Term
| What do you call the locus of all points in visual space that are imaged on corresponding points in each eye when the eyes are converged to aim at a particular fixation |
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Definition
| Theoretical point horopter |
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Term
| What are the five horopter criteria? |
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Definition
SSSMZ
1) When objects appear the same distance away from the observer as the fixation point, they define the horopter. This is called the AFPP, the Appparent Frontoparallel plane.
2) When objects appear to be lying in a single visual direction, the images of those objects must be formed on corresponding retinal points
3) Singleness-objects near the phoropter will be seen singly
4) Minimum stereoacuity threshold-the finer the closer the point in space to the horopter
5) Zero Vergence-Points seen as equidistant will not generate a motor fusional response. |
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Term
| Which method of measuring the horopter is the most precise? |
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Definition
| Identical visual direction, but it takes too long |
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Term
| What method allows the patient to view a rod such that one eye can only see the top half of the rod and the other eye can see the bottom half? |
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Definition
1)Grid nonius method-filters are used in front of each eye such that each eye only sees one part of the grid
2)or oppositely oriented polaroid filters on the top and bottom of the rod |
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Term
| Why is the horopter rarely used to determine the presence of fixation disparity in a patient as well as its effects on the perception of visual space by the patient? |
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Definition
| Identical visual direction too time consuming. |
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Term
| What method of measuring the horopter is more precise with untrained patients? |
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Definition
| Tje eqia; dostamce pr sterepscp[oc depth-matching horopter (also known as the apparent frontoparallel lane method) AFPM |
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Term
| Which method of measuring the horopter takes advantage of the fact that corresponding retinal points have zero retinal disparity. |
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Definition
| Equal distance or stereoscopic depth-matching horopter, or the apparent frontoparallel plane method |
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Term
| In which type of horopter test does the subject move the rods until they all appear to be the same distance away appearing to be in a flat plane? |
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Definition
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Term
| What are the shape of horopter settings be in relation the shape of the frontoparallel plane? |
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Definition
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Term
| Which horopter measures the extent of Panum's fusional area by moving a rod in until it appears double to the fixation rod and then moving it out until it appears double to the fixation rod? |
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Definition
| Singleness or haplopia horopter |
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Term
| Which horopter measured by fixating a central rod while measuring the stereoscopic thresholds for a sencond more eccentric rod, that is detecting the smallest change in stereoscopic depth that can be detected for a rod? It takes advantage of the fac |
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Definition
| 1) Maximum stereoacuity horopter |
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Term
| Which method of measuring the horopter has the patient fixate on a central image and then flashes a second image. It then collects all image points that do not stimulate fusional eye movements when the subject bifixated a central location. |
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Definition
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Term
| When R0 equals 1 what is the slop of the horopter at the fixation line? |
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Definition
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Term
| When R0 is less than one, the ______eyes image is larger and the horopter skews toward the _______ eye |
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Definition
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Term
| The difference in curvature between the horopter and the Vieth Mueller circle as measured at the fixation point. |
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Definition
| Hering-Hillebrand horopter deviation |
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Term
| What does H>1 indicate about the horopter? |
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Definition
| The horopter is less curved than the Vieth Mueller circle |
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Term
| What does H<1 indicate about the horopter? |
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Definition
| The horopter is more curved than the Vieth Mueller circle? |
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Term
| What does the fact that human H values are between +0.1 and +0.2 indicate? |
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Definition
| The human horopter is flatter than the Vieth Mueller circle due to neural magnification by the arrangement of corresponding points in the retina |
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Term
Which direction does the vertical horopter tilt? How do we perceive horizontal surfaces? Why is the tilt less than expected? |
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Definition
| The vertical horopter tilts away from the observer. We perceive horzontal surfaces as being tilted slightly upward. The perceptual system compensates almost completely for this under normal conditions. |
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Term
| What type of strabismics possess a Flom notch and what is it? |
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Definition
| Esotropes possess a Flom notch, a large notch in the horopter near the fixation point and the crossing of the visual axes such that the horopter deviates closer to the patient. |
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Term
| What happens to the Flom notch as the objective angle of strabismus is reduced? |
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Definition
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Term
| What do you call the disorder in adult esotropes that is a seeming avoidance of fusion by the patient? |
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Definition
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Term
| What causes the sudden motion at the position of superimposition by patients with horror fusionis? |
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Definition
| The target of the deviating eye is passing the rapidly changing portion of the Flom notch |
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Term
| What do you call a flat lens with parallel front and back surfaces that changes the magnification of an image without any dioptric power? |
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Definition
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Term
| What do you call a size lens with magnification in only one meridian? |
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Definition
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Term
| What is the only factor that the magnification of an afocal lens depends on? |
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Definition
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Term
| What is it called when the horopter rotates opposite the geometric plane? |
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Definition
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Term
| In what effect is the horopter rotated toward the magnified eye and the world rotated away from the magnified eye? |
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Definition
the geometric effect, Remember that the magnifier in front of the eye must be axis 90 to see a horizontal magnification |
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Term
| What type of room helps obscure monocular cues to depth? |
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Definition
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Term
| If you place a magnfier axis 90 in front of the right eye, which side of the uniform square leaf room will look bigger and be perceived as bigger and further away? |
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Definition
| The right side, the horopter will be closer to the right eye |
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Term
| What causes the downward slant of the floor and the upward slant of the roof in the rightward direction? |
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Definition
Not the horizontal magnfier. It's the apparent size and distance of the side walls that creates a secondary illusion of slant in the floor and ceiling. |
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Term
If you place a 180 degree magnifier (vertical) in front of the right eye and it looks the same as a 90 degree magnifier in front of the left eye at low magnifications, what do you call this? |
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Definition
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Term
| What do you call the identical visual direction horopter? |
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Definition
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Term
| What happens when you magnify an image a small amount in both the vertical and horizontal meridian of one eye? |
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Definition
| The induced effect and the geometric effect cancel each other out. However consistent fusion of the two images may still be difficult. |
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Term
| What do you call converging to bifoveally fixate on a target that is not on the vertical midline? What is the effect? |
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Definition
| asymmetric convergence, One eye is closer to the object than the other yielding a difference in retinal image size between the two eyes. |
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Term
At what relative magnification does the equalizing image size of the induced effect break down? |
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Definition
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Term
| What happens with magnification in the 45 degree meridian (axis 135) OS, and magnification in the 135 degree meridian (axis 45) OD? |
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Definition
| The inclination/declination effect. The upper part of the room appears further away and larger |
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Term
| What eye movements compensate for oblique magnification? |
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Definition
| Cyclorotary eye movements, such as those induced by converging the eyes and looking down. They can't completely correct the effect though because cyclovergence eye movements are limited in amplitude. |
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Term
| Why would an axial anisometropic myope corrected with contact lenses experience less aniseikonia that spectacle correction? |
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Definition
| The eye is stretch in myopia, making the photoreceptors spread out, thus the magnification introduced more closely matches the magnification of the photoreceptor array |
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Term
| Which technique for measuring aniseikonia puts up two penlights and a Maddox rod over the right eye? What is the sign of aniseikonia? |
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Definition
| Brechner Maddox rod technique. The distance between the dots is different than the distance between the columns of light |
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Term
| What type of instrument works by increasing or decreasing the magnification to reduce the amount of apparent rotation of the targets, thus finding the iseikonic Rx? |
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Definition
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Term
| What does the fact that R (uniform magnification) can vary but H (nonuniform magnification) cannot vary indicate? |
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Definition
| The manipulations to the horopter are optical, not neural. |
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Term
| Which way does the image bow with base out prism? |
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Definition
| The image bows out in the middle because the apex of the prism has more magnification than the base. The world bends toward the subject at its edges and away in the middle. The horopter is the opposite. |
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Term
| Which way does the image move with base in prism? |
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Definition
| The image moves away at the edges and closer in the middle. The ends look bigger through the apex of the prism and hence look further away than they reallly are. |
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