9-10 Visual Acuity Flashcards
How do convert radians to degrees?
How do you convert degrees to radians?
Multiply by 180/pi….57.3
To minute…1/60
Multiply by pi/180…. 0.0174
How can we best express the separation of two stars??
Miles
ArcSec
Radians
Light years
ArcSec
What’s the formula for apparent viewing angle?
Target size (h)/ target distance (d)
What’s the formula for visual acuity?
1/ MAR (arcmin)
In a corrected eye, what two things cause blur?
Diffraction and aberrations
A more confined PSF is achieved with…
Less confined PSF?
A LARGER pupil
SMALLER pupil
Which of the following is a diffraction limited PSF?
Data with one large spike
Data all over spread out
Data with medium spike and some spreading
One large spike, looks like a large cone. The rest is smooth!
Better vision is achieved with…
With MORE confined PSF
With LESS confined PSF
PSF size doesnt matter
MORE CONFINEDDDDD
Formula for angular resolution limit?
Theta min= 1.22 X lambda/D
Diameter of pupil
Smaller the pupil, larger the angle, smaller the acuity
Under dim light, resolution is better… T/F?
True visual acuity is better!
Larger pupil=smaller MAR
Smaller pupil = larger MAR (poor acuity)
Which of the following can be parametrized? (Pick two)
Lambda=0.55um
N=1.336
D= 2mm
Lambda
D
When given photos of PSF measurements, the airy disk corresponding to _._mm is going to be larger and closest together, _._mm will be slightly smaller, and _._mm is very very small and bad m’kay
- 5mm
- 8mm
- 6mm
Who are the forefathers of visual acuity? (Two)
Who said “sharpness of vision can be expressed in a ratio of letter size to viewing distance”?
Herman Snellen
Francisco Cornelius Donders. Ratio too
The vision of the standard eye can recognize an optotype when its detail (lines or gaps) subtended 1 _______.
Arcmin
______ ______= 1/MAgnificaiton Requirement
MAgnification requirement is the magnification required to _____________ for reduced vision; actual measurement
Visual acuity
Compensate
