the human eye Flashcards
the cornea (located ______) causes _____ refraction than the lens
on outside / more
the cornea refracts the light _______ way, ________________
the same / regardless of the location of the object
the lens can _______ and _________, allowing it to focus light from both nearby and distant objects on ______
change shape / refract light / retina
the human eye forms a ____ and ______ image on the retina, but the brain processes the images it receives and gives you sense that it is ________
real / inverted / upright
which parts of the eye are responsible for detecting colour (in retina)?
cones
which parts of the eye are responsible for detecting light (in retina)?
rods
the human eye can detect which colours best?
red, blue, green
what causes the “after image”?
overstimulation of photoreceptors in the eye
what is the iris?
coloured part of eye surrounding pupil; lies between cornea and lens
what is the function of the iris?
widens/narrows pupil to control amount of light entering eye
what is the pupil?
round, dark centre of eye
what is the function of the pupil?
opens and closes to regulate amount of light reaching retina
what is the cornea?
clear part of eye covering iris and pupil
what is the function of the cornea?
lets light into eye, permitting sight
what is the lens?
round, spherical body in eye; located behind cornea
what is the function of the lens?
focuses light rays into retina
what is vitreous gel?
part of eye between lens and retina; clear (to allow light to pass through) jellylike substance
what is the function of the vitreous gel?
helps maintain structural stability of eye and retinal health but can be removed without harming vision
what is the optic nerve?
nerve carrying electrical impulses from photoreceptor cells (rods and cones) in retina to visual cortex in brain; located at back of eye
what is the function of the optic nerve?
transmits signals to brain to be converted to images
what is the retina?
sensory membrane lining eye
what is the function of the retina?
receives images formed by lens and converts them into signals that reach the brain via optic nerve
what is the sclera?
the white of the eye
what is the function of the sclera?
protective covering
what is the “blind spot”?
the point of entry to the optic nerve on the retina; insensitive to light
what is peripheral vision?
the part of vision occurring outside the very centre of the field of view
what is myopia?
when the eyeball is too long: light rays converge at a focal point before reaching the retina= farther images are blurry
how can myopia be treated?
using a diverging lens to bend light rays to meet after reaching the cornea
what is hyperopia?
when the eyeball is too short: light rays converge at a focal point behind the retina= closer images are blurry
how can myopia be treated?
using a converging lens to bend light rays to meet before reaching the cornea
which is myopia and hyperopia with respect to nearsightedness and farsightedness?
myopia = farsightedness hyperopia = nearsightedness
what is astigmatism?
a condition in which the cornea is slightly cone shaped rather than spherical
what is presbyopia?
a condition caused by loss of elasticity in the lens (eye muscles become stiff and ciliary muscles can no longer shape lenses); cannot focus on nearby objects
how can presbyopia be corrected?
bifocals
how can astigmatism be corrected?
toric lenses or surgery
what are the 3 steps to laser eye surgery?
cut a thin flap in cornea; pull back
alblate surface into desired shape
replace flap
pros to laser eye surgery
improved vision
less need for glasses/contact lenses
cons to laser eye surgery
dry eyes oversensitivity to light poor perception of contrast double vision perception of ghosted images, starbursts, halos around light sources
