Eyes

• tough outer covering (white of the eye) • maintains shape and protect

• bulge of the sclera at front of eye (transparent) • allows light entry into eye (bends light) • needs oxygen but no blood vessels. get oxygen from tears

• made up of rod (light level) & cone ( red, blue green) cells • convert light wave to nerve impulse

• transparent fluid in chamber behind cornea • supplies nutrients to cornea • maintans shape • no blood bc cornea needs to be clear

• middle layer • has blood vessels to nourish retina • has melanin • absorb blue light

• Sclera • Choroid • Retina

• thin circular muscle • coloured part of eye • controls size of pupil (constriction/dilation)

• opening that allow light in eye • focus the image on the retina • bends light but also FOCUS

• alter shape of lens

• cloudy jelly like material • fills the eye interior chamber • maintain shape of eye • permit light transmission to retina

• area at centre of retina where cones are most dense and vision is sharpest • rods are around it but not in it • colour/light reception

no rods or cones here - optic nerve comes in contact with retina - absence of photosensitive cells therefore called blind spot

photoreceptor that operate in dim light to detect light in black and white - used for peripheral vision (at the periphery of the retina) - see black and white only - low energy to activate so use @ night and peripheral vision - one type therefore monochromatic vision - many rods connected to one bipolar cell therefore retinal convergence

photoreceptors that operate in bright light (high intensity light) to identify colour - 3 types (red, green, blue) - cone shaped - at the fovea so oy have enough energy to do an impulse - high energy to activate - one cone to one bipolar cell therefore no convergence

cones

flatten/elongated muscles relax

rounded muscles contract

• Light enters the eye through the pupil and reaches the retina • Absorbed by photocells (rods + cones) • Passed to bipolar cells • Passed to ganglion cells • Optic nerve

• hyperopia • can’t see things close up • eyeball is too short causing image to focus behind retina • solution: biconvex lens

• myopia • cant see things far away • eyeball too long and lens cant flatten enough. image is in front of retina. • solution: concave lens

clouding of lens

pressure build up of aqueous humour

lens or cornea irreglar shaped

after image: when you look at an optical illousion and see an image after negative image: fatigue of the cones. positive image: overstimulation of rods + cones (eg: seeing spots after staring at the sun)