• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Eyesight coursework

Extracts from this document...

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.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Microscopes & Lenses section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Microscopes & Lenses essays

  1. Marked by a teacher

    Tuberculosis and its treatment

    4 star(s)

    Before the attack is over, a few bacteria may escape into the bloodstream and are carried elsewhere in the body where are again walled in. If the immune system fails to stop the infection, and it is left untreated , the disease progresses to the second phase, where the germ

  2. The World Demand for Power

    then, one-fourth to one-half the oil is usually left in the reservoir. In an effort to extract this remaining oil, oil companies are now beginning to use chemicals to push the oil to the well, or to use fire or steam in the reservoir to make the oil flow easier.

  1. Biology Beetroot Coursework

    * Stop Clock * Thermometer * 16 Cuvettes * 10cm3 pipette Method 1) Use a cork borer to cut out a cylinder from a beetroot. 2) Using a ruler and scalpel, cut the cylinder into a series of discs with the same size and thickness, approximately 5mm on the tile.

  2. A Comparative Study of the Density of Patella Vulgata (Common Limpets) in the Optimum ...

    When there is no tide, the limpet clamps down onto the rock using its strong muscular foot and secretion of a chemical, which prevents water loss. The shell prevents evaporation that might take place from the soft tissue inside.

  1. Weed study. Dandelions - descrption and characteristics. Investigation to dandelion distribution.

    > Photographic light meter - this was used to measure the light intensity. My investigation includes the abundance of dandelions within a shaded and unshaded area. This is the most accurate way of attaining data about the light intensity. This again is very reliable and the most precise way to measure light intensity.

  2. Yeast Coursework

    The lock and key hypothesis is the mechanism of enzyme action. Enzymes are proteins folded into a three-dimensional shape. The part of the enzyme that allows it to act as a catalyst is called the active site, which is shown on the next page.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work