Flashcards in Visual Field 4 Deck (25)
what kind of defect will lids/ptosis make
will give a superior defect/depression bc they are in front of the nodal point
-sup defect secondary to location to nodal point
how does the corneal dystrophy look
MD, total dev, pattern dev?
what kind of vf loss?
total deviation decreased
pattern deviation looks normal
diffuse visual field loss secondary to cornea irregulatirty
how can cataracts affect vf
-usually associated w/ generalized overalld epression, esp nuclear opacities
-can be assoicated w/ scotomas or localized depression depending on location and density
what does a posterior cortical do to vf
diffuse overall field loss, all #s down
what does a posterior subcapsular cataract do?
right on the axis, so field loss is closer to fixation and will look like a relative scotoma
what does a big cataract in the anterior lens do? posterior lens?
anterior lens: it will be before the nodal point and therefore cause a field loss in the same relative area (inf lens gives inf defect)
posterior lens: may or may not be found in front of the nodal point, so it will be harder to predict the defect location
where are the four main territories for defects after the nodal point?
territory 1: retinal rods and cones
territory 2: retinal ganglion cells and axons, NFL and optic nerve
territory 3: optic chiasm, usually cuased by pituitary adenomas
territory 4: optic tract, LGN, optic radiations, visual cortex
in the retinal defect position, how will the vf defect look
vf defect will be inverted and reversed from the retinal defect (territory 1)
what are some retinal issue that can create vf defects
macular degeneration: geographic macular degeneration "retinal rot"-field loss close to fixation, prob dense central scotoma
-macula hole (test w/ amsler 20/200)
retinal detachment: if detachment sup, get inf depression, usually sloping margins
retinitis pigmentosa: bone spicules start mid-periphery, usually btwn 25 and 50 from fixation, gives a ring scotoma as a result, night blindness
waht do lesions interrupting the papillomacular bundle produce
either a central scotoma or a centrocecal (cecocentral) scotoma
how does a central scotoma develop?
how does a centrocecal scotoma develop?
central: develop when the macular ganglion cells or their axons malfunction
centrocecal: caused by involvement of ganglion cells or axons rising both from the fovea and from the retina btwn the fovea and the optic disc
how do arcute bundles look
what do lesions interrupting the arcuate bundle produce?
surround the papillomacular bundle and are arcuate (arching) nerve fibers originating from above, below, and temporal to the fovea and converging upon the sup and inf poles of the optic nerve
-bundles sep into upper and lower portions which are divided by a line that corresponds to the nasal horiz meridian
-produce either arcuate defects or portions of arcuate defects
the fibers nearest the optic nerve travel most ______ in the retina and enter the optic nerve most _______
-this is why the last thing to go in glauc is the far periphery, but doesnt explain why the field loss in glauc starts as a paracentral anywehre btwn 5 and 20 degrees of fixation
how do nerve fiber bundles converge in a temporal wedge?
nerve fiber bundles originating in the ganglion cells nasal to the optic disc converge upon the disc radially in a wedge like pattern
what meridian do optic nerve defects respect
usually respect the horizontal meridian nasally and not temporally
-do not respect the vertical
what is the most common eye conditions which create territory 2 defects
most common is glaucoma
-nasal step 5%
-both paracentral and nasal step 10%
-temporal wedge 5%
what are some eye conditions which create territory 2 defects
myelinated nerve fibers
drusen on the ONH
ischemic optic neuropathy
what are territory 3 defects caused by?
where is the pituitary located related to the chiasm?
pituitary is located inf to the chiasm
what causes a classic bitemporal hemianopsia?
tumors press on both the inf chiasm and its blood supply and produce that
what do territory 4 defects produce
occipital cortex lesion are usually ______
optic tract and radiations produce _______ hemianopsia
how do you name the field loss
by the field that is missing
ex. right part of field missing it is right homonymous and damage will be on the left side of the brain
what is the frequency doubling controlled by
-M cells responsible for low-contrast, high temporal frequency stimulus detection
M cells make up ____% of the total number of axons in the eye
-my cells are ___% of the total axons in the eye