The Eye

Anatomy of the Eye Sclera Choroid Retina Aqueous humor Iris Blood vessels Pupil Cornea Optic nerve Lens Blind spot Ciliary muscle Vitreous humor Label the diagram of the eye!

Sclera and Cornea (outer layer) Tough, white outer layer; Protects and supports the eye Tough, clear outer layer; Refracts (bends) light toward the pupil Sclera

Choroid layer Did you know that many nocturnal animals also have an iridescent layer of tissue called the tapetum lucidum which helps reflect light back into the eye? Choroid - A black layer within the eye that prevents light from scattering and provides the retina with nutrients.

Anatomy of the Eye - Iris The coloured part of the eye A muscle that contracts to control the size of the pupil; controls the amount of light entering the eye Iris scans can be used as a method of identification because each person has unique banding of colour in their eye

Anatomy of the Eye - Pupil The hole in the middle of the iris Where light enters the eye Size changes depending on the amount of light present in the environment

Anatomy of the Eye - Lens Transparent structure behind the iris Helps focus light rays onto the retina Changes shape based on the distance of the object

Aqueous Humour and Vitreous Humour - Jelly-like material at the front of the eye behind the cornea; supplies cornea with nutrients, bends light and maintains shape Vitreous Humour - Bends light and gives the eye structure Iris scans – identification because each person’s iris has a different color pattern

Anatomy of the Eye - Retina Nerve layer at the back of the eye Senses light and creates nerve impulses Location of the: Rods: detect black and white Cones: detect red, blue, & green

Rods and Cones Humans have 125 million rods and 6 million cones Rods allow us to see black and white Peripheral vision appears to be black and white because the cones are concentrated at the fovea

Color blindness Color blindness occurs when one or more cones are defective Red-green color blindness is most common Caused by a genetic defect on the X chromosome What numbers do you see?

Color blindness How do we see colour?

Normal Vision Reduced sensitivity to blue

Normal Vision Reduced senitivity to red http://enchroma.com/test/instructions/

Fovea centralis (macula) Most sensitive area of the retina, highest concentration of CONES = greatest visual acuity To find the fovea, draw a straight line from the center of the lens

Anatomy of the Eye – Optic Nerve Carries nerve signals from the retina to the brain, where the image is interpreted

Where the retina attaches to the optic nerve. There are Blind Spot Where the retina attaches to the optic nerve. There are NO rods or cones in the blind spot Hold text book 30 cm away. Close your right eye and look at the black cross with the left eye. Slowly move your left eye towards the figure and when the dot disappears, the image is falling on the blind spot. You don’t notice the blind spot because one eye will compensate for the other. Blind Spot test! Open to page 472 Optic nerve carries info to the occipital lobe

Ciliary Muscle Ciliary Body Alters the shape of the lens; important in accommodation

Pink eye (conjunctivitis) = Conjunctiva Conjunctiva Thin layer on top of the cornea for protecting the eye; blocks entry of pathogens into the eye Pink eye (conjunctivitis) = infection of the conjunctiva

Anatomy of the Eye – Eye Muscle Helps to move the eye Eye muscles operate in antagonistic pairs (ex: one muscle must relax and the other muscle contracts to move the eye)

Who do you see? https://www.youtube.com/watch?v=tB5-JahAXfc

Who do you see?

Who do you see?

Optical Illusions! http://www.michaelbach.de/ot/fcs-thompsonThatcher/index.html http://www.michaelbach.de/ot/lum-adelsonCheckShadow/index.html http://www.michaelbach.de/ot/mot-silencing/index.html

Vision Problems and Corrective Lenses Hyperopia – “Far sightedness” Description: Person CAN see far objects; has difficulty seeing nearby objects Solution: Glasses with converging lenses

Vision Problems and Corrective Lenses Myopia – “Near sightedness” Description: Person CAN see close objects; has difficulty seeing far objects Solution: Glasses with diverging lenses

Presbyopia

Astigmatism Irregularly shaped eye causes different focal lengths in the horizontal and vertical directions

Cataracts Clouding of the lens leading to decreased vision and eventual blindness.