eyeball Flashcards
visual activity
ability to see, measured w/ Snellen Eye chart
Snellen Eye Chart
1st number= distance from chart
2nd number=feet person w normal vision can see chart
cone
a type of photo receptor cell in retina, sees directly in front of you, three types see different wavelengths -red -blue -blue malfunction = color blindness
rod
photo receptor sees gray, sees to the side of you, optic nerve + chaism to reach oppcipital lobe
optic nerves
assists rods+cones
depth perception
the ability to tell how close/far objects are to you and each other
1= sees two dimenensional
2= see+processes dif views of same object
-allows us to see optical illusions
refraction
- density of light rays change they switch mediums while traveling through different parts of the eye, denser mass than air speed will change causing direction to change
- denser medium=more angle it changes
accommodation
- lens +cornea work to expand or shrink to refocus light on retina
- cornea carries process, lens finely adjusts
- combo of reflex actions
- lens keeps focal length+distance between its center + focal point constant
- CILIARY MUSCLES help lens
Convex lens
- larger to smaller
- lens is responsible
- sees far away objects
- light rays pass through eye and shrink and focus
- light waves converge at back of retina
concave lens
- when light rays expand as passing through eye
- for focusing on close up objects
- light diverges to reach retina
hyperopia
- far sided vision, things close up appear blurry and unclear
- emmertropia= normal 20/20
- when eyeball is short (not deep enough) or lens does not converge enough
- images hit retina before being focus, images go beyond retina
Myopia
- near sided vision things far away = blurry/unclear
- eyeball too deep/long or when lens= too convex/curved
- images are projected to front of retina
astigmatism
- condition = when cornea or lens is irregularly shaped + cause light rays to refract/ dont converge properly + not focus at certain point on retina
- causes blurry/ distorted images
- can be fixed w glasses, contacts, refractive surgery
blind spot
- optic nerves exists through retina otw to brain
- no light sensitive receptors
- images that fall here cant be seen
- brain ignores the hole in visual input
peripheral vision
- ability to see things not directly in front of you
- rods are close to edge of retina to control this, brain adds color based on surroundings and past sighting of these images
- stronger in dark
optical illusion
-visual trick based on how brain perceives images in the visual cortex not the actual image the eye sees
after image
- optical illusion that effects vision after staring at an image for long time then looking away
- bc of constant light stimulation of cones
- after looking away cones that were less stimulated make image appear+be perceived as a negative image
retina
- layer of light sensitive sells @ back of eye
- directs images focused by cornea+ lens
- optic nerve connects it to brain
cornea
-tough clear covering of iris
-protects eye+bends light for image production
cornea carries lens, 1st step
pupil
dark circle in iris hole that lets light enter
aqueous humor
-liquid that keeps cornea rounded
iris
- muscle that controls how much light enters
- suspended by cornea+lens
- come in dif colors
lens
-clear flexible structure
-makes image on retina
changes shape to focus
sciera
-thich tough white liner of eyeball
