eye(1).pptx chicken pox irises in chicken

Eyes and iris

1. EYE

2. The eye detects light that has been reflected from an object and coverts it into nerve impulses. The impulses are transmitted along the optic nerve to the brain which translates them into a precise picture of the object The brain, not the eye is where the actual process of seeing is performed

3. The eye is situated in bony sockets of the skull called orbits and has muscles attached to move them The orbit protect the back of the eye from damage The eyelids close to protect the eye against dust and bright light The eyelashes keep the front of the eye free from dust and dirt Tears is produced by tear gland and keeps the eyes moist and wash away foreign particles and contain enzyme lysozyme which kill bacteria

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5. Light rays from the objects travel in a straight line to the eyeballs. They pass through the structures at the front of the eye ball, through the pupil and are focused on the retina The light stimulates light sensitive cells of the retina which send impulses along the optic nerve to the brain. The brain then forms an image of size, shape, colour and distance away from the object Image formation

6. In order to see the cornea refracts (bends) the light towards the retina Image formation

7. The adjustment of the lens for focusing on near and distant objects is called accommodation. The lens is connected by ligaments to the ring-shaped ciliary muscle. Contraction and relaxation of the ciliary muscle affects the tension in the ligaments which changes the shape of the lens. When focusing on distant objects the ciliary muscle relax and contracts when focusing on a near object. ACCOMODATION

8. The size of the pupil control the amount of light that enters the eye. Muscles of the iris control the pupil size Control of light entering the eyes

9. A person with short sight can see near objects, but distant objects are out of focus Short sight occur if the eyeball is too long from front to back or lens is to thick It is corrected by wearing diverging (concave) lens as spectacles or contact lens Short sight (myopia)

10. A person with long sight can see distant objects , but near objects are out of focus long sight occur if the eyeball is too short from front to back or lens is to thin or flat It is corrected by wearing converging ( convex) lens as spectacles or contact lens Long sight ( hypermetropia )

11. Cataracts