Cataracts occur when the natural clear lens inside the eye, located behind the iris, becomes cloudy over time. This lens is important for focusing light on the back of the eye (the retina) so that images appear clear and without distortion, and the clouding of this lens during cataract formation distorts our vision. Cataracts are usually a very gradual process of normal aging but can occasionally develop rapidly. They commonly affect both eyes, but it is not uncommon for a cataract in one eye to advance more rapidly. Cataracts are very common, affecting roughly 60% of people over the age of 60, and over 1.5 million cataract surgeries are performed in the United States each year.
Precisely why cataracts occur is unknown; however, most cataracts appear to be caused by changes in the protein structures within the lens that occur over many years and cause the lens to become cloudy. Rarely, cataracts can present at birth or in early childhood as a result of hereditary enzyme defects. Severe trauma to the eye, eye surgery, or intraocular inflammation can also cause cataracts to develop more rapidly. Other factors that may lead to development of cataracts at an earlier age include excessive ultraviolet light exposure, diabetes, smoking, or the use of certain medications, such as oral, topical, or inhaled steroids. Other medications that are more weakly associated with cataracts include the long-term use of statins and phenothiazines.
Experts have estimated that in the United States, visual disability associated with cataracts accounts for over 8 million physician office visits a year. This number will likely continue to increase as the proportion of people over the age of 60 rises. When people develop cataracts, they begin to have difficulty doing activities they enjoy. Some of the most common complaints include difficulty driving at night, reading, or traveling. These are all activities for which clear vision is essential.
Cataract development is often equated to looking through a dirty windshield of a car or smearing grease over the lens of a camera. Cataracts may cause a variety of complaints and visual changes, including blurred vision, difficulty with glare (often with bright sun or automobile headlights while driving at night), dull color vision, increased nearsightedness accompanied by frequent changes in eyeglass prescription, and occasionally double vision in one eye. A change in glasses may help initially once vision begins to change from a cataract; however, as the cataract continues to grow, vision becomes cloudy, and stronger glasses or contact lenses will no longer improve sight.
Cataracts typically develop gradually and are usually not painful or associated with any eye redness or other symptoms unless they become extremely advanced. Rapid and/or painful changes in vision raise suspicion for other eye diseases and should be evaluated by an eye-care professional.
Cataracts are detected by the finding of lens opacification during a medical eye examination by an eye-care professional. The abnormal lens can be seen using a variety of specialized viewing instruments. Using a variety of tests, your doctor is able to tell how much a cataract may be affecting your vision. Usual eye tests include testing visual acuity, glare sensitivity, color vision, contrast sensitivity, and a thorough examination of all other parts of the eye. Your doctor will make sure vision loss is not due to other common eye problems, including diabetes, glaucoma, or macular degeneration.
Most cataracts associated with aging develop slowly, and many patients may not notice visual loss until it is fairly advanced. Despite being told that you have cataracts, it is not imperative to have surgery to remove them until they begin to affect your vision. The development of cataracts is unpredictable; some cataracts remain small and never progress to the point where they affect vision and require treatment, while others progress more quickly. Thus, the decision and timing to proceed with cataract surgery is individualized for each patient. Your doctor will be able to tell you how much of your vision loss is due to cataracts and the type of visual recovery that may be expected if surgery is chosen.
Eye-care professionals may mention during a routine eye exam that you have early cataract development even if you are not yet experiencing visual symptoms. Although your doctor will be able to tell when you first begin to develop cataracts, you will generally be the first person to notice changes in your vision that may require cataract surgery. Clouding of the lens may start to be seen at any age, but it is uncommon before the age of 40. However, a large majority of people will not begin to have symptoms from their cataracts until many years after they begin to develop. Cataracts can be safely observed without treatment until you notice changes in your vision.
Surgery is recommended for most individuals who have vision loss and are symptomatic from a cataract. If you have significant eye disease unrelated to cataracts that limits your vision, your ophthalmologist may not recommend surgery. Sometimes after trauma to the eye or previous eye surgery, a cataract may make it difficult for your eye-care professional to see the retina at the back of the eye; in these cases, it may still be appropriate to remove the cataract so that further retinal or optic nerve evaluation and treatment can occur. The mode of surgery can be tailored to individuals based on coexisting medical problems. Cataract surgery is generally performed with minimal sedation and generally takes less than 30 minutes. Therefore the surgery does not put significant strain on the heart or the lungs.
The standard cataract surgical procedure is performed in a hospital or in an ambulatory surgery center. The most common form of cataract surgery today is a process called phacoemulsification. With the use of an operating microscope, your surgeon will make a very small incision in the surface of the eye in or near the cornea. A thin ultrasound probe, which is often confused for a laser, is inserted into the eye and uses ultrasonic vibrations to dissolve (phacoemulsify) the clouded lens. These tiny fragmented pieces are then suctioned out through the same ultrasound probe. Once the cataract is removed, an artificial lens is placed into the thin capsular bag that the cataract occupied. This lens is essential to help your eye focus after surgery.
There are three basic techniques for cataract surgery:
As the natural lens plays a vital role in focusing light for clear vision, artificial lens implantation at the time of cataract surgery is necessary to yield the best visual results. Because the implant is placed in or near the original position of the removed natural lens, vision is restored, and peripheral vision, depth perception, and image size are not affected. Artificial lenses usually remain permanently in place, require no maintenance or handling, and are neither felt by the patient nor noticed by others.
There are a variety of intraocular lens styles available for implantation, including monofocal, toric, and multifocal intraocular lenses.
Prior to the day of surgery, your ophthalmologist will discuss the steps that will occur during surgery. Your ophthalmologist or a staff member will ask you a variety of questions about your medical history and perform a brief physical exam. You should discuss with your ophthalmologist which, if any, of your routine medications you should avoid prior to surgery. Prior to surgery, several calculations will be made to determine the appropriate power of intraocular lens to implant. A specific artificial lens is chosen based on the length of the eye and corneal curvature (the clear portion of the front of the eye).
It is important to remember to follow all of your preoperative instructions, which will usually include not eating or drinking anything after midnight the day prior to your surgery. As cataract surgery is an outpatient procedure, arrangements should be made with family or friends to transport you home after the surgery is complete. Most cataract surgery occurs in either an ambulatory surgery center or a nearby hospital. You will be required to report several hours before the scheduled time for your surgery. You will meet with the anesthesiologist who will work with the ophthalmologist to determine the type of sedation that will be necessary. Most cataract surgery is done with only minimal anesthesia and numbing drops without having to put you to sleep.
During the actual procedure, there will be several people in the operating room in addition to your ophthalmologist. These include anesthesiologists and operating-room technicians. While cataract surgery does not involve a significant amount of pain, medications are used to minimize the amount of discomfort. The actual removal of the clouded lens will take approximately 20 minutes. You may notice the sensation of pressure from the various instruments used during the procedure. After leaving the operating room, you will be brought to a recovery room where your doctor will prescribe several eye drops that you will need to take for a few weeks postoperatively. While you may notice some discomfort, most patients do not experience significant pain following surgery; if you do you experience decreasing vision or significant pain, you should contact your ophthalmologist immediately.
Following surgery, you will need to return for visits within the first few days and again within the first few weeks after surgery. During this time period, you will be using several eye drops which help protect against infection and inflammation. Within several days, most people notice that their vision is improving and that they are able to return to work. During the several office visits that follow, your doctor will monitor for complications, and once vision has stabilized, will fit you with glasses if needed. The type of intraocular lens you have implanted will determine to some extent the type of glasses required for optimal vision.
While cataract surgery is one of the safest procedures available with a high rate of success, rare complications can arise. Your ophthalmologist will discuss the specific potential complications of the procedure that are unique to your eye prior to having you sign a consent form. The most common difficulties arising after surgery are persistent inflammation, changes in eye pressure, infection, or swelling of the retina at the back of the eye, and retinal detachment. If the delicate bag the lens sits in is injured, then the artificial lens may need to be placed in a different location. In some cases, the intraocular lens moves or does not function properly and may need to be repositioned, exchanged, or removed. All of these complications are extremely rare but can lead to significant visual loss; thus, close follow-up is required after surgery.
In some cases, within months to years after surgery, the thin lens capsule may become cloudy, and you may have the sensation that the cataract is returning because your vision is becoming blurry again. This process is termed posterior capsule opacification, or a "secondary cataract." To restore vision, a laser is used in the office to painlessly create a hole in the cloudy bag. This procedure takes only a few minutes in the office, and vision usually improves rapidly.
