CATARACTS

Normal lens vs. cataract

A cataract is defined as any opacity or cloudiness in the lens of the eye. The lens of the eye is a normally clear structure located behind the pupil and iris. The pupil is the round opening in the middle of the iris or colored part of the eye. The pupil usually constricts or becomes smaller when exposed to light, and tends to dilate or become larger under low lighting or dark conditions. The human lens can be thought of as being similar in shape to a magnifying lens. This lens is held in place by many tiny fibers (zonules) which stretch from the innermost layer of the wall of the eyeball, to attach to the edge of the lens all the way around. The normal human lens is elastic; it can stretch when it is pulled by the attaching fibers. Many people think that a cataract is a film that grows over the front of the eye, but in fact, it is a cloudiness of the lens which is located inside the front of the eye.

Cataracts can develop as a result of the aging process, but they can also be present at birth (congenital). A congenital cataract in an baby can be a medical emergency. If it is visually significant, it can cause permanent poor vision, unless it is quickly removed with surgery. Anything that affects the quality of vision, whether it be a corneal scar or cataract, can interrupt normal visual development, resulting in a poorly seeing or amblyopic (“lazy”) eye. Once normal vision has fully developed, usually by 6-7 years of age, for all purposes, a cataract will rarely cause irreversible loss of vision.

Are there different types of cataract?
A cataract can be classified or named in many ways. One way is based on where the cloudiness is located. A normal lens has a inner core or nucleus, and an outer layer called the cortex. The entire lens is wrapped in a clear outer coating called the capsule. The capsule can be thought of a kind of shrink wrap, the elastic wrap that’s used to package loose vegetables in the grocery store. One type of cataract is a nuclear sclerotic cataract , when the nucleus is cloudy. In a cortical cataract , the outer cortex layer is cloudy. When the cloudiness is located just underneath the capsule, you have a subcapsular cataract . A subcapsular cataract can be further named by its location; if it is at the back of the lens, it is posterior (back) subcapsular; if it is in the front of the lens, it is an anterior (front) subcapsular cataract. A person can have cloudiness that only affects one layer of the lens, or any combination of two or more layers. As an example, a person can have both a nuclear sclerotic and cortical cataract.

Who is affected by cataracts?
Cataracts that develop as part of the aging process typically will start after the ages of 30-40, and are progressive (worsen with time). Cataracts can also be caused by trauma, diabetes and other systemic metabolic diseases, radiation, and some drugs and chemicals. One drug which can cause cataract formation, usually posterior subcapsular, is prednisone, a steroid medication. A cataract can also be the result of other eye diseases, such as iritis, an inflammatory condition of the eye. Long-term use of glaucoma medications may contribute to cataract formation. A strong link between cigarette smoking and nuclear sclerotic cataracts has been demonstrated.

How will I know if I have a cataract?

Glare

Night Halo

Regardless of the type of cataract, or the cause, the problem it can cause is decreased vision. If a cataract is primarily nuclear sclerotic, there may be more of an effect on distance vision. Some patients with nuclear sclerotic cataracts will develop “second sight”, being able to read without glasses, though the distance vision will be blurry. For some of these patients, a change of glasses prescription may allow for improved distance vision. Other patients may have more problems with their near or reading vision, as can occur with the posterior subcapsular type of cataract. Other symptoms of cataract include glare when it’s sunny outdoors, or at nighttime with the headlights of oncoming cars. Halos or rings around lights, and double and multiple images can also be caused by cataracts.

The rate at which a cataract grows can be unpredictable. Nuclear cataracts tend to be slow growing, while subcapsular cataracts can progress or grow quickly, but these are generalizations. One method of grading the severity of a cataract uses a numbering system from 0 to 4+, with 0 being no cataract and 4+ being the most severe.

When is cataract surgery indicated?
One of the most frequently asked questions is when cataract surgery should be performed (see Cataract surgery below). In general, surgery is reasonable when the best-corrected vision in an eye is unsatisfactory to the patient. Best-corrected vision is the vision a person gets with the most up-to-date glasses or contacts. A person may decide to get surgery because he or she has problems seeing road signs, recognizing faces of people, trouble reading or reading for long periods of time, glare on sunny or bright days, glare with headlights when driving at night, and double or multiple vision. Color vision may also be changed.

People have different visual needs. Some people don’t require sharp vision to enjoy good quality of life. Others need crystal-clear vision to perform job duties or hobbies. There was a time when patients were advised to wait until their cataracts became “ripe” or “mature”. This is an out-of-date concept. Obviously, a cataract needs to be present, but more importantly, a patient needs to feel he or she is not enjoying good quality of life because of visual difficulty. There are patients who have 4+ nuclear sclerotic cataracts and are content with their vision because they can watch televison comfortably. Other patients have 2+ cataracts and are miserable because they can’t read clearly.

The decision to have cataract surgery is made on a case-by-case basis. It is a joint decision made by both patient and doctor. A patient should not feel pressured to have surgery; waiting is nearly always an option. Cataract surgery is nearly always elective; it is the rare instance when cataract surgery needs to be done right away. The bottom-line is that if a patient does not feel he or she is having visual difficulty, surgery is usually not required. A few exceptions to this rule include the following: 1) your eye doctor has difficulty looking at the back of the eye to follow the progress of a disease such as diabetic retinopathy or age-related macular degeneration; 2) the cataract is pushing the iris forward as it grows, compromising the angle of the eye to cause narrow angle glaucoma (see Glaucoma); and 3) the cataract becomes hypermature, with leakage of lens material through the capsule, causing inflammation and a type of glaucoma. Not meeting state standards of safe driving vision may also prompt the need for cataract surgery.

What does cataract surgery involve?
Cataract surgery is one of the most commonly performed surgeries in the United States. It is an outpatient-type of surgery where staying overnight in a hospital is almost never required. It is done under local anesthesia, so the patient is awake. Generally, an intravenous line is started in an arm vein, so that sedatives can be given to relax the patient. After surgery, the patient is taken to a recovery room before being sent home. The one thing patients are most concerned about, is whether there is any pain. I tell my patients that cataract surgery is painless; it is the rare patient who feels anything at all. Anesthetic or numbing eyedrops are instilled into the eye having surgery, and additional anesthetic is used to bathe the inside of the eye. Patients are sometimes worried they may move or be unable to keep their eyes open during surgery. This is almost never a problem. Through a combination of reassurance, sedation, and instrumentation, the eye surgeon can safely guide a patient through surgery.

Artificial implant

Implant injector

Implant in eye

Cataract surgery involves two major steps, removal of the cloudy lens and replacement with an artificial lens implant. The implant takes over the job of focusing that the old lens used to do. In the early days of cataract surgery, lens implants were not available, hence, patients used to wear unsightly thick cataract glasses. This is no longer an acceptable means of restoring vision. Successful cataract surgery requires use of an implant.

Modern cataract surgery is done using phacoemulsification . This technique uses an instrument that vibrates at ultrasonic frequency, to emulsify or break up and remove the cataract. Most surgeons make a tiny incision, usually less than 3.5 millimeters in length, through which the cataract is removed. This incision is made in such a way that it is self-sealing or closing, so that stitches are rarely required. Prior to actual surgery, a patient’s eye is dilated, that is, the pupil is made larger with eyedrops. The surgeon makes the incision in the cornea (clear dome that arches over the colored part of the eye), where it meets the sclera, the white part of the eye. This incision is so tiny, it cannot be seen with the naked eye. Through this small incision, the surgeon makes an round opening in the capsule, the shrink-wrap that is wrapped around the cloudy lens. The phacoemulsification instrument which is held like a pencil, is placed through the incision, and the inner portions of the cloudy lens is removed through the opening in the capsule. What is left, is a clear, empty sack or capsular bag, with the opening in the front. The surgeon then slides an intraocular lens implant into the eye, and places it inside the capsular bag. To take advantage of the tiny incision, most surgeons use a foldable implant, an implant that can be folded like a taco shell. This folded implant can be inserted through the small incision (without making it larger). Once the implant is inside the capsular bag, it unfolds and opens up to its full size. The implant looks like a miniature magnifying lens which has tiny “feet” or haptics that spread open inside the bag to hold the lens in place. After the position of the implant has been checked, the surgeon makes sure the incision does not leak (water-tight). Antibiotic and anti-inflammatory eyedrops are usually instilled into the eye. A protective eye shield is taped over the eye, before the patient is taken to the recovery room. Surgery usually takes less than half an hour.

Another method of cataract surgery involves the use of a laser to break up the cataract. It does not work well with hard cataracts, and at present, does not offer any significant advantage over phacoemulsification. This laser technology should not be confused with the Nd:Yag laser (Yag Capsulotomy ) which is used to remove “secondary cataracts”. The back part of the capsular bag, in which the intraocular lens implant is placed, can become cloudy, months to years after the cataract surgery. This cloudy membrane can be removed in an office-setting with the Nd:Yag laser. Water jet technology, in which a high speed stream of water is used to break up a cataract is being tested.

Are there any risks?
Cataract surgery is one of the safest surgeries being done today. Like all surgeries, however, there is some risk of which patients need to be aware. Your surgeon can minimize risk by fully evaluating your eyes, and taking steps to tailor surgery for your circumstances. Some patients require special steps or instrumentation which can be planned in advance. Many surgeons start patients on antibiotic eyedrops before the actual surgery, to hopefully decrease the risk of infection. The benefit of starting these antibiotics before surgery has not been proven beyond a shadow of a doubt, but it seems reasonable. The risk of a serious eye infection is about one in a thousand cases. Besides infection, there is risk of retinal detachment, perhaps one percent or less in the Medicare population. Any discussion of risk should balance the benefit of surgery with the risk. It is presumed that you are having enough difficulty with your quality of life (because of visual difficulty), to warrant the risks of surgery. Patients differ in what they feel is acceptable vision, and the amount of risk they will tolerate. Your surgeon should help you make sense of the relative risks and benefits. All surgeons, no matter how skilled, have complications. The most skilled surgeons have fewer complications and may be better able to deal with those complications. Most complications can be handled with a satisfactory outcome. If your surgeon tells you there is no risk, or he or she has never had a complication, you should seek a second opinion.

One question that is frequently asked, is whether cataract surgery can worsen age-related macular degeneration. Thus far, study results are mixed. Macular degeneration can spontaneously progress or worsen even when cataract surgery is not performed. At present, there is no overriding evidence to suggest that cataract surgery aggravates macular degeneration. Remember, the vast majority of patients have excellent outcomes with cataract surgery.

How can I prevent cataracts from developing?
Avoid smoking and take steps to protect your eyes from sunlight exposure. If you are diabetic, be sure to maintain strict control of your blood sugar. Be careful using steroid medications; these types of medications are undeniably beneficial for certain medical conditions, but they can contribute to cataract formation.

Outside the United States, eyedrops are available that are supposed to slow or stop the development of cataracts. These drops contain antioxidants. As of yet, there are no good scientific studies which show these are effective.