |
| How can Astigmatism be treated ? |
| Usually astigmatism is treated with spectacles and contact lenses. Many people with astigmatism can achieve better vision with specially designed Toric lenses. They're made with the same materials as regular contact lenses. It has an additional power element called a cylinder. This cylinder has greater light-bending powers to focus light clearly. Corneal modification is another option for people with astigmatism - this is done by surgical operations. Laser-assisted in situ keratomileusis (LASIK) is the most commonly performed refractive procedure — a flap is cut through the top of the cornea, a laser removes some corneal tissue and then the flap is dropped back into place. It smoothes an irregular cornea into a more normal shape. Astigmatic Keratotomy (AK) is also used to correct astigmatism. Incisions are strategically placed on the steepest curves. The steep areas flatten, and the cornea heals into a more spherical shape. This allows light to focus more precisely on the retina. Astigmatic Keratotomy (AK) can be performed alone or in conjunction with other refractive procedures. Limbal Relaxing Incision (LRI) is performed to correct mild astigmatism. This procedure is similar to Radial Keratotomy. Incisions are made at the limbus, (the visible borderline between the clear window (cornea) and the white globe (sclera) of the eye) and the cornea is made more spherical and is relaxed, to give a clear vision. |
| More Valuable Information about Astigmatism... |
| We don't really see objects; rather, we see light reflected by them or generated by them. The light is collected by our eyes and focused on the retina, where it is converted into nerve impulses and sent to the brain, where it is formed into images.
Modern contact lenses first appeared in the 1940's.
The average person has approximately 100-150 eyelashes on the upper eyelid. Each eyelash has a “life span” of approximately 5 months. |
| Frequently asked questions about Astigmatism... |
| Which specialist should I consult if I have Astigmatism? You should consult an Ophthalmologist. What is Refractive Surgery? Refractive surgery is an outpatient procedure that corrects vision problems such as nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. The surgery restores the eye's normal curvature and its ability to bring images into focus. What is PRK? Photorefractive keratectomy (PRK) uses the excimer laser to remove microscopic amounts of corneal tissue on the front of the corneal surface to correct nearsightedness, farsightedness and astigmatism. PRK is an outpatient treatment which takes only a few minutes and does not require an incision. What does atoric mean? Atoric simply means ‘not toric,’ just as aspheric means not spherical. An atoric lens surface varies slightly from a toric surface (a surface containing cylinder) in order to provide optical compensation for lenses with sphere and cylinder powers. |
| Glossary | |
| Astigmatism: Objects are blurred at all distances because the shape of the cornea is not uniform. Contact lenses: Lenses which fit directly on the eyeball under the eyelids. Cornea: The clear tissue in front of the eye resembling a crystal of a watch. Diplopia: The seeing of one object as two. Nystagmus: An involuntary, rhythmical movement of the eyeballs. Opthalmoscope: Device for viewing the interior of the eye or the retina. Optic nerve: The nerve which carries visual impulses from the retina to the brain. Optician: A technician who designs, verifies and dispenses lenses, frames and other fabricated optical devices upon the prescription of an ophthalmologist or an optometrist. Opthalmologist: A physician who is qualified and especially trained to diagnose and treat all eye and visual system problems, as well as diagnose general diseases of the body. Photophobia: Abnormal sensitivity to light. Refractive error: A defect in the eye that prevents light from being brought to a single focus exact on the retina. Pupil: Apeture allowing light to enter into the eye regulated by the iris and ciliary muscles. Retina: Light sensitive membrane at the back of the eye. Light is focused onto this membrane and the retina then transmits this information to the brain as impulses which the brain interprets as sight. Sclera: The firm white fibrous membrane that forms the white part of the eye. Visual Acuity: Clarity of vision, with corrective glasses.
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