Term
| What are the advantages and disadvantages of having a pinhole pupil? |
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Definition
A: increased depth of field, tell light direction, protect the retina
D: Less light equals a faint image, increased diffraction |
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Term
| What are the advantages and disadvantages of having a tapetum lucidum? |
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Definition
A: can see better at night
D: reduced daytime vision |
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Term
| What are the advantages and disadvantages of having an iris coloboma? |
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Definition
A: less need for accommodation,
D: glare is a problem, too much light getting in. |
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Term
| What are the advantages and disadvantages of having a compound eye? |
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Definition
A: Increased visual field, microscopic near vision, great motion detectors
D: very nearsighted, poor stereopsis |
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Term
| What are the advantages and disadvantages of seeing ultraviolet light? |
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Definition
A: see particular flowers, targets invisible to other species.
D: Seeing UV would be really cool. |
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Term
| What are the main visual advantages of Topical pilocarpine & corneal trauma |
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Definition
| Topical pilocarpine and corneal trauma both cause pupil constriction which increases depth of field |
|
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Term
| What are the main visual advantages of rod monochromatism |
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Definition
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Term
| What are the main visual advantages of an Iris coloboma |
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Definition
| Increased light entering the eye would be an advantage in low light conditions |
|
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Term
| What are the main visual advantages of monocular vision |
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Definition
| Reduced chance of diplopia, increased visual field |
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Term
| What are the main visual advantages of age-related Macular Degeneration (AMD) |
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Definition
| Is going blind an advantage? Increased hearing sensitivity. |
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Term
| 1. Why do we see the Purkinje Tree under the slit lamp, but not in the sunshine? |
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Definition
| Because the light is moving with the slit lamp and our retina is being held still. In nature the opposite is true. |
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Term
| 2. Why are flying corpuscles better described as flying spots? |
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Definition
| Corpuscles is an old word for White Blood Cells and does not describle all the situations where flying spots can occur. |
|
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Term
| 3.Which entoptic phenomena can be used by an observant patient to monitor glaucoma? Which can be used to monitor diabetic retinopathy? |
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Definition
Retinal phosphenes can be used for glaucoma.
Diabetic retinopathy can be watched using a penlight to view the Purkinje image for hemorrhages. |
|
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Term
| 3.What part of the retina causes the polarization responsible for the Hadinger Brush effect? |
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Definition
Plane-oriented pigment molecules in the fovea
He also talked about the NFL polarizing light.
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Term
| 4.What is Maxwell’s spot? When is it seen? |
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Definition
A dark reddish circle surrounded by a clear ring and brighter blue halo when looking at a diffuse, flickering blue light. Xanthophyll (yellow pigment)is responsible
Maxwell's spot is a close relative of Haidinger's brush.
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Term
| 1.What are the six functional layers of the retina? Which of the traditional ten layers are not functional? |
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Definition
1. RPE
2. photoreceptor layer
3. horizontal cell layer
4. bipolar cell layer
5. amacrine cell layer
6. ganglion cell layer
The external limiting membrane, the outer and inner plexiform layers, nerve fiber layer, and internal limiting membrane are not functional layers |
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Term
| 2.Define melanin and tight junctions and their uses in the human eye. |
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Definition
| Melanin is a cellular pigment used in the eye to absorb free radicals from nutrients and UV light. Tight junctions between RPE cells keep blood out of the eye making the cells filter what gets in to control substances in the eye. |
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Term
| 3.Name the nine reasons that humans have a retinal pigment epithelium. |
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Definition
| 1. Retinal metabolism, 2. Toxin Shield, 3. Light shield, 4. Receptor alignment, 5. Photopigment regeneration, 6. Control of accommodation, 7. Standing electrical potential, 8. Retinal growth hormone, 9. Phagocytosis |
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Term
| 4.Define: the photomechanical effect, phototoxicity and the retinal railroad concept. |
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Definition
| The retinal railroad is the path that photopigment has to travel between the RPE where it gets regenerated (in light) and the photoreceptors where it is stored (in dark). Phototoxicity probably has to do with certain steps of photobiochemistry being toxic to the cells. |
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Term
| 5.What is retinal growth hormone? What is its relationship to electro-oculography (EOG)? |
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Definition
| The presumed substance that causes an eye to increase axial length, both electrical and chemical. |
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Term
| 1.Between which layers does a retinal detachment typically occur? |
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Definition
| Tears usually happen at the photoreceptors cilium - the weakest point. |
|
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Term
| 2.What is the Stiles-Crawford Effect (of the first kind)? What are the clinical consequences for daytime and nighttime vision? |
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Definition
| The light entering a receptor (cone) on axis is more likely to be absorbed and trigger a perception than is light entering a cone at an angle. |
|
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Term
| 3.When do the rod photoreceptors renew their photopigments? When do the cones? |
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Definition
| Rods slough their discs in the morning, Cones at night. |
|
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Term
| 4.Which pigments are in the macula of the healthy eye? Which is highest concentration in the fovea? Hint: they are both xanthophylls. |
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Definition
| Chlorolabe and Erythrolabe |
|
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Term
| 5.What is the aging pigment in the macula if youre unlucky or dont take care of yourself? |
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Definition
|
|
Term
| 1.Where on the retina is the density of the rods the greatest? How about the cones? |
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Definition
| Rods: 20 degrees out from the fovea, 150k/mm^2. Cones: Central fovea, 115k - 225k/mm^2 |
|
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Term
| 2.Which receptor is most sensitive when properly adapated -- rods or cones? |
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Definition
| Rods - 100x more sensitive |
|
|
Term
| 3.What is the spatial threshold for rods? For cones? |
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Definition
| Rods: 10 arc min, cones: 1 arc min |
|
|
Term
| 4.What is the temporal resolution threshold for rods? For cones? |
|
Definition
| 100ms for rods, 10ms for cones |
|
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Term
| 5.Define Blochs and Riccos and laws. |
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Definition
| Bloch's: Luminance x time = constant, explains the relationship between luminance and the duration of a light. Ricco's: The larger the area the higher the luminance needed for summation effects to be seen. |
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Term
| 1.What is the shape of the dark adaptation curve if there is a cone problem? A rod problem? |
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Definition
| Cone problem: The cones regenerate pigment faster than rods so the vision would be bleached out and the curve would have the rod/cone break sooner and at a higher threshold. Rod problem: the cones would hit their minimum threshold and level off without the rods taking over. |
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Term
| 2.On dark adaptation, a patient is missing her rod-cone break and has a high threshold that is reached in under 10 minutes. Which ocular diseases could account for this? |
|
Definition
| Retinitis pigmentosa - rods are not functioning properly |
|
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Term
| 3.If the dark adaptation curve is missing the rod-cone break and has a low threshold it takes 30 minutes to reach, which ocular diseases could explain it? |
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Definition
| Cones are not functioning properly, AMD, cataract? |
|
|
Term
| 1.What are the limits of the visible spectrum? |
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Definition
|
|
Term
| 2.What is visual purple an old name for? |
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Definition
|
|
Term
| 3.How many rods and cones are there in the average human eye? What is the ratio of rods to cones? |
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Definition
| 120 million rods, 6 million cones. Ratio = 20:1 |
|
|
Term
| 4.What is hyperpolarization? How does it differ from depolarization? |
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Definition
| The cell is more negatively charged than the normal resting state. Depolarization is the charge on the cell approaching 0mV. |
|
|
Term
|
Definition
| The flow of Na+ ions through the photoreceptors that happens in the dark and allows for the cells to become hyperpolarized when light hits them. |
|
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Term
| 1.What are the eight ways the rods and cones are different? |
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Definition
| 1. Shape, 2. Discs, 3. Disc Construction, 4. Function, 5. Synapses, 6. Staining, 7. Sloughing, 8. Photopigment |
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|
Term
| 2.What are the four photopigments? What are their peak wavelengths of absorption? |
|
Definition
| Rhodopsin = 507nm, Cyanolabe = 426nm, Chlorolabe = 530nm, Erythrolabe = 557nm |
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|
Term
| 3.What is the first rule of quantal (photon) absorption? |
|
Definition
| 1. Not all photons that hit a molecule of photopigment will be absorbed, |
|
|
Term
| 3. What is the second rule of quantal (photon) absorption |
|
Definition
| 2. The probability of absorption depends on the chemical nature of the pigment and energy of the photons, |
|
|
Term
| 3. What is the third rule of quantal (photon) absorption |
|
Definition
| 3. Principle of univariance - the energy of a photon determines the probability that it will be absorbed but not the magnitude of the response. |
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|
Term
| 3. What is the fourth rule of quantal (photon) absorption |
|
Definition
| If a photoreceptor absorbs multiple photons at the same time, the degree of hyperpolarization is proportional to the log of the number of photons absorbed. |
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|
Term
| 3. What is the fifth rule of quantal (photon) absorption |
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Definition
| Mutiple absorptions yield larger and faster hyperpolarizations, from which the retina takes longer to recover. |
|
|
Term
| 4.What are the six steps to the receptor pump mechanism that make the dark current happen? |
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Definition
| 1. Na+ is pumped out at the inner segment, 2. Na+ flows around the receptor from the inner to the outer segment and leaks back in the outer segment through pores, 3. Na+ flows through the inside of the receptor from inner to outer segments through the cilium, 4. The cilium controls the rate that Na+ can flow from the outer to inner segment, 5. This Na+ current flows in the dark and can be measured, 6. Called the Dark Current |
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|
Term
| 1.Which are the two types of horizontal cells? The four types of bipolar cells? |
|
Definition
| H1 and H2 Horizontal Cells. Midget, S-cone, Diffuse, and Rod Bipolars. There is an On and Off for each type but Off only in cones. |
|
|
Term
| 2.Which neurotransmitter is used by horizontal cells? By bipolar cells? |
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Definition
| Horizontal: GABA, Bipolar: Glutamate |
|
|
Term
| 3.What do horizontal and bipolar receptive fields look like? Which is smaller, and which is larger? |
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Definition
| The bipolar receptive fields have an off or on center surrounded by the opposite in the periphery. Horizontal cells have a smaller field that are only inhibitory or off. |
|
|
Term
| 4.Which are the most common type of synapses with horizontal and bipolar cells? |
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Definition
| Bipolar: Conventional (flat), Unusual, Triad. Horizontal: Rods and Cones in triad synapses. |
|
|
Term
| 1.What is the optic tectum? Do humans have one? |
|
Definition
| A retinal signal processing center in frogs, in humans it is called the superior colliculus |
|
|
Term
| 2.Where do action potentials begin in the retina? |
|
Definition
|
|
Term
| 3.How many ganglion cells are there per eye? What is the ratio of receptors to ganglion cells? |
|
Definition
| 1.2 million ganglion cells per eye, 100:1 |
|
|
Term
| 4.How many primary colors are there at the ganglion cell level? What are they? |
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Definition
| 4, blue, red, green, yellow |
|
|
Term
| 5.Do ganglion cells demonstrate graded potentials or action potentials? Where do they first synapse outside the retina? |
|
Definition
|
|
Term
| 6.What do amacrine and ganglion receptive fields look like? How many types are there? |
|
Definition
| On and off center with on and off surround |
|
|
Term
| 1.What are the three main types of ganglion cells? Which is most prevalent, and which most rare? |
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Definition
| Midget, parasol, small bistratified. Midget are most common, bistratified are least. |
|
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Term
| 2.What is the parvocellular information stream? Which ganglion cells begin it? What types of light information do they carry? |
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Definition
| Central vision, the "what is it" stream, midget ganglions, high contrast and color but slow. |
|
|
Term
| 3.What is the magnocellular information stream? Which ganglion cells begin it? What types of light information do they carry? |
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Definition
| Peripheral vision, the "where is it" stream, parasol ganglions, low contrast but very fast. |
|
|
Term
| 4.What is the koniocelluar information stream? Which ganglion cells begin it? What types of light information do they carry? |
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Definition
| Moderate light frequencies, Bistratified cells, involved in blue-yellow color vision and large receptive fields |
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|
Term
| 1.What is the best target for maximum response from the photoreceptors and horizontal cells? |
|
Definition
| Both photoreceptors and horizontal cells only hyperpolarize to light so any target size will provoke a resonse, respond to simple light or dark |
|
|
Term
| 2.What is the best target for the bipolar, amacrine and ganglion cells? |
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Definition
| All three have center/surround fields whether off or on so they respond best to contrast, particularly if it is the size of the center of the receptive field. |
|
|
Term
| 3.Which are the three primary colors distinguished by the cones? Which fourth color is found in the ganglion cell receptive fields? |
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Definition
| Red, blue, and Green, Yellow is found at the ganglion cell level although it is made at the Amacrine cell level which mix M and L cone input. |
|
|
Term
| 4.What are Mach bands? What is their biological purpose? |
|
Definition
| A dark or light band at the border between solid color borders, Lateral inhibition enhances edges so we can see monocular depth |
|
|
Term
| 5.What is a SWAP visual field? Which part of the retina does it test? |
|
Definition
| Short Wavelength Automated Periphery, - Uses 578nm light which stops the M and L cones from working, they get bleached out. |
|
|
Term
| 1.Name three functions of Mueller cells. |
|
Definition
| Responsible for External and Internal limiting membrane, Provide structure and a metabolic buffer/storage mechanism, play an important role in the voltage across the eye and retina. |
|
|
Term
| 2.What are Interplexiform cells? What is the centrifugal pathway? |
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Definition
| Provide feedback from ganglions to receptors via the centrifugal pathway which is the pathway the cells go through to get back to the photoreceptors. |
|
|
Term
| 3.Which information streams involve the red green and blue-yellow ganglion cells? Are they different? |
|
Definition
| Parvocellular is red - green, bistratified is blue - yellow. I think |
|
|
Term
| 4.What are SWAP visual fields? How do they differ from standard and FDT fields? |
|
Definition
| Short Wavelength Automated Periphery, differs in the wavelength of the field. |
|
|
Term
| 1.What does the human contrast sensitivity (CS) curve look like? |
|
Definition
| Somewhat like a bell curve, similar to the scotopic sensitivity curve. |
|
|
Term
| 2.What is the expected peak of contrast sensitivity, in cycles per degree and Snellen fraction? |
|
Definition
| 4 cycles/degree or 20/150 |
|
|
Term
| 3.What is the Nyquist Theorem? Does it explain the limits of low, moderate, or high contrast sensitivity? |
|
Definition
| The limit to visual acuity, relates to the size of the cones/rods and the frequency of contrast, If the grating bars used for contrast get smaller than the size of the cones then they cannot be resolved. Explains the limits of high contrast sensitivity. |
|
|
Term
| 4.What is veiling glare? How does it affect contrast? |
|
Definition
| Light is scattered by the media inside the eye resulting in a reduction of contrast - cataracts. |
|
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Term
| 5.What is the role of ganglion receptive fields on CS? |
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Definition
| Ganglion cells have fewer receptive fields with large (20/400) centers and surrounds than small (20/20) receptive fields. Contrast sensitivity should get worse for lower spatial frequencies until 100% contrast targets would not be seen as edges but as surfaces. |
|
|
Term
| 1.Name three pathological reasons for the low spatial frequency falloff of the CS curve. |
|
Definition
| Glaucoma, retinitis pigmentosa, peripheral cataracts |
|
|
Term
| 2.Which is the most common cause of loss of mid spatial frequencies contrast? |
|
Definition
| Corneal edema due to CL overwear or ocular hypertension |
|
|
Term
| 3.Which is the most common cause of high spatial frequency reduction of CS? |
|
Definition
|
|
Term
| 4.What is the difference between the Bailey-Lovie and Pelli-Robson contrast sensitivity eye charts? |
|
Definition
| The Bailey-Lovie chart has low contrast with decreasing letter size, the Pelli-Robson chart keeps the letters the same size but reduces contrast down the page. |
|
|
Term
| 5.How is very young and very old age expected to affect contrast sensitivity? |
|
Definition
| Elderly patients lose high frequency resolution, infants have decreased contrast sensitivity for all frequencies. |
|
|
Term
| 1. Depth can be determined monocularly by pictoral cues. Name the seven pictoral cues to depth. |
|
Definition
| Interposition, Clarity, Lighting and Shadow, Linear Perspective, Texture, Familiar size, Relative size |
|
|
Term
| 2. Name three other non-binocular cues to depth. |
|
Definition
| Accommodation, Angular Declination, Motion Parallax |
|
|
Term
| 3. Name the two binocular depth cues. |
|
Definition
| Convergence, Retinal Disparity |
|
|
Term
| 4.Which ocular diseases affect binocular depth perception, and which affect monocular depth? |
|
Definition
| Diseases affecting both eyes will affect monocular depth. Diseases affecting one eye will affect binocular depth (Corneal edema, keratoconus, amblyopia, media opacities). |
|
|
Term
| 5. Explain at least one optical illusion that appears monocularly, but not binocularly |
|
Definition
| Hollow mask illusion, paper dragon. |
|
|
Term
| 1.What are the differences between active and passive 3D technology? Which is closer to a dissociated phoria? Which is like an associated phoria? Which involves flicker? |
|
Definition
| Passive: use polarized light - anaglyph, oblique, or circular polarizers. LG 3D TV's, some movie theaters. Active: Flicker, Called strobe or flicker stereoscopy, Samsung 3D TV's, digital movie theaters, Nike Strobe |
|
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Term
| 2. Which three types of ocular disease can lead to problems in temporal vision? Where in the visual system does each occur? |
|
Definition
| Photosensitive Epilepsy, Optic Neuritis, Optic Neuropathy |
|
|
Term
| 3. Which flicker frequency causes photic driving and epilepsy in photosensitive patients? Which wavelengths (colors) of light are most likely to cause it? |
|
Definition
|
|
Term
| 4. How do the Nike Strobe flicker specs work? |
|
Definition
| By strobing both lenses together they force your brain to fill in the blanks . |
|
|
Term
| 5.Compare and contrast the Humphrey FDT and Matrix. Which is best suited for threshold fields? |
|
Definition
| The FDT uses a 10 degree target at 25Hz, the Matrix uses a 5 degree target at 12 Hz. The Matrix is best suited for threshold fields. |
|
|
Term
| 1.Define the following laws of temporal perception: Ferry-Porter, Granit-Harper, and Talbot-Plateau. How do they differ? |
|
Definition
| Ferry-Porter - For a given contrast, CFF increases as the log level of light increases. Granit-Harper - CFF increases linearly with the log of the stimulus (retinal) area. Talbot-Plateau - The brightness of a fused flickering light is matched by the brightness of a steady light having the same mean luminance. |
|
|
Term
| 2. What are the CFF frequencies of the rods and cones? |
|
Definition
| Rods = about 20Hz, Cones = about 70Hz |
|
|
Term
| 3. What is the Troxler phenomenon? How does it differ from Brucke-Bartley Brightness Enhancement? |
|
Definition
| Images that are fixed on the retina fade from view, differs from BBB enhancement in that a flickering light (about 10Hz) appears brighter than a steady light of the same luminance |
|
|
Term
| 4. Mix and match: forward and backward masking, metacontrast and paracontrast. Give examples of each. |
|
Definition
| Forward Masking (Paracontrast): a very bright light will mask an event that happens directly after it because the system is recovering. Backward masking (Metacontrast): A very bright light can also mask an event that happened directly before it |
|
|
Term
| 5. Give a common clinical example of what might cause the Pulfrich Effect in patients, and how it would affect them. |
|
Definition
| Dimming the image seen by one eye, such as by a monocular cataract, slows down the encoding and transmission information from that eye. This causes an object moving back and forth in front of a patient to appear to be moving in an elipse. |
|
|
Term
| 1.What is the Broca-Sulzer Effect? How does it differ from Brucke-Bartley Brightness Enhancement? |
|
Definition
| A suprathreshold flash of light that is 50 - 100ms long will appear brighter than either a shorter or longer flash of the same magnitude. The BBBE is a special case of the Broca-Sulzer effect where the light is repeating at 10Hz (50ms on, 50ms off) |
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Term
| 4. What is the crowding phenomenon? Name one ocular disease that is most commonly affected by it. |
|
Definition
| If a masking light and a target are present at the same time one might interfere with the other - such as with amblyopia where a patient can read a letter by itself better than a line of same sized letters. |
|
|
Term
| 1.What is the difference between Beta and Phi stroboscopic motion? Are they considered first or second order motion? |
|
Definition
| Phi is where lights are flickering at a rate of 5 - 15Hz and as a result appear to be moving. Beta is slightly faster at 17Hz, the rate of movies, television, and computer animation. These are first order motion (one dimension). |
|
|
Term
| 2.What is a random dot kinematogram, and is it first or second order motion? |
|
Definition
| Kinematograms involve dots moving in two dimensions. Second order. |
|
|
Term
| 3.What is biological motion, and where is it processed in the brain? |
|
Definition
| Activates the posterior superior temporal sulcus when we see human or animal movement. Helps us recognize familiar biological moving shapes. |
|
|
Term
| 4. We have seen three distinct visual information streams at the retinal level -- magno, parvo- and konio-. Which processes motion? Careful! |
|
Definition
| Magno processes fast motion, konio processes medium motion, parvo do very little motion processing. |
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