Cataracts - a condition so common, that by age 80, more than half of Americans will have developed or been treated for it. Because the disorder can develop over time, it is best to educate yourself about the risk factors and symptoms.
What Is a Cataract?
A cataract is a clouding of the lens of the eye that makes objects look as though you were viewing them through foggy glasses or a frost-covered window. The condition is called cataract or cataracts - either term is correct. It can occur in one or both eyes. If both eyes are affected, the cataracts may progress (become larger or more opaque) at different rates, but the condition is not contagious and does not spread from one eye to the other. 
Cataracts are not painful and do not irritate the eyes or cause them to produce tears.
The lens is a transparent, layered structure that lies behind the iris - the colored part of the eye.
For a visual image to be processed, the lens must focus light on the retina, the back part of the eye. The clearer the lens is, the sharper your vision will be. A hazy lens will cause the brain to perceive filmy images, rather than crisp and distinct ones.
Types of Cataract
Age-related cataracts
Cataracts are categorized according to their cause, and there are several types of cataract, as we’ll explain below. But unless otherwise specified, the term usually refers to age-related cataracts. The lens is made up primarily of water and protein fibers, which are arranged in a way that optimizes visual clarity. But year by year, the lens becomes thicker and heavier, and these protein fibers begin to break down. The proteins form clumps that distort light as it penetrates the lens and reaches the retina
. A cataract can form in any part of the lens, but the closer it is to the center, the more likely it is to obscure vision.Other types of cataract
Secondary. Age-related cataracts is considered to be a primary disease because it evolves by itself, rather than as the unintended consequence of a surgical procedure, as a medication side effect, or as a result of some other condition. A secondary cataract is one that can be linked to another cause, such as those listed below:
Eye surgery, such as for glaucoma or for a previous cataract in the same eye
Use of medically approved medications, such as corticosteroids (for example, prednisone), chlorpromazine, and phenothiazine
Other conditions, such as diabetes, retinitis pigmentosa, hypoparathyroidism, atopic dermatitis, and uveitis
Congenital. A baby born with cataracts is said to have congenital cataracts, although the condition may be either inherited (genetically transmitted) or congenital (acquired in the womb by means of illness or an infection such as rubella [measles]). Cataracts that develop during early childhood is also usually called congenital cataracts.
Traumatic. A traumatic cataract is one that occurs after an injury, either right away or years after the event. Almost any kind of traumatic injury can be responsible:
Blunt trauma, like getting punched in the eye during a fist fight
Penetrating trauma, such as when a shard of glass or metal pierces the eye during an auto accident
Alkaline chemical burns
Electrical trauma, such as being shocked with a Taser (stun) gun
Radiation. The word radiation simply refers to radiant heat, such as the heat of the sun’s rays. Radiation cataracts, sometimes called toxic cataracts, is a form of the disease caused by ultraviolet radiation from sunlight or by exposure to other forms of radiation. For example, the development of cataracts among workers who cleaned up the Chernobyl nuclear reactor accident was linked to their radiation exposure at the plant. Even radiation therapy intended to shrink a cancerous tumor can cause cataracts as a side effect.
Classification of Cataract
The lens of the eye is made up of three layers the nucleus, or core, of the lens is surrounded by a cortex. This cortex, or cortical layer, is in turn enveloped by a capsule, or capsular layer. It might help to picture the lens as a candy-coated chocolate-covered almond. The almond is the nucleus, the chocolate is the cortex, and the candy shell is the capsule that surrounds the chocolate-covered almond. When a vision specialist diagnoses a cataract, he or she classifies it according to type and according to its location on the lens:
Nuclear
When the nucleus of the lens hardens or becomes opaque (clouded), it's called a nuclear cataract. This type of cataract tends to have a muddy, dark-brown or a milky, opalescent appearance and poses the greatest threat to visual acuity because it lies behind the pupil, obscuring central vision. People with this kind of cataract tend to become more nearsighted as the cataract distorts the light entering the pupil. They may actually have better vision in dim light because pupil dilation allows them to see around the dense area of the lens.
Cortical
A cataract on the cortex of the lens is called a cortical cataract. This type of cataract has a distinctive spoked or striated appearance. Nearly two-thirds of all cataracts fall into this category.
Posterior subcapsular
A lacy, dense area that forms just in front of the posterior lens capsule (that is, the back of the lens capsule) is called a posterior subcapsular cataract (PSC). PSCs often make the person sensitive to glare and make it difficult for them to focus on objects in the near distance. A PSC often combines with one of the other types of cataract as they progress to more advanced stages.
Other types
When two or more types of cataract combine in a person with advanced cataract disease, the area is referred to as a mixed cataract. When the lens becomes completely veiled, the cataract is said to be mature or ripe. A hypermature cataract may cause pain or inflammation that necessitates surgery.
Weighing Your Options
If a vision care provider discovers that you or a friend or loved one has a cataract
, it’s time to take stock of your options. But take heart - remember, most cataracts progress slowly and do not cause low vision for several years after they’re detected.The good news is treatment is available and cataract surgery is extremely effective. Luckily, many people don’t require surgery at all, but rather need to be monitored by their doctors to track the progression of this condition.
Cataract Symptoms
Cataracts: Risk Factors and Symptoms
Why do some of us develop cataracts and not others? Who is most likely to develop the condition, and how can we tell if we have it? In the following sections, we’ll outline the risk factors for cataracts and tell you what signs and symptoms to be alert for.
Who Is At Risk?
As with heart disease and most other chronic health conditions, some risk factors for cataracts—getting up in years, for instance—are beyond our control. But specific behavioral and lifestyle choices we make, such as smoking, may magnify our risk. Cataracts is a multifactorial disease—that is, several factors contribute to its development even within a single individual. Let’s take a look at some of them:
Age. As the crow’s feet and laugh lines become more deeply etched in our features, the risk for cataracts inevitably increases .
Ethnicity. Some evidence suggests that our ethnic ancestry influences the likelihood of developing cataracts. In fact, cataracts is the leading cause of treatable vision loss among African-Americans age 40 and over, and it’s the number one cause of low vision among Americans of Latino, African, and European descent.
Gender. For reasons that are unclear, women are more likely than men to develop cataracts.
Sunlight exposure. A higher level of exposure to ultraviolet radiation from the sun’s rays makes the development of cataracts more likely.
Diabetes. According to the American Diabetes Association, people with diabetes are 60% more likely than those without diabetes to develop cataracts, and the condition tends to affect them at a younger age and to progress more rapidly than in people with cataracts who do not have diabetes.
Poor nutrition. Although further study is needed, vision researchers believe that a diet high in saturated fat may be linked to the development of cataracts. They’re also investigating the possibility that low blood calcium levels may contribute to cataract development.
Smoking. In addition to the dangers that everyone already knows, smoking also puts you at a higher risk for caracts. The relationship is dose related, so heavy smokers have a higher risk than people who smoke less.
Alcohol intake. A higher incidence of cataracts has been found among people who chronically abuse alcohol.
Researchers have proposed several other factors that may increase the risk of cataracts. They include a family history of the disease, myopia (nearsightedness), obesity, use of statin (cholesterol lowering) medications, and high blood pressure.
The most important way you can protect yourself is simply by making sensible lifestyle choices—eating a low-fat diet, wearing UV-filtering sunglasses, and not smoking or quitting smoking are good ways to start. Some studies suggest that taking an antioxidant vitamin supplement might cut your risk of cataracts, too.
What Are the Symptoms?
Okay, let’s say you or someone in your care has a few of the risk factors listed above—most of us do. How do you know whether to consult a vision care provider? Following are some common signs and symptoms of cataracts:
Blurry or dim vision. Your vision may be cloudy, as though you were looking out the window on a foggy day. Sharp outlines may seem to fade into the background, and you may lose the ability to perceive fine detail.
Sensitivity to glare. Glaring light may cause frequent headaches, or you may have eye strain that prompts you to blink continually in an effort to refocus your eyes.
Muted color perception. Colors may appear dull or yellowed.
Poor night vision. Headlights and street lights may seem to be surrounded by a halo, making it dangerous to drive after dark. Inside, you may find yourself using brighter reading lamps or other task lighting, or you may require indirect lighting.
Poor central vision. When a cataract forms behind the pupil, called a nuclear cataract, it may be hard to discern objects in the center of your visual field for an explanation of how cataracts are classified). This kind of cataract is a common cause of low vision.
Double vision. You may perceive duplicate images in a single eye.
Frequent changes in your eyeglasses or contact lens prescription. Although a cataract clouds your vision little by little, your prescription will change more often than usual as the condition progresses. In particular, your ability to see objects close to you may improve suddenly, while your ability to see things far away declines. A posterior capsular cataract develops more rapidly than the other types, necessitating even more frequent prescription adjustments.
What If I Suspect Cataracts?
If you believe that you or a friend or loved one has cataracts, a thorough eye examination by a vision care specialist is in order. The provider will review your medical history and risk factors, ask about your symptoms, examine your eyes, and perform specialized tests to check for cataracts and to rule out other eye diseases. If you do have cataracts, your provider will explain the treatment options or advise taking a "wait and see" approach
Diagnosing Cataracts
Sophisticated diagnostic tests now allow vision care specialists to determine the type, location, and stage of a cataract, helping you and your provider decide in advance whether surgery is prudent and likely to be successful . In the following article, we’ll describe the tests that might be used to gather this information and prepare you for surgery.
Diagnostic Steps
An optometrist, ophthalmologist, or general practitioner can diagnose cataracts, but only an ophthalmologist - a physician who specializes in eye care - can perform cataract surgery. Your provider will want to determine whether you have a cataract or cataracts, confirm whether or how much the condition is impairing your vision, rule out other eye diseases that could account for your low vision, and check for any conditions that might make surgery risky.
Cataracts can be diagnosed from your description of signs and symptoms, a visual acuity test using an eye chart, and a physical examination of the eyes. Specialized tests can be used to evaluate particular problems. Below are descriptions of some of the diagnostic tests your provider is likely to perform.
Standard Eye Examination
Visual Acuity Testing
Most of us are familiar with the "big E" chart, so named for the large block letter at the top. This chart measures how well you see at various distances. From a specified distance, usually 20 feet, the provider will ask you to read aloud progressively smaller rows of high-contrast (black type on a white background) capital letters and numbers.
However, a person's score on the visual acuity test may not reflect functional impairments, such as glare sensitivity and reduced contrast sensitivity. Specialized tests can be performed to measure diminished function.
Ophthalmoscopy Followed by Slit-Lamp Examination
Cataracts can be seen with an ophthalmoscope, a hand-held, microscope-like viewing instrument. After using special drops to dilate your pupils, your vision care provider will examine the internal structures of the eye to assess the cataract, if one is found, and to check for other eye diseases. A slit lamp, which is a high-intensity light source combined with a low-power microscope, will then be used to examine the frontal structures of the eye.
Tonometry
A tonometer is a hand-held instrument that measures intraocular pressure (the pressure of fluids inside the eye) after anesthetic drops are instilled. This test is performed to rule out glaucoma.
Keratometry and A-Testing
To fit you with an IOL of the proper size and magnification, your vision care provider will use keratometer to measure the curvature of your cornea. Then the length (optical axis) of your eye will be measured using painless ultrasound waves to determine the ocular power of the IOL lens. This test is called an A-scan.
Specialized Tests
Contrast Testing
People who have good visual acuity but poor contrast sensitivity may fail to see low-contrast objects, such as curbs and steps, under conditions of reduced visibility, such as in the shade or twilight. They may also have trouble reading and walking at a normal speed, identifying faces from a distance, and doing tasks such as sewing and preparing food.
Contrast sensitivity testing assesses the eye’s ability to detect subtle shade variations by asking you to view letters and numbers or groups of figures, such as gray bars, that vary in contrast, luminescence, and spatial frequency.
Glare Sensitivity Testing
Glare is simply scattered light that reduces visibility. Reading lamps, illuminated computer monitors, street lights, and headlights are various sources of glare that can interfere with the ability to see targets in the visual field. These objects might range from text on a glossy magazine page or a laptop screen to a jogger on the shoulder of the road at dusk.
Cataracts disperse light that enters the lens, reducing the contrast of the retinal image. Glare sensitivity is markedly increased in those with advanced cataracts, so testing for it can help indicate the stage of the opacity. You may be asked to read a chart under simulated lighting conditions that include direct sunlight, a partly cloudy day, and fluorescent lighting. Your performance will then be compared to your score under ideal lighting conditions.
Corneal Endothelium Testing
The corneal endothelium, a layer of tissue that lines the posterior surface of the cornea, is particularly apt to be injured during surgery, so your provider must examine its condition microscopically before operating. A low cell density indicates that the cornea may not function well after cataract surgery, eventually necessitating a transplant.
Potential Acuity Testing
Potential acuity testing uses a meter to examine macular function. The purpose of the test is to estimate how well you can expect to see after surgical removal of a cataract. It is most accurate if your cataracts are not advanced.
Wavefront Mapping
Symptoms are sometimes disproportionate to the degree of cataract formation observed during the physical examination. New wavefront technology uses computer analysis of a laser beam to track the distortion of light as it passes through the eye. This technology can corroborate a person’s report of disabling symptoms, establishing that a medical need exists (for insurance reimbursement) and allowing surgery to take place earlier in the disease’s progression.
Living with Cataracts
Ultimately, only those who live with cataracts can say whether the condition is merely a nuisance or is significantly compromising their quality of life - or perhaps falls somewhere in between. Most people with cataracts, however, do not proceed immediately to the operating room. You and your provider may prefer to take a "wait and see" approach and monitor the progression of the condition.
Unless your work requires visual precision, making small adjustments may suffice early in the course of the disease. For example, you can reposition lights to reduce glare, rearrange furniture and rugs to remove hazards, update your eyeglasses prescription frequently, and read large-print publications when available.
When accommodating the condition becomes too burdensome, though, most people with cataracts can undergo safe, effective surgery to restore their sight
