Lecture 10 Visual Systems Flashcards
What are the layers of the retina?
Internal limiting membrane Nerve fiber layer: axons of ganglion cells Ganglion cell layer Inner plexiform layer: synaptic zone for bipolar, amacrine and galngion cells Inner nuclear layer Outer plexiform layer Outer nuclear layer: soma of receptors External limiting membrane Layer of rods and cones Pigmented epithelium
Which photoreceptor is absent in fovea centralis?
rods
Clinically, lesions of the visual system are always described int terms of what?
their visual field deficits from the perspective of the patient’s right or left
What does the visual field project onto the retinal field?
inverted and reversed
What constitutes the primary pathway for visual invormation?
retinogeniculocalcarine pathway
Where do fibers of the hemiretina course in the optic chiasma ? (First rule of retinotopic projection)
Fibers from the temporal hemiretina do NOT cross in the optic chiasma
Fibers from nasal hemiretina cross in the optic chiasma
What is the Rule of L’s?
information from the Lower hemiretina projects to the Lateral part of the Lateral geniculate body, the Loop of meyer and the Lingual gyrus
What is maintained throughout the system from the retina to visual cortex?
retinotopic organizations
Describe homonymous visual fields
left nasal visual field = right temporal visual field
Describe heteronymous visual fields
refer to noncorresponding visual fields
What is hemianopia?
blindness of one-half of the visual field
What is quadrantanopia?
blindness of a quadrant of the visual field
Most common is upper nasal quadrant of one eye and the upper temporal quadrant of the other eye
Cant see out of one eye
unilateral lesion of optic nerve = monocular blindess
Binasal hemianopia
bilateral lesion of lateral aspect of the optic chiasma
Heteronymous blindness in nasal fields of each eye
Unilateral nasal hemianopia frequently due to what?
atherosclerosis of the internal carotid arteries
Lateral aspect of optic chiasma necrosis
Nasal hemianopia of the ipsilateral eye
describe right hemianopia of the left eye
blindness of right visual field (nasal field) of the left eye
Due to lesion of lateral aspect of the left optic chiasma
Bitemporal hemianopia
Midline lesion of medial portion of the optic chiasma
Heteronymous deficit usually caused by pituitary tumors
Contralateral homonymous heminaopia
unilateral lesions of the lateral geniculate body, complete optic radiations, or visual cortex
Cut on right side = left visual field gone
Contralateral superior quadrantanopia
Unilateral lesions of the loop of Meyer
Tumor in posterior temporal lobe
Left Superior quadrant gone = right loop of Meyer lesion
Incongruent contralateral homonymous hemianopia with macular sparing
unilateral lesion of the visual cortex
Obstruction of PCA
What optic reflex does tabes dorsalis/ syphilis interrupts?
light reflex
Pretectum interference
What Optic reflex does horner’s syndrome interrupt?
sympathetic neurons to cause pupillary dilator mm to dilate pupil
What type of response is accommodation?
cortically mediated visual respone
What is the triad of accommodation?
convergence of vision, pupillary constriction and thickening of the lens
What is Argyll-Roberston pupil?
result of syphilis infection
Pupils unreactive to light but constrict during accommodation
Destruction of pretectum
What is Holmes-Adie pupil
lesion of ciliary ganglion
pupils unreactive to light but slow to react to accommodation
