Cataract is the leading cause of blindness worldwide. It can be treated by simple and cost-effective surgery.
What are cataracts?
Cataract is a cloudiness in the lens of the eye.
Normally, the lens is completely clear and acts to adjust the focus of light rays entering the eye onto the retina to form a clear image.
The proteins which form the lens are normally very precisely layered and arranged and it is this feature which allows the proteins to be completely transparent. If this internal structure deteriorates and the proteins become damaged or disorganised, the lens itself starts to become cloudy or brownish and this interferes with the transmission of light back onto the retina.
There are several patterns of cataract formation but the end result is the same. The greater the cloudiness, the worse the vision becomes until finally only light and dark can be distinguished.
The early stages of cataract may have no symptoms at all but early symptoms include glare sensitivity, reduced perception of fine detail and reading difficulties. Work and domestic activities become affected, and activities such as driving become impossible.
Finally, the person becomes visually impaired, particularly when both eyes are affected. People who are blind generally have a severe reduction in their personal and economic quality of life and may even die prematurely.
What causes cataract?
Cataract should be regarded as a 'risk factor' disease. The main risk factor by far is age. The incidence of cataract rises rapidly from the sixth decade (from the age of 50-60) and keeps rising until the end of life.
Other significant risk factors include family predisposition, eye trauma, diabetes and a history of dehydration in children from severe diarrhoeal infection and fevers.
This latter risk factor may help to explain the apparent higher age-specific incidence of cataract in countries like India.
Lesser risk factors include the use of some drugs, the presence of other eye conditions, particularly inflammation in the eye and sunlight exposure.
Children and babies can have cataract and sometimes be born blind from it. This is called congenital cataract and is uncommon. When it occurs, early treatment is important to prevent a life of blindness.
Can cataract be prevented?
Because of the way the risk factors such as age and family predisposition determine the likelihood of getting cataract, it is not generally possible to prevent cataract.
Obviously however, the prevention of diabetes, the avoidance of eye trauma, the treatment of inflammatory diseases, the reduction of the burden of diarrhoeal diseases in communities and the avoidance of unnecessary use of certain drugs will result in some reduction of the load of cataract blindness.
There is no known effective medical treatment which can prevent cataract from developing or slow its progress once it appears.
Access to screening and good quality specialist eye services is crucial for people with cataract to get appropriate and timely advice about management and the need for surgery. The prevention of cataract presents one of the great public health challenges.
Can cataract be treated?
The treatment of cataract is surgical. Basically, two things need to occur: firstly, the cloudy tissue has to be removed surgically and secondly, the lens power of the eye needs to be restored.
There are a number of ways to do these things and there have been different techniques developed over the centuries.
Modern cataract surgery has a number of specific features:
- It is one of the most successful and cost-effective surgical procedures of all time
- It is done by microsurgical techniques, using an operating microscope and specialised instruments
- It is done using local anaesthetic in most instances. Most people do not experience pain or distress from the surgery
- The cloudy tissue is removed from the internal part of the lens, leaving part of the lens capsule behind to act as a support for a lens implant called an intraocular lens (IOL).
- This IOL replaces the lens power of the eye and allows the patient to see more clearly. If an IOL is not used, the lens power has to be restored using either a thick spectacle lens or a contact lens.
There is nothing mysterious about the process of removing the cloudy lens tissue. Because the central part of the lens is usually quite tough, to remove it requires an incision in the eye which is big enough to slide it out in one piece (Manual Extracapsular Cataract Surgery, or ECCE) or the use of a device to break it up inside the eye so that it can be flushed out through a very small incision. This device is called a phacoemulsifier (‘Phaco') and the surgery is called Phaco surgery.
A small incision is desirable because it is safer, the technique is faster and it heals rapidly without stitches (sutures), allowing a rapid return of good vision and normal activities.
There is a technique of surgery, Small Incision Sutureless Cataract Surgery (SICS) which combines features of the small incision of Phaco surgery with the technological simplicity of ECCE. In most cases no sutures are used with this technique and the results are comparable to those of Phaco surgery, but the equipment and running costs are far less.
Phaco surgery is now the standard of care for cataract surgery in developed countries but its high cost and the complexity of the equipment mean that ECCE and SICS are the main means used in low-resource countries. SICS is rapidly gaining in popularity because of its speed, low cost and rapid recovery time compared to ECCE.
Most cataract surgery with IOL implantation has excellent visual and functional results.
Note: This information is general in nature and is not a substitute for specialist medical advice. Have your eyes checked regularly every two years, even if you have not noticed any symptoms or changes.
About the author
Dr David Moran, Ophthalmologist MB BS (Hons) FRANZCO
David first met Fred Hollows in the mid 1970s, and worked with him on the ground-breaking National Trachoma and Eye Health Program. David has been involved with The Foundation since its earliest days, and was a board member for five years until May 2010. A practising ophthalmologist, David has presented at numerous conferences and authored many papers and publications related to eye health.
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