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Cortical Cataracts

A person might reasonably think that the ‘cortex' of anything is the core, but in fact the word comes from Latin referring to the skin or rind of a fruit. Cataracts are the development of cloudiness within the lens of the eye, so in cortical cataracts that cloudiness begins at the outer edges of the lens before progressing inwards. Looked at closely, as by an optician or ophthalmologist (MD), cortical cataracts are white and wedge-shaped and progress to the center (‘nucleus') of the lens like spokes of a wheel.

Cortical cataracts are rarely seen in persons younger than about 45 years old. It is from this approximate age on that the lens begins to harden, which is not a cataract itself but seems to presage possible development of one. The main risk factors for cortical cataracts are excessive exposure to ultraviolet (UV) light and diabetes. UV light is not visible, but consists of short wavelengths of electromagnetic radiation that carry a high level of energy, their harm thought to be due to this.

The most common eye complication from diabetes is diabetic retinopathy, but cortical cataracts are not uncommon in diabetics. This is true of both type 1 (childhood) and type 2 (adult onset) diabetes. The disease is of course associated with excess of the sugar glucose in the blood. In the eye, glucose is converted to a sugar called sorbitol, and higher-than-normal levels of this in the eye are thought to lead to cortical cataracts. The eyes of diabetics also show sign of "oxidative stress," meaning there is a relative lack of anti-oxidant molecules such as vitamins C and E. However, the exact mechanism by which diabetes induces cortical cataracts remains unclear at this time.

Initial symptoms of cortical cataracts can be very minimal. As they move toward the center of the lens the glare of lights may become more noticeable, along with problems in seeing contrast and in a person's distance vision. The older a person is the more likely they are to have company in having cataracts. About 20% of people over sixty-five years of age have cataracts, and well over one million cataract operations performed each year in the US make it the most common of all surgery types. While initial changes with cortical cataracts can be accommodated, in the long run surgical removal and replacement with an artificial intraocular lens (IOL) is the most likely outcome. Fortunately this is a very common and relatively very safe surgery – in fact, the most commonly performed operation in the US.

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