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Different types of cataracts

The word cataract means waterfall or clouding as it looks like a waterfall on examination. I once thought that a cataract was just one condition, but actually, a cataract is any opacity within the substance of the human lens, and it can take different patterns and have different effects on your vision.  A cataract that affects the centre of the lens is called a nuclear cataract, and this can make you more near-sighted or may even appear to improve your near reading vision temporarily. However, once the nuclear cataract becomes more yellow, densely yellow, and then brown, or even opaque, it will progressively cloud your vision. Once you have yellowing or browning of the lens, it becomes challenging for you to distinguish between different colours and they all look rather washed out and faded.  If you have a cataract which is found to be affecting the edges of the lens called a cortical cataract, it will look like a whitish wedge-shaped opacity or streaks in the outer edge of the lens cortex. This type of cataract only progresses and grows across the front of the lens. These fibres extend towards the centre and then interfere with light passing through the heart of the lens. You see this interference as a distortion or halos around lights or glare at night. A cataract can also affect the back of your lens, right by the lens capsule and this is called a posterior subcapsular cataract. This type of cataract starts as a small opaque area that eventually forms a sheet across the back of the lens right in the middle of the path of light. A posterior subcapsular cataract often interferes with your reading vision and significantly reduces your vision in bright light and causes glare or halos around lights at night. The visual interference of a posterior subcapsular cataract is worse when the pupil is small, as in bright light, and it can significantly and suddenly affect your vision when you switch between different light conditions and go from one to another different light condition. This type of cataract progresses very fast.  Some people are born with a congenital cataract or develop it through childhood. These cataracts can be genetic or associated with an intrauterine infection, dehydration or trauma.  Lastly, cataracts can be due to certain metabolic conditions and syndromes. Studies associate cataracts with diabetes, galactosaemia, myotonic dystrophy, neurofibromatosis and rubella.  As we have already said in a previous blog post, congenital cataracts do not always affect your vision, but if they do you can certainly have surgery for them.  


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