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Presentation on eye

  1. 1. Understanding Vision Lens Focal Point Cornea
  2. 2. The cornea is a clear, dome-shaped surface that covers the front of the eye. It is the first and most powerful lens in the eye's optical system. To keep it transparent the cornea contains no blood vessels. Tears that flow over it and aqueous humor in the chamber behind it keep
  3. 3. Pupil  The pupil is the hole in the center of the iris that light passes through. The iris muscles control its size. Retina  The retina is the film of the eye. It converts light rays into electrical signals and sends them to the brain through the optic nerve. The sides of the retina are responsible for our peripheral vision. The center area, called the macula, is used for our fine central vision and color vision.
  4. 4.   This Iris is the colored part of the eye: brown, green, blue, etc. It is a ring of muscle fibers located behind the cornea and in front of the lens. It contracts and expands, opening and closing the pupil, in response to the brightness of surrounding light. Just as the aperture in a camera protects the film from over exposure, the iris of the eye helps protect the sensitive retina.
  5. 5.  Sc l e r a The sclera is the white, tough wall of the eye. It along with internal fluid pressure keeps the eyes shape and protects its delicate internal parts.
  6. 6.           Lens Transparent body enclosed in an elastic capsule Made up of proteins and water Consists of layers, like an onion, with firm nucleus, soft cortex Gradient refractive index (1.38 - 1.40) Young person can change shape of the lens via ciliary muscles Contraction of muscle causes lens to bulge At roughly age 50, the lens can no longer change shape Becomes more yellow with age: Cataracts The graph on the right shows the optical density (-log transmittance) of the lens as a function of wavelength. The curves show the change in density with age. More short wavelength light is blocked at increases ages.
  7. 7.  ciliary body (muscles)  *circular muscle that surrounds the edge of the lend * connected to the lens by suspensory ligaments *changes the shape of the lens
  8. 8.  The blind spots in each eye are aligned symmetrically so that most of the time, one eye’s field of vision will compensate for the loss of vision in the other. The diagram above shows where the blind spots are located.
  9. 9.    To find the eye’s blind spot, you can do the following tests. In order to find the blind spot of the right eye, it is necessary to close the left eye, focus the right eye on a single point, and see if anything vanishes from vision some 20 degrees right of this point. The following diagram has a set of characters on the left hand side, and black circle on the right.Keeping your head motionless, with the right eye about 3 or 4 times as far from the page as the length of the red line, look at each character in turn, until the black circle vanishes. optic nerve
  10. 10.  Some eye problems are minor and fleeting. But some lead to a permanent loss of vision. Common eye problems include,Cataracts clouded lenses  Glaucoma - damage to the optic nerve from too much pressure in the eye.Retinal disorders problems with the nerve layer at the back of the eye.Conjunctivitis an infection also known as pinkeye.  Your best defense is to have
  11. 11.           Cataract A cataract is a clouding of the lens in your eye. It affects your vision. Cataracts are very common in older people. By age 80, more than half of all people in the United States either have a cataract or have had cataract surgery. Common symptoms are Blurry vision Colors that seem faded Glare Not being able to see well at night Double vision Frequent prescription changes in your eye wear Cataracts usually develop slowly. New glasses, brighter lighting, anti-glare sunglasses or magnifying lenses can help at first. Surgery is also an option. It involves removing the cloudy lens and replacing it with an artificial lens. Wearing sunglasses and a hat with a brim to block ultraviolet sunlight may help to delay cataracts.
  12. 12.  Disorders  The Retinal retina is a layer of tissue in the back of your eye that senses light and sends images to your brain. In the center of this nerve tissue is the macula. It provides the sharp, central vision needed for reading, driving and seeing fine detail.  Retinal disorders affect this vital tissue. They can affect your vision, and some can be serious enough to cause blindness. Examples are
  13. 13.  Glaucoma Glaucoma damages the eye's optic nerve. It usually happens when the fluid pressure inside the eyes slowly rises, damaging the optic nerve. Often there are no symptoms at first, but a comprehensive eye exam can detect it.  People at risk should get eye exams at least every two years.  Early treatment can help protect your eyes against vision loss. Treatments usually include prescription eyedrops and/or surgery. 