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CATARACTS


EXPLAINED

Age-related Macular Degeneration
Glaucoma


A dense cataract seen through a dilated pupil
A posterior subcapsular cataract

A dense cataract seen through a normal pupil

A dense cataract seen through a dilated pupil

A snowflake cataract

A cataract with obvious clefts

A cortical cataract

A christmas tree cataract so called because of its appearance

 WHAT ARE CATARACTS?

A cataract is simply the name given to a cloudy condition of the crystalline lens in your eye. As the lens becomes too cloudy, light cannot pass through it properly and so you are less able to see clearly. It's a bit like looking through a window which hasn't been cleaned for a while. Cataracts are the most common cause of blindness world-wide affecting 17 million people and in the UK is the number one cause of loss of vision in the UK for the over 55 age group.

Cataract operations are the most common operation carried out on the NHS with over 2.3 million carried out every year and anyone reaching full life expectancy is more likely to have a cataract extraction than the 9 next most common operations combined.


A CATARACT INSIDE THE EYE


 WHAT CAUSES CATARACTS?

The crystalline lens inside the eye contributes about one third of the refractive power of the eye and consists of regularly arranged concentric fibres containing proteins. The lens is quite transparent throughout the first three or four decades of life but as one gets older it begins to lose its transparency by the accumulation of yellow chromatophores in the central lens nucleus.

The main risk factor for acquiring a cataract is predominately genetic although smoking tobacco, receiving excessive amounts of ultra-violet rays from the sun and car exhausts also contribute as they cause the production of substances called free radicals. Antioxidants can neutralise the damaging effect of free radicals. Various substances such as ascorbic acid, carotenoids and bioflavinoids have antioxidant properties and certain foods contain antioxidants such as melon, spinach and seafood. Vitamin C has been shown to protect the eyes against UV induced cataract in the guinea pig.

 WHAT HAPPENS TO MY VISION WITH CATARACTS?

Because cataracts develop slowly, you are likely to experience a very gradual deterioration in your vision and you may not even notice that anything is wrong until the cataracts are well advanced. When fully developed, however, cataracts can cause a significant loss of vision. Vision can be affected by a loss of transparency, a change in the refractive power or an increase in forward scatter from the crystalline lens.

 CATARACT SURGERY HISTORY

Before cataracts were extracted, the cloudy lens was dislodged using a lance by a process known as couching. Lances have been found from excavations in Greece dating back to between 1000-2000 years BC.  Jacques Daviel, a French doctor, is credited with carrying out the first cataract extraction in 1753.

ALL ABOUT CATARACTS

 WHAT WILL AN EYE EXAMINATION REVEAL?

Although many cataracts never develop sufficiently to require an operation, it is important to visit your optometrist regularly so that your eyes can be examined for any evidence of cloudiness. Furthermore, recent evidence suggests that cataracts are made worse by excessive UV light. Therefore, in the height of the summer, or in the winter if skiing at high altitude, where the levels of ultra-violet light are greater, it is advisable to protect your eyes with sunglasses or spectacle lenses containing an ultra-violet ray blocker.

 HOW ARE CATARACTS DETECTED?

There are a number of means by which to detect the presence of a cataract. The simplest way is to look into your eye using a special type of torch microscope called an ophthalmoscope and one can also use a retinoscope or a slit-lamp biomicroscope for further confirmation.

 HOW DO YOU KNOW IF YOU NEED A CATARACT OPERATION?

The assessment of your vision will determine how well you see and this together with an examination of the extent of the cataract, will determine whether an operation would be considered a viable proposition.

 CATARACTS AND THEIR TREATMENT

Cataracts can be treated with a very straightforward operation which usually takes about twenty minutes. An eye surgeon will remove your own cloudy crystalline lens and replace it with a new clear plastic lens. The procedure of choice is known as phakoemulsification with the implantation of a posterior chamber intra-ocular lens. Phakoemulsification was devised by Professor Charles Kelman at New York Medical College. An ultrasonic probe is inserted through a 3mm incision in the white of the eye which vibrates at high speed and with the instillation of an enzyme aids the emulsification of the cataractous crystalline lens. The same probe sucks out the liquid and the foldable lens implant is inserted through the same incision and positioned where the natural lens was.

Following cataract surgery, the long distance vision is generally quite good, but reading glasses will be needed. This is because the plastic replacement lens is not flexible like a young person's own crystalline lens, although a new operation undergoing trials at St.Thomas's Hospital may improve the near reading vision as well. They use a lens with four hinges, which become activated by the ciliary muscle which effectively moves the lens 1.5mm forward, rather like a zoom lens in a camera. The cost of this lens is £200 compared with £70 for the currently used lens, so it is thought unlikely to become available on the NHS. Other hospital consultants favour the use of progressive or bifocal replacement lenses which take a couple of weeks to get used to but are said to be very successful.

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