What Are Cataracts? What Causes Cataracts?

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Main Category: Eye Health / Blindness
Also Included In: Seniors / Aging
Article Date: 15 Jul 2009 - 0:00 PDT

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Cataracts are cloudy areas in the lens inside the eye - which is normally clear. Cataracts can develop in one or both eyes. If they develop in both eyes, one will be more severely affected than the other. A normally clear lens allows light to pass through to the back of the eye, so that the patient can see well-defined images. If a part of the lens becomes opaque light does not pass through easily and the patient's vision becomes blurry - like looking through cloudy water or a fogged-up window. The more opaque (cloudier) the lens becomes, the worse the person's vision will be.

According to Medilexicon's medical dictionary, cataract is "Complete or partial opacity of the ocular lens.".

There are two types of cataracts:

• Age related cataracts - they appear later in life; the most common form.


• Congenital cataracts (childhood cataracts) - these may be present when the baby is born, or shortly after birth. Cataracts may also be diagnosed in older babies and children - these are sometimes referred to as developmental, infantile or juvenile cataracts. Researchers from the University Zurich were the first to identify the chromosomal location and exact molecular defect in the coding region of the gene responsible for a childhood cataract.

The rest of this article focuses just on age-related cataracts.

A patient with cataracts will eventually find it hard to read, or drive a car - especially during the night. Even seeing people's facial expressions becomes difficult. Cataracts are not usually painful. The patient's long-distance vision is more severely affected at first.

As cataracts develop very slowly most people do not know they have them at first. However, the clouding progresses and vision will gradually get worse. Stronger lighting and eyeglasses can help improve vision. Nevertheless, eventually the vision impairment affects the patient's ability to carry out everyday tasks. At this point the individual will need surgery. Fortunately, cataract surgery is usually a very effective and safe procedure.

Cataracts cause more vision problems globally than any other eye condition or disease - especially in developing countries, where they are much more common among poor people, according to a study carried out in Kenya, The Philippines, and Bangladesh.

Some studies indicate that cataracts are more common among elderly people further down the socioeconomic ladder in the USA - prevalence of cataracts causing significant visual problems appears high among older U.S. Hispanics who also often encounter barriers to access to care (in the USA "Hispanics" refers to Americans of Latin American origin, not people who originate from Spain).

Both men and women are affected equally.

According to the National Health Service (NHS), UK, approximately one third of people aged 65 or over have cataracts in one or both eyes.

Factors that may increase the risk of developing cataracts

We are all at risk of developing cataracts because we will all get old one day - the greatest risk factor is age. In the USA approximately 50% of people aged 65 or more have some degree of lens clouding. 70% of Americans aged 75 or more have their vision significantly impaired by cataracts.

Researchers at the Wilmer Eye Institute at The Johns Hopkins Medical Institutions, Baltimore predicted that the number of people in the USA affected by cataracts is estimated to rise to 30.1 million people in the next 20 years, an increase of 50 percent, because people will live longer.

The following factors may increase a person's chances of developing cataracts:

• Age


• Close relatives who have/had cataracts (family history)


• Diabetes


• Ionizing radiation exposure - airline pilots have an increased risk of nuclear cataracts compared with non-pilots, and that risk is associated with cumulative exposure to cosmic radiation, scientists from the University of Iceland reported.
  
  The five-year incidence of nuclear cataract was 40% lower for statin users after adjusting for several factors, compared to non-statin users, another study found.


• Long-term exposure to bright sunlight


• Long-term use of corticosteroids - many people with asthma rely on inhaled, and sometimes oral, steroids, as do people with chronic obstructive pulmonary disease. A study conducted by the Centre for Vision Research, University of Sydney, Australia, revealed that cataract risk is higher for patients taking these medications.


• Previous eye inflammation


• Previous eye injury


• Exposure to lead - lifetime lead exposure may increase the risk of developing cataracts, scientists from the National Institute of Environmental Health Sciences, USA revealed.


• Crystallins loss of function - A specific type of protein (crystallins) begins to lose function as the eye ages. As the protein loses function, small peptides, made of 10 to 15 amino acids, start forming and accelerate cataract formation in the eye, a study revealed.

What are the symptoms of age-related cataracts?

Symptoms usually creep up many years after onset - usually when the person is elderly. Progressively, more of the lens becomes cloudy. People with mild cataracts will not notice they have it for a long time.

Cataracts often affect both eyes, but rarely equally.

People with cataracts may have the following symptoms:

• Blurry, cloudy, or misty vision.


• Some describe it as similar to looking through frosted glass.


• Vision may be affected by small spots or dots.


• The patient sees small patches which blur parts of his/her field of vision.


• Vision gets worse when lights are dim.


• Vision is sometimes worse when light is very bright (glare).


• Some people with cataracts also comment that colors appear less clear and faded.


• Reading becomes very difficult, and eventually impossible.


• Glasses need to be changed more frequently.


• Eventually wearing glasses becomes less effective.


• In some rare cases patients can see a halo around bright objects, such as car headlights or street lights.


• Double vision in one eye (rare).

As the person's vision deteriorates, and the glare of oncoming headlights and street lights gets worse, driving becomes awkward and potentially very dangerous - research carried out by optometrists and psychologists in Australia shows that motorists suffering from cataracts are less able to spot potentially dangerous hazards on the roads. Drivers with cataracts eventually start suffering from eyestrain and find themselves blinking more frequently in an attempt to clear their vision.

Cataracts do not usually cause any change in the appearance of the eye. Any discomforts, such as irritation, aching, itching or redness are most likely caused by some other eye disorder.

Cataracts are not hazardous to the sufferer's health, or the health of the eye. If the cataract becomes hypermature (completely white), the sufferer may experience inflammation, headache and some pain. Hypermature cataracts need to be removed if there is inflammation or pain.

How are cataracts diagnosed?

Anybody who experiences vision problems should see a GP (general practitioner, primary care physician), an ophthalmologist, or an optometrist. The GP will most likely refer the patient to an ophthalmologist, or an optometrist.

• Ophthalmologist - a doctor who specializes in the medical and surgical care of the eye.


• Optometrist - a person practicing eye care, but does not perform surgery.

The eye specialist will carry out a number of tests. These may include:

• Visual acuity test - this tests how clearly the individual can see an object. It tests the person's sharpness of vision. The patient reads letters from across a room. The two eyes are tested separately (one is covered). By using a chart with progressively smaller letters, the specialist can determine how acute the patient's vision is. The chart is called a Snellen Eye Chart.
  
  Sometimes the chart has to be read twice - once with, and once without bright lights. This will give an indication of glare sensitivity.


• Slit-lamp examination - this is a microscope which allows the specialist to see the structures at the front of the eye. An intense line of sight (a slit) is used to illuminate the cornea, iris, lens, as well as the space between the iris and the cornea. The slit makes it possible for the specialist to see these structures in small sections, making it easier to spot any problems.


• Retinal examination - eye drops are administered which dilate the pupils, providing a bigger window to the back of the eyes. The specialist examines the lens for signs of cataract with either an ophthalmoscope or a slit lamp. If signs of cataract are found, the specialist can also determine how dense the clouding is. Most specialists will check for glaucoma at the same time, and perhaps some other eye conditions/diseases.
  
  The pupils will remain dilated for a few hours after the examination before the eye drops gradually lose their effect. During this time the patient may find it harder to focus on close objects. It is advisable to wear sunglasses, especially if it is a bright day. Driving is not advisable until the pupils are back to their normal size.


• Measuring a protein related to cataract formation - A device based on a laser light technique called dynamic light scattering can safely eye test for measuring a protein related to cataract formation, according to researchers at the National Eye Institute, USA.

Although an eye test may help confirm a cataract diagnosis, it may not always reflect the patient's quality of life. Some patients who do badly in a test seem to have no problem with daily function, while others who may do well insist that their eyesight is poor and does interfere with ordinary activities.

Treatment for cataracts

If the patient is found to be only mildly affected surgical treatment may not be needed. During its early stages, stronger glasses and brighter lights may help improve vision. The following simple approaches may assist people who are not ready yet to have surgery:

• Make sure your glasses are the most accurate prescription possible.
• Use a magnifying glass for reading.
• Get brighter lamps for your house. Halogen lights may help a lot.
• Wear sunglasses to reduce glare on sunny days.
• Try to refrain from driving at night.

Surgery

However, these are only temporary measures - the cataracts will continue developing and gradually impair eyesight more.

Patients who take alpha-blockers or are considering taking alpha-blockers should be aware that the drugs may increase the difficulty of cataract surgery. While Flomax (an alpha-blocker) is largely prescribed to men to treat prostate enlargement, some women also take the drug to treat urinary retention problems. Other alpha-blockers are used to treat hypertension. The American Academy of Ophthalmology and the American Society of Cataract and Refractive Surgery issued an advisory telling patients and GPs to inform their surgeon if they are taking alpha-blockers, or took them in the past. Once informed, the ophthalmologist can anticipate certain problems and employ different surgical techniques that help to achieve excellent outcomes.

When the cataracts are severe the only effective treatment is surgery. The specialist will recommend surgery if the patient:

• Is having trouble looking after himself/herself.
• Is having difficulties looking after someone else.
• Cannot drive, or finds driving difficult.
• Has problems leaving the house.
• Finds it hard to see or recognize people's faces.
• Has problems doing his/her job.
• Cannot read properly.
• Can no longer watch television properly.

The cloudy lens is removed from the eye and an artificial clear plastic one is put in its place - an intraocular implant (intraocular lens). In most developed countries, and a growing number of developing countries, cataract operations are performed as keyhole surgery. The patient will be given a local anesthetic. He/she will not usually have to spend the night in hospital. The operation is commonly known as phacoemulsification or phaco extracapsular extraction. Laser surgery is not used for cataract procedures. (There are more details about the operation further down this page)

Pre-operative assessment (assessment before surgery)

The specialist will assess the patient's eyes and general health. During the pre-operative assessment the eye will be measured so that the replacement artificial lens can be prepared.

The day of the operation - before it begins

Eye drops that dilate (widen) the pupils will be administered just before the procedure. Sometimes the eye drops will also have anesthetic in them, or the doctor may inject the tissue around the eye for a local anesthetic. As soon as the anesthetic starts working the area will be numbed and the patient will feel nothing. During the operation he/she will be aware of a bright light, but will not be able to see what is happening.

Various types of replacement lenses may be used:

• Monofocal lens - this is a fixed-strength lens which is set for one level of vision - usually distance vision.


• Multifocal lens - this type of lens may have two or more different strengths; near and distance vision.


• Accommodating lens - this type of lens is the most similar to the natural human lens. It allows the eye to focus on near and distant objects.

The operation

The eye surgeon makes a tiny cut in the cornea at the front. He/she then inserts a minute probe through the cut. The probe uses ultrasound and breaks up the cloudy lens into very small pieces which are sucked out.

The artificial lens is then inserted through the cut. The lens sits in the lens capsule to keep it in place - the lens capsule is like a little pocket. When it is first inserted the lens is folded - it unfolds when in position.

The whole procedure should not take more than about 30 minutes. Most patients will wear an eye pad for protection for a short while.

Other procedures

• Manual extracapsular extraction - the lens is removed in one piece. No ultrasound is used to break it up. The surgeon will make a slightly larger cut in the eye.


• Intracapsular extraction - the lens capsule as well as the lens is removed. The artificial lens is sewn into the eye. This type of procedure is much less common.

After the operation

Most patients will experience vision improvement virtually immediately. It may take a while for the eye to settle down completely. The cut in the eye may occasionally need a stitch - in most cases, however, it is so small that it heals by itself.

Patients should avoid vigorous activities for a while. Most individuals find they can go about their daily activities as soon as they get home. An appointment will be made to test the patient's vision. Most patients will need different glasses after their operation. The new glasses can only be determined after his/her vision has settled down - this can take several weeks.

There is no other way to cure cataracts. Medications, dietary supplements, exercise or optical devices are not effective. As mentioned earlier, during the early stages there are some things the patient can do to help see things better - but they are only temporary.

Prevention of cataracts

To prevent suffering the complications of cataracts it is advisable to have regular eye exams, especially as you get older. The following steps are advisable to lower your risk of developing cataracts - some of them have convincing circumstantial evidence of their worth, while others (smoking, diet) are proven measures:

• Give up smoking - several studies have indicated that a higher percentage of smokers develop cataracts, compared to non-smokers. There are also indications that smokers are likely to experience cataract symptoms earlier. Smoking also increases the risk of other eye disease/conditions.


• Nutrition - eat plenty of fruits and vegetables, whole grains, unrefined carbohydrates, good quality fats (avocado, olive oil, omega oils), and either plant sourced proteins or lean animal sourced proteins.
  
  The findings by researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, USA suggest that vitamins and polyunsaturated fatty acids - two categories of nutrients believed to have health benefits - may both affect cataract development, although not necessarily in beneficial ways.
  
  Women who consume plenty of dark leafy vegetables which are rich in lutein and zeaxanthin, as well as sufficient vitamin E from supplements/foods seem to have better protection against developing cataracts, scientists from the Brigham & Women's Hospital and Harvard Medical School, Boston found.


• Sunlight - wear sunglasses that block ultraviolet B rays (UV radiation). Many people are not aware of the damage UV radiation can cause to the eyes - a study found that only 49% of Americans said UV protection was the most important factor when purchasing sunglasses.


• Sleep - make sure you get at least 7 hours of good quality, continuous sleep every night.


• Obesity - obesity significantly raises the risk of developing diabetes type 2, which in turn is an important cataract risk factor. Keeping your weight within the recommended limits will help prevent your risk from increasing.


• Diabetes - be careful to have your diabetes under control; follow your treatment plan assiduously.


• Exercise - Researchers from the U.S. Department of Energy's Lawrence Berkeley National Laboratory reported that running reduces the risk of both cataracts and age-related macular degeneration.

Complications

• Blindness - If the cataracts are left untreated, they may lead to blindness.


• Higher mortality rates - people aged 49 and older with cataract and those aged 49 to 74 years with age-related macular degeneration appear to have higher mortality rates over an 11-year period than those without such visual impairments, according to a study carried out by researchers at the University of Sydney, Australia.

Written by Christian Nordqvist


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