Visual Field Defects Flashcards
visual field
area of space perceived by the eye
perimetry
-used in the general assessment, diagnosis, prognosis and to monitor progression of opthalmologic and neurologic conditions
basic concepts
- temporal field to 90 all the way over
- nasal to 60/70
- top and bottom 60-70
- 17/18 degrees is optic nerve
- 10 degrees from macula is most clear vision
- nasal retina receives temporal vision and vice versa
- macula/fovea is vertical meridian
binocular visual fields
- 60 overlaps on both sides to make binocular vision
- extra beyond 60 on each lateral side is monocular
- temporal crecsent
traquair’s island of vision
vertical island with 20/20 vision at the top, where the macula is
-z is sensitivity
visual sensitivity/threshold
- depends on several factors
- age
- attention level
- refractive status
- pupil size
- media opacities
- characteristics of stimulus:
- size
- intensity
- color
- duration
- movement
kinetic perimetry
- elephant vs mosquito
- dimmer and smaller at top of island
- can see brighter and bigger at bottom of island
static perimetry
- comes from top of island to bottom
- how computer does it
- you hit button when you see it
strategies for visual field testing
- confrontation
- amsler grid
- tangent screen
- goldmann perimeter
- humphrey perimeter (automated)
confrontation visual fields 1
- inexpensive, fast, practive
- examiner dependent- no standardized way of doing it, as sophisticated as examiner and examinee, many different ways
- examinee dependent-can be tailored for each pt, may be only test you can do in children, lethargic or inattentive pts
confrontation visual field-general and practical rules
- well lit room
- examiner at arms length away
- examiner situated at same level/height as pt
- pt covers one eye- test Right, cover left first with palm of hand and looks at examiners eye-fixation/attention
- examiner closes contralateral eye (Right)
- stimulus is presented half way from examiner/examinee distance
- use different strategies and keep in mind characteristics of field you are plotting
confrontation visual fields-strategies
- use examiners face (tests central 10-15 degrees, central scotomas, hemianopias)
- finger counting (psuedo-static, consider temporal>nasal, simultaneous stim)
- finger moving, hand moving (peripheral, monocular temporal crescent)
- red object-sensitivity
- palms side by side at midline- hemianopias
amsler grid
- held at 33 cm
- tests 10 central degrees of VF
- pt reports any area missing, blurred, distorted
- pt can monitor VF at home and report any change
tangent screen
- manual kinetic
- examiner at 1 meter, can look at examinee to assure good fixation
- tests central 20 degrees of VF
- may be used as pseudo static
goldmann
- manual kinetic
- pt faces bowl, examiner assures fixation from peephole
- tests entire VF
- primarily kinetic stimuli, can do static
- stimulus size, light intensity, isotoper
humphrey
- automated
- pt faces bowl, fixation is 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)
scotoma
-portion of VF thats missing
arcuate
arc like shape defect produced by retina nerve fiber bundle damage
altitudinal
- superior or inferior defect that respects horizontal median
- splits horizontally
hemianopia
- nasal or temporal defect that respects the vertical median
- splits vertically
quadrantanopia
-affects one quarter
complete/incomplete
-extension of type of defect
relative/absolute
-to the type of stimuli
homonymous
- defect is on the same side of both eyes
- right side of both eyes
heteronymous
- defect on different side
- right side of right eye and left side of left eye
congruous
-defect is similar in both eyes
incongruous
defect is different in both eyes
retina
- axons of ganglion cells converge to form the optic nerve
- a vertical line that crosses the fovea constitutes the nasal-temporal demarcation
- the horizontal raphe divides the retina into superior and inferior
- right next to macula are HOV- straight to optic nerve
retina-pattern of field loss
- may also have decreased VA
- general or focal field deficits
- focal defects correspond to visual lesions
- central scotoma from foveal lesion
- arcuate defect in glaucoma
optic nerve patter of field loss
- decrease VA and color vision
- RAPD in asymmetric process
- no pathognomonic VF defect, but have:
- altitudinal defect in NAION (ischemia)
- central depression
- central scotoma-hereditary, toxic, nutritional
- see slides
projection of nasal visual fibers
- temporal fibers carrying nasal information don’t cross
- nasal carrying infratemporal cross above
- nasal carrying supratemporal cross below and go through wilbrand’s knee- lesion there will get R optic nerve and nose supratemporal
projection of the papillomacular bundle
- macular fibers form a chiasm within the chiasm
- macular fibers that cross the optic chiasm do so in its central and posterior portion
- 20/20 point crosses to both hemispheres
classic field loss in center chiasm lesion
- bitemporal hemianopsia (right of right eye and left of left eye)
- a little farther behind only does crescents on both sides
junctional syndrome
- willibrands knee
- whole right eye and pie of left
- just before knee is total right eye
lesion right after chiasm R crossing to L
nasal half of left eye and 2/3 of right half of right eye
-homonymous
(right eye is less because after crossing over)
anterior chiasmal syndrome
- ipsilateral optic neuropathy
- decrease VA, color vision, RAPD
- contralateral junction scotoma with normal VA and color
body of the optic chiasm
- bitemporal field defect
- quad, hemi, central, peripheral
- pituitary adenoma
rules of retrochiasmal visual pathway
- beyond optic chiasm, lesions to the visual pathway produce homonymous field defects
- the more posterior the lesion, the more congruous
optic tract
- visual fibers maintain their relative position
- pupillary fibers depart optic tract into midbrain
LGN
- retinal ganglion cells synapse
- fibers rotate 90 degrees medially
- intricate retinotopic organization, lesions produce variety of defects
- VF tend to be homonymous and may be incongruous
- vascular lesions tend to respect these boundaries and cause a sector defect (theory)
optic tract pattern of field loss
- beyond chiasm, homonymous
- optic tract- incongruous
- hemi, quad, scotomatous, complete/incomplete
- VA spared
- contralateral RAPD
- contralateral hemiparesis
optic radiations
- parietal carry inferior and go straight back
- temporal carry superior and go front then back
temporal optic radiations: pattern of field loss
- anterior lesion in Meyer’s loop: right homonymous incomplete superior quad- pie in the sky
- posterior lesion- right homonymous complete superior quad (doesn’t respect horizontal meridian)
parietal optic radiations: pattern of field loss
- homonymous inferior visual field defects are characteristic
- more congruous than temporal lobe lesions
occipital lobe and visual cortex
- lesions in general cause homonymous congruous defects
- posterior lobe lesion (central field) 50% of cortex devoted to the central 10 degrees of field
- anterior lobe lesion, monocular field loss
- intermediate lesion between 10 and 60 degrees
- upper bank lesion causes lower field defect and vice versa
calcarine cortex loss
- doesn’t cut out total left field at macula- still remains circular-macular sparing
- can cause variety of visual field defects- sparing of crescent
- inferior altitudinal central scotomas, bilateral homonymous hemianopic central scotomas with macular sparing
