What is cataract?

Normally, the crystalline lens of the eye and its capsule is clear and allows ordered refraction of rays of light to the retina so that we can see everything clearly. Cataract is a state of opacification of this crystalline lens of the eye or its capsule, as shown in the diagram above. Due to this opacification rays of light entering the eye get dispersed in an unorderly fassion causing glare, foggy vision, and reduced visual acuity. The amount of light entering the eye varies with the amount of opacification of the lens or the capsule of the lens.

Why does it occur?

By far the most common form of cataract seen is "age related", starting somewhere in the late 50's or 60's. Theoretically cataract occurs due to either water imbibement into the lens fibres or their coagulation, causing opacification. The former is reversible, the later is not. There are numerous hypotheses as to why such changes occur in the lens. Some of the common causes of lens opacification are listed below.

As a normal ageing process
Due to the presence of Diabetes Mellitus
Due to physical or chemical injury to the eye
Due to a local disease of the eye (for example iridocyclitis)
Due to medications instilled in the eye; for example for glaucoma, steroids for iritis, etc.
Due to exposure to Ultraviolet or Infrared radiations, X-rays, persons exposed to such radiations in their professions develop cataract earlier
Profound debilitation or illness
Following sever diarrhoea, dehydration, undernutrition, starving, unsupervised dieting

Cataract in the eyes of the young are usually due to genetic defects and such syndromes, in which case they may be seen at birth or immediately after birth. The other common cause in children is injury to the eye.
Any of the above insults to the cyrstalline lens of the eye cause disruption in the ordered arrangement of lens fibres within the lens causing opacification (cataract).

Types of cataracts

Cataract types include:

Cataracts that affect the center of the lens (nuclear cataracts). A nuclear cataract may at first cause you to become more nearsighted or even experience a temporary improvement in your reading vision. But with time, the lens gradually turns more densely yellow and further clouds your vision. Nuclear cataracts sometimes cause you to see double or multiple images. As the cataract progresses, the lens may even turn brown. Advanced yellowing or browning of the lens can lead to difficulty distinguishing between shades of color.
Cataracts that affect the edges of the lens (cortical cataracts). A cortical cataract begins as whitish, wedge-shaped opacities or streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the center and interfere with light passing through the center of the lens. Problems with glare are common for people with this type of cataract.
Cataracts that affect the back of the lens (posterior subcapsular cataracts). A posterior subcapsular cataract starts as a small, opaque area that usually forms near the back of the lens, right in the path of light on its way to the retina. A subcapsular cataract often interferes with your reading vision, reduces your vision in bright light and causes glare or halos around lights at night.
Cataracts you're born with (congenital cataracts). Some people are born with cataracts or develop them during childhood. Such cataracts may be the result of the mother having contracted an infection during pregnancy. They may also be due to certain inherited syndromes, such as Alport's syndrome, Fabry's disease and galactosemia. Congenital cataracts, as they're called, don't always affect vision, but if they do they're usually removed soon after detection.

Symptoms

Symptoms vary with the amount of lens opacity and the location of the lens opacity. If the opacity is situated in the center of the lens, vision is reduced in bright light due to constriction of the pupils and better in the evening or night due to dilation of the pupils. Similarly with peripheral opacities, vision is better during the day, or in good light, and worse at night or in poor light.

Patients with cataract experience "glare" due to haphazard dispersion of light in the eye due to opaque lens fibres. Some patients also experience "colored haloes" around sources of light at night due to prismatic dispersion of rays by the lens opacitites.

Another early symptom of cataract is "foggy" vision, as if seeing through a fog or a misty glass pane. This is because of opacification of the lens which is not sufficient to grossly reduce the entry of light into the eye, just disperse it.

Advanced cataracts gradually produce reduced vision, inability to make out faces, read, watch television,
Occasionally neglected cataracts can "hypermature" causing an increased pressure within the eyeball (glaucoma), causing pain, loss of vision, redness, and watering from the affected eye. This is a medical emergency and should be attended at once, or eyesight may be permanently lost.

How is Cataract detected?

To detect a cataract, an eye care professional examines the lens. A comprehensive eye examination usually includes:

Visual acuity test: This eye chart test measures how well you see at various distances.
Pupil dilation: The pupil is widened with eyedrops to allow your eye care professional to see more of the lens and retina and look for other eye problems.
Tonometry: This is a standard test to measure fluid pressure inside the eye. Increased pressure may be a sign of glaucoma.

Your eye care professional may also do other tests to learn more about the structure and health of your eye.

How is it treated?

For an early cataract, vision may improve by using different eyeglasses, magnifying lenses, or stronger lighting. If these measures don't help, surgery is the only effective treatment. This treatment involves removing the cloudy lens and replacing it with a substitute 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 that decision together. In most cases, waiting until you are ready to have cataract surgery will not harm your eye. If you decide on surgery, your eye care professional may refer you to a specialist to remove the cataract. If you have cataracts in both eyes, the doctor will not remove them both at the same time. You will need to have each done separately.

Sometimes, a cataract should be removed even if it doesn't 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.

Is cataract surgery effective?

Cataract removal is one of the most common operations performed today. It is also one of the safest and most effective. In about 90 percent of cases, people who have cataract surgery have better vision afterward.

How is a cataract removed?

There are two primary ways to remove a cataract. Your doctor can explain the differences and help determine which is best for you:

Phacoemulsification, or phaco. Your doctor makes a small incision on the side of the cornea, the clear, dome-shaped surface that covers the front of the eye. The doctor then inserts a tiny probe into the eye. This device emits ultrasound waves that soften and break up the cloudy center of the lens so it can be removed by suction. Most cataract surgery today is done by phaco, which is also called small incision cataract surgery.

Extracapsular surgery. Your doctor makes a slightly longer incision on the side of the cornea and removes the hard center of the lens. The remainder of the lens is then removed by suction.

In most cataract surgeries, the removed lens is replaced by an intraocular lens (IOL). An IOL is a clear, artificial lens that requires no care and becomes a permanent part of your eye. With an IOL, you'll have improved vision because light will be able to pass through it to the retina. Also, you won't feel or see the new lens. Some people cannot have an IOL. They may have problems during surgery, or maybe they have another eye disease. For these people, a soft contact lens may be suggested. For others, glasses that provide powerful magnification may be better.

What happens before surgery?

A week or two before surgery, your eye care professional will do some tests. These may include tests to measure the curve of the cornea and the size and shape of the eye. For patients who will receive an IOL, this information helps your doctor choose the right type of IOL. Also, doctors may ask you not to eat or drink anything after midnight the morning of your surgery.

What happens during surgery?

When you enter the hospital or clinic, you will be given eye drops to dilate the pupil. The area around your eye will be washed and cleansed.
The operation usually lasts less than 1 hour and is almost painless. Many people choose to stay awake during surgery, while others may need to be put to sleep for a short time. If you are awake, you will have an anesthetic to numb the nerves in and around your eye.
After the operation, a patch will be placed over your eye and you will rest for a while. You will be watched by your medical team to see if there are any problems, such as bleeding. Most people who have cataract surgery can go home the same day. Since you will not be able to drive, make sure you make arrangements for a ride.

What happens after surgery?

It's normal to feel itching and mild discomfort for a while after cataract surgery. Some fluid discharge is also common, and your eye may be sensitive to light and touch. If you have discomfort, your eye care professional may suggest a pain reliever every 4-6 hours. After 1-2 days, even moderate discomfort should disappear. In most cases, healing will take about 6 weeks.

After surgery, your doctor will schedule exams to check on your progress. For a few days after surgery, you may take eyedrops or pills to help healing and control the pressure inside your eye. Ask your doctor how to use your medications, when to take them, and what effects they can have. You will also need to wear an eye shield or eyeglasses to help protect the eye. Avoid rubbing or pressing on your eye.

Problems after surgery are rare, but they can occur. These can include infection, bleeding, inflammation (pain, redness, swelling), loss of vision, or light flashes. With prompt medical attention, these problems usually can be treated successfully.

When you are home, try not to bend or lift heavy objects. Bending increases pressure in the eye. You can walk, climb stairs, and do light household chores.

When will my vision be normal again?

You can quickly return to many everyday activities, but your vision may be blurry. The healing eye needs time to adjust so that it can focus properly with the other eye, especially if the other eye has a cataract. Ask your doctor when you can resume driving.
If you just received an IOL, you may notice that colors are very bright or have a blue tinge. Also, if you've been in bright sunlight, everything may be reddish for a few hours. If you see these color tinges, it is because your lens is clear and no longer cloudy. Within a few months after receiving an IOL, these colors should go away. And when you have healed, you will probably need new glasses.

What is an "after-cataract"?

Sometimes a part of the natural lens that is not removed during cataract surgery becomes cloudy and may blur your vision. This is called an after-cataract. An after-cataract can develop months or years later.
Unlike a cataract, an after-cataract is treated with a laser. In a technique called YAG laser capsulotomy, your doctor uses a laser beam to make a tiny hole in the lens to let light pass through. This is a painless outpatient procedure.

Risk factors

Increasing ageFactors that increase your risk of cataracts include:

Diabetes
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
Obesity
Previous eye injury or inflammation
Previous eye surgery
Prolonged use of corticosteroid medications
Smoking

Expectations (prognosis)

Vision may not improve to 20/20 after cataract surgery if other eye diseases, such as macular degeneration, are present. Ophthalmologists can usually, but not always, determine this in advance.

Prevention

The best prevention involves controlling diseases that increase the risk of a cataract, and avoiding exposure to factors known to promote cataract formation.
Wearing sunglasses when you are outside during the day can reduce the amount of ultraviolet (UV) light your eyes are exposed to. Some sunglasses do not filter out the harmful UV. An optician should be able to tell you which sunglasses filter out the most UV. For patients who smoke cigarettes, quitting will decrease the risk of cataracts.