Flashcards in Module 5: Visual Pathway Deck (70)
Anatomy of the visual pathway
Eye-optic nerve-chiasm-optic tract-lateral geniculate-optic radiation-occipital
Examination of visual system
Visual acuity, Visual field, Pupillary light reflex, Extraocular muscles & Fundoscopy "VV PEF"
To assess for macular degeneration
The optic nerve: etiology of dysfunction
Compression, inflammation, Infarction & Alterations in blood supply "CIAA"
Decussation of visual and pupil fibers. Multiple neighboring influences: ______, ______, ______ & ______.
Optic chiasm. CSF, Vascular, Skull & Pituitary.
In __________, the defects become homonymous, on the same side as the visual space. A ___________ localizes only to the retrochiasmal area.
Retrochiasmal lesions. Complete homonymous hemianopsia.
In retrochiasmal lesions, ________ are identical in size, shape and depth: applies only to _________. Imply a more _______: cortical anatomy.
Congruous lesions. Incomplete hemianopsia. Posterior lesion.
Lesion in congruous homonymous hemianopsia
Lesion in incongruous homonymous hemianopsia
Retrochiasmal field defects: occipital lobe
Homonymous quadrant, Temporal crescent & Macular sparing "HTM"
Retrochiasmal field defects: lateral geniculate
Retrochiasmal field defects: temporal lobe
Homonymous "pie in the sky"
Carry fibers to the LGB. Carry pupil fibers to the midbrain enlage of _________ via the brachium of the superior colliculus. ________ field defects.
Edinger Westphal. Incongruous.
Located in the posterolateral thalamus. Retinotopic organization: layer _____ from contralateral eye. Layer ____ from ipsilateral eye. The _____ projects to 50% of the LGB.
Lateral geniculate. 1, 4 & 6. 2, 3 & 5. Fovea.
Meyer's loop: temporal lobe. Parietal lobe path direct. Majority of fibers from other thalamic nuclei.
Striate cortex V1. Caudal 50% encode central __ degrees. Middle 40% encodes ___ degrees. Rostral 10% encodes __ degrees. (The temporal crescent)
Occipital cortex. 10. 10-60. 60-90.
The where pathway
The what pathway
Confrontation, Patient drawing & Bowl perimetry "CPB"
Bowl perimetry. Kinetic: ________.
Bowl perimetry. Static: ________.
May occur unilateral or bilateral. Poor vision with small nerve. May occur in isolation or with ocular or forebrain abnormalities. When bilateral and accompanied by poor vision and nystagmus, usually other developmental abnormalities observed.
Optic nerve hypoplasia
Disturbance of axonal metabolism in the presence of a small scleral canal. Increase in size with time, more visible with time due to calcium deposition. Associated visual defect at times not noticed by the patients.
Optic disc drunsen
Possible association with increased abuse of alcohol and drugs. Phenytoin, quinine, alcohol, LSD and cocaine. Maternal diabetes. Perimetry: irregular borders, stable overtime.
Optic nerve hypoplasia
Central cup absent, anomalous vascular branching, vessels arising from the apex of the nerve, retention of vascular detail. Transillumination and irregular disc margin. No hemorrhage or cotton wool spots.
Disc drunsen (ophthalmoscope)
Causes are protean. Papilledema: elevated ICP and disc edema. Space occupying lesion. Disruption of axoplasmic flow at the level of the lamina cribrosa: fast and slow. Subsequent hypoxia and vascular changes on the disc. May take hours to resolve.
Swollen optic nerve
Elevated ICP: headache,nausea,TOV & tinnitus. Normal neurologic exam. Elevated CSF pressure with normal parameters & normal imaging to exclude mass lesion or dural sinus thrombosis. Transient obscurations of vision. Neck stiffness. Neck, shoulder or arm pain. Diplopia (CN VI palsy)
Idiopathic intracranial hypertension
Acquired optic nerve disease without disc edema. Painless progressive loss of vision over first week. Predominantly monocular. Preceding viral illness & sinus symptoms. Loss of acuity, abnormal visual field, color vision & afferent pupil defect.
Most common cause for disc swelling over age of 50.
Ischemic optic neuropathy.