Neuro-ophthalmology

4 Neuro-ophthalmology




Anatomy of the Visual Pathway


Optic nerve → chiasm → optic tract → lateral geniculate body → optic radiation → occipital lobe (Figure 4-1)






Optic nerve


composed of 1.2 million nerve fibers; approximately 1.5 mm in diameter, enlarges to 3.5 mm posterior to lamina cribrosa due to myelin sheath; located 3–4 mm from fovea; causes absolute scotoma (blind spot) 15° temporal to fixation and slightly below horizontal meridian; approximately 45-50 mm in length (1 mm intraocular, 25 mm intraorbital, 9 mm intracanalicular, 10–15 mm intracranial) (Figure 4-2); acquires myelin posterior to lamina cribosa
















Other areas











Physiology




Testing












Visual Field (VF) Defects (Figure 4-9)



Types

















Neurologic VF defects












Eye Movements under Supranuclear Control








Nonoptic reflex systems


integrate eye movements with body movements











Eye Movement Disorders




Horizontal Gaze Palsies






Acquired














Vertical Gaze Abnormalities









Nystagmus


Rhythmic involuntary oscillations of the eyes due to disorder of SEM system. Direction named after fast phase (brain’s attempt to correct problem), even though abnormality is noted with slow phase






Acquired Nystagmus


Pattern helps localize pathology, may have oscillopsia














Cranial Nerve Palsies (FIGURE 4-16)




Oculomotor Nerve (CN 3) Palsy






7 syndromes (Figure 4-17)



















Jun 4, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Neuro-ophthalmology
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