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Methods Block 12 > Perimetry > Flashcards

Perimetry Flashcards

1
Q

Meaning and purpose of perimeter

A
  • the study of the visual field

- the VF is the area in which objects can be seen in the peripheral vision while the eye is focused on a central point

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2
Q

Do we test VF monocularly or binocularly

A

Monocularly

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3
Q

Purpose of perimetry

A

Provides a more standardized assessment of the visual field

-assessment of visual function throughout the visual field for detection and analysis of damage along the visual pathway

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4
Q

Superior boundaries of the monocular field

A

60 degrees from the point of fixation

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5
Q

Nasal boundary of monocular field

A

60 degrees from the point of fixation

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6
Q

The inferior boundary of the monocular field

A

75 degrees from fixation point

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7
Q

Temporal boundary of the monocular field

A

100 degrees from the point of fixation

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8
Q

Monocular fields of vision in both eyes

A

Overlap

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9
Q

Temporal crescent

A

Most temporal portion of vision from approximately 70-100 degrees which is seen only by one

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10
Q

Why do glaucoma patients not realized they are losing vision

A

Because the VF in each are overlap, so the better eye can make up for the worse eyes loss

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11
Q

Blind spot

A
  • corresponds to the ONH

- located 10-15 degrees temporally

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12
Q

The eye has a small and stable preferred retinal locus of fixation

A

Most people it is the macula, but low vision patients can have it elsewhere

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13
Q

The center of ifixation correpsonds to

A

The anatomical center of the fovea where cone density is highest

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14
Q

Dipalsment of the fovea and the center of fixation associated with

A

Vision loss

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15
Q

Nasal retina projects to

A

Temporal VF

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16
Q

Temporal retina projects

A

Nasal VF

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17
Q

Inferior retina projects

A

Superior VF

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18
Q

Superior retina projects into the

A

Inferior VF

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19
Q

Limit of VF: nose

A

May limit or affect the nasal and inferior visual field

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20
Q

What are the things limiting the VF

A

Nose
Overhanging brow
Small pupils

21
Q

Overhanging brow

A

Limits superior field

22
Q

Small pupil and VF limitation

A

A pupil less than 2.5mm in diameter can decrease the amount of light reacting the retina and can increase diffraction leading to visual distortions

23
Q

What can cause small pupils

A

Cocaine, opioids, diabetes, old people

24
Q

Sensitivity

A

The ability to respond to physical stimuli or to register small physical amounts or differences

25
Q

Threshold

A

The Manila intensity of light at which a stimulus is perceived by the visual system at a specific location in the field of vision

26
Q

Brightness

A

The attribute of visual sensation according to which an area appears to emit more or less light

27
Q

Humphrey visual field

A

Static perimetery

28
Q

Goldmann perimetry

A

Kinetic perimetry

29
Q

Two perimetry techniques used to determine the shape of the hill of vision

A

Static perimetry: Humphrey

Kinetic: Goldmann

30
Q

Gold standard for VF

A

Humphrey visual field

31
Q

Which is more sensitive, static or kinetic

A

Static

32
Q

Why is Humphrey gold standard

A

Because it is static and it is more sensitive than kinetic

33
Q

Set size and brightness, Moving from non-seeing to seeing

A

Kinetic

34
Q

Involves moving target of constant brightness horizontally, from wher its is not visible, toward the center until it intersects with the HOV

A

Kinetic

35
Q

Advantages of static

A

Best strategy for assessing the central VF
Reproducible conditions
Sensitive to VF defects

36
Q

Disadvantage of static

A
  • does not directly plot borders of vision as single points are chosen for strategies
  • tedious
  • expensive instrumentation
37
Q

Advantages of kinetic

A
  • rapidly evaluate the peripheral field
  • rapidly plot deep defects
  • quick and accurate for steep-bordered defects
38
Q

Disadvantages of kinetic

A
  • difficult to recognize early field defects

- examiner has much influence on field; must be well trained or will affect the test

39
Q

The weakest stimulus which is just barely visible (50% of the time) for a particular retinal point being tested

A

Threshold

40
Q

Infra-threshold (subliminal)

A

Below threshold and not visible

41
Q

Worst disadvantage of kinetic

A

Examiner has a lot of influence on the field

42
Q

Supra-threshold (supraliminal)

A

Above threshold and visible

43
Q

Factors affecting visibility (threshold) of the stimulus

A

Size
Luminance
Background luminance
Duration of stimulus presentation

44
Q

How does stimulus size affecting threshold

A

Increased in stimulus size with decrease threshold

45
Q

Sensitivity equals

A

Height of HOV

46
Q

Luminance and threshold

A

The average luminance os the dimmest test object that cab be seen is determined

47
Q

Background luminance and threshold

A

Webers law

  • when the background luminance decreases, cones adapt more quickly
  • controls adaptation over time
  • controls sensitivity profile
  • some VF defects are more pronounced with difference background levels
  • should keep both stimulus and background constant and reproducible
48
Q

Background luminance: what todo to keep it reproducible

A

Should keep both the stimulus and background constant and reproducible

49
Q

Increase in stimulus size

A

Decrease threshold secondary to spatial summation

Methods Block 12 (4 decks)

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