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Chapter: 11th 12th standard bio zoology Human Body higher secondary school

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Human Eye : Cataract, Lens Replacement

Cataract is the opacity in the lens of the eye. The normal lens allows light to reach the retina when it becomes opaque and does not allow light to reach the retina, the person is unable to see clearly.

Cataract

 

Cataract is the opacity in the lens of the eye. The normal lens allows light to reach the retina when it becomes opaque and does not allow light to reach the retina, the person is unable to see clearly. Cataract is due to (coagulation) changes in the delicate protein fibres within the lens, cataract never causes complete blindness but causes increased loss of transparency. The clarity and the detail of the image is progressively lost. The front part of the lens becomes densely opaque and whiteness is visible in the pupil.

 

The causes for cataract formation in the adult is related to aging, sun light exposure, smoking, poor nutrition, eye trauma, systematic diseases like diabetes mellitus, infection and injuries and certain medications such as steroids. Sometimes German measles in pregnant mothers causes cataract in the child.

 

To delay the onset of cataract one should have nourishing diet, protect eye from excessive exposure to sun rays, X-rays, intense heat and injuries. Diseases like diabetes and syphilis should be treated early and effectively.

 

Two types of cataracts are dense nuclear cataract (cataract in the center of the lens) and Peripheral cataract (cataract in the periphery of the lens). There is no medical treatment for cataract. The only treatment is surgery. Once the cataract is removed, the eye is unable to focus, as there is no lens. So one has to use an artificial lens. This can either be glasses, contact lenses or insertion of introcular lenses.

 

Today modern medical advances have made cataract surgery very successful. New surgical techniques and intracular lenses can restore excellent vision (97%).

 

Lens Replacement

 

For individuals who are over 40 years of age, considering refractive surgery to decrease dependence on glasses and contact lenses, Clear Lens Replacement (CLR) is an exciting option. In essence, this procedure entails removing the natural lens of the eye and replacing it with an intraocular lens (IOL) implant.

 

CLR may be an excellent alternative to these procedures for people already wearing bifocals since CLR requires removal of the natural lens of the eye, the patient is subsequently unable to focus (accommodate) at near by objects . This is why CLR is best suited for patients over 40 who are already wearing bifocals. One potential solution to this problem of accommodative loss is implantation of the multifocal IOL (Intra Occular Lens) implant. This implant allows focusing at both near and far object.


 

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