Vision Science I
Exam 2
31 October 2016
1) Mr. Jack O’Lantern, pictured here, had an unfortunate accident that has
caused brain damage, resulting in unequal pupil sizes. Specifically, the
right eye is normal but the left eye has an extremely large 15 mm pupil.
Assuming this pumpkin head has eyes like a human, which of the
following is NOT TRUE regarding Mr. O’Lantern’s vision in each eye?
A) The eye with the big pupil gets more light into it than the normal eye.
B) The eye with the big pupil should have a sharper image than the
normal eye, if Jack has no aberrations in his optics.
C) The eye with the big pupil will have a larger point spread function
than the normal eye, if Jack has a lot of aberrations in his optics.
*D) The eye with the big pupil will have worse flicker sensitivity than
the normal eye because of the difference in light levels in the two eyes.
E) The eye with the big pupil will have more Trolands (retinal
illuminance) than the normal eye when they both look at an object with
the same candelas per square meter (luminance).
2) Which of the following visual judgments is NOT an example of testing
resolution acuity?
*A) What is the smallest bright spot that you can just detect?
B) What is the smallest gap between two parallel lines that you can just
see?
C) What is the smallest letter that you can just read?
D) What is the highest spatial frequency grating that you can just see?
E) None of the above- all of them are measures of resolution acuity.
3) If the eye had perfect optics over the whole pupil, which pupil size in this
list would give the best optical resolution?
A) .5 mm
B) 1 mm
C) 2 mm
D) 2.5 mm
*E) 5 mm
4) The term “Cortical Magnification” refers to
*A) The fact that the visual field mapping to cortex is distorted, with
more area representing the fovea compared to the periphery.
B) The perception that bright things look larger than dim things, even
though they are the same size
C) The change in brain size through evolution from protohumans to
humans
D) The optical effect of the lens in the eye of people with “cortical
cataract”
E) The change in perceived contrast when a grating’s spatial frequency is
reduced.
5) If grating resolution acuity is 15 cycles per degree, what is the equivalent
Snellen Fraction?
*A) 6 / 12
B) 6 / 8
C) 6 / 40
D) 6 / 4.5
E) 6 / 3
6) Which of the following is not an equivalent expression of visual acuity?
A) Decimal acuity of 2
B) Snellen fraction of 20/10
C) MAR of .5
*D) logMAR of 2
E) Grating acuity of 60 cpd
7) On average, which is the most likely value for best-corrected visual acuity
in healthy patients with no vision diseases or disorders?
A) 20/10
*B) 20/16
C) 20/20
D) 20/25
E) 20/40
8) Which of the following is NOT an expression of standard acuity?
A) Decimal acuity of 1
B) Snellen fraction of 6 / 6
C) MAR of 1
D) log MAR of 0
*E) Grating acuity of 1 cpd
9) The US National Eye Institute has defined Blindness as…
A) 20/30 to NLP
B) 20/40 to NLP
C) 20/40 to 20/200
*D) 20/200 to NLP
E) NLP
10) The US National Eye Institute has defined Low Vision as…
A) 20/30 to NLP
B) 20/40 to NLP
*C) 20/40 to 20/200
D) 20/200 to NLP
E) NLP
11) In Texas, if you are NOT wearing spectacles or contacts when you come
in for your eye test at the Department of Motor Vehicles, you will be
given a license to drive with no vision restrictions as long as each eye and
both togther are
A) 20/20 or better
B) 20/25 or better
*C) 20/40 or better
D) 20/50 or better
E) 20/70 or better
12) For letter acuity, how much blur in sphere diopters is required to make
acuity worse than 20/200?
A) 1 D
B) 2 D
*C) 4 D
D) 8 D
E) 16 D
13) On an ETDRS acuity chart, the letter size in each row is different from
the next by…
*A) 0.1 log units
B) 1 log unit
C) 1 arc minute
D) .1 arc minutes
E) a factor of 2
14) For a normal, healthy eye with typical optics, resolution acuity in the
central fovea is limited by
*A) Optical blur
B) Cone spacing
C) Rod spacing
D) Ganglion cell spacing
E) Amacrine cell spacing
15) In Japan, in 1997, a large number of children suffered seizures because
of
A) Badly flickering fluorescent lighting at school
B) Riding a school bus past flashing neon signs
C) Being forced to wear blue tinted lenses
*D) Watching a flickering Pokemon cartoon
E) Class demonstrations about how flickering lights can be annoying and
weird looking
16) When a light flickers ON and OFF at a frequency near the peak of the
TCSF, it often appears to be brighter than even the ON level. This
phenomenon is called
A) the Talbot Plateau Law
B) the Ferry-Porter effect
*C) the Brucke-Bartley effect
D) the Granit-Harper law
E) the Lambreghts’ Law of SuperLuminosity
17) What is the Weber Contrast of a letter E with luminance 0 cd/m2
(completely black!) on a background of 80 cd/m2?
A) 80%
B) -80%
C) 100%
*D) -100%
E) 33%
18) What is the Michelson Contrast of a grating with dark bar luminance 50
cd/m2 and bright bar luminance of 100 cd/m2?
A) 80%
B) -80%
C) 100%
D) -100%
*E) 33%
19) Why does Dr. Stevenson turn off the front row of lights in the classroom
at the start of lecture?
A) The bright light makes students pupils smaller, making letters on the
screen appear smaller and harder to read
B) Dimmer light allows both rods and cones to function, improving the
visibility of dark areas in the slides
*C) Overhead light hitting the screen reduces the contrast of projected
images. And like he says, “it is all about contrast!”
D) The blue tint from the overhead lights disrupts student’s napping
during class.
E) The front row of lights reflects off his bald spot and blinds the people
in the front row.
20) The Modulation Transfer Function (MTF) of the eye plots
A) the ratio of retinal image luminance over object luminance as a
function of retinal eccentricity
B) the ratio of retinal image contrast over object contrast as a function of
temporal frequency
*C) the ratio of retinal image contrast over object contrast as a function
of spatial frequency
D) the ratio of retinal image size over object size as a function of object
size
E) the ratio of retinal image spatial frequency over object spatial
frequency as a function of time.
21) In the standard spatial CSF, sensitivity to low spatial frequency is worse
than middle spatial frequency, a feature called the “low spatial frequency
roll-off”. This feature goes away (so that low SF sensitivity is the same as
middle SF sensitivity), if the test gratings
*A) Are flickering instead of steady
B) Are horizontal instead of vertical
C) Are scaled with eccentricity
D) Are expressed as “cycles per millimeter of cortex”
E) Are extremely bright
22) The star Aldebaran, the “eye” of Taurus the Bull, is many light years
away, but is detectable because it is so bright. The image of this star ON
THE RETINA, has an angular subtense of around:
A) 0.02 seconds of arc
B) 1 second of arc
*C) 1 minute of arc
D) 1 degree
E) 10 degrees
23) If a subject adapts to a 7 cpd grating by staring at it for a long time, what
effect will this have on the spatial contrast sensitivity function?
A) There will be no change, because contrast sensitivity does not adapt.
B) All spatial frequencies above 7 cpd will show a loss of sensitivity
C) All spatial frequencies below 7 cpd will show a loss of sensitivity
D) The entire spatial CSF will show a loss of sensitivity
*E) Spatial frequencies close to 7 cpd only will show a loss of sensitivity.
24) Normally, the Temporal Contrast Sensitivity Function is tested with one
eye viewing or else the same flicker to both eyes. What happens if the
flicker is out of phase in the two eyes, going bright in one eye at the same
time it goes dark in the other eye?
A) Out of phase flicker has no affect on the TCSF
B) Out of phase flicker is invisible because the two eyes cancel each
other out.
C) Out of phase flicker is easier to see, especially at high frequencies.
*D) Out of phase flicker is harder to see, especially at low frequencies.
E) Out of phase flicker is easier to see at all frequencies.
25) CFF in the lower visual field, with targets scaled up for eccentricity, is
about
A) 1 Hz
B) 10 Hz
*C) 80 Hz
D) 240 Hz
E) 1000 Hz
26) For most people with their natural optics, the narrowest Point Spread
Function occurs when the pupil diameter is about
A) 0.5mm
*B) 2.5 mm
C) 4.5 mm
D) 6.5 mm
E) 8.5 mm
27) Which best describes the function of the Pelli-Robson chart?
*A) It measures contrast sensitivity at around the peak of the CSF
B) It measures letter acuity at high contrast
C) It measures grating acuity at low contrast
D) It measures the low spatial frequency cut-off of the CSF
E) It measures vernier acuity at high contrast
28) Legal blindness in the Unites States is defined by an acuity cut off. In
terms of MAR, what is the value that defines legal blindness?
A) 1 arc minute
*B) 10 arc minutes
C) 60 arc minutes
D) 200 arc minutes
E) 400 arc minutes
29) Which of the following is a FALSE statement about the EDTRS letter
chart?
A) ETDRS stands for Early Treatment of Diabetic Retinopathy Study
*B) The number of letters on each line goes up as the letter size goes
down.
C) It is now a standard chart widely used for clinical trials
D) The letters are Sloan optotypes
E) The chart is designed to be useful at various viewing distances.
30) The normal spatial Contrast Sensitivity Function (CSF) has a peak at
around what spatial frequency?
A) 0.004 cpd
B) 0.04 cpd
C) 0.4 cpd
*D) 4 cpd
E) 40 cpd
31) In the United States and Liberia, a standard Snellen fraction of 6/6
would be expressed as “20/20” because
A) They use a standard viewing distance of 20 meters instead of 6
meters
B) Their population is very short sighted so acuity values are larger.
*C) These two nations never converted to the “metric system” when all
the rest of the world did, so American and Liberian children are still
forced to learn inches, feet, yards and miles while other children only
have to learn what a meter is.
D) Their standard Optotype letters are 20 arc minutes but the rest of the
world uses 6 arc minute letters.
E) They think “6/6” sounds too much like “666,” the Mark of the Beast.
32) Newborn grating acuity, as measured with the Visual Evoked Potential
technique, is about
A) 0.5 cpd
*B) 6 cpd
C) 16 cpd
D) 30 cpd
E) 45 cpd
33) A patient has a myopic refractive error of 5 diopters sphere in each eye.
With her spectacles, she is 20/20 in each eye. If she takes off her
spectacles, is she considered to be “legally blind”? If not, why not?
*A) NO, because the definition of legal blindness applies to “best
corrected acuity”, and her best corrected acuity is 20/20.
B) NO, because the definition of legal blindness requires that you have
“No Light Perception” and she can see light even without her glasses.
C) NO, because her distance acuity without spectacles is very bad, but
her near acuity is just fine, so the law describes her as having “low
vision”.
D) NO, because without her glasses, her 5 diopters of refractive error
should give her a distance acuity of about 20/25, not bad enough to meet
the definition of legally blind.
E) YES, because her acuity will be worse than the cutoff for the
definition of legal blindness.