The Structure and Function of the Eye SCIENCE

The Structure and Function of the Eye SCIENCE CLASS 8 UZMA AMER

Windows to the World • Eyes are photosensitive organs designed to detect light and pass on the information as electrical signal to the brain. • Vision such as ours and animals are know as ‘camera’ like vision. • Camera like vision has evolved at least seven separate times through out natures history. 12/15/2021 Structure and Function of the Eye 2

The External Structure of the Eye 12/15/2021 Structure and Function of the Eye 3

Structure of the Eye 12/15/2021 Structure and Function of the Eye 4

Sclera • The sclera, commonly known as "the white of the eye, " is the tough, opaque tissue that serves as the eye's protective outer coat. 12/15/2021 Structure and Function of the Eye 5

The Iris • The coloured part of the eye is called the iris. It controls light levels inside the eye similar to the aperture on a camera. • The round opening in the centre of the iris is called the pupil. • The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size. 12/15/2021 Structure and Function of the Eye 6

The Cornea • The cornea is the transparent, dome-shaped window covering the front of the eye. It is a powerful refracting surface, providing 2/3 of the eye's focusing power. Like the crystal on a watch, it gives us a clear window to look through 12/15/2021 Structure and Function of the Eye 7

Conjunctiva • The conjunctiva is the thin, transparent tissue that covers the outer surface of the eye. • It begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids. • It is nourished by tiny blood vessels that are nearly invisible to the naked eye. 12/15/2021 Structure and Function of the Eye 8

Lens • The purpose of the lens is to focus light onto the back of the eye. • The nucleus, the innermost part of the lens is surrounded by softer material called the cortex. • The lens is encased in a capsular-like bag and suspended within the eye by tiny guy wires called zonules. 12/15/2021 Structure and Function of the Eye 9

Lens: Focusing Light 12/15/2021 Structure and Function of the Eye 10

Lens: Sight Defects 12/15/2021 Structure and Function of the Eye 11

Retina • The retina is a very thin layer of tissue that lines the inner part of the eye. • It is responsible for capturing the light rays that enter the eye. Much like the film's role in photography. • These light impulses are then sent to the brain for processing, via the optic nerve. 12/15/2021 Structure and Function of the Eye 12

Optic Nerve • The optic nerve transmits electrical impulses from the retina to the brain. • It connects to the back of the eye near the macula. • The visible portion of the optic nerve is called the optic disc. 12/15/2021 Structure and Function of the Eye 13

Optic Nerve: Blind Spot • Where the optic nerve meets the retina there are no light sensitive cells. It is a blind spot. • Take a piece of paper and draw a dot and 10 cm to the left an x. • Close your right eye and hold the paper at arms length. • Look at the dot and move the paper towards you. • What happens to the X? • It disappears into the blind spot! 12/15/2021 Structure and Function of the Eye 14

Eyes and Animation (Off Syllabus) • There is a. 4 second delay in response from the time the image falls on the retina. The sensation may persist for up to 2 minutes. • This after image effect is exploited by film, TV and computer monitors which display a rapid succession of still images, which are refreshed before the perceptual image has decayed. 12/15/2021 Structure and Function of the Eye 15

Eye Disorders (Off Syllabus) • About one in ten men and one in a hundred women experience some form of divergent colour perception. • The most common is confusion between red and green. This can cause some problems in colour matching. • The genes for colour blindness located on the X chromosome. 12/15/2021 Structure and Function of the Eye 16

Colour Blindness Test 12/15/2021 Structure and Function of the Eye 17

Colour Blindness Test 12/15/2021 Structure and Function of the Eye 18

Colour Blindness Test 12/15/2021 Structure and Function of the Eye 19

Colour Blindness Test 12/15/2021 Structure and Function of the Eye 20

Colour Blindness Test 12/15/2021 Structure and Function of the Eye 21