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Updated 13 February 2013

Cataracts

Cataracts are clouding of the normally clear lens portion of the eye. This is a gradual process that can eventually impair vision.

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Summary

  • Cataracts are the clouding of a normally clear lens of the eye.
  • Cataracts will affect most people – if they live long enough.
  • Symptoms include double or blurred vision.
  • Cataracts can be diagnosed when the doctor examines the eyes with a viewing instrument.
  • Treatment for cataracts involves the surgical implantation of a new lens.
  • Sunglasses can help to prevent cataracts.

Description

Cataracts are a clouding of the normally clear lens portion of the eye. This is a gradual process that can eventually impair vision.

The lens of the eye focuses light, so that you can see objects clearly at different distances. It must remain transparent for clear vision. The lens is mostly made up of water and protein, in a precise composition to keep the lens clear and allow light to pass through. With age, changes in the chemical composition of the lens occur: parts of the protein may clump together and start to cloud a small area of the lens. This is how most cataracts are formed. Over time, the cataract may grow larger and cloud more of the lens. As the developing cataract blocks or distorts light entering the eye, those affected will experience a gradual, persistent and painless blurring of vision.

Cause

The following are causes of cataracts:

  • Cataracts are associated with ageing and are common in older adults. About 75 percent of all cataracts are age-related.
  • Exposure to ultraviolet (UV) radiation (e.g. from sunlight)
  • Eye injuries. Sharp or blunt injuries may cause a cataract.
  • Diabetes, especially when blood sugar is poorly controlled.
  • Cataracts may develop as a secondary effect of other eye ailments, such as glaucoma (raised pressure within the eye) or uveitis (inflammation in the eye).
  • Long-term use of certain medications, most notably steroids, may cause cataracts.
  • Radiation treatment to the head or even when struck by lightning or electrocution
  • Some babies are born with cataracts (congenital cataracts) or develop them shortly after birth.
  • Hereditary factors

Symptoms

Common symptoms of cataracts include:

  • Hazy vision; decrease in visual acuity
  • Double or blurred vision
  • Difficulty performing normal activities due to vision problems
  • Sensitivity to light and glare
  • Impaired vision at night, often causing difficulty while driving at night
  • Less vivid colour perception (colours look less bright)
  • Need for frequent changes in eye-glass prescriptions
  • Unexpected improvement in near vision
  • A milky white, opaque or yellowish appearance to the normally transparent lens of the eye (advanced case)

Prevalence

Everyone eventually gets cataracts if they live long enough. The lens can start clouding at any age, but most often it is after the age of 60 that cataracts typically start to impede vision. Cataracts are the leading cause of blindness worldwide, accounting for almost 20 million cases, and the number is projected to reach 40 million by the year 2020. Despite these numbers, the disease is one of the less serious eye disorders, as surgery can restore lost vision in most cases.

Course

A cataract has little effect on vision at first. Often cataracts develop so slowly that you are unaware of them. If the cataract is on the outer edge of the lens, no change in vision may be noticed. Cloudiness near the centre of the lens usually interferes with sight.

Small cataracts that do not affect vision may not require treatment. However, cataracts progress and become larger or denser, progressively clouding the lens and causing significant vision changes. Severe cataracts can interfere with an independent lifestyle by preventing older adults from performing normal activities. Eventually the entire lens becomes white and will cause blindness, which is usually reversible with an operation. Glaucoma or inflammation can be a complication of advanced cataracts.

Diagnosis

Diagnosis of cataracts is primarily based on medical history and eye examination. Vision problems are compared with results of an eye examination and visual acuity tests to:

  • Confirm presence of cataracts
  • Rule out other conditions that may cause vision loss

The doctor can see the abnormal lens with a hand-held viewing instrument (ophthalmoscope). The usual test for visual acuity, the letter eye chart, may not, however, reflect the true nature of visual loss. Other tests, which measure glare sensitivity, contrast sensitivity, night vision, colour vision, and side or central vision, can help with the diagnosis.

Should your doctor find a cataract, he or she can monitor it and advise you on future treatment.

During the diagnostic examination, an ophthalmologist will measure the shape, size and general health of the eye to determine whether a lens implant will be effective.  

Infants are checked for cataracts at birth and during routine visits to a health professional, or parents may detect cataracts in an infant by noticing a white pupil or poor vision in their child.If cataracts are suspected in an infant or a child, he or she should immediately be referred to an ophthalmologist for evaluation and treatment.

Treatment

Surgery

The only treatment for cataract at present is surgery. If the doctor finds a cataract, you may not need cataract surgery for several years. Have your vision tested regularly. When a cataract interferes with normal activities you should consider surgery. Many people with cataracts are able to use vision aids, such as spectacles, to avoid or delay surgery. People who depend greatly on their eyes for work and leisure activities may want their cataracts removed earlier than others.

Cataract surgery is safe, fast and virtually painless and one of the most common surgeries performed. Improvement in vision after surgery depends on the initial health of the eye and the operative result. Certain diseases of the retina can limit the final visual result.

Surgery involves replacing the clouded lens with an implanted clear plastic, acrylic or silicone intraocular lens (IOL). The implant is placed in or near the original position of the removed natural lens, so vision is restored with good peripheral vision and depth perception, yet with minimal magnification and distortion. IOLs remain permanently in place, require no maintenance or handling, and are neither felt by the recipient nor noticed by others. Spectacles with thin lenses for near or distant viewing may still be required.

One of the disadvantages of IOLs is the fixed focus of the lens, meaning the patient can only see far or only near. New developments in IOLs are the development of multifocal IOLs that provide refractive correction for close vision and distance, so that patients do not lose their accommodative ability. There are some disadvantages to multifocal IOLs, like reduction in contrast sensitivity, presence of glare and halos, especially at night. You ophthalmologist will discuss these advantages and disadvantages with you before deciding to implant a multifocal IOL.

Preparation for surgery

Once you and your ophthalmologist (eye specialist) have decided on cataract surgery, you will be measured for the appropriate lens implant  (specific to each patient) and the surgery date will be set.

Procedure for implantation of an IOL

The procedure is carried out under general or local anaesthetic. Looking through an operating microscope, the surgeon makes a minute incision in the surface of the eye. The clouded lens is emulsified with an ultrasonic probe and suctioned out of the eye, usually leaving intact the rear wall of the transparent capsule that encloses the lens.

The new lens – a clear, plastic disc – is placed behind the iris and up against the back wall of the capsule. Two tiny C-shaped arms attached to the lens hold the lens firmly in place. The incision is closed with tiny, nearly invisible stitches or in some cases no sutures are needed. The whole operation usually takes less than an hour.

Post-operative recovery

Oneusually starts using the eye the morning after surgery. Vision is usually remarkably clear the day after the procedure and improves over the following weeks.

You can resume most of your normal activities, but will be asked to minimise lifting, bending and straining for the month after surgery. You should avoid getting water in the operated eye for one to two weeks.

Following surgery, you should wear a protective eye shield at nightfor at least two weeks after surgeryto prevent rubbing of the eye during sleep.

Returning to work and driving varies from one patient to another. Many people are back at work a few days after the operation.

During the first six to eight weeks after surgery the doctor checks for infections or other complications and fits you for glasses. To prevent infection and reduce inflammation, your physician may recommend that you apply antibiotic and steroid ointments or drops to your eye. Risks associated with cataract surgery include complications such as bleeding, infection, swelling of the cornea, glaucoma, swelling of the retina, and retinal detachment, which can occur during or after surgery in a small percentage of people.

Once the cataract has been removed, it does not recur. Some patients may develop thickening of the capsule behind the new lens implant, which causes blurred vision. However, this thin film can easily be treated with a laser and does not require repeat surgery. This painless procedure takes a few minutes and improvement is usually immediate.

A lens implant will not wear out and should last a lifetime.

Leaving a cataract in the eye is not dangerous, but with time cataracts do increase in size and hardness and cause progressively worsening vision.

Prevention

Long-term exposure to ultra-violet radiation may be associated with development of cataracts. Wearing a wide-brimmed hat and sunglasses that filter out UVB rays from a young age slows the development of cataracts.

If you are over age 60, you should have an eye examination at least once a year.

Since a baby can develop cataracts if the mother has a German measles (Rubella) infection during pregnancy, women who are considering pregnancy should be immunised before becoming pregnant if they do not already have immunity, and should avoid contact with other people with Rubella during pregnancy.

Reviewed by Dr L.C. Boezaart, M.B.Ch.B, M.Prax.Med, M.Med (Ophth).

Reviewed by Dr M J  Labuschagne M.B.Ch.B, M Med(Ophth), (OSSA member), November 2010

 
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