Human EYEs

1. HumanEYEs Don By : Ali Abdul Hameed Al-Hammadi ةmohammadfahad اhazzahamad Grade :12-06 Supervised by: RIYAD ALSHAIKH

2. Topics that will be covered • General Information about Eye’s • how does the eye work analogous to a camera. • The Camera and the Eye • Describe three vision defects • Nearsightedness • Farsightedness • and Astigmatism • Explain which kinds of lenses are needed to correct the previous vision defects. • Lenses picture. • Correction of Common Vision Defects

3. How eyes works? The individual components of the eye work in a manner similar to a camera. Each part plays a vital role in providing clear vision. So think of the eye as a camera with the cornea, behaving much like a lens cover. As the eye's main focusing element, the cornea takes widely diverging rays of light and bends them through the pupil, the dark, round opening in the center of the colored iris. The iris and pupil act like the aperture of a camera

4. The Camera and the Eye Images are formed in a camera by refraction in a manner similar to image formation in the eye. However, accommodation to image closer objects is done differently in the eye and camera

6. What is nearsightedness ? Nearsightedness, or myopia, is the inability to see distant objects clearly. (You are "near-sighted," so things up-close are clear but things far away are blurred. What causes nearsightedness One or more of the following physical factors causes myopia: 1) the cornea is too steep; 2) the lens inside the eye is too curved; 3) the eyeball is too long. Whichever factors are involved, the eye focuses light too quickly — in front of the retina instead of directly on it

7. How is nearsightedness treated Like astigmatism, myopia can be corrected with prescription eyeglasses, contact lenses and refractive surgery. Nearsightedness can also be corrected non-surgically with a special type of gas permeable (GP) contact lens fitting called orthokeratology (or "ortho-k"). In ortho-k, you wear specially designed GP lenses while you sleep, then remove them during the day. Ortho-k provides only temporary correction of myopia, however. The nearsightedness will return if you discontinue wearing the cornea-reshaping lenses at night.

9. What is farsightedness ? Farsightedness, or hyperopia, is the inability to see clearly at any distance without excessive focusing effort. Usually, farsightedness affects near vision more than distance vision. But in severe hyperopia, vision is blurred at all distances. What causes farsightedness? Hyperopia is caused by 1) the cornea being too flat; 2) the lens inside the eye being too flat; 3) the eyeball being too short; or a combination of these factors. The result is that the eye focuses light too slowly — behind the retina instead of directly on it. Farsightedness can be present in childhood; it can also worsen later in life.

10. What is astigmatism? Astigmatism is blurred or distorted vision at all distances What causes astigmatism Astigmatism typically is caused by an irregularly shaped cornea (the clear front surface of the eye). A common analogy used to describe astigmatism is that your eye is shaped more like a football than a baseball. A relatively uncommon condition called keratoconus can cause severe irregular astigmatism

12. The End Hop to enjoy it