• 21Nov

    What causes cataract?

    Any opacity in the lens of eyes is called a cataract. It is a common cause of visual impairment, especially in the elderly. It results in visual impairment. On clinical examination, it appears as white opacity in the pupils. The density of the opacity depends on severity of the cataract

    How does cataract occur?

    The mechanism of occurrence of cataract is not understood completely. A normal lens is made of protein fibres arranged in such a fashion that light rays pass through without being affected. In certain diseases, there is alteration in the protein structure which results in scattering of light. This reduces the lens transparency. Some protein alterations result in yellow or brown discoloration. On microscopic examination, fluid filled vesicles have been noticed between the lens fibres. These changes are related to free radical induced oxidative damage, effect of ultraviolet rays and malnutrition. Once a change occurs in the lens fibres, no amount of medical treatment can reverse those chemical changes of cataract formation. 

    What are the causes of cataract?

    The commonest cause of cataract is old age. Ageing brings about degenerative changes in proteins which results in appearance of lens opacities. Scientific studies have shown that the prevalence of cataract is 50% in people aged 65 and reaches nearly 70% in those above 75 years of age. The other risk factors or causes include direct trauma, toxic chemicals, smoking, hereditary factors and diabetes mellitus.

    Cataract affects nearly 50% in people at the age of 65.

    Cataract affects nearly 50% in people at the age of 65.

    What are the types of cataract?

    Cataract is classified into two types depending on the opacity of lens. A mature cataract is one in which the whole of lens is opaque. The immature cataract has areas of opacity with remaining transparent lens. Sometimes the proteins liquefy and leak out of its capsule. The resulting shrunken lens results in hypermature cataract. The various types of cataract depending on their cause are discussed below.

    Age related cataract

    After middle age, the central part of lens called nucleus becomes harder and is called nuclear cataract. In these patients, the near vision improves due to an increase in focusing power of the central area of lens. These patients usually remain asymptomatic. Some patients develop opacities in the outer layers of lens called cortex. This is due to increased hydration of lens proteins which results in their separation and an alteration of vision. This is called cortical cataract. Age related cataract progresses slowly and usually surgery is not required. When indicated, surgery for extraction of lens improves vision dramatically.

    Traumatic Cataract

    Traumatic cataract occurs due to a blow to the eyeball where the lens is damaged or displaced. There may be a foreign body stuck inside the lens. Some of the common causes include injuries from fireworks, air rifle pellets, rocks, arrows, exposure to heat or x-rays. Most of these injuries are preventable. Simple use of protective glasses saves many eyes. Any injury to the lens capsule results in entry of fluid (aqueous or vitreous) between the lens fibres. The lens becomes white very soon associated with pain and visual impairment.

    Complicated Cataract

    Cataract due to another eye disease is called complicated cataract. It results as a complication of intra-ocular disease. Conditions like uveitis, glaucoma, retinitis pigmentosa and retinal detachment result in cataract formation. These cataracts usually affect one eye and deterioration of vision occurs. The recovery of vision is poor if at all it occurs.

    Cataract Associated with Systemic Disease

    Cataract in both eyes occurs in many diseases like diabetes mellitus, hypocalcemia due to any cause, allergic dermatitis, galactosemia and Down’s syndromes.

    Drug-Induced Cataract

    Prolonged use of steroids, whether systemic or instillation of eye-drops can result in cataract. Other drugs which may cause this condition include phenothiazines, amiodarone, and phospholine iodide eye drops.

    Cataract is a common disorder of the aged. It may occur early in certain occupations or due to causes discussed above. Reduction in visual acuity affect quality of life, hence one should take precautions to avoid trauma or exposure to harmful agents.

    Anna L.

    It’s all about health!
    I have academic background in drugs related Chemical Technology, as well as extensive professional experience in pharma and medical companies. My main area of interest is everyday life medicine. The goal of my articles is to give people informative answers to the questions that bother them, to dispel doubts and some common misbeliefs and also to inspire everyone to keep healthy lifestyle.

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