Cataract

Treatment overview

Surgery for cataracts involves removing all or part of the lens and replacing it with an implant. Cataract removal is the most frequently performed surgery in people over age 65 and is considered by many doctors to be the most effective surgical procedure in all of medicine.

If the eye is normal except for the cataract, surgery will improve vision in more than 95 percent of cases. Because the implant is designed to correct nearsightedness or farsightedness, 85 percent of people undergoing cataract surgery achieve at least 20/40 vision--good enough to drive a car--one year after the operation. (People with 20/40 vision are able to see at 20 feet what a person with normal vision can see at 40 feet.) After cataract surgery, however, most people will still need to wear glasses to read small print or do close handwork.

Significant postsurgical complications occur in only 1 percent to 2 percent of operations and include inflammation, infection, bleeding, swelling, retinal detachment, and glaucoma. People with other eye diseases and serious medical problems are most at risk for complications.

This section has more on:

• Deciding whether to have cataract surgery
• About cataract surgery
• Types of cataract surgery
• Lens replacement
• After surgery
• Possible complications of surgery

Deciding whether to have cataract surgery

Immediate removal of a cataract is rarely necessary. Instead, the decision of when to have the surgery almost always rests with the patient. The decision is based on the cataract's interference with day-to-day activities like reading and driving, the balance between the operation's benefits and risks, and the presence of other health conditions that might affect the outcome. In some cases, people with another major vision disorder, such as advanced glaucoma or age-related macular degeneration, may be discouraged from having cataract surgery because it may not improve their vision. On the other hand, cataract removal might benefit people with certain types of retinal damage.

About cataract surgery

Before the 1970s, most surgeons performed cataract surgery with the naked eye or with the aid of loupes--specialized glasses that provide a small amount of magnification. Today, microsurgery is the rule: An operating microscope is placed over the eye undergoing surgery.

If both eyes have cataracts that require surgery, they are most often operated on one at a time, with at least several weeks--and more often months--between the two operations.

Cataract surgery usually takes less than an hour to perform. About 90 percent of the surgeries are done on an outpatient basis with a local anesthetic, given either by injection or eyedrops. (General anesthesia is used only in people who are extremely anxious or allergic to local anesthetics.) Patients often are given a sedative before the surgery to make them drowsy.

Types of cataract surgery

The two main types of cataract surgery are intracapsular and extracapsular.

Intracapsular surgery. Intracapsular cataract surgery removes the entire lens--the capsule, cortex, and nucleus. The procedure is rarely performed today but still is used in some situations, such as when the lens is partially or completely dislocated.

Extracapsular surgery. Extracapsular surgery is by far the most common type of cataract surgery because it minimizes trauma to the eye and is associated with fewer postoperative complications than intracapsular surgery. In extracapsular surgery, the surgeon makes an incision at the side of the cornea (the transparent, dome-shaped disk covering the iris and pupil) and removes the front of the lens capsule, followed by the nucleus and cortex. The back of the lens capsule remains intact. This back portion of the capsule provides support for the intraocular lens implant.

Lens replacement

Once a lens has been removed, the refractive power of the lens must be replaced so that light can focus onto the retina, the innermost layer of the eye, which consists of light-sensitive nerve tissue. The three most common replacement options are intraocular lens implants, glasses, and contact lenses.

Intraocular lens implants. By far the most frequent type of lens replacement is an intraocular lens implant, which is placed at the time of cataract surgery. More than a hundred brands of implants are available. Intraocular lens implants have been in wide use since 1977, and most ophthalmologists believe they are very safe.

The most common type of lens implant is the single-focus lens. Unlike the natural lens of the eye, a single-focus lens cannot alter its shape to bring objects at different distances into focus. As a result, the surgeon generally selects a lens that will provide good distance vision, and the person wears reading glasses for near vision. Alternately, the surgeon can correct one eye for distance and the other for near vision; this is called monovision.

In general, new eyeglasses cannot be prescribed until about three weeks after cataract surgery because the prescription changes as the eye heals. Still, if the eye is otherwise normal, people with lens implants often have functional vision as early as the first day after surgery.

The first multifocal lens implant, which provides both distance and near vision, was approved by the U.S. Food and Drug Administration several years ago. Although these lenses reduce the need for eyeglasses, many people still have to wear glasses for certain tasks. In addition, multifocal lenses can cause visual side effects such as glare and halos.

The newest type of lens implant, called an accommodating lens, contains a hinge that allows for both distance and near vision. The FDA approved the first of these devices, the CrystaLens, in 2003.

Although most people do achieve 20/40 vision or better with the implant, the range of vision varies, and improvements in near vision may decrease over time.

Once inserted, lens implants require no care of any kind. Like any device, however, complications can occur. The most common complication is glare or reduced vision when the intraocular lens is not aligned with the pupil.

Not all people who undergo cataract surgery are able to receive an intraocular lens implant, however. For example, lens implantation may not be possible in people with certain eye diseases including severe, recurrent uveitis (inflammation of the iris, ciliary body, or choroid), some cases of proliferative diabetic retinopathy (new blood vessel growth onto the back surface of the vitreous humor, the thick, gel-like substance that fills the back of the eyeball behind the lens), and rubeosis iridis (new blood vessel growth on the iris, which usually occurs in people with diabetes).

Glasses. Another option for lens replacement is cataract glasses. Although effective, these glasses are rarely used after routine cataract surgery because they are heavy and awkward. The glasses magnify objects by about 25 percent, causing them to appear closer than they actually are--a somewhat disorienting sensation. Because of the thickness and curvature of the lenses, cataract glasses magnify objects unequally and so have a distorting effect as well. In addition, they tend to limit peripheral vision.

Contact lenses. Like cataract glasses, contact lenses are not routinely used after cataract surgery. The lenses provide almost normal vision, but their major drawback is that people often have difficulty handling, removing, and cleaning them.

Both the contacts and glasses can be prescribed four to eight weeks after surgery.

After surgery

Most people experience minimal discomfort after cataract surgery; a mild painkiller (such as Tylenol can be taken if needed. Some redness, scratchiness, or morning discharge may be present during the first few days after surgery. In addition, it is common to see a few black spots or shapes (called floaters) drifting through the field of vision. A protective patch is generally worn over the eye for 24 hours. Glasses must be worn during the day to avoid trauma to the eye, and an eye shield is used at night for several days to a few weeks to prevent accidentally rubbing or poking the eye while asleep.

Vision varies widely when the patch is first removed. In most people, vision remains blurred for several days to weeks, then gradually improves as the eye heals. In some cases, the sutures in the eye alter the shape of the cornea and result in temporary blurring. This problem generally goes away on its own, though it may require removal of the sutures--a simple and painless procedure. In general, vision improves faster in those who receive intraocular lens implants than in those with cataract glasses or contact lenses. However, surgery usually changes the corrective prescription for the eye (even in those with lens implants), and new eyeglasses will be needed to correct any remaining nearsightedness or farsightedness. The patient is considered fully recovered when the eye is completely healed and vision has stabilized so that a final corrective prescription can be obtained.

Possible complications of surgery

Though cataract surgery is associated with a low rate of complications, problems may arise, especially in older adults or those with general health problems such as diabetes. Patients should contact their doctor if any of the following symptoms develop during recovery from surgery: unusual pain or aching, persistent redness, bleeding, excessive tearing or discharge, any sudden vision changes, or seeing many bright flashes of light.

In up to 20 percent of extracapsular surgeries--surgery that removes the front of the lens capsule while leaving the back of the lens capsule intact--the back of the lens capsule subsequently becomes cloudy and causes vision difficulties similar to those of the original cataract. Fortunately, recent advances in lens material and design have substantially reduced the risk of this complication. When cloudiness occurs, laser treatment is an effective remedy.

About 1 percent of people, particularly those who are very nearsighted, may develop retinal detachment after cataract surgery. Retinal detachment is a vision-threatening condition in which the retina becomes separated from the underlying layers of the eye.

Cystoid macular edema (a specific pattern of swelling of the central retina) is another common eye-related complication of cataract surgery. If the swelling does not go down on its own, eyedrops may be prescribed.

About 1 in 1,000 people develops an infection of the vitreous humor, called endophthalmitis, after cataract surgery. Patients who experience an increasingly red eye, blurred vision, and pain should see their ophthalmologist promptly. Typically, this condition can be treated with antibiotics and removal of some of the vitreous humor.

Other complications of cataract surgery, such as significant bleeding inside the eye or large pieces of the cataract falling into the back of the eye (dropped nucleus), are rare.

This section has more on:

• laser treatment following extracapsular surgery
• dealing with a detached retina

Laser treatment following extracapsular surgery

A YAG (yttrium, aluminum, and garnet) laser is used if vision is blurred by clouding of the back of the lens capsule that remains in the eye following extracapsular surgery. The YAG laser produces a hole in the back of the lens capsule by focusing a burst of energy on it. The procedure, called a YAG capsulotomy, leads to prompt clearing of vision.

The risk of retinal detachment with YAG capsulotomy is small, affecting approximately 1 in 300 people within three to four years of surgery. This risk is increased in younger people and those who are extremely nearsighted.

Dealing with a detached retina

Floaters and flashes that appear suddenly may signal a serious eye problem. Nearly everyone experiences floaters--small dots, lines, clouds, or "cobwebs" across the visual field--from time to time. This phenomenon is caused by shadows cast on the retina by microscopic structures within the vitreous humor (a thick, gel-like substance that fills the back of the eyeball behind the lens). Seeing flashes of light, which occurs when this fluid shifts, is another common ocular phenomenon.

In most cases, flashes and floaters are harmless and temporary, though they can be frequent and annoying. Sometimes, though, they indicate that the retina (the innermost layer of the eye that consists of light-sensitive nerve tissue) is tearing or in danger of detaching from the underlying layers of the eyeball. Retinal detachment may be a medical emergency that can result in blindness, but prompt treatment generally preserves vision.

How the retina detaches: Vitreous humor is a gelatinous fluid that adheres to the retina and fills most of the space inside the eye. As we age, the fluid gradually liquefies and becomes more mobile. Eventually, the vitreous humor begins to shift within the eye. Sometimes, this movement prompts the posterior surface of the vitreous to slide or pull away from the retina, a condition called posterior vitreous detachment.

PVD develops in 10 percent of adults by age 50 and in two thirds of those 70 and older. In most instances it causes no problems. But sometimes the vitreous humor remains adherent to the retina in some areas; as it pulls away, it can tear the retina. Tears are not necessarily harmful, but they may permit fluid to collect underneath the retina. If the fluid spreads, the retina may peel away and detach from the back of the eye--a so-called retinal detachment.

Who's at risk: Retinal detachment is a serious complication associated with cataract surgery. The problem develops in up to 1 percent to 2 percent of those who have a cataract removed, about half the time within a year of surgery. People who are severely nearsighted are also at increased risk, possibly because the elongated eyeball characteristic of the condition stretches and weakens the retina.

Additional risk factors include a personal or family history of retinal detachment, other eye problems (such as lattice degeneration, which causes retinal thinning), and eye trauma. People with diabetes are vulnerable to another, less common mechanism of retinal detachment related to the formation of scar tissue within the eye.

When to worry: Retinal tears are not painful, and symptoms may vary. Symptoms that do occur often appear in only one eye at a time and may develop either gradually or suddenly. The most distinctive clue is a shower of hundreds or thousands of little black dots across the field of vision, which may signal a hemorrhage caused by tearing across a blood vessel. Floaters or sudden flashes of white light also are characteristic. If the retina detaches, it may seem that a dark curtain or shade is spreading across the visual field.

Prompt evaluation by an ophthalmologist is necessary if you experience a shower of dots or a curtain spreading across the visual field, new and unexplained blurred vision, or an unusually high number of floaters or intensity of light flashes. Call your eye doctor, and do as he or she advises. If you don't have an eye doctor and can't locate one, you can go to an emergency room. Not all hospitals provide emergency eye care on site, however, so calling the hospital first may help you locate an appropriate facility.

Treating a tear or retinal detachment: Numerous procedures may be used to treat retinal tearing and detachment, depending on their extent and location. In certain cases, small holes in the retina require no treatment. In others, combinations of more than one surgical approach may be required. Many are performed on an outpatient basis. The amount of vision restored and preserved with all procedures is greater if the macula is still attached--but even if the prognosis is poor, treatment usually is still advisable.

After treatment, medication can be prescribed to ease any pain. For the first few days following surgery, physical activity is usually restricted, although reading, writing, and watching television are generally possible soon after surgery. Improvement of vision in the affected eye may take weeks or months. The chances of reattaching the retina are high for all types of retinal detachment surgery for uncomplicated cases, as more than 90 percent of retinal detachments can be repaired. The actual amount of vision restored, however, can vary greatly. A great advantage of the available techniques--laser therapy, cryotherapy, scleral buckling, vitrectomy, and pneumatic retinopexy--is that if one fails, another can be undertaken immediately or in a matter of days.