Neuro-opthalmology Flashcards Preview

Nervous System: Unit III > Neuro-opthalmology > Flashcards

Flashcards in Neuro-opthalmology Deck (12):
1

Aniscoria definition

  • difference in size (diamter) between a person's pupils
  • physiologic < 1 mm
  • pathologic = efferent nervous system disturbance to innervation of muscles of the iris
  • not a manifestation of vision loss

2

Nervous system control of pupil size

  • parasympathetic ==> sphincter muscle ==> pupil contraction
    • parasymp dysfxn ==> mydriatic pupil poorly responsive to light
  • sympathetic ==> radial muscle ==> pupil dilation
    • sympathetic dysfxn ==> miotic pupil poorly responsive to dark

3

Clinical evaluation of anisocoria

  • goal: try to determine which pupil is abnormal
  1. observe pupil sizes in light and dark
  2. observe pupillary response to light

4

Determining source of abnormal pupil constriction

  • greater anisocoria in dark + normal light response = smaller pupil is abnormal (due to symp dysfxn)
  • greater anisocoria in light + abnormal light response ==>
    • Tonic pupil due to parasymp dysfxn (if meet 3 criteria)
    • damage to iris (if 3 criteria not met + structural abnormality)
    • No tonic pupil or structural damage ==> ptosis and extraocular paresis = 3rd nerve palsy 

5

Criteria for Tonic Pupil

  • greater anisocoria in light  + larger pupil has poor response to light +
  1. pupil response to near target > ligth

  2. tonic dilation to distant target

  3. segmental palsy = partial iris sphincter constriction

  • common cause = diabetes

6

Characteristics of Horner Syndrome

  • disruption in sympathetic fibers ==> ptosis, miosis, anhidrosis
  • aniscoria = dark > light
    • normally pupillary response to light
    • dilation lag of miotic pupil
  • 1st order = brain stem (neuron from hypothalamus to cervical spinal cord)
  • 2nd order = spinal cord (cervical spinal cord to superior cervical ganglion)
  • 3rd order = carotid/cavernous sinus (neuron from superior cervical ganglion to iris sphincter)

7

Visual pathway

  • optic nerve ==> optic chiasm ==> optic tract ==>
  • LGN (lateral geniculate nucleus @ thalamus) ==> optic radiations ==> occipital cortex

8

Hallmakrs of visual field defects from neurologic visual pathway disturbances

  1. defect respects vertical and/or horizontal meridians (@ optic nerve or beyond)
  2. defect is homonymous = involves same area of visual field in each eye (@ optic tract or beyond)
  3. defect is a combo of homonymous defect + respect of vertical meridian (@ optic tract or beyond)

9

Findings w/optic nerve dysfxn

  • monocular vision loss = blurred, missing, dark
  • subject color vision loss

  • on exam:
    • vision loss of acuity, field, or both
    • unilateral defect ==> Marcus Gunn Pupil = afferent pupillary defect (AFD)
      • swinging flashlight test ==> less constriction/(apparent) dilation @ affected eye
    • optic nerve abnormality:
      • edema or pallor

10

Diplopia definition

"double vision"

11

Evaluation of diplopia

  1. Diplopia: binocular only? (i.e. goes away when one eye is closed)
    1. if yes = ocular misalignment
  2. Diplopia: horizontal vs. vertical
  3. Diplopia: worse w/any position of gaze
  4. Diplopia: worse @ near or distance viewing?

12

Common cause of oscillopsia

  • = appearance of movement of visual world due to an eye movement disturbance
  • common cause = nystagmus = involuntary rhythmic oscillation of eyes
    • pendular: slow-slow phases
    • jerk: fast-slow phases
    • mixed: slow-slow + fast-slow
    • can be localized @ CN VIII or CNS structures (usually @ brainstem/cerebellum)