Term
| How are pictorial and nonpictorial monocular cues to depth different? |
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Definition
| Pictorial cues are cues to depth that can be seen in a picture or a photograph |
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Term
| What law states that the perceived size of an object producing a retinal image of a given fixed size is proportional to its perceived distance? |
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Definition
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Term
| How does retinal image size and perceived distance change to produce the moon illusion? |
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Definition
| Retinal image size of the moon stays the same, but the perceived distance at the horizon is larger than the perceived distance at the azimuth (apex), (even though it really is not). Hence a photo of the moon at the horizon will show a smaller moon than what is perceived under normal viewing. |
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Term
| What law is the moon illusion an example of? |
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Definition
| The perceived size of the moon produing a retinal image of a given fixed size is proportional to the moons perceived distance. This is an application of Emmert's law. |
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Term
| What phenomena allows objects that produce different retinal image sizes to be perceived as the same size if these objects are judged to be at different distances? |
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Definition
| Size constancy, (A car 10 feet away looks the same size as a car 20 feet away even though the car 20 feet away produces only half the visual angle.) |
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Term
| What is the monocular cue that states distant objects are not only perceived as smaller but also as more densely packed than are near objects? |
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Definition
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Term
| What do you call the pictorial monocular cue that states that is the percept of parallel lines or edges converging toward a distant vanishing point at the horizon? e.g. railroad tracks, where the tracks are perceived as converging toward each other and the ties are perceived as being smaller? |
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Definition
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Term
| What pictorial monocular cue to depth is due to distant objects appearing less sharp than near objects due to scatter by the air? |
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Definition
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Term
| What pictorial monocular depth cue is exemplified by an illusory triangle occluding a second triangle and therefore being perceived as floating above the second background triangle it occludes? |
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Definition
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Term
| What pictorial monocular depth cue do artist use when they color the bottom of the dot darker than the top to change where its perceived in depth? |
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Definition
| shading, remember the dominoe |
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Term
| What nonpictorial monocular cue to depth states that an object closer than the fixation point will exhibit against motion proportional to the distance between the object and the fixation point? |
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Definition
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Term
| If you fixate a direct opthalmoscope iris and move it side to side will an object in the anterior chamber exhibit against or with motion? |
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Definition
| An object in the anterior chamber will exhibit against motion, while an object in the posterior chamber will exhibit with motion |
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Term
| What do you call the nonpictorial cue to depth that is similar to motion parallax in that the motion of parts of an object (e.g. a wire bent into a 3D shape projected onto a screen) can reveal their relative position in three-dimensional space? |
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Definition
| Shape from Motion commonly demonstrated by the kinetic depth effect |
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Term
| What happens to the perception of object size and distance as base out prism is increased in front of a patient? |
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Definition
| The object looks smaller and closer. |
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Term
| What are the pictorial cues to depth? |
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Definition
RLTAIS SAIL To Rome 1) retinal image size 2) Linear Perspective 3) Texture gradient 4) aerial perspective 5) Interposition 6) Shading |
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Term
| What are the nonpictorial monocular cues to depth? |
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Definition
SAM 1) Accomodation 2) Motion Parallax 3) Shape from motion |
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Term
| Is accomodation a good cue to judging distance? |
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Definition
No, it is a weak cue at best. |
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Term
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Definition
| The target is perceived as smaller when the image is moved inward (Base Out Prism) and larger when the image is moved outward (Base In Prism) although retinal image size is constant. Patients should be warned but they will adjust to this in time. |
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Term
| Is stereopsis better at judging absolute or relative distance? |
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Definition
| Stereopsis is a poor judge of absolute distance but a better judge of relative distance, especially for close up work. |
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Term
| Why do vertical imbalances need to be corrected more quickly? |
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Definition
| The binocular system is unable to correct them, and unable to use them to gain information on depth. |
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Term
| Name six ways to create the sensation of depth without actual physical separation of targets? |
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Definition
1) Orientation Disparity 2) Spatial Disparity (Diffrequency) 3) Temporal Disparity (Pulfrich Phenomenon) 4) Color Disparity 5) Television Stereopsis 6) Spectral Disparity |
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Term
| If the pendulum direction and the filtered eye are the same, what type of disparity is observed? |
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Definition
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Term
| What is it called when the image of red lights are displaced nasally on relative to blue lights? |
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Definition
| transverse chromatic abberation |
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Term
| What do you call the fact that blue light is refracted more than red light? |
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Definition
| longitudinal chromatic abberation |
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Term
| What do you call the fact that red light appears closer than blue light? |
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Definition
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Term
| Under which two conditions are chrmoatic abberation observed? |
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Definition
1) Whenver the target is off the visual axis 2) Whenever the observer views the target through an artificial or natural pupil which is not well centered on the visual axis. |
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Term
| What is the smallest disparity you can see that will allow you to achieve stereopsis? |
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Definition
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Term
| How can a person have good stereoacuity and yet still display poor depth perception? |
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Definition
1) Even if he can detect a difference in depth he may still underestimate or overestimate that difference in depth due to depth perception bias. 2) He may be able to see crossed disparities but not uncrossed disparities or vice versa |
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Term
| Why do we measure stereoacuity in the clinic if it is possible to have good stereoacuity and still have poor depth perception? |
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Definition
| Clinically stereoacuity is measured to see if the patient is capable of stereopsis when presented with a binocular disparity. |
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Term
| If we are so sensitiv to disparity why do most clinical tests of steropsis use a 40" arc disparity? |
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Definition
| We use 40" arc disparity in clinical tests because 95% of the population (two standard deviations from the norm) has 40" arc or better stereopsis. The clinical tests are used to screen for poor stereopsis and ibnocular problems, but they are not used to quantify a stereoacuity threshold. |
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Term
| What eleven factors effect how well we see disparity? |
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Definition
1) Practice 2) Luminance 3) Color 4) Exposure Duration 5) Retinal eccentricity 6) Unequal contrast between the eyes monocular images 7) Blur or defocus 8) Spatial frequency of the target 9) Motion 10) Sign of disparity 11) Crowding |
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Term
| Does monocular or binocular blur effect stereopsis most? |
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Definition
| monocular has a much greater effect, bincoular blur changes depth perception very little |
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Term
| Is lateral or stereomotion more harmful to depth sensitivity? |
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Definition
Stereomotion (movement up and back) has a much greater effect on depth perception. |
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Term
| Will patients with yoked nystagmus have better stereoacuity than visual acuity? |
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Definition
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Term
| What type of stereoscope is the keystone Telebinocular instrument a form of? |
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Definition
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Term
| Name three ways to view stereopsis without an instrument? |
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Definition
1) free fusion 2) anaglyph 3) vectogram |
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Term
| How does tilting the head mess up a vectographic stereo vision test? |
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Definition
| The vectographic stereo test makes the left eye image only visible to the left eye by using two polaroid filters, one in the book and one in the glasses thus cutting out all transmittance from the opposite eye. |
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