Vision Science Exam 1
Cones are generally less sensitive than rods at detecting dim flashes in the dark. The cones are MORE sensitive if tested with a wavelength of?
700 nm
A vision scientist measures detection for a spot of light at 20 degrees in the periphery with zero background and complete dark adaptation. She finds that subjects can reliably detect a 3 millisecond flash with just 100 photons in it. If she reduces the size of the spot from 3 arc minutes to 1 arc minute and keeps everything else the same, how many photons should it take to reach threshold? a) 11 photons b) 30 photons c) 100 photons d) 300 photons e) 900 photons
?
The electromagnetic spectrum, from power transmissions up to gamma rays, spans about 66 octaves of frequency (or wavelength) change. The range of wavelengths the eye can see span about A) 0ne octave B) Five octaves C) 10 octaves D) 20 octaves E) 300 octaves
A) 0ne octave
If a clinician maps a patient's isopter with kinetic perimetry using a large target, and then switches to a small target size, you would expect the second isopter measured to be A) A larger ring, outside the first one B) The same as the first C) Smaller than the first D) Square instead of oval E) Impossible to measure
A) A larger ring, outside the first one
If a clinician maps a patient's isopter with kinetic perimetry using a large target, and then switches to a small target size, you would expect the second isopter measured to be A) A smaller ring, inside the first one B) The same as the first C) Larger than the first D) Square instead of oval E) Impossible to measure
A) A smaller ring, inside the first one
Which photometric unit is specific to light entering the eye and has no radiometric equivalent? A) The Candela B) The Apostilb C) The Troland D) The Lux. The Lumen
C) The Troland
Which of the following is FALSE regarding the anatomy of the macula? A) There are no retinal blood vessels in the very center B) It has a pigment in it that absorbs long wavelengths and therefore looks orange C) The retina is thickest in the very center because of all the extra ganglion cells D) The very center has L and M cones, but no rods or S cones E) The very center has cones that are so long and thin, they look like rods.
C) The retina is thickest in the very center because of all the extra ganglion cells
If a subject in a dark adaptation experiment turned out to have a Vitamin A deficiency, how would you expect the dark adaptation curves to change? A) The subject would not be able to adapt to the light, and so would always have very low, scotopic thresholds even after a bright adapting light. B) The subject would have normal, high thresholds after the bright adapting light, but would never be able to recover sensitivity in the dark, no matter how long you waited. C) The subject would eventually dark adapt and recover scotopic vision, but it might take many hours D) The subject would show a normal cone recovery but not a normal rod recovery, because Vitamin A is only used in Rod photopigments E) The subject would show a more rapid recovery than normal, because there is not as much pigment to be "bleached" in Vitamin A deficiency.
C) The subject would eventually dark adapt and recover scotopic vision, but it might take many hours
Which of the following is FALSE regarding the background light level used in Standard Automated Perimetry (for example, in the Humphrey Field Analyzer commonly used in clinic). A) The background is set to be low enough that rods can contribute to threshold in the periphery. B) The background is set to be in the middle of the Weber's law part of the threshold vs. background curve. C) The background is about 10 cd/m2. D) The background is in the photopic range of light levels. E) The background is about 31.5 apostilbs.
D) The background is in the photopic range of light levels.
Which of the following is the SI base unit for photometric measurement, defined as 1/683 Watts at 555 nm? A) The Lumen B) The Nit C) the apostilb D) The Candela. E) The Troland
D) The Candela.
The outer segments of the photoreceptors get their nourishment from?
The choroid
What layer is between the retina and the sclera?
the choroid
Why does the macula have a YELLOW tinge?
the macular pigment screens out blue light
Mie scattering in the atmosphere gives rise to which of the following? a) The blue sky b) The red sunset c) The white fog d) The yellow snow e) The purple haze
c) The white fog *mie scattering is when the particle is larger than the wavelength (water droplet --> cloud)
Comparing the dark adapted sensitivity of rods and cones using the best wavelength for each, you would expect to see the rods be more sensitive by a factor of about a) 2 b) 4 c) 10 d) 100 e) 10,000
d) 100
A vision scientist has a stack of three filters, and each of the filters is 3.0 ND. She shines a bright laser through the stack of filters and measures the power coming out on the other side. If the laser power coming out of the stack of filters is 1 microWatt (a millionth of a Watt), what was the laser power going into the stack of filters? a) 3 microWatts b) 9 microWatts c) 16 Watts d) 1000 Watts e) 1.21 GigaWatts
d) 1000 Watts ATTENUATION: 3.0ND + 3.0ND + 3.0ND = 9.0ND attenuates the light 10^9 = 1000000000 fold. 1 uW = 1x10^-6 W (1x10^-6W) * (10^9) = 1000W
In the same experiment as the last question where the threshold was 100 photons, if the spot is kept the same size (3 arc minutes), but the duration of the flash changes from 3 milliseconds to 1 millisecond, how many photons should it take to reach threshold? a) 11 photons b) 30 photons c) 100 photons d) 300 photons e) 900 photons
d) 300 photons ***???
A vision scientist measures the threshold for an increment of light on three different steady background levels, and finds that the increment needed is about 14% of the background level in each case. Which of the following does NOT fit this result? a) The light levels were probably scotopic. b) The results follow Weber's law c) The light was probably detected by rods d) The light was probably a small 650 nm spot in the foveola e) The results plot in a straight line on a "tvi" curve.
d) The light was probably a small 650 nm spot in the foveola
A vision scientist has a stack of four filters, and each of the filters is 2.0 ND. She shines a bright laser through the stack of filters and measures the power coming out on the other side. If the laser power coming out of the stack of filters is 1 microWatt (a millionth of a Watt), what was the laser power going into the stack of filters? a) 4 microWatts b) 8 micro Watts c) 16 microwatts d) 10 milli Watts e) 100 Watts
e) 100 Watts 2.0 ND *4 = 8 ND (1*10^-6)*(10^8)= 100 W
The blind spot of the eye lacks rods and cones. What area of the retina lacks rods but has cones A) The Ora Serrata B) The foveola C) The perifovea D) The optic disc E) The uvea.
(B) The foveola
A vision scientist measures detection for a spot of light at 20 degrees in the periphery with zero background and complete dark adaptation. She finds that subjects can reliably detect a 3 millisecond flash with just 100 photons in it. If she reduces the size of the spot from 3 arc minutes to 1 arc minute and keeps everything else the same, how many photons should it take to reach threshold? a) 11 photons b) 30 photons c) 100 photons d) 300 photons e) 900 photons
(d) 300 photons ***???
Which of the following is FALSE regarding the crystalline lens of the eye? A) It provides almost all of the optical power of the eye B) It changes shape to allow near objects to be seen clearly C) It becomes stiffer with age D) It becomes less transparent with age E) It absorbs short wavelength light much more than long wavelengths.
A) It provides almost all of the optical power of the eye
Light bulbs used to be rated in Watts, now they are rated in Lumens. Which of the following is FALSE regarding lumens? A) Lumens are the fundamental base unit of photometry in the SI system of units. B) Lumens are the photometric units of luminous flux C) Lumens describe the total visible light going off in all directions from the bulb D) Lumens are the photometric units that are comparable to the radiometric unit Watts. E) Lumens include a compensation for the human photopic luminous efficiency function, Vλ ("V lambda").
A) Lumens are the fundamental base unit of photometry in the SI system of units. (the photometric SI unit is a Candela(cd) = lumen(lu)/steradian(w))
Class 2 lasers are visible lasers (400-700 nm) that do not exceed MPE level for exposure durations less than 0.25 seconds. Why does the definition use this value of 0.25 seconds? A) That is the typical reaction time for a person to blink or look away from a bright light. B) That is the time it takes for heat to dissipate away from a hot spot in retinal cells. C) That is the usual time it takes for retinal tissue to build up enough heat to burn. D) That is the time that most lasers will shine continuously before they overheat. E) It is completely arbitrary, just chosen to divide the classes into safety categories.
A) That is the typical reaction time for a person to blink or look away from a bright light.
Class 2 lasers are visible lasers (400-700 nm) that do not exceed MPE level for exposure durations less than 0.25 seconds. Why does the definition use this value of 0.25 seconds? A) That is the typical reaction time for a person to blink or look away from a light bright B) That is the time it takes for heat to dissipate away from a hot spot in retinal cells. C) That is the usual time it takes for retinal tissue to build up enough heat to burn. D) That is the time that most lasers will shine continuously before they overheat E) It is completely arbitrary, just chosen to divide the classes into safety categories.
A) That is the typical reaction time for a person to blink or look away from a light bright
The visual axis passes through what two features of the eye? A) The pupil center and the fovea B) the ciliary body and the optic disc C) The cornea and the ora serrata D) The pupil center and the optic disc E) The lens and the optic nerve
A) The pupil center and the fovea The OPTIC axis hits in-between the fovea and optic disc
The "hill of vision" doesn't change shape over a range of high background luminances because of A) Weber's law B) Murphy's law C) DeVries/Rose Law D) Humphrey's law E) Goldmann's law
A) Weber's law
Which of the following pigments is found in short wave sensitive cones? A) cyanolabe B) chlorolabe C) erythrolabe d) rhodopsin e) melanopsin
A) cyanolabe
Which photometric unit describes retinal illuminance and used to be called the photon? A) The Candela B) The Apostilb C) The Troland D) The Lux E) The Lumen
C) The Troland
Light damage from the use of ophthalmic instruments is a concern. Which of the following statements is FALSE regarding this risk to patients? A) The MPE level for avoiding damage is based on healthy eyes, and may not be appropriate for some diseased eyes. B) Commercial ophthalmic instruments like fundus cameras are designed to exceed the MPE in most cases. C) Long exposure times during observation of the retina with an instrument might exceed the MPE, even if the normal brief flash used to take a fundus photo does not D) Commercial ophthalmic instruments like fundus cameras use visible light, but thermal damage is still a concern E) The MPE levels are supposed to be a factor of ten below the damage levels, so there should still be a margin of safety for lights that are close to the MPE
B) Commercial ophthalmic instruments like fundus cameras are designed to exceed the MPE in most cases.
As light enters the eye and eventually reaches the photoreceptors, it must first pass through all the following structures or layers except one. Which one? A) Ganglion cell layer B) Retinal pigmented epithelium C) Cornea D) Vitreous Humor E) Nerve fiber layer
B) Retinal pigmented epithelium
Normally a person's visual field extends the farthest in which direction? A) Nasal B) Temporal C) Superior D) Inferior
B) Temporal
An article in the New England Journal of Medicine described the case of a 15 year old who got retinal burns from a handheld "laser pointer". Which of the following is FALSE about this case? A) The "laser pointer" was at least 30 times more powerful than those normally sold for lecturing. B) The burns were located in and around the optic disc, . C) A standard laser pointer (Class 3) would not have caused the same damage as seen in this patient if aimed at the fovea for the same amount of time. D) The damage to the retinas included subretinal hemorrhage, retinal edema, and hyperpigmented spots. E) The "laser pointer" in this case was powerful enough for popping balloons from a distance and burning holes in his sister's sneakers.
B) The burns were located in and around the optic disc. (he stared directly at the laser in a mirror -> damage was on his fovea)
When a photon is absorbed, the Principle of Univariance says that A) The membrane voltage always becomes more negative B) The cell responds the same way, no matter what the wavelength was C) variability of the response produced is constant D) Only one photopigment molecule is required to absorb the photon E) Only one photon is required to make a rod respond to a flash
B) The cell responds the same way, no matter what the wavelength was
If a subject in a dark adaptation experiment turned out to have a Vitamin A deficiency, how would you expect the dark adaptation curves to change? A) The subject would not be able to adapt to the bright light in the beginning, and so would always have very low, scotopic thresholds even after a bright adapting light. B) The subject would eventually dark adapt and recover scotopic vision, but it might take many hours. C) The subject would have normal, high thresholds after the bright adapting light, but would never be able to recover sensitivity in the dark, no matter how long you waited. D) The subject would show a normal cone recovery but not a normal rod recovery, because Vitamin A is only used in Rod photopigments E) The subject would show a more rapid recovery than normal, because there is not as much pigment to be "bleached" in Vitamin A deficiency.
B) The subject would eventually dark adapt and recover scotopic vision, but it might take many hours.
Which type of retinal neuron has axons that leave the eye and form the optic nerve? A) Cone photoreceptors B) Bipolar Cells C) Ganglion Cells D) Horizontal Cells E) Amacrine Cells
C) Ganglion Cells
Which type(s) of photoreceptors is(are) responsible for mesopic vision?
Both rods and cones
A target that subtends 1 degree would be 1 centimeter tall at what distance from the eye? A) 1 centimeter B) pi centimeters C) 180/pi centimeters D) 180 centimeters E) 1 meter
C) 180/pi centimeters
A target that subtends 1 degree would be 1 centimeter tall at what distance from the eye? A) 1 centimeter B) pi centimeters C) 180/pi centimeters D) 180 centimeters E) 1 meter
C) 180/pi centimeters = 57.3 cm tan(deg)=height/distance distance = radius = radian 2*pi radians = 360 deg 1 radian = 180/pi = 57.3 deg 1/ 57.3 of a rad = 1 deg @ small angle arc length ~ height
Refer to the figure at right for the following calculation Wavelength 2 is presented on one side of a display, and a combination of wavelengths 1 and 3 are presented on the other side. How many Watts of wavelength 2 in one light (sensitivity .4) would be required to match a combination of 5 Watts of wavelength 1 (sensitivity .8) and 20 Watts of wavelength 3 (sensitivity .2) in the other light? A) 8 B) 10 C) 20 D) 30 E) 40
C) 20
Light reaching the eye does not all get focused into the proper place on the retina. Which of the following rays passing through the cornea and lens would contribute to veiling glare and reduced contrast? A) A reflected ray B) A backscattered ray C) A forward scattered ray D) An absorbed ray E) A refracted ray
C) A forward scattered ray
How wide are the monocular crescents at the extreme left and right edges of the visual field? A) About 10 degrees B) About 20 degrees C) About 40 degrees D) About 60 degrees E) About 100 degrees
C) About 40 degrees
A fifteen year old boy recently damaged the foveola of his eye with a 150 mWatt "laser pointer". Based on this description, which of the following is TRUE regarding this incident? a The laser was class 1 B) The laser would not have burned him if he had blinked or looked away after it hit his retina. c) damage was in his foveola, which means he looked right into the laser d) The laser he used was a typical laser pointer like those used in lectures. e) The laser must have had infrared light, because visible light won't burn the eye
C) damage was in his foveola, which means he looked right into the laser
Refer to the figure at right for the following calculation: Wavelength 2 is presented on one side of a display, and a combination of wavelengths 1 and 3 are presented on the other side. How many Watts of wavelength 2 in one light (sensitivity .4) would be required to match a combination of 10 Watts of wavelength 1 (sensitivity .8) and 50 Watts of wavelength 3 (sensitivity .2) in the other light? A) 8 B) 10 C) 20 D) 45 E) 50
D) 45 W2(0.4)=W1(0.8)+W3(0.2) W2=(10(0.8)+50(0.2))/(0.4)
In a dark adaptation curve, if the eyes have been adapted to very bright light, the recovery may show 5 log units of sensitivity change over the course of an hour. How much is 5 log units in this context? A) A factor of 5 B) A factor of 50 C) A factor of 150 D) A factor of 100,000 E) A factor of 10 billion
D) A factor of 100,000 (10^5 = 100,000)
Which of the following is FALSE regarding the visible part of the electromagnetic spectrum? A) Our vision covers about one octave of frequency range. B) The peak of our visual sensitivity is close to the peak output of the sun C) The peak of the visible range shifts slightly when we go from photopic to scotopic vision. D) All the wavelengths that we can see are longer than one micron E) The eye absorbs light at the short wavelength end of the spectrum before it even reaches the photoreceptors.
D) All the wavelengths that we can see are longer than one micron (Visible light 350nm-750nm wavelength = 0.35-0.75 microns)
The Humphrey Field Analyzer uses a 10 arc minute spot for testing. What would the "hill of vision" look like if they had used a 200 arc minute spot? A) It would have the same shape, but just higher in overall sensitivity. B) It would have a much sharper peak at the fovea compared to the 10 minute spot. C) It would have a flatter shape, and sensitivity would be worse. D) It would have a flatter shape, and sensitivity would be better. E) Spot size makes no difference, as long as it is 10 minutes or larger.
D) It would have a flatter shape, and sensitivity would be better.
Which of the following is the SI base unit for photometric measurement, defined as 1/683 Watts @ 555 nm? A) The Lumen B) The Nit C) The Apostilb D) The Candela E) The Troland
D) The Candela
Which of the following is FALSE regarding the anatomy of the macula? A) There are no retinal blood vessels in the very center B) It has a pigment in it that absorbs short wavelengths C) There is a pit at the center because all the cells besides photoreceptors are displaced to the sides D) The very center has L and S cones, but no rods or M cones E) The very center has cones that are so long and thin, they look like rods.
D) The very center has L and S cones, but no rods or M cones *It has L and M, but no S or rods
The "hill of vision" doesn't change shape over a range of high background luminances because of A) Ricco's law B) Bloch's law C) DeVries/Rose Law D) Weber's law E) Goldmann's law
D) Weber's law
In the rod part of the dark adaptation curve, what rate of recovery should you expect for a normal subject? Specifically, how long will it take for the subject's threshold to improve by a factor of 10? A) About 1 second B) About 4 seconds C) about 1 minute D) about 4 minutes E) about 1 hour
D) about 4 minutes *remember the Y-axis on Dark adaptation curve is in log units! The rod threshold will increase ~ 10^5 over 40 min.
Light reaching the eye does not all get focused into the proper place on the retina. Which of the following rays passing through the cornea and lens would actually be part of a well focused image? A) A reflected ray B) A backscattered ray C) A forward scattered ray D) An absorbed ray E) A refracted ray
E) A refracted ray
Light reaching the eye does not all get focused into the proper place on the retina. Which of the following rays passing through the cornea and lens would actually be part of a well focused image? A) A reflected ray B) A backscattered ray C) A forward scattered ray D) An absorbed ray E) A refracted ray
E) A refracted ray
Before an experiment begins, how long should an eye be patched in order to be fully dark adapted? A) About 1 second B) About 5 seconds C) About 1 minute D) About 5 minutes E) About 1 hour
E) About 1 hour
Before an experiment begins, how long should an eye be patched in order to be fully dark adapted? A) About 1 second B) About 5 seconds C) About 1 minute D) About 5 minutes E) About 1 hour
E) About 1 hour Dark Adaptation - photopigment (11-cis retinal) must be fully regenerated (rods are unresponsive until about 93% 0f pigment is regenerated) slow process
Light hitting the retinal photoreceptors has much less short wavelength energy than light emitted from the sun because of absorption by A) The Ozone layer B) Spectacles, Contact lenses and/or sunglasses, C) The crystalline lens D) The macular pigment E) All of the above
E) All of the above
Light hitting the retinal photoreceptors has much less short wavelength energy than light emitted from the sun because of absorption by A) The Ozone layer B) Spectacles, Contact lenses and/or sunglasses, C) The crystalline lens D) The macular pigment E) All of the above
E) All of the above
Vision operates over a very large range of intensities, from dim to dazzling. On a bright sunny day, if you look up at the sky, photons from the sun pour through your pupil in great numbers. If each photon was one drop of water, the amount entering your pupil from the sun when you look at the sky would be like A) Opening your mouth in a heavy thunderstorm B) Drinking from a garden hose nozzle on full blast C) Putting your head under Niagara falls and opening your mouth D) All the water from the entire Niagara falls going into your mouth E) All the water from 2 MILLION Niagara falls going into your mouth
E) All the water from 2 MILLION Niagara falls going into your mouth
Vision operates over a very large range of intensities, from dim to dazzling. On a bright sunny day, if you look up at the sky, photons from the sun pour through your pupil in great numbers. If each photon was one drop of water, the amount entering your pupil from the when you look at the sky would be like A) opening your mouth in a heavy thunderstorm B) Drinking from a garden hose nozzle on full blast c) Putting your head under Niagara falls and opening your mouth D) All the water from the entire Niagara falls going into your mouth E) All the water from 2 MILLION Niagara falls going into your mouth
E) All the water from 2 MILLION Niagara falls going into your mouth
Which of the following is TRUE about the optic disc? A) It has rods throughout, but not cones B) It is almost always square shaped, except in certain diseases. C) It is visible in a fundus image because of the macular pigment overlying it. D) The center of the disc has densely packed cones, but no rods and no other retinal layers. E) Both veins and arteries can be seen emerging from the disc in a fundus image.
E) Both veins and arteries can be seen emerging from the disc in a fundus image.
Which cells in the retina send their axons to the brain through the optic nerve? a) Photoreceptors b) Bipolar cells c) Amacrine cells d) Horizontal cells e) Ganglion cells
E) Ganglion cells
Which of the following is FALSE regarding the iris of the eye? A) It is part of the Uvea. B) It helps regulate the amount of light entering the eye. C) It is the colored part of the eye surrounding the pupil D) It influences the sharpness of the retinal image. E) It produces aqueous humor, which provides nutrients to the lens and cornea.
E) It produces aqueous humor, which provides nutrients to the lens and cornea. (aqueous humor is produced by ciliary body)
Light damage from the use of ophthalmic instruments is a concern. Which of the following statements is FALSE regarding this risk to patients? A) The MPE level for avoiding damage is based on healthy eyes, so the MPE might not be safe for patients with eye disease, such as retinitis pigmentosa. B) Commercial ophthalmic instruments like fundus cameras are designed to be at or below the MPE in most cases. C) Long exposure times during observation of the retina with an instrument might exceed the MPE, even if the normal brief flash used to take a fundus photo does not. D) Commercial ophthalmic instruments like fundus cameras use visible light, but thermal damage is still a concern. E) The MPE levels are supposed to be a factor of one thousand below the damage levels, so there should still be a wide margin of safety for lights that are close to the MPE.
E) The MPE levels are supposed to be a factor of one thousand below the damage levels, so there should still be a wide margin of safety for lights that are close to the MPE. (The MPE levels are a factor of TEN below damage levels) *be careful he switches this one up each year
Which part of the macula has the largest are on the retina?
Perifovea
Which of the following pigments is found in short wave sensitive cones? a) cyanolabe b) chlorolabe c) erythrolabe d) rhodopsin e) melanopsin
a) cyanolabe S-cones think blue light =cyan M-cones think green light =chloro L-cones think red light =erythro
In terns of visual angle, the blind spot of the eye is?
about 15 deg in the temporal visual field
The relationship between sensitivity and duration is summarized by what we call a) Ricco's Law b) Bloch's Law c) Martial Law d) The code of Hammurabi E) The
b) Bloch's Law
Which of the following is FALSE regarding bleach and recovery in rods and cones? a) Cones recover faster than rods b) Recovery is much faster than bleaching c) Rods eventually recover more sensitivity than cones d) The brighter the light that bleaches the rods and cones, the longer it takes to completely recover. e) The point in time during recovery when rods become more sensitive than cones is called the "rod-cone break"
b) Recovery is much faster than bleaching
Which of the following is FALSE regarding bleach and recovery in rods and cones? a) Cones recover more quickly than rods b) Recovery is much faster than bleaching c) Rods eventually recover more sensitivity than cones d) The brighter the light that bleaches the rods and cones, the longer it takes to completely recover. e) The point in time during recovery when rods become more sensitive than cones is called the "rod-cone break".
b) Recovery is much faster than bleaching
Rayleigh scattering in the atmosphere gives rise to which of the following? a) The green sea b) The red sunset c) The white fog d) The yellow snow e) The purple haze
b) The red sunset Rayleigh scattering causes the blue hue of the daytime sky and the reddening of the sun at sunset (light must pass through more of the atmosphere) -Particle scattering light is smaller than the wavelength.