Frequently Asked Questions-cont'd
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Questions and Answers on the following topics are available: | Amblyopia
| Cataracts | Diabetic
Retinopathy | Dry Eye | Floaters and Flashes | Glaucoma
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Q: What is it? A: Glaucoma, one of the leading causes of blindness in the United States, is a disease which damages the optic nerve. It is a progressive eye disease usually associated with too much pressure within the eye. The pressure reduces the blood supply to the retina progressively destroying nerve cells. There are four basic types of glaucoma. Chronic simple glaucoma is the most common type. The pressure rising within the eye is not the result of any known underlying factor. It usually begins in the middle years and may be hereditary. Chronic secondary glaucoma is caused by something specific. The causes can vary from: complications of another eye problem, inflammation from an eye infection, an allergic reaction within the eye, trauma to the eye, or scar tissue. Cataract complications can also cause this type of glaucoma. Acute glaucoma is a rare condition. The rise in pressure is fast as well as high. The eyeball becomes very hard. The pressure is so great that it causes severe pain and damage to the whole eye. Congenital glaucoma is also quite rare. It is either present or develops during infancy. Surgery is usually required, and must be performed early if permanent loss of sight is to be avoided. Anyone at any age can get glaucoma, but it generally occurs after middle age. Q: Can children get it? Yes. Many cases in babies and young children result from prenatal and hereditary factors. Q: Is aging a factor? Yes. The older the person, the greater the risk of developing glaucoma. Q: Does it run in families? Yes. There is a heredity tendency. Glaucoma occurs about four times more frequently among persons who have blood relatives with glaucoma. Q: What causes it? A: Glaucoma is caused by an increase in the fluid pressure in the eye. The eye contains a clear, nourishing fluid called the aqueous which constantly circulates through the eye...leaving the eye through a drainage system and returning to the blood stream. Glaucoma occurs when the system becomes blocked, causing fluid pressure to rise. The high fluid pressure causes damage to the optic nerve, resulting in permanent vision loss. The exact reason the eye's drainage system stops functioning properly is not completely understood. Much research is being done in this area to further our understanding of glaucoma. Q: What are the signs or symptoms? A: In most cases, glaucoma is detected in a routine eye examination before the patient experiences any problems. An evaluation for glaucoma is painless and includes several different tests. If any sign of glaucoma is detected, the patient's field of vision is tested for blind spots and any shrinkage in peripheral vision. A combination of eye drops, medication, laser surgery and conventional surgery are used to treat glaucoma. Treatment is concentrated on lowering the pressure inside the eye to prevent damage to the optic nerve. While Glaucoma can not be prevented, blindness can generally be prevented through early detection and appropriate treatment. Q: How often should a person be checked for glaucoma? A: People with a family history of glaucoma should be checked once a year. People with no family history of the disease should be checked every two years, especially after the age of 35.
Q: How does the eye work? A: Like a finely engineered machine, in order for the eye to see properly, all of the eye's parts must function properly, all of the eye's parts must function in perfect synergism. The transparent surface of the eye through which light enters is called the cornea. The cornea must be absolutely clear. If the cornea should become diseased or opaque it can be replaced with a new cornea from a donor, through a procedure called a corneal transplant. Once the light enters the eye through the cornea, it passes through a small hole in the iris called a pupil. The iris works very much like the lens of a camera. It opens up the pupil (dilates) to let in more light when it is dark and closes up the pupil (constricts) to let in less light when it is very bright. Directly behind the pupil is a clear, gelatin-like lens, wrapped in a clear protective membrane called its capsule. The lens is responsible for focusing the images that you see to the back of the eye. If the lens becomes opaque, then the lens becomes known as a cataract. Q: How does the image then get to the brain? A: The image passes through the vitreous, a clear gel that fills the eye, and the image is then focused onto the retina at the back of the eye. The retina records the image, very much like film in a camera, and sends the image by way of the optic nerve to the brain. Q: How does the retina function? A: The retina is responsible for changing images into electrical impulses which are sent to the brain. The retina is nourished by tiny blood vessels located in the layers in the back of the eye. There are areas on the retina that are responsible for different types of vision. One such area located near the optic disk is the macula. The macula is responsible for straight ahead, or central vision. Located throughout the retina are light sensing cells called rods and cones. Cones are responsible for color and central vision. Rods are responsible for night and side vision. Q: How does the movement of the eye happen? A: Movement of the eyes...up, down, sideways,
is controlled by a set of six muscles attached to the eyeball.
To see correctly, both eyes must move at the same time, the same
distance and the same direction. To do this the brain tells a
set of muscles to pull and the opposite set of muscles to relax...thus
the eye can move in all directions. If the eye muscles are not
coordinated in their movement, double vision may occur. This
uncoordinated movement is called strabismus. If the wandering
eye is not corrected, loss of vision may occur, leading to an
extreme case of amblyopia.
Q: What is it? A: Macular degeneration is a degenerative eye disease of the blood vessels located in the macula which is part of the retina. The macula is responsible for sharp central vision. The most common type is senile macular degeneration which is associated with the aging process. Other types include those caused by nearsightedness, by heredity, by other bodily disorders such as infection or general disease (arteriosclerosis, diabetes), by severe injury to the eye, or by exposure to excessive light. There is also a condition known as juvenile macular degeneration which affects children. Most anyone can get macular degeneration. Macular degeneration is the leading cause of blindness in persons age 75 and over and is the most common cause of new cases of blindness among those who are 65 and over. The disease may be hereditary in young people and sometimes in adults. Hereditary conditions include Best's disease, Stargardt's disease, and fundus favimaculatus or "flecked retina". Q: What causes it? A: With time, the retinal tissue breaks down and becomes thin. This deterioration causes a loss of function of the macula. In about 10% of the cases, aging of the retina is compounded by leakage of the tiny blood vessels which nourish the retina. Growth of new, abnormal blood vessels in the scar tissue that forms from the leaking blood vessels is also common. Blood and leaking fluid destroy the macula, causing vision to become distorted and blurred. Q: What are the signs and symptoms? A: The most notable symptom of macular degeneration is blurry or distorted central vision. Difficulty in reading, doing close work, or driving may be noticed. A person with macular degeneration may also experience blurry words on a page, distortion at the center of vision, a dark or empty area in the center of vision, or the distortion of lines. Macular degeneration may also cause a dimming of color vision. Fortunately, the disease does not cause total blindness, as side vision is not affected. Macular degeneration only affects central and color vision. Macular degeneration can be determined by using a lighted instrument called an ophthalmoscope to examine the retina. In addition, some special tests may also be administered. The Amsler Grid Test is used to detect blind spots or distortions. A color vision test will indicate damage to the macula if the patient cannot detect symbols or letters camouflaged in colored patterns. If macular degeneration is detected, a procedure called fluorescein angiography may be done to check for blood vessel leakage. Q: How is it treated? A: Despite ongoing medical research, there is no cure yet for the condition. There are a number of treatments designed to help individuals cope with the vision impairment, and various low vision optical devices can help to minimize the effects of macular degeneration. Because side vision is usually not affected, a person's remaining sight can be very useful. A wide range of support services, programs and devices are available to help people with macular degeneration continue their favorite activities.
Q: What is it? A: Strabismus is a visual defect in which the eyes are misaligned and point in different directions. We've become accustomed to referring to this condition as crossed eyes, but actually strabismus refers to any situation where the eyes are not pointed in the same direction. This occurs when the muscles that control eye position and movement do not work together properly. When that happens, one eye might be pointing in or out, or up or down, while the other eye is looking straight ahead. If the eyes are looking in two different directions, they will each see a different image. Then, not only is it difficult or impossible to judge depth, but the brain learns to favor one image over another. Crossed eyes, if not corrected early, can lead to a condition known as lazy eye, or what eye specialists call amblyopia. This occurs when the same eye always turns away and becomes weaker or lazy. If not treated, that eye will eventually become useless. The two most common types of strabismus are esotropia and exotropia. Esotropia describes an inward turning eye. Exotropia describes an outward turning eye. Children as well as adults can have strabismus. Strabismus affects about 4% of the children's population. Strabismus can be hereditary. However, many people have strabismus with no trace of the problem in any other family member. Q: What are the signs or symptoms? A: The primary symptom of strabismus is an eye that is not straight. Sometimes a child will squint one eye in bright sunlight or tilt their head in a specific direction in order to use their eyes together, signs of faulty depth perception may also be noticed. Adults who acquire strabismus will usually have double vision. It's difficult for a parent to determine whether or not an infant's eyes are working together properly. At birth, and for the first few months of life, a baby's eyes sometimes seem to be moving independently of one another. Yet the eyes are gaining in strength and coordination, and usually by six months of age they are functioning as they should. Q: What causes it? A: The exact cause of eye misalignment that leads to strabismus is not fully understood. To line up and focus both eyes on a single object, all eye muscles of each eye must be balanced and working together with the corresponding muscles of the opposite eye. The brain controls the eye muscles, which explains why children with disorders that affect the brain, such as cerebral palsy, Down's syndrome, hydrocephalus and brain tumors, often have strabismus. A cataract or eye injury that affects vision can also cause strabismus. Q: How is it detected? A: Children should have a thorough medical examination during infancy and preschool years to detect potential eye problems. This is particularly important if a relative has strabismus. Q: How is it treated? A: Treatment goals for strabismus are to preserve vision, and to straighten the eyes, and to restore binocular vision. The simplest treatment is corrective lenses. Eye drops may be prescribed. In some cases, eye exercises are helpful. Eye patches, used in combination with glasses or surgery are beneficial to some patients. Surgery not only permits the eyes to develop normally, but it also improves one's appearance. Early surgery is recommended to correct strabismus because younger infants can develop normal sight and binocular vision once the eyes are straightened. As a child gets older, the chance of developing normal sight and binocular vision decreases, although side vision may improve. Correction of strabismus after age 6 will improve appearance, but cannot provide a second chance to learn binocularity.
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