Vision Science I Exam 2 31 October 2016

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2 Vision Science I Exam 2 31 October ) 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?

3 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

4 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

5 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?

6 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

7 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

8 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) 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

9 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.