Wednesday, October 22, 2014

Definition

A cataract is a clouding of the normally clear and transparent lens of the eye. It is not a tumor, a new growth of skin or tissue over the eye, but a fogging of the lens itself.

Description

Normally, the lens of the eye is clear. When a cataract develops, the lens becomes cloudy, similar to a frosted window.

Located near the front of the eye, the lens focuses light on the retina at the back of the eye. Light passes through it to produce a sharp image on the retina. When a cataract forms, the lens can become so opaque and unclear that light cannot easily be transmitted to the retina.

Often, however, a cataract covers only a small part of the lens and if sight is not greatly impaired, there is no need to remove the cataract. If a large portion of the lens becomes cloudy, sight can be partially or completely lost until the cataract is removed.

There are many misconceptions about cataracts. For instance, cataracts do not spread from eye to eye, though they may develop in both eyes at the same time. A cataract is not a film visible on the outside of the eye, is not caused from overuse of the eyes, and using the eye does not make it worse. Cataracts usually develop gradually over many years; rarely over a few months. Finally, cataracts are not related to cancer, and having a cataract does not mean a patient will be permanently blind.

Depending on the size and location of the cloudy areas in a lens, a person may or may not be aware that a cataract is developing. If the cataract is located on the outer edge of the lens, no change may be noticed in vision, but if the cloudiness is located near the center of the lens, it usually interferes with clear sight. As cataracts develop, there may be hazy, fuzzy and blurred vision. Double vision may also occur when a cataract is beginning to form. The eyes may be more sensitive to light and glare, making night driving difficult.

With cataracts, there may be a need to change eyeglass prescriptions frequently. As the cataract worsens, stronger glasses are no longer able to improve sight. It may help to hold objects closer to the eye when reading or doing close-up work. The pupil, which is normally black, may undergo noticeable color changes and appear to be yellowish or white.

Causes

There are many types of cataracts. Most are caused by a change in the chemical composition of the lens resulting in a loss of transparency. These changes can be caused by aging, injuries to the eye, certain diseases, conditions of the eye and body, and heredity or birth defects.

The normal process of aging may cause the lens to harden and turn cloudy. These are called senile cataracts and are the most common type. They can occur as early as age 40. Children, as well as adults of any age, can develop cataracts. When cataracts appear in children, they are sometimes hereditary or can be caused by infection or inflammation, which affect the pregnant mother and the unborn baby. These are congenital cataracts and are present at birth.

Eye injuries can cause cataracts at any age. A hard blow, puncture, cut, intense heat or chemical burn can damage the lens, resulting in a traumatic cataract. Certain infections or diseases of the eye (such as diabetes) can also cause the lens to cloud and form a secondary cataract.

Symptoms

Symptoms of developing cataracts include double or blurred vision, sensitivity to light and glare (which may make driving difficult), less vivid perception of color and frequent changes in eyeglass prescriptions.

Cataracts are typically detected through a medical eye examination. The usual test for visual acuity (the letter eye chart) may not reflect the true nature of visual loss. Other tests that measure glare sensitivity, contrast sensitivity, night vision, color vision, and side or central vision help to nail down the diagnosis.

Because most cataracts associated with aging develop slowly, many patients may not notice their visual loss until it has become severe. Some cataracts remain small and never need treatment; others grow more quickly and progressively larger. Only when a cataract seriously interferes with normal activities is it time to consider surgery. People who depend on their eyes for work, play and other activities may want their cataracts removed earlier than those whose needs are less demanding.

Treatment

Cataract Surgery

Cataract surgery is recommended only when vision loss interferes with normal activities such as reading or driving, or if the cataract is preventing the treatment of another problem.

The decision to perform surgery should be based on the patient's own assessment of functional impairment combined with the results of the eye examination and measurement of visual acuity using the Snellen test. When visual acuity is 20/40 or better, the potential for benefiting from the surgery decreases and the risk relative to potential benefit rises. In general, the better the visual acuity is, the greater is the need for verification of functional disability before performing surgery.

Two types of cataract surgery most often performed are equally effective in restoring vision. These are:

Extracapsular surgery, in which the lens is removed and the back half of the capsule behind the lens (the posterior capsule) remains in the eye

Photoemulsification, a type of extracapsular surgery in which the lens is softened with sound waves and removed through a needle. The posterior capsule remains.

Intracapsular surgery is a third, rarely used type of surgery, in which the surgeon removes the entire lens, including the capsule. Usually the lens is replaced by an Intraocular lens, which becomes a permanent part of the eye. If a condition or disease prevents the use of an Intraocular lens, a soft contact lens may be prescribed instead.

Cataracts usually develop in both eyes, but surgery should not be done on both eyes until the results of the first eye surgery are known, so that the benefits and risks can be weighed. The indications for cataract surgery in the second eye are the same as for the first eye.

The period of postoperative care extends from surgery until the goal of surgery is achieved and the patient has stable, improved vision. If complications arise - such as increased pressure, bleeding or infection in the eye; damage or dislocation of the intraocular lens; or swelling or clouding of the cornea - prompt care is crucial. Optical correction (contact lenses or glasses) usually can be prescribed 6 to 12 weeks after surgery. The timing and frequency of refraction depend on patient needs, astigmatism and consistency of measurement.

Today, cataract surgery usually takes less than an hour, thanks to advances in microsurgery and suturing. The procedure is done on an outpatient basis in virtually all instances; the patient arrives in the morning and goes home in the early afternoon. The procedure itself involves a small incision directly into the eye. The clouded lens is removed, a plastic one is inserted and the surgical opening is closed.

The surgery requires anesthesia around the eye and some patients may receive a mild sedative to help them relax. Although some patients can drive without difficulty after cataract surgery, it's a good idea to have someone else available to do the driving. The patient wears a patch for a day.

Some people notice a mild, scratchy irritation, but most report no discomfort. Most patients can resume normal activities within a day to a week, but strenuous activity, especially heavy lifting, should be avoided from four to six weeks.

Occasionally, improvement in vision occurs almost immediately after cataract surgery, but more often, the improvement occurs gradually over several months. It's important to note that a lens implant does not guarantee perfect vision. In fact, most people will continue to need glasses to correct either distance or near vision.

Small Incision Cataract Surgery

In a newer surgical method, called small-incision (no-stitch) cataract surgery, the nucleus is broken up (emulsified) by an ultrasound probe. No-stitch surgery requires only a single, 1/8-inch incision. A small incision means faster healing. Redness and inflammation of the eye disappear in two to three weeks with small-incision surgery, vs. six to eight weeks with extracapsular extraction. A special advantage of small-incision surgery is that it is less likely to cause astigmatism. This is blurred vision that results when tension on the stitches distorts the cornea. Small-incision surgery involves an incision not on the cornea, but on the less sensitive sclera (the white of the eye).

Because of its advantages, many eye surgeons have adopted the no-stitch technique. Others feel strongly that extracapsular surgery is just as good. But after the eye heals completely, there is generally little difference between the results from extracapsular and small-incision surgery. A patient may not be a candidate for the no-stitch method, in that advanced cataracts tend to be too hard to emulsify easily. In such cases, extracapsular surgery may be the better choice.

In the past, people who underwent cataract surgery had to wear thick "Coke bottle" eyeglasses. Now, immediately after the removal of the cataract, the surgeon implants a plastic lens directly into the space left by the removal of the clouded lens. This intraocular implant helps the cornea focus light onto the retina to give a clear image.

There are many different implants on the market and they fall into two general categories, based on their location in the eye:

Posterior chamber implants, the more popular type, are placed behind the iris, occupying the exact position of the original lens. There are now smaller oval and foldable lenses that can be used with small-incision surgery.

Anterior chamber implants are inserted into the fluid-filled space between the iris and the cornea.

Some experts estimate that about 88 of every 100 persons receiving IOLs (intraocular lenses) will achieve 20/40 vision or better. (An individual with 20/40 vision can read letters on an eye chart from 20 feet away. While a person with normal 20/20 vision can read the chart from 40 feet away, 20/40 vision is good enough to get a driver's license in most states.) Among those who do not have other eye diseases, about 94 of 100 will achieve 20/40 vision.

Questions

Do any additional tests need to be done to diagnose?

What type of cataracts are there?

What is the cause of the cataracts?

If the cataracts are just starting, is there anything that can be done to keep them from getting worse?

How fast will the cataracts progress?

Is surgery the only means of treatment?

How many surgeries have you performed, and what types?

How successful is this surgery? How is the surgery performed?

What are the possible complications?

What can be expected after surgery?