Vision Flashcards
What are the features of vision?
Colour, shape, depth, movement
what is the wavelength of visible light
400-750nm
what are the 2 features of light
wavelength and amplitude
What happens to the amplitude if the lights are turned off
it will decrease
what are the 2 basic components of the eye
the optical and neural component
what does the optical component do
collects and focuses light onto the planbt of the retina
what does the neural component do
converts light energy into patterned changes of membrane potential that he brain can decode to create visual perceptions
holds lense in place
zonule fibers
maintains intraocular pressure
aqueous humor
move eye around the skull
extraocular muscles
depression in the retina where we have the strongest vision
fovea
ganglion cells in the back of the eye
retina
densely pigments cells help absorb light (albino people dont have this)
choroid
the white bits of the eye
sclera
what is optics
refraction of the eye
what is refraction
the bending of light as it passes from one substance to another
what part of the eye is responsible for the eyes ability to bend light
the cornea
what is the refractive power
the ability of a substance to bend light and it is measured in diopters
what is the power of a lens that converges light to a focal point 1 meter beyond the lens
1 diopters
what is the power of a lens that converges light to a focal point 0.5 m meter beyond the lens
2 diopters
What is the refractive power of the eye
60 diopters - focal point of 17mm beyond the lens
what process occurs when shifting gaze from distant to near objects?
Accommodation, constriction of pupil and convergence of eyes
what is accomodation
it is the contraction/relaxation of cillary muscles to alter lens shape and change refractive power
What do the cilary muscles do when looking at distant objects
they are relaxed due to low parasympathetic activity so the zonular fibres are taut and the lens is flattened
firing of parasympathetic nerves contracted ciliary muscles, slackened zonular fibers, rounded lens
near object with accomodation
normal sight (faraway object is clear)
emmertopia
nearsighted (eyeball is too long)
myopia
farsignted (eyeball is too short)
hypermetropia (hyperopia)
the curvature of the cornea and or the lens being aspherical resulting in different amounts of refraction in different planes and is corrected with cylindrical lens
astigmatism
