The Eye

Front 1

the eye

Back 1

● two eyes necessary for depth perception
● photoreceptor cells (rods and cones) are stimulated by light.
● stimulant translated into a nerve impulse that travels along the optic nerve to the cerebrum. where an image is formed.

Front 2

yellow spot/fovea

Back 2

clearest vision. consists of cones.

● cones are for colour

● rods are for black and white

Front 3

refraction of light by the cornea and lens

Back 3

light rays enter the eye passing through the cornea , aqueous humour, pupil,lens,vitreous humour and fall on the retina .

cornea refracts light rays and the lens focuses light sharply onto the retina

Front 4

accommodation

Back 4

near vision (less than 6m)

● ciliary muscles contract which pulls ciliary process and choroid towards the lens.
● tension on suspensory ligaments is released
● elastic lens becomes more convex. increasing its refracting power
● clear image formed on retina

Hint 4

distant vision ( greater than 6m)

● ciliary muscles relax and ciliary process and choroid return to normal position.
● tension on suspensory ligaments increases.
● elastic lens becomes less convex. decreasing refracting power
● clear image formed on retina

Front 5

pupillary mechanism

Back 5

bright light

● circular muscles of iris contract and radial muslces relax
● pupil size decreases allowing less light to enter eye

Hint 5

dim light

● circular muscles relax. radial contract.
● pupil size increases to allow more light to enter eye

Front 6

binocular vision/stereoscopic vision

Back 6

each eye forms a different image of an object. both images from each eye are sent to the cerebrum, where a 3D image is formed. this enlarges the visual field and helps the person to estimate size distance and depth

Front 7

normal vision

Back 7

short sightedness / myopia

glasses with concave lens

Hint 7

far-sightedness/ hyperopia

glasses with convex lens

Front 8

astigmatism

Back 8

normal eye

Hint 8

caused by unequal curvature og lens or cornea. only part of image is focused

Front 9

cataracts

Back 9

results when the lens becomes cloudy and vision is impaired. mainly affects older people. diabetics and hypertension people

Hint 9