What is a cataract?
A cataract is a clouding of the normally clear lens of the eye. It can be compared to a window that is frosted or "fogged" with steam. There are many misconceptions about cataract. It is:
-  Not a film over the eye;
-  Not caused by overusing the eyes;
-  Not a cancer;
-  Not spread from one eye to the other;
-  Not a cause of irreversible blindness.
-  Common symptoms of cataract include:
-  A painless blurring of vision;
-  Glare, or light sensitivity;
-  Frequent eyeglass prescription changes;
-  Double vision in one eye;
-  Needing brighter light to read;
-  Poor night vision;
-  Fading or yellowing of colors.
-  The amount and pattern of cloudiness within the lens can vary. If the cloudiness is not near the center of the lens, you may not be aware that a cataract is present.

What causes cataract?
The most common type of cataract is related to aging of the eye. Other causes of cataract include:
-  Family history;
-  Medical problems, such as diabetes;
-  Injury to the eye;
-  Medications, such as steroids;
-  Long term, unprotected exposure to sunlight;
-  Previous eye surgery.

How is a cataract detected?
A thorough eye examination by your ophthalmologist (medical eye doctor) can detect the presence and extent of a cataract, as well as any other conditions that may be causing blurred vision or discomfort. There may be other reasons for visual loss in addition to the cataract, particularly problems involving the retina or optic nerve. If these problems are present, perfect vision may not return after a cataract removal. If such conditions are severe, removal of the cataract may not result in any improvement in vision. Your ophthalmologist can tell you how much visual improvement is likely.

How fast does a cataract develop?
How quickly the cataract develops varies among individuals, and may even vary between the two eyes. Most cataracts associated with aging progress gradually over a period of years. Other cataracts, especially in younger people and people with diabetes, may progress rapidly over a few months and cause vision to worsen. It is not possible to predict exactly how fast cataracts will develop in any given person.

How is cataract treated?
Surgery is the only way your ophthalmologist can remove the cataract. However, if symptoms are mild, a change of glasses may be all that is needed for you to function more comfortably. There are no medications, dietary supplements, exercises or optical devices that have been shown to prevent or cure cataracts. Protection from excessive sunlight may help prevent or slow the progression of cataracts. Sunglasses that screen out ultraviolet (UV) light rays or regular eyeglasses with a clear, anti-UV coating offer this protection.

When should surgery be done?
Cataract surgery should be considered when cataracts cause enough loss of vision to interfere with daily activities. It is not true that cataracts need to be "ripe" before they can be removed. Cataract surgery can be performed when your visual needs require it. You must decide if you can see to do your job and drive safely, if you can read and watch TV in comfort. Can you perform daily tasks, such as cooking, shopping, yard work or taking medications without difficulty?

What can I expect from cataract surgery?
Over 1.4 million people have cataract surgery each year in the United States, 95% without complications. During cataract surgery, which is usually performed under local anesthesia as an outpatient procedure, the cloudy lens is removed from the eye. In most cases, the focusing power of the natural lens is restored by replacing it with a permanent intraocular lens implant. Your ophthalmologist performs this delicate surgery using a microscope, miniature instruments and other modern technology. Although it is a common misconception, lasers are not used to remove cataracts. In approximately one-fifth of people having cataract surgery, the natural capsule that supports the intraocular lens will become cloudy. Laser surgery is used to open this cloudy capsule, restoring the clear vision. After cataract surgery, you may return almost immediately to all but the most strenuous activities. You will have to take eyedrops as your ophthalmologist directs. Several postoperative visits are needed to check on the progress of the eye as it heals. Cataract surgery is a highly successful procedure. Improved vision is the result in over 90% of cases, unless there is a problem with the cornea, retina or optic nerve. It is important to understand that complications can occur during or after the surgery, some severe enough to limit vision. As with any surgery, a good result cannot be guaranteed.

Conclusion
Cataracts are a common cause of poor vision, particularly for the elderly, but they are treatable. Your ophthalmologist can tell you whether cataract or some other problem is the cause for vision loss or discomfort, and help you decide if cataract surgery is appropriate for you.

American Academy of Ophthalmology
P. O. Box 7424 San Francisco, CA 94120-7424
http://www.eyenet.org
Copyright 1984 American Academy of Ophthalmology

Strabismus
What is strabismus? Strabismus is a visual defect in which the eyes are misaligned and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward or downward. You may always notice the misalignment, or it may come and go. The turned eye may straighten at times and the straight eye may turn. Strabismus is a common condition among children. About 4% of all children in the United States have strabismus. It can also occur later in life. It occurs equally in males and females. Strabismus may run in families. However, many people with strabismus have no relatives with the problem.

How do the eyes work together?
With normal vision, both eyes aim at the same spot. The brain then fuses the two pictures into a single three-dimensional image. This three-dimensional image gives us depth perception. When one eye turns, two different pictures are sent to the brain. In a young child, the brain learns to ignore the image of the misaligned eye and sees only the image from the straight or better seeing eye. The child then loses depth perception. Adults who develop strabismus often have double vision because the brain is already trained to receive images from both eyes and cannot ignore the image from the turned eye.

Amblyopia
Good vision develops during childhood when both eyes have normal alignment. Strabismus may cause reduced vision, or amblyopia, in the weaker eye. The brain will recognize the image of the better-seeing eye and ignore the image of the weaker or amblyopic eye. This occurs in approximately half of the children who have strabismus. Amblyopia can be treated by patching the "good" eye to strengthen and improve vision in the weaker eye. If amblyopia is detected in the first few years of life, treatment is usually successful If treatment is delayed until later, amblyopia usually becomes permanent. As a rule, the earlier amblyopia is treated, the better the visual result.

What causes strabismus?
The exact cause of strabismus is not fully understood. Six eye muscles, controlling eye movement, are attached to the outside of each eye. In each eye, two muscles move the eye right or left. The other four muscles move it up or down and at an angle. To line up and focus both eyes on a single target, all of the muscles in each eye must be balance and working together. In order for the eyes to move together, the muscles in both eyes must be coordinated. The brain controls the eye muscles. Strabismus is especially common among children with disorders that affect the brain, such as:
-  Cerebral palsy;
-  Down syndrome;
-  Hydrocephalus
-  Brain tumors.
-  A cataract or brain injury that affects vision can also cause strabismus.

What are the symptoms of strabismus?
The main symptom of strabismus is any eye that is not straight. Sometimes children will squint one eye in bright sunlight or tilt their head to use their eyes together.

How is strabismus diagnosed?
Strabismus can be diagnosed during an eye exam. It is recommended that all children have their vision checked by their pediatrician, family doctor or ophthalmologist (medical eye doctor) at or before their fourth birthday. If there is a family history of strabismus or amblyopia, an ophthalmologist can check vision even earlier than age three. The eyes of infants often seem to be crossed. Young children often have a wide, flat nose and a fold of skin at the inner eyelid that can make the eyes appear crossed. This appearance of strabismus may improve as the child grows older.

A child will not outgrow true strabismus.
An ophthalmologist can usually tell the difference between true and false strabismus.

How is strabismus treated?
Treatment for strabismus works to:
-  Preserve vision;
-  Straighten the eyes;
-  Restore binocular (two-eyed) vision.

After a complete eye examination, an ophthalmologist can recommend appropriate treatment. In some cases, eyeglasses can be prescribed for your child. Other treatments may involve surgery to correct the unbalanced eye muscles or to remove a cataract. Covering or patching the strong eye to improve amblyopia is often necessary.

Most common types of strabismus
Esotropia
Esotropia, where the eye turns inward, is the most common type of strabismus in infants. Young children with esotropia do not use their eyes together. In most cases, early surgery can align the eyes. During surgery for esotropia, the tension of the eye muscles in one or both eyes is adjusted. The tight inner muscles may be removed from the wall of the eye and placed further back on the eye. This adjustment weakens their pull and allows the eyes to move outward. Sometimes the outer muscles are tightened by shortening the muscle length to allow the eyes to move outward.
Accommodative esotropia
Accommodative esotropia is a common form of esotropia that occurs in farsighted children two years or older. When a child is young, he or she can focus the eyes to adjust for the farsightedness, but the focusing effort (accommodation) to see clearly causes the eyes to cross. Glasses reduce the focusing effort and can straighten the eyes. Sometimes bifocals are needed for close work. Eye drops, ointment or special lenses called prisms can also be used to straighten the eyes.
Exotropia
Exotropia, or an outward turning eye, is another common type of strabismus. This occurs most often when a child is focusing on distant objects. The exotropia may occur only from time to time, particularly when a child is daydreaming, ill or tired. Parents often notice that the child squints one eye in bright sunlight. Although glasses, exercises or prisms may reduce or help control the outward turning eye in some children, surgery is often needed.

How is strabismus surgery done?
The eyeball is never removed from the socket during any kind of eye surgery. The ophthalmologist makes a small incision in the tissue covering the eye to reach the eye muscles. Certain muscles are repositioned during the surgery, depending on which direction the eye is turning. It may be necessary to perform surgery on one or both eyes. When strabismus surgery is performed on children, a general anesthetic is required. Local anesthesia is on option for adults. Recovery time is rapid. People are usually able to resume their normal activities within a few days. After surgery, glasses or prisms may be useful. In many cases, further surgery may be needed at a later stage to keep the eyes straight. For children with constant strabismus, early surgery offers the best chance for the eyes to work well together. In general, it is easier for children to undergo such surgery before school age. As with any surgery, eye muscle surgery has certain risks. These include infection, bleeding, excessive scarring and other rare complications that can lead to loss of vision. Strabismus surgery is usually a safe and effective treatment for eye misalignment. It is not, however, a substitute for glasses or amblyopia therapy.

Injections
Boxtox, a new drug approved by the U.S. Food and Drug Administration for limited use, is an alternative to eye muscle surgery for some individuals. An injection of the drug into an eye muscle temporarily relaxes the muscle, allowing the opposite muscle to tighten and straighten the eye. Although the effects of the drug wear off after several weeks, in some cases the misalignment may be permanently corrected.

American Academy of Ophthalmology
P. O. Box 7424 San Francisco, CA 94120-7424
http://www.eyenet.org
Copyright 1984 American Academy of Ophthalmology