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Eyesight coursework

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Introduction

Eyesight project Describe causes and symptoms of long and short sight and how they are corrected Introduction These extremely common problems are the result of small variations in the shape of the eyeball that affect the ability of the lens to focus light on the back of the eye. This focuses by varying the thickness of the lens, using tiny muscles around its perimeter. If the eyeball is either too short or too long in relation to the maximum power of the lens then the light can never be focused and vision is blurred. Short sight, myopia, results from having an eyeball too long for the focusing power of the lens. This means that light gets focused in front of the retina unless the object is brought extremely close to the eye. The opposite situation is the case in long sight, where the eyeball is short in relation to the power of the lens. In this case the point of focus is further behind the retina. The size and shape of the eyeball is something that we are all born with; the power of the lens to contract and expand and, therefore, to vary its focus changes over time. ...read more.

Middle

Presbyopia Treatment: Surgery New surgical options to treat presbyopia are being researched and are already available in many countries. One example is Refractec Inc.'s conductive keratoplasty, or CK, treatment, which uses radio waves to create more curvature in the cornea for a higher "plus" prescription to improve near vision. The method was FDA-approved for the temporary reduction of presbyopia in April 2004. (In 2002 it had been approved for mild farsightedness.) Read more about how CK works. A highly experimental treatment is a soft, elastic polymer gel that researchers say would be injected into the capsular bag, the cavity that contains the natural lens. In theory, the gel would replace the natural lens and serve as a new, more elastic lens. Animal testing may begin in 2004. See if you can find out how bifocal and varifocal lenses work Bifocal lenses Bifocal lenses are effectively two lens powers combined together to assist with both near and distance vision. The most common use of bifocals is for reading correction in the lower lens together with a modest distance correction in the upper lens, giving sharp vision at two distinct distances. Bifocals can also be supplied with a clear (upper) ...read more.

Conclusion

Once a clouded lens develops, surgical removal is the only remedy. Each year about 1.3 million cataract operations are performed, making it the most common operation in the country in people over 65. Cataract surgery is improves vision in up to 95% of cases. Newer techniques, however, have made it safer and even more efficient to operate in earlier stages. There is, in fact, considerable evidence that, because of the ease and relative safety of the procedure, it may be performed more often than needed. Patients having operations now tend to have better preoperative vision than those operated on ten or 20 years ago. In a study of 800 cataract operations, a quarter of the patients said that clouding had had no obvious effect on their lives before the procedure. What is Glaucoma? Glaucoma is a group of eye diseases that gradually steals sight without warning and often without symptoms. Vision loss is caused by damage to the optic nerve. This nerve acts like an electric cable with over a million wires and is responsible for carrying the images we see to the brain. It was once thought that high intraocular pressure (IOP) was the main cause of this optic nerve damage. Although IOP is clearly a risk factor, we now know that other factors must also be involved because even people with "normal" IOP can experience vision loss from glaucoma. ...read more.

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