Resolution and Acuity Flashcards
Define Spatial Acuity ?
The smallest spatial detail can be detected, resolved or identified
What types of Spatial acuity are there?
Detection acuity
Hyperacuity
Resolution acuity
Identification Acuity
What is detection acuity ?
Angular size of the smallest spot or width of line that can just be detected
is it there or is it not (2AFC)
What are small objects detection depend on?
Illuminance of the retinal image and not size
increment threshold delta L/L
What is retinal image size limited for small objects?
differaction and abberation
What is increment threshold?
The ability to detect if one stimulus intensity differs from another
What is increment threshold dependent on?
Stimulus size, duration wavelength, and retinal location
What is detection acuity of spot?
0.25-0.33’ arc
What is detection acuity of a line ?
0.0083-0.017’ arc
What happens to retinal luminance as object gets smaller ?
Retinal luminance decreases
How can you detect really small spots/lines?
If they are sufficientyly intense
Define hyperacuity?
Smallest spatial offset or difference in location that can be resolved
Give examples of hyperacuity?
Displacement
vernier
tilt
stereoacuity
What is displacement hyperacuity?
Relative location or displacement of dots or lines
What is vernier acuity?
Smallest spatial offset or difference in location that can be resolved
What is tilt?
Smallest spatial difference in location that can be resolved
What is stereoacuity ?
Smallest spatial difference in location that can be resolved
What are results of Hyperacuity?
Under opimum condition with high contrast stimuli 2-6’ arc
When is hyperacuity suggested to be used?
Media opacities to test neural function- cataract
What is resolution acuity?
Smallest separation of two points or lines that can be discriminated
What condition does resolution acuity need to be in?
Under optimum conditions 0,5’ arc
How is it hard to do resolution acuity>?
> need lines of different size, and thickness otehrwise px will know
high luminance causes smaller pupil size more deffraction
astigmatism repeat test on all orientation with lines
What does high luminance cause?
Smaller pupil size
diffraction
reduced resolution
How does grating resolve problems?
Highest spatial frequency gratings (thin) that subject can detect
