A cataract is a clouding of the eye’s natural lens, which lies behind the iris and the pupil.
Cataracts are the most common cause of vision loss in people over age 40 and is the principal cause of blindness in the world. In fact, there are more cases of cataracts worldwide than there are of glaucoma, macular degeneration and diabetic retinopathy combined, according to Prevent Blindness America (PBA).
Today, cataracts affect more than 22 million Americans age 40 and older. And as the U.S. population ages, more than 30 million Americans are expected to have cataracts by the year 2020, PBA says.
Types of cataracts include:
- A subcapsular cataract occurs at the back of the lens. People with diabetes or those taking high doses of steroid medications have a greater risk of developing a subcapsular cataract.
- A nuclear cataract forms deep in the central zone (nucleus) of the lens. Nuclear cataracts usually are associated with aging.
- A cortical cataract is characterized by white, wedge-like opacities that start in the periphery of the lens and work their way to the center in a spoke-like fashion. This type of cataract occurs in the lens cortex, which is the part of the lens that surrounds the central nucleus.
Signs and symptoms of cataracts include:
- Clouded, blurred or dim vision
- Increasing difficulty with vision at night
- Sensitivity to light and glare
- Seeing “halos” around lights
- Frequent changes in eyeglass or contact lens prescription
- Fading or yellowing of colors
- Double vision in a single eye
At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye’s lens and you may be unaware of any vision loss. As the cataract grows larger, it clouds more of your lens and distorts the light passing through the lens. This may lead to signs and symptoms you’re more likely to notice.
The human lens is transparent so that light can travel through it easily. It has no blood supply and is 65 percent water. Although new cells are being made for the lens continuously throughout our lifetime, many factors combine as we age to cause areas in the lens to become cloudy, hard, and dense. The lens can then no longer transmit a clear picture to the retina where it can be processed and sent through the optic nerve to the brain. Cataracts can have many causes, as described below.
This is the most common kind of cataract. There are three subclassifications, based on location: nuclear, cortical, and posterior subcapsular.
Although it is not common, some babies are born with cataracts or develop them within the first year of life.
This type of cataract results from an injury to the eye.
This is a cataract that is caused either by medications (most commonly prednisone or other corticosteroids) or disease, like diabetes. Cataracts are 10 times more common in diabetic patients than in the general population.
For most people, cataracts are a natural result of aging. Often cataracts develop in both eyes at the same time. The symptoms vary, but include a gradual blurring of vision, halos around lights, glare and double vision. The very worst cataracts where the iris appears almost entirely clouded over can cause a total loss of vision.
Factors that increase your risk of cataracts include:
- Increasing age
- Drinking excessive amounts of alcohol
- Excessive exposure to sunlight
- Exposure to ionizing radiation, such as that used in X-rays and cancer radiation therapy
- Family history of cataracts
- High blood pressure
- Previous eye injury or inflammation
- Previous eye surgery
- Prolonged use of corticosteroid medications
Cataracts – Surgery
Surgery for cataracts involves removing the clouded lens of the eye(the cataract). The lens can be replaced with an artificial lens called an intraocular lens implant (IOL). Or, if an IOL cannot be used for any reason, it will be left out and contact lenses or, in rare cases, eyeglasses can compensate for its absence. Most people will get an IOL during surgery.
Before surgery, ask your doctor about what types of IOLs can go in your eye. Or, if you will not be getting an IOL, find out why, and ask about the pros and cons of contact lenses or eyeglasses.
Options to help you see better after surgery
- Intraocular lens (IOL)Intraocular lens (IOL). A variety of IOL types are available. Work with your doctor to choose the best one for you.
- Contact lens Contact lens. You will need to insert, remove, and clean the lenses on a regular basis. A contact lens may not be a good choice for young children or older adults who have a hard time properly placing the lens on the eye.
- Cataract glasses. Cataract glasses were used for decades when there were no other options for lens replacement. Because they are thick and heavy, they are rarely used now.
For most adults, surgery is only needed when vision loss caused by a cataract affects your quality of life. The goals of surgery in adults who have cataracts include:
- Improving vision.
- Helping you return to work, leisure, and other daily activities.
How is a cataract treated?
The symptoms of early cataract may be improved with new eyeglasses, brighter lighting, anti-glare sunglasses, or magnifying lenses. If these measures do not help, surgery is the only effective treatment. Surgery involves removing the cloudy lens and replacing it with an artificial lens.
A cataract needs to be removed only when vision loss interferes with your everyday activities, such as driving, reading, or watching TV. You and your eye care professional can make this decision together. Once you understand the benefits and risks of surgery, you can make an informed decision about whether cataract surgery is right for you. In most cases, delaying cataract surgery will not cause long-term damage to your eye or make the surgery more difficult. You do not have to rush into surgery.
Sometimes a cataract should be removed even if it does not cause problems with your vision. For example, a cataract should be removed if it prevents examination or treatment of another eye problem, such as age-related macular degeneration or diabetic retinopathy. If your eye care professional finds a cataract, you may not need cataract surgery for several years. In fact, you might never need cataract surgery. By having your vision tested regularly, you and your eye care professional can discuss if and when you might need treatment.
If you choose surgery, your eye care professional may refer you to a specialist to remove the cataract.
If you have cataracts in both eyes that require surgery, the surgery will be performed on each eye at separate times, usually four to eight weeks apart.
Many people who need cataract surgery also have other eye conditions, such as age-related macular degeneration or glaucoma. If you have other eye conditions in addition to cataract, talk with your doctor. Learn about the risks, benefits, alternatives, and expected results of cataract surgery.