VSP perimetry

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VSP perimetry
2012-04-21 14:55:03
VSP perimetry

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  1. What is a measure of the perimeter of the area of visual field within which a test spot of constant luminance and size is visible?
    Kinetic Perimetry
  2. What is a measure of the increment threshold luminance for a spot of constant size at different visual field locations?
    Static Perimetry
  3. What type of perimetry is most often performed with automated perimeters?
    Static Perimetry
  4. Which type of perimetry involves a moving stimulus?
    Kinetic Perimetry
  5. What are the normal limites of the monocular visual field?
    • 60*, 100*, 75*, 60*
    • Superior, temporal, inferior, nasal
  6. Is the blind spot on the same or oposite side of the visual field as the eye being tested?
    Ex: OD blind spot on right or left of visual field?
    Or... is the blind spot nasally or temporally located?
    Same side (OD blind spot on right); temporally
  7. What part of the visual field is seen by both eyes at once?
    Binocular VF
  8. The area of VF that are only seen by one eye is called...?
    Monocular Temporal Crescents
  9. What are the normal total and binocular visual field limits?
    Total: 200* horizontal; 135* vertical

    Binocular: 120* horizontal; 135* vertical
  10. Who described the visual vield as an island hill of vision surrounded by a sea of blindness?

    Why did he use this discription?

    The sensitivity of the VF is different depending on where you are in that field; fovea is extremely sensitive, so that is the peak
  11. How are isopter size and intensity and size of stimulus related?
    The isopter increases in size as you increase the intensity and/or the size of a stimulus
  12. What kind of stimulus might be used to get a large isopter?
    large and/or bright
  13. What type of perimetry can be used to test for scotomas?
    Static or kinetic, depending on expected results
  14. What is the term used for the actual perimeter of the patient's visual field?
  15. The perimeter of VF is measured using: 4
    • a single stimulus
    • of a specific size
    • and a constant, specific luminance
    • under specified viewing conditions
  16. For a person with a normal VF, what will be the effect on the isopter if we make the stimulus larger but keep the luminance the same?
    The isopter will be larger
  17. For a person with a normal VF, what will be the effect on the isopter if we increase the stimulus luminance, but keep the stimulus size the same?
    The isopter will be larter
  18. What type of perimetry is used to determine isopters for patients in the Goldmann Bowl Perimeter and who designed it?
    • Kinetic
    • Goldmann
  19. What are the characteristics of size and intensity used in the Goldmann Kinetic Perimeter? Which is the highest? How much of a change in intensity for each step?
    • Size: 0-V with V being the largest
    • Intensity: 1-4, with 4 being the highest; 0.5 log unit change
    • Intensity: a-e, with e being the highest; 0.1 log unit change
  20. What is the maximum intensity difference for the Goldmann Kinetic Perimeter? Units?
    10,000 apostilbs
  21. How many combinations of stimulus size and intensity are available for the Goldmann Kinetic Perimeter? How many are actually used/needed?
    • >100
    • only a few
  22. What size stimulus gives more accurate results?
    Smaller because it will detect edges better
  23. What is the modern version of the Goldmann perimeter called?
  24. What type of perimetry is most commonly used now and why?
    • Static perimetry
    • It takes less time
  25. What are the two ways isopters can be plotted on a VF graph?
    • flat circles; like looking down at the isopters
    • 2-D "hill of vision"; shows sensitivity well
  26. What type of perimetry is a Humphrey VF?
    Static perimetry
  27. What photoreceptors are being tested when using an HVF? Why?
    • Cones!
    • The patient is not dark adapted, so any defect shown will be to the cones, not rods.
  28. What is changed in an HVF?
    • luminance
    • size is kept constant
  29. How does the HVF test fixation?
    It shows a stimulus where the patient's physiological blind spot is located
  30. Normal vision requires that targets presented to the periphery have (more/less) luminance that the central target.
  31. What do the dark spots on an HVF indicate?
    The patient needed more luminance in these areas than a normal patient of teh same age would need to see the stimulus
  32. Under photopic conditions, the tests (VF) are ______. They are detecting a change in luminance from the _______ luminance.
    • increment threshold tests
    • background
  33. Under scotopic conditions, the tests (VF) are _____ because the patient is ______ _______ and the background luminance is ______.
    • simple detection tests
    • dark adapted
    • zero
  34. Most current automated perimeters normally use a background luminance of what? Units? In what range is this?
    • 10 candelas/m2 or 31.4 apostilbs (candela/pi*m2)
    • low photopic
  35. Describe the graph of the influence of dark/light adaptation on VF results. Why does it look this way?
    • The top line (0 asb), looks like the scotopic island and the bottom line (1000 asb) looks like the photopic island, with some transition lines in between
    • The top line dips down because the fovea does not function under scotopic conditions
    • The bottom line has a peak because the fovea is most sensitive in potopic conditions
  36. When testing with peripheral targets, the target should be either ____ or ____.
    bigger or brighter
  37. What increases with increasing retinal eccentricity and increased dark adaptation?
    Spatial summation
  38. What increases with increased light adaptation and proximity to the fovea?
    Lateral inhibition
  39. Describe the data on the graph of weber's constant vs. size looks like. Axis?
    large stimulus + photopic conditions = flat line; because several ganglion receptive fields are stimulated at once

    Smaller stimulus + photopic conditions = peak; because fewer ganglion receptive fields are stimulated at once, so it is more sensitive

    • X= retinal location
    • Y= log of stimulus luminance/ background luminance
  40. The best static perimetry stimulus duration is (longer/shorter) than the saccadic eye movement latency and (longer/shorter) than the critical duration for complete temporal summation
    • shorter
    • longer
  41. The tendencyfor the patient to want to look directly at a stimulus that is flashed in the periphery is called what? How long does this take?
    • Saccadic eye movement latency
    • 250msec
  42. What is the stumulus duration used by most commercial automated perimeters?
  43. What do the numbers mean on the printout for an automated static perimetry? Units?
    They are measurements of sensitivity called decibels
  44. An _______ is an absolute unit of luminance traditionally used in perimetry to simplify calculations involving circular stimuli
  45. The ________ scale is a relative, inverted logarithmic scal incorporated in perimetry to measure the sensitivity of the hill of vision
  46. Does a sensitivity of zero decibels on a VF mean the patient is blind at that location?
    No! Since there is a limit to the amount of brightness the machine will use, the patient was just unable to see the brightest stimulus used.
  47. What kind of scotoma has an increased threshold but is still measurable?
    relative scotoma
  48. What kind of scotoma coresponds to NLP vision?
    Absolute scotoma
  49. Everyone has an absolute scotoma. (T/F)
  50. What kind of scotoma is the patient aware of the loss in sensitivity?
    Positive scotoma
  51. What kind of scotoma is the patient unaware of the loss in sensitivity?
    Negative scotoma
  52. Give an example of a Negative scotoma.
    physiological blind spot
  53. What is the phenomenon that allows a negative scotoma or blind spot to go unnoticed?
    Perceptual filling in
  54. What is perceptual visual neglect?
    failure to attend to, or represent, sensory information from one side of the body or VF
  55. What is motor visual neglect?
    failure to execute movements fully in or towards (usually in the contralateral) one half of the VF
  56. Visual neglect is usualy related to contralateral lesions of the ________ extra-striate visual pathways.
  57. List 3 tests for visual neglect.
    • line bisection task
    • cancelation task
    • visual extinction field
  58. This sensory deficit (visual neglect) only emerges when stimuli are presented simultaneously to the left and right sides
    Visual Extinction
  59. On double simultaneous stimulation, the stimulus presented to the area of the visual field ________ to the side of the brain with the lesion goes undetected.
  60. How is a patient's "useful" VF measured?
    by requiring the patient to identify an object at fixation and a different object simultaneously presented at different positions within the peripheral VF