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Neuroscience > Week 2 - Perimetry and Clinical Correlation of Visual Field Defects > Flashcards

Week 2 - Perimetry and Clinical Correlation of Visual Field Defects Flashcards

1
Q

what does the visual field refer to? what is the normal “degree” for temporal and nasal? where is the blind spot?

A

area of space perceived by the eye

  • 100 degrees temporally, 65 degrees nasally
  • blind spot is where the optic nerve is
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2
Q

what does perimetry refer to?

A

the general assessment, diagnosis, prognosis, and monitor of progression of ophthalmologic and neurologic conditions

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3
Q

what sides do the nasal and temporal retina go to?

A

nasal retina = temporal side

temporal retina = nasal side

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4
Q

which are the binocular and monocular visual fields?

A

binocular are the nasal sides of both eyes (65 degrees overlap somehow, from temporal retina)
monocular are hemifields on the temporal sides of both eyes (65 to 100 degrees from nasal retina, as monocular temporal crescent)

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5
Q

what does Traquair’s island of vision represent?

A

a 3D representation of the visual sensitivity and threshold

  • the very tip of the island is where the macula focuses for 20/20 vision
  • if it moves even a couple degrees, acuity drops a lot
  • has a blind spot corresponding to optic nerve
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6
Q

what does visual sensitivity and threshold depend on?

A

age, attention level, refractive status (glasses), pupil size, media opacities (cataracts), and characteristics of stimulus (size, intensity, color, duration, movement)

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7
Q

what does kinetic perimetry refer to?

A

using Traquair’s island of vision, as objects are entering your field of vision from the temporal side, the dimmer and smaller something is (mosquito), the longer it will take to be seen (in front of your face), but the bigger and brighter something is (elephant), the sooner it will be seen (in your periphery)

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8
Q

what does static perimetry refer to?

A

using Traquair’s island of vision, a dot anywhere in your field of vision is easier to see if it’s bright, but harder if it’s dark
-they test by putting a dim dot somewhere in sight, and then brightening it, and pressing a button when it’s bright enough to see

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9
Q

what are 5 strategies for visual field testing?

A
  1. confrontation
  2. Amsler grid
  3. tangent screen
  4. Goldmann Perimeter
  5. Humphrey (automated) Perimeter
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10
Q

what is confrontation visual fields testing?

A

inexpensive, fast, and practical

  • examiner dependent (no standardization, so sophistication depends on physician doing it)
  • examinee dependent (tailored for each patient, and may be only test available for children, lethargic, or inattentive patients)
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11
Q

what are general and practical rules for confrontation visual field testing?

A

well-lit room

  • examiner one “arm length” away, situated at same height as patient
  • pt covers one eye, and looks as examiner’s same eye
  • ex covers contralateral eye (so if patient closes right eye, ex closes left eye, so contralateral eyes are open)
  • stimulus presented halfway from ex-pt distance
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12
Q

what are strategies for confrontation visual field testing?

A
  • use examiner’s face (tests central 10-15 degrees for central scotomas or hemianopias)
  • finger counting (only 4 places, usually 1-2 fingers)
  • finger moving (peripheral testing)
  • red object (higher sensitivity, moving outside in)
  • hand moving (for monocular temporal crescent in early chiasmal syndrome
  • examiner palms side by side closed to midline
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13
Q

what is the Amsler grid?

-what does it test?

A

20 x 20 grid held 33 cm away, testing central 10 degrees of visual field
-patient reports any area missing, blurred, or distorted, and can monitor at home and report any change

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14
Q

what is the tangent screen?

-what does it test?

A

manual kinetic (use light on black screen, with patient covering an eye at a time)

  • examiner at 1 meter away to look at examinee and assure good fixation
  • tests central 20 degrees of visual field
  • may be used as “pseudo-static” stimuli
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15
Q

what is the Goldmann test?

-what does it test?

A

manual kinetic

  • pt faces satellite dish-like bowl (w/ chin rests et al), and examiner assures fixation from peephole
  • tests almost entire visual field
  • primarily kinetic stimuli, but also static
  • tests stimulus size and light intensity (isopter is combination)
  • tests printed out on flat circle that circles the area that is seen, and leaves the area that’s not seen
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16
Q

what is the Humphrey test?

-what does it test?

A

automated static

  • pt faces bowl, and fixation monitored by computer
  • standardized, not examiner-dependent
  • begins by plotting blind spot (monitors fixation and reliability)
  • checks for false positives (sound only) and false negatives (stimulates known seeing area) to ensure not cheating
  • prints out document that shows fixation losses (if too high, not credible), mean deviation, and pictoral representation of fields by greytones (black = bad)
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17
Q

what does a scotoma mean?

A

a portion of the visual field that is missing

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18
Q

what does an arcuate defect mean?

A

arc-like shape defect made by retinal nerve fiber bundle damage (can be in one hemisphere either horizontally or vertically)

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19
Q

what does an altitudinal defect mean?

A

superior or inferior defect that respects the horizontal meridian (splits horizontally)

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20
Q

what does a hemianopia defect mean?

A

nasal or temporal defect that respects vertical meridian (splits vertically)

21
Q

what does a quadrantanopia defect mean?

A

a defect that affects one quarter (split both vertically and horizontally)

22
Q

what does a complete VS incomplete defect mean?

A

extension of type of defect (so, for incomplete, it’s just a part of what would be affected by a complete)

23
Q

what does a relative VS absolute defect mean?

A

depends on the type of stimuli (if it’s big or bright, might be able to see if it’s a relative defect, but not an absolute defect)

24
Q

what does a homonymous defect mean?

A

defect is on the same side (so it’s on the nasal side of the left eye but temporal of the right eye, meaning it’s the entire right side of both eyes with defects)

25
Q

what does a heteronymous defect mean?

A

defect is on different side (so it’s on the temporal side of both eyes, meaning the “middle vision” is fine, but not periphery)

26
Q

what does a congrous VS incongruous defect mean?

A

defect is similar in both eyes for congrous (so both have scotomas), or different for incongrous (one has scotoma, the other has hemianopia)

27
Q

what forms the optic nerve?

A

axons of ganglion cells converging

-it’s nasal to the retina, which creates a temporal blind spot

28
Q

what constitutes the nasal-temporal demarcation

A

vertical line that crosses fovea

29
Q

what does the horizontal raphe do?

A

divides retina in superior and inferior parts

30
Q

what are retinoic patterns of field loss?

A
  • may have decreased visual acuity
  • general or focal field deficits
  • -focal deficits correspond to viable lesions, usually central scotoma from foveal lesion or arcuate defect in glaucoma
31
Q

what are optic nerve patterns of field loss?

A
  • decreased visual acuity and color vision
  • relative afferent pupillary defect (RAPD); affected pupil constricts to light faster than another
  • no pathognomonic visual field defect, but some characteristics are
  • -altitudinal defect (typical of NAION; non-arteric anterior ischemia of optic nerve)
  • -central depression
  • -central scotoma (hereditary, toxic, nutritional)
32
Q

how does projection of nasal visual fibers differ in upper or lower nasal quadrants?

A

UNQ: from upper nasal retina, and crosses at the top of the chiasm
LNQ: from lower nasal retina, and crosses at belly of chiasm
-“Wilbrand’s knee” in the opposite optic nerve is part of its path
they both undergo crossing (decussation) for nasal fibers, whereas temporal fibers don’t

33
Q

what kind of defect is caused by a pituitary adenoma?

A

bitemporal superior visual field defect (due to an inferior chiasmal syndrome)

34
Q

what does the projection of the papillomacular bundle entail for vision?

A

macular fibers form “little chiasm within chiasm”

-fibers that cross optic chiasm do so in central and posterior position

35
Q

what are 2 types of anterior chiasmal syndrome?

A

in both, one eye is entirely cut, and the other has a “pie in the sky” cut

  • contralateral junctional scotoma with normal visual acuity and color vision
  • ipsilateral optic neuropathy; decreased VA, color vision, RAPD
36
Q

what is the hallmark of lesions that affect body of chiasm?

A

bitemporal field defects of all kinds
-can be either inferior (superior visual field defect, as in pituitary edema) or superior (inferior visual field defect, as in hydroencephalus)

37
Q

what are the rules for retrochiasmal visual pathway?

A

beyond optic chiasm, lesions to visual pathway make homonymous field defects
-the more posterior in the pathway a lesion occurs, the more congrous; more anterior is incongrous

38
Q

what are the 2 types of fibers in the optic tract and what do they do?

A

visual fibers - maintain relative position

pupillary fibers - depart optic tract into midbrain

39
Q

what is the lateral geniculate nucleus for?

A

retinal ganglion cells synapse, and fibers rotate 90 degrees medially

40
Q

what are optic tract patterns of field loss (NOT THE SAME AS OPTIC NERVE)

A

beyond chiasm, defects are homonymous

  • in tract, there are incongrous field defects, but visual acuity is spared
  • contralateral RAPD (b/c most pupillary fibers decussate at chiasm)
  • contralateral hemiparesis (posterior internal capsule)
41
Q

what is the anatomy of the lateral geniculate body?

A

intricate retinotopic organization

  • lesions make variety of field defects
  • visual field is homonymous and may be incongrous (since anterior) or congrous (posterior)
  • vascular lesions (more common) respect boundaries and cause sectoranopia (since unique blood vessels to each of 6 sectors, so ischemia and blindness to only one sector)
42
Q

what are lateral geniculate patterns of field loss?

A

these are “theoretical field defects”

-usually congrous and homonymous, but always sectoranopia

43
Q

typical defect in optic radiations?

A

homonymous quadrantanopia

44
Q

how do optic radiations reach calcarine sulcus?

A

parietal carries inferior field, and goes straight to calcarine
temporal carries superior field, and loops inferiorly (4 cm from start of temporal lobe) and then curves posteriorly to calcarine

45
Q

temporal optic radiations patterns of field loss

-anterior VS posterior lesions

A

AL: Meyer’s loop; right homonymous incomplete superior quadrantanopia (pie in sky; slightly incongruous)
PL: right homonymous incomplete superior quadrantonopia (but not respecting horizontal meridian)

46
Q

parietal optic radiations patterns of field loss

A

homonymous inferior visual field defects

-more congrous than temporal lobe (more posterior)

47
Q

what do lesions in occipital lobe usually cause?

  • posterior lobe
  • anterior lobe
  • intermediate
  • upper bank
A

lesions cause homonymous congrous defects (b/c so posterior)

  • PL: in central field, where 50% of cortex is devoted to central 10 degrees of field (so blind there)
  • AL: monocular field loss (monocular temporal crescent)
  • I: between 10 and 60 degrees
  • UB: causes lower field defect and vice versa
48
Q

what are calcarine cortex patterns of field loss?

A
  • macular sparring is common, but not exclusive, of occipital lobe lesions
  • -may be due to testing artefact, bilateral representation of macula, or incomplete damage to visual pathway (could just heal itself)
  • sparring of monocular temporal crescent from right occipital damage sparring most anterior aspect of striate cortex

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