Meaning of the word 'Cataract'
In modern language the word CATARACT describes a clouding of the eye’s natural lens. To achieve good vision the eye’s natural lens should be clear to allow light to pass into the eye and focus on the central retina. When the lens becomes cloudy and opaque this is called a cataract. It prevents entry of light into the eye and the vision deteriorates.
The term cataract has its origins in ancient Latin and Greek, where the term describes ‘white water’ akin to the appearance of an advanced opacity of the eye’s natural lens.
Greek: kataraktes
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- something that swoops or rushes down, including a waterfall, meaning that rapidly running water turns white.
Latin: cataracta
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- waterfall, floodgate, portcullis.
English:
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- large waterfall in which water plummets over a precipice; early 16th century to describe clouding of the eye’s natural lens.
Cataract types
Cataract occurs due to a build-up of cells in the eye’s natural lens, changes in lens cell proteins and structures, or a combination of these. The pattern of changes determines the type of cataract that develops. All cataract types are treated the same way, which is a fast and painless procedure to remove the cataract and replace it with a clear lens implant, or intraocular lens (IOL). There are different types of IOL that can provide clear vision without glasses are various distances.
The different types of cataracts share many similarities in terms of the symptoms patients experience, but there are some differences in symptoms as well as the speed at which the cataract can develop and the rapidity of the decline in vision.
Posterior capsular cataract
A plaque of cells on the back surface of the eye’s natural lens. As well as a decline in vision this type of cataract often produces sensitivity to light such as glare and starburst.
It usually develops more rapidly than nuclear cataract leading to a faster decline in vision and increasing sensitivity to light, over months rather than years.
Cortical cataract
Lines of opaque cells growing on the front surface of the eye’s natural lens, with an appearance like the spokes of a wheel.
This cataract type can be fast-growing and lead to a faster decline in vision and increasing sensitivity to light, over months rather than years.
Congenital cataracts
Cataract that is present at birth.
Nuclear cataract and nuclear sclerotic cataract
The main body of the eye’s natural lens is called the nucleus of the lens. It is the main part of the lens that lies in between the front and back surfaces of the lens. When cells build up in the main body of the lens, the lens becomes yellow and cloudy, and this is called a nuclear or nuclear sclerotic cataract. It is the most common type of cataract and generally develops slowly over a period of years. The decline in vision is usually slow and patients may adapt (or get used) to having reduced vision. This can lead to patients driving when the vision is not within the legal standard to do so and many patients attend for private cataract surgery because an optician has advised them to stop driving until the vision is improved by having a cataract operation.
Christmas tree cataract
Probably the ‘prettiest’ type of cataract, the Christmas tree cataract has a multicoloured sparkly appearance in the lens. The change is caused by an accelerated breakdown of membrane-associated denatured proteins induced by elevated calcium levels.
Diabetic cataract
Diabetes is associated with early development of cataract. If left untreated high blood sugar can slowly damage blood vessels throughout the body (including the tiny blood vessels in the eyes).
Bilateral cataracts
Cataract usually occurs in both eyes (bilateral). It is unusual for a cataract to occur in only one eye (unilateral) without any sign of cataract in the other eye. It is possible, however, to have bilateral cataract but for the cataract of one eye to be more advanced that the other and leading to worse vision on that side.
Sometimes, patients with bilateral cataract report being troubled by the vision in only one eye. Then, after having that cataract removed and regaining excellent vision, they notice the poor vision in the eye they thought was still seeing well and request the same operation for the second eye.
Blue dot cataract
Blue dot cataract is exactly that: many round, blue opacities seen throughout the body of the lens and causing the usual symptoms of cataract.
Snowflake cataract
An uncommon cataract made of small white opacities within the lens, giving the appearance of snowflakes. It is associated with diabetes but can occur in non-diabetics also.
