Vision Science I Exam 1 23 September ) The plot to the right shows the spectrum of a light source. Which of the following sources is this

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1 Vision Science I Exam 1 23 September ) The plot to the right shows the spectrum of a light source. Which of the following sources is this spectrum most likely to be taken from? A) The direct sunlight B) A green laser pointer C) A violet laser pointer D) An incandescent light bulb *E) A fluorescent light bulb. 2) A friend buys a laser pointer over the internet and shows it to you. You read the label and it says 900 nm, 150 milliwatts. Which statement below would be TRUE? A) That is very low power laser, so it can t hurt you. B) That laser will look extremely bright, so you would look away quickly if it shone in your eye. C) That is not actually a laser, because the wavelength is 900 nm. A laser is always visible light. That is called an IR-LED. *D) You wasted your money on a dangerous, but almost invisible laser pointer. E) Since you bought it on the Internet, it must be safe. Otherwise, the Internet would get sued. 3) Which of the following bands has the highest energy per photon? A) Radar B) Infrared C) Visible D) Ultraviolet *E) X-rays 4) Which of the following wavelengths is most absorbed by the eye s lens? *A) 350 nm B) 450 nm C) 550 nm D) 650 nm E) 750 nm

2 5) When a ray of light enters the eye, it can interact with the tissues of the eye in one of several ways. Which of the following rays going into the patient s eye allows you to see opacities in the lens or cornea during a slit lamp exam? A) A reflected ray *B) A backscattered ray C) A forward scattered ray D) An absorbed ray E) A refracted ray 6) The total light energy per second falling on a surface is measured as A) Radiant Flux, in watts B) Luminance, in candelas per square meter C) Retinal illuminance, in Trolands *D) Irradiance, in watts per square meter E) Luminous intensity, in lumens 7) In scotopic vision, which is TRUE regarding the relative appearance of two lights, one at 405 nm and one at 505 nm wavelength? Assume they are too dim to be seen by cones. A) They will look the same if they have the same power in watts. B) The 405 nm light will look brighter if they have the same power in watts. *C) The two lights can be made to look the same if the 450 nm light has a lot more power than the 505 nm light. D) The 405 nm light and the 505 nm light will appear as different colors, so they never look the same even if the brightness is matched. E) The 505 nm light is too far away from the eye s spectral sensitivity range to ever be seen, no matter how intense. 8) Sometimes people use a milliradian (1/1000 th of a radian) as an angular measure. How many arc minutes is one milliradian? A) 1000 B) C) *D) 3.44 E) ) Which of the following is normally found in the very center of the foveola? A) A retinal capillary B) A Retinal Ganglion cell *C) A long wave sensitive cone ( L Cone ) D) A rod photoreceptor E) A short wave sensitive cone ( S Cone )

3 10) Which photopigment, with peak absorption at 480 nm, is not found in either rods or cones? A) Cyanolabe B) Chorlolabe C) Erythrolabe D) Rhodopsin *E) Melanopsin 11) The S cones do not contribute proportionally very much to our overall photopic spectral sensitivity curve because *A) S cones are a small proportion of total cones, only about 8 %. B) S cones are less sensitive to light because short wavelengths have less energy. C) S cones do not show a Stiles-Crawford effect, so they are not efficient at getting light from the pupil. D) S cones contribute to Scotopic, not Photopic vision. E) S cones are ignored by all the other retinal cells, who think S cones are just Stupid. 12) Which of the following terms used in describing the phototransduction cascade in the eye refers to something that is NOT a variant of Vitamin A? That is, which one is the MOST DIFFERENT from all the others? A) cis Retinal B) chromophore C) trans Retinal *D) opsin E) trans Retinol 13) Photoreceptor cells have an electric current, which has the effect of depolarizing the cell, and causing neurotransmitter release. This current changes, depending on conditions. Which condition produces the most current in the photoreceptor? *A) complete darkness after dark adapting for several minutes B) a sudden flash of very bright light C) a slowly increasing light level D) a bright light after light adapting to it for several minutes E) a sudden loss of light after light adapting to a bright field.

4 14) In the center of the optic disc, you should find which one of the following? A) Cone outer segments. B) Rod outer segments. C) Bipolar cell terminals. D) Amacrine cell dendrites. *E) Ganglion cell axons. 15) The human retina has about how many rod photoreceptor cells? A) 120 B) 1 thousand *C) 120 million D) 10 trillion E) 2 million Niagara Falls worth 16) This question asks you to compare cones in the central fovea with cones in the periphery. Which statement is FALSE? A) Foveal cones are long and look almost like rods. *B) Peripheral cones are much thinner (smaller diameter) than foveal cones. C) Peripheral cones have rods filling the spaces between them. D) Foveal cones connect to ganglion cells that are off to the side of the central fovea. E) Peripheral cones are slanted so that they point toward the center of the pupil, not toward the center of the eyeball. 17) Weber s Law says that A) The increment of light that you can just detect is a fixed proportion of the background light level. B) The threshold for detection in the dark is proportional to the square root of the area stimulated. C) The duration of a flash is proportional to the time in milliseconds that it is on. D) The wavelength of light that is easiest to see is proportional to the size of the pupil. E) The time it takes to fully dark adapt is proportional to the intensity of the pre-test light.

5 18) To measure a classic dark adaptation curve, the subject is adapted to very bright light initially and then tested with 550 nm light and a relatively large spot. With these conditions, the curve usually shows a rod-cone break at about minutes. Which of the following would cause this rod-cone break to happen earlier during the dark adaptation period? *A) Adapting to moderate room illumination, instead of bright light, before starting the dark adaptation phase. B) Testing in the central fovea with a small spot. C) Testing with a 650 nm light instead of a 550 nm light. D) Testing a rod monochromat. E) Testing a patient with advanced AMD. 19) Comparing the light sensitivity of rods and cones, which of the following is true? *A) Rods respond better than cones to very dim light (absolute threshold), but rods do not respond as well as cones to small changes in light (increment threshold). B) Rods are less sensitive than cones for both absolute and increment thresholds. C) Rods are more sensitive than cones for both absolute and increment thresholds D) Rods and cones have the same absolute and increment sensitivity to light, but there are many more rods than cones so they have a numerical advantage. E) Rods have better increment sensitivity than cones, but do not respond as well as cones in very dim light. 20) The monocular crescent refers to A) The rim of the optic disc *B) The part of the visual field seen only by one eye C) The junction of choroid and sclera at the foveal center D) The angle between the iris and the cornea E) The region of cortex that represents the blind spot of the eye 21) When a person carefully fixates the eye on a small target, like a letter on the eye chart, which part of the eye does the image fall on? A) The canal of Schlemm *B) The foveola C) The limbus D) The optic disc E) The ciliary body

6 22) Suzy gets a new pair of sunglasses that are absurdly dark, cutting the light by a factor of 100. A vision scientist would describe her lenses as A) 1.0 ND *B) 2.0 ND C) 3.0 ND D) 0.1 ND E) 0.01 ND 23) 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 24) 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 300 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 25) If a clinician maps a patient s isopter with kinetic perimetry using a small target, and then switches to a larger 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) A smaller ring, inside the first one D) Square instead of oval E) Impossible to measure 26) When rods are saturated which of the following is FALSE? A) The dark current is shut off B) The rods cannot respond to changes in light level C) At least 10% of the pigment in the rod is bleached D) The rod increment threshold is unmeasureable *E) The rods are following Weber s law.

7 27) Surgical lasers, like the LensX system in our surgery center, create incisions in tissue through the mechanism of A) Thermal Damage B) Photochemical Damage *C) Thermoacoustic Damage D) none of the above 28) 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. 29) 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 is about *A) 400 to 700 nm B) 200 to 1000 nm C) 505 to 550 nm D) 600 to 700 nm E) 200 to 400 nm 30) 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

8 31) 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. 32) 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 33) A target that is 57 cm from the eye would subtend one degree of visual angle if its size is a) 2 centimeters *b) 1 centimeter c) 2 millimeters d) 1 millimeter e) 2 inches END