Ophtho3- Blindness

  1. Describe the localization of afferent lesions causing anisocoria. (4)
    retina, optic nerve, optic chiasm, optic tracts
  2. Describe the localization of efferent lesions causing anisocoria. (3)
    • parasympathetic
    • sympathetic
    • mechanical
  3. With a unilateral afferent lesion causing anisocoria, there is ___________ because...
    • mild anisocoria; of unequal distribution of decussated fibers.
    • In the dark, pupils will dilate to equal sizes b/c sympathetic innervation is not affected
  4. When there is a unilateral pre-chiasm lesion, describe the resultant anisocoria.
    • ipsilateral pupil more dilated
    • [this is b/c of decussation of optic nerve fibers; each optic tract contains most fibers from the opposite eye]
  5. When there is a unilateral post-chiasm lesion, describe the resultant anisocoria.
    • contralateral pupil more dilated
    • [this is b/c of decussation of optic nerve fibers; each optic tract contains most fibers from the opposite eye]
  6. If there is a unilateral afferent lesion, the __________ pupil is more dilated
  7. Describe the ipsilateral (affected) pupil with a unilateral afferent lesion. (4)
    • absent direct PLR
    • positive consensual PLR (unaffected eye)
    • positive marcus gunn response
    • complete loss of vision on affected side
  8. Describe the results of an optic chiasm lesion.
    • complete destruction- vision and PLR are absent
    • partial destruction- loss of lateral/ peripheral vision, maintained central visual field
    • may be causes by pituitary tumors, very rare
  9. Describe the results of an optic tract lesion.
    • mild static anisocoria w/ contralateral pupil MORE dilated b/c of decussation [most of the fibers come from the opposite eye]
    • more mydriatic pupil in contralateral eye persists despite which eye is stimulated
    • lateral visual field loss on contralateral eye d/t loss of medial side retina's optic tract fibers
    • medial visual field loss on ipsilateral side d/t loss of lateral side of retina's optic tract fibers
  10. When might there be blindness without anisocoria?
    • lesions of the lateral geniculate nucleus, optic radiations, visual cortex
    • [b/c pupillary fibers split off before LGN]
    • clinically, patient may seem completely blind on contralateral side b/c 75-90% of fibers from that side are lost
  11. Anisocoria with _________ lesions are more marked than with _________.
    efferent; afferent
  12. Efferent lesions typically result in ___________.
    complete loss of pupil function
  13. Anisocoria resulting from an efferent lesions to the sympathetic innervation-->
    • static anisocoria with ipsilateral miosis
    • affected pupil does not dilate in the dark
    • anisocoria more dramatic in the dark, when normal pupil dilates
  14. Anisocoria resulting from an efferent lesions to the parasympathetic innervation-->
    • all lesions affect the ipsilateral pupil--> mydriasis and static anisocoria
    • pupils dilate in the dark to equal sizes b/c sympathetic innervation of contralateral eye is intact
  15. Describe a PS or CN III lesion in dogs and in cats.
    • Dogs: complete pupil dilation, ptosis, ventrolateral strabismus- internal and external ophthalmoplegia
    • Cats: as above OR they may have a selective lesion of the nasal or temporal short ciliary nerve, leading to a D-shaped pupil
  16. What is cavernous sinus syndrome?
    • CN 3, 4, 5, and 6 and autonomic nerves pass through the cavernous sinus
    • neoplastic or inflammatory masses result in progressive neurologic signs
  17. What are clinical signs of cavernous sinus syndrome? (6)
    • internal ophthalmoplegia (CN 3 PSN fibers)
    • external ophthalmoplegia (loss of ocular movement and ventrolateral strabismus)
    • ptosis (CN 3)
    • extorsion (lateral globe deviation- CN 3)
    • loss of corneal and ocular sensation (CN 5)
    • loss of globe retraction// corneal reflex (CN 6)
  18. 4 ways in which bilateral changes can affect vision.
    • opacification of the clear ocular media (cornea, aqueous, lens, vitreous)
    • failure of retina to process images
    • failure in transmission of image by optic nerve
    • failure in final processing of image by visual cortex in brain
  19. What can cause opacities of the cornea, leading to decreased vision? (5)
    pigment, scar, vessels (vascularization d/t chronic irritation), edema, cells
  20. What can cause increase opacity of the aqueous humor, leading to decreased vision? (3)
    severe aqueous flare (lipid, etc), hyphema (hypertension, etc), fibrin (d/t uveitis)
  21. What causes opacity of the lens, leading to decreased vision?
  22. What can cause increased opacity to the vitreous, leading to decreased vision? (3)
    flare, cells (infectious), blood (trauma, hypertension, retinal detachment)
  23. Most patients blinded by retinal degeneration will have ___________ and __________
    visible changes on fundic exam; abnormal PLRs
  24. What are signs of retinal lesions that lead to decreased vision? (4)
    • vessel attenuation
    • tapetal hyperreflectivity
    • optic nerve atrophy/ pallor
    • pigmentary disturbances and accumulations
  25. What are nutritional retinal diseases? (4)
    • taurine deficiency in cats--> feline central retinal degeneration
    • equine motor neuron disease
    • Vit E deficiency--> hunting dogs
    • Vit A deficiency--> cattle
  26. Lesions causing blindness with loss of the PLR. (2)
    • optic nerve atrophy
    • optic nerve elevation (papilledema- usually vision still present, papillitis)
  27. What are examples of some optic nerve/ conducting system lesions? (7)
    • optic nerve hypoplasia
    • granulomatous encephalomyelitis
    • CDV- related encephalitis
    • FIP meningoencephalitis
    • systemic mycoses
    • optic chiasm tumors
    • traumatic optic nerve avulsion (proptosis)
    • [vision loss, normal PLR, normal electroretinogram--> dx of exclusion, but you know it's in the conducting system b/c of big 3 things i just said]
  28. Describe cortical blindness.
    • blindness with normal PLR [b/c PLR pathway branches off before LGN]
    • lesions in LGN, optic radiations, or visual cortex
  29. What are causes of cortical blindness? (7)
    • hydrocephalus
    • cerebral malformations
    • distemper encephalomyelitis
    • systemic mycosis
    • GME
    • hepatoencephalopathy
    • head trauma
Card Set
Ophtho3- Blindness
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