CH 16 VISION & PERCEPTION
photopic vision contains _____ out of _____ light sensitive pigments
1, 3
scotopic vision can generate neurologic impulse when struck by as few as ______ light photons
15
if objects are close together, only approximately ___% difference needed
2
orthogonal images are ___ separate images at a right angle to each other
2
single radiographic image can only display _____ of 3 dimensions
2
if objects are far apart, difference of greater than ___% needed
20
to control image in space, radiographic images are ______ displays of _______ anatomy
2D, 3D
3D to 2D must have two _______ degree oppossing views to perceive depth
90
a __________ spot is created by fovea centralis at _______ distance
blind, 9"
a ____________ effect occurs because the visual system has difficulty perceiving contrast differences that are distant from one another
boundary
______________ light is an example of a mach effect
bright
photopic vision requires _________ light to function
bright
scotopic vision cannot function in __________ light
bright
cones detect changes in _______________
brightness
scotopic vision cannot perceive ___________ in low light
colors
photopic vision is controlled by ____________
cones
poor peripheral vision due to lack of _________ in the rest of retina
cones
rods are not as concentrated as __________ and distributed over the peripheral retina
cones
photopic vision permits greater _____________ perception
contrast
visual acuity improves ___________ perception
contrast
when expected patterns are not recognized, a diagnostic "________________" can exist
conundrum
more x-ray photons used in _____________ image compared to number of light photons striking retina to ________ image
creating, view
having an understanding of __________-________________ anatomy can hep in understanding the concept of an "image in space"
cross sectional
misperceptions can be ___________ in radiography
dangerous
photopic is ___________ vision and is controlled by ___________
daylight, cones
positioning is intednded to "____-________________" anatomy
de-superimpose
veil glare _______________ contrast perception
decreases
changes in radiographic ______________ can cause a change in neural signals sent to the brain from the retina
densities
conventional radiographic images are missing ______________
depth
preshyopia = _____________
difficulty with close objects
edge enhancement makes boundary more __________
distinct
___________ _____________ is a visual illustration that can cause a misperception on image information
edge enhancement
mach effect occurs when the eye perceives an ____________ boundary
exposure
hyperopia = ______________
farsighted
cones primarily located within _________ _______________ of retina
fovea centralis
edge enhancement compresses ___________ scale
gray
photopic vision permits _________ density difference recognition
greater
regarding visual acuity, best in ___________ light conditions
high
__________ concentration of cones at fovea centralis results in _________ daylight vision
high, sharp
veil glare is reduced or eliminated by ___________ masking
image
scanning while viewing images _____________ contrast perception
improves
x-ray to light conversion for vision is extremely ___________
inefficient
radiographers position area of ___________ so image __________ will be improved
interest, quality
corrective ___________ focus light onto fovea centralis for highest ____________ acuity
lenses, visual
higher image contrast can _________ the boundary effect
lessen
aqueous humor, cornea, iris, and lens gather and focus ___________
light
rod and cone cells emit neurologic impulses when stimulated by __________
light
retina cells transform _________ to nervous impulses
light (rods and cones)
the human eye catches __________, transforms it to ____________ signal, and transmit it to ___________ for processing
light, nervous, brain
effective positioning skills include knowledge of:
location of structures, shapes of structures, relationship of structures to one antoher
scotopic vision is sensitive to ________ light levels
low
the neurologic basis for boundary effect is the _____________ effect
mach
certain structures must be _________________ to demonstrate area of interest
manipulated
myopia = ____________
nearsighted
rads ___________ image information presented in a consistent manner
need
scotopic vision = _____________ vision
night
stotopic is ____________ vision and is controlled by ___________
night, rods
___________ nerves transmit nervous signal to brain
optic
scanning minimizes ___________ saturation
optical
__________ images are taken to provide a 3-D perspective
orthogonal
comparing mental images of patterns (anatomical, physiological, historical) for diagnostic opinions is known as _____________ ____________________
pattern recognition
dim objects are best viewed _______________
peripherally
very large discrepancy between the number of emitted x-ray ____________ and the number of __________ photons that ultimately strike the retina
photons, light
regarding the mach effect, some situations _____________ neurologic impulses from being transmitted by retina
prevent
image conversion occurs in the _____________
retina
________ cover the rest of retina
rods
eye motion causes photosensitive cells of retina to reach _____________ point quickly
saturation
during veil glare, bright light _____________ inside eye
scatters
_________________________ of anatomical structures is a huge challenge for non-radiologist
superimposition
the visual phenomenon associated with viewing extremely small objects and details is known as ____________ detection
threshold
T/F there are more rods than cones
true
regarding viewing distance, light intensity __________ (inverse square law)
varies
radiologist overcome blind spots by ______________ their viewing distance to improve ____________ acuity
varying, visual
when intense light floods eyes directly, it is called _________ ___________
veil glare
data concerning threshold detection indicate that results change is called ______________ distance
viewing
regarding controlling an image in space, one should start by mentally ________________ the object floating _____________ the body
visualizing, within
scotopic vision cannot distinguish light _______________ but most sensitive to __________ light
wavelenghts, green