Day 12 (4): Neuro-Ophthalmic Evaluation Flashcards
What are the pertinent symptoms elicited in the history of neuro-ophthalmology patients?
- Abnormal vision
- Double vision
- Eye deviation
- Unequal pupils (anisocoria)
- Facial asymmetry: ptosis, Bell’s palsy, spasm
- Facial or eye pain
What are the common descriptors used to describe abnormal vision?
- Blurred or dim
- With a cloud/screen/curtain
- Blind
- Distorted
- Poor color vision
- Difficulty of movement and ambulation due to abnormal vision
What are the pertinent points in the history of pts presenting with abnormal vision?
- Etiology: differentiate using Pinhole Test
- Optical: IMPROVES with pinhole
- Neurosensory: NO improvement - Onset: Sudden or Gradual
- Sudden: occurred without warning
- Gradual: subtle and insidious progression - Duration
- Seconds: Papilledema, Transient Visual Obscurations
- Minutes: Transient Ischemic Attack, Atherosclerosis, Carotid Artery Disease
- Hours: Migraine
- Days: Optic neuritis/neuropathy - Timing or Progression
- transient, fluctuating or constant
- improving or worsening
Remember:
Time Course (onset and duration): most important clue to the etiology
How is strabismus classified according to the angle of deviation in the different gaze directions?
COMITANT/NON-PARALYTIC
- misalignment or angle of deviation is EQUAL in ALL gaze directions (within 5 PD)
- NO under- or overaction of EOMS
- FULL ocular motility (ductions and versions)
- NORMAL motor evaluation
INCOMITANT/PARALYTIC
- misalignment or angle of deviation VARIES with the gaze direction
- SECONDARY deviation (affected eye is fixating) is GREATER than the PRIMARY deviation (normal eye is fixating)
- INVOLVES under- or overaction of EOMS
- angle INCREASES with gaze TOWARDS the affected muscle
- angle DECREASES with gaze AWAY from the affected muscle
Types based on the EOMs involved:
A. Horizontal Muscle Incomitance
- involve horizontal muscles (MR, LR)
- horizontal angle of deviation in L gaze is different from that in R gaze
- affected eye is the eye with the UNDERacting horizontal EOM
- NO such thing as overacting horizontal muscle
B. Cyclovertical Muscle Incomitance
- involve cyclovertical muscles (SO, IO, SR, IR)
- vertical angle of deviation is unequal in the different vertical and oblique gaze directions
Types based on EOM pathology:
A. PARALYTIC
- UNDERaction or paresis of the involved muscle in that direction of gaze
B. RESTRICTIVE
- OVEraction or tightness of the antagonistic muscle in that direction of gaze, preventing the eye from moving towards that gaze direction
How is double vision characterized?
MONOCULAR DIPLOPIA
- RESOLVES when AFFECTED eye occluded
- PERSISTS when UNAFFECTED eye occluded
- due to pathologies that affect transmission and focusing of light into the fovea
BINOCULAR DIPLOPIA
- RESOLVES when EITHER eye is occluded
What is monocular diplopia?
- occurs when TWO images are seen by a SINGLE eye
- RESOLVES when AFFECTED eye occluded
- PERSISTS when UNAFFECTED eye occluded
- may be unilateral or bilateral
- may even involve triplopia or polyopia
Causes:
1. Eyelid abnormalities
2. Tear film dysfunction
3. Refractive errors and corneal malformations
4. Media opacities: cornea, aqueous, vitreous
5. Iris abnormalities
6. Lens shape and position abnormalities
7. Maculopathies: edema, CSR, membranes
8. Foreign bodies
9. Cerebral polyopia
10. Psychogenic: diagnosis of exclusion
Pathophysiology:
1. Light Diffraction
- images of a single object fall on BOTH foveal and extrafoveal area resulting in multiple images of different clarity:
+ foveal: clear and crisp
+ extrafoveal: hazy and ghost-like
- the brain’s attempt to fuse the two images result in diplopia
- resolves with PINHOLE: focuses light on the fovea and prevents light from reaching extrafoveal areas
- Metamorphopsia
- distortion of retinal images
- due to maculopathies: edema, CSR, membranes
- does NOT resolve with pinhole - Cerebral Polyopia
- BILATERAL monocular diplopia:
+ equal image clarity
+ no overlapping of images
- diplopia PERSISTS WHICHEVER is closed
- perception of multiple images due to pathologies in the central visual pathway or visual cortex
What is binocular diplopia?
- RESOLVES when EITHER eye is occluded
- due to misalignment of visual axes of the eyes
- images fall on exceedingly DISPARATE areas OUTSIDE of the Panum’s Area
+ fixating eye: on the fovea
+ deviated eye: on an extra-foveal area - usually due to involvement of the EOMs and the innervating cranial nerves
- angle of deviation and the separation of the images is GREATEST when the object is viewed in the direction of the field-of-action of the paretic muscle
- may be transient (MG) or constant (neurologic)
Remember:
1. Cortical fusion of two disparate retinal images can only occur if they BOTH fall in the Panum’s Area (meaning only a small degree of retinal disparity).
- Stereopsis
- results from the FUSION of two slightly DISPARATE retinal images that both still fall WITHIN the Panum’s Area - Diplopia
- due to NON-fusion of two overly DISPARATE retinal images that already fall OUTSIDE the Panum’s Area
What are the components of the basic neuro-ophthalmologic eye exam?
- Observation: posture, behavior, appearance
- Visual Acuity: BCVA, PHVA
- Refraction: BCVA
- Pupillary exam
- Motility testing
- Visual field testing
- Ophthalmoscopy
- Neurologic exam
How is visual acuity tested?
- Test with no correction (UCVA)
- If abnormal, repeat testing with pinhole (PHVA) or the best available correction (BCVA)
- Test for both distance and near VA
Discuss the components of the pupillary exam.
Normal Pupil
- balance between the parasympathetic and sympathetic innervation
- round
- 2 - 3 mm symmetric
- equally briskly reactive to light
Components:
1. Direct light reflex:
- response of the examined pupil to light shone directly on that eye
- Consensual light reflex:
- response of the contralateral pupil to light shone on one eye - Swinging light test (RAPD)
- detect a pupillary AFFERENT pathway defect - Anisocoria tests
- detect a pupillary EFFERENT pathway defect
What is an RAPD and how is it tested?
Relative Afferent Pupillary Defect/Marcus Gunn Pupil
- Defect in the Pupillary pathway on the Afferent side Relative to the other eye
- NOT observed in defects anterior to the retina and posterior to the optic tract
- requires two eyes BUT only one working pupil
Test:
Swinging Light Test
- sensitive and objective method of detecting unilateral or bilateral but asymmetric defects along the pupillary light pathway
- patient is placed in a dark room and a bright light is alternately swung between the two eyes while the patient fixates at a distance
Grading:
+1 or +2: barely detectable; initially no change but gradually dilates
+3 or +4: apparent and immediate dilation
What is Anisocoria and how is it diagnosed?
UNEQUAL pupil size
- Physiologic/Essential (20%)
- size difference </= 0.5 mm
- no changes in the size difference in both light and dark conditions - Pathologic/Acquired (80%)
- size difference > 0.5 mm
- anisocoria decreases or increases depending on light conditions
Tests:
1. Pupillary light reflex of each pupil
2. Measure pupil size in both bright and dim conditions
Results:
1. Sympathetic lesions
- SMALLER pupil is pathologic
- EQUALLY reactive to light
- Dark: anisocoria increases
- Light: anisocoria decreases (reversal)
- Parasympathetic lesions
- LARGER pupil is pathologic
- SLUGGISH constriction in affected eye
- Dark: anisocoria decreases (reversal)
- Light: anisocoria increases
What are the levels of EOM motor control?
SUPRANUCLEAR
1. Frontal Eye Fields: saccades, vergence
2. Parieto-Occipito-Temporal Junction: pursuits
NUCLEAR
- location of the cranial nerve nuclei responsible for eye movements
- pre-motor coordination of conjugate eye movements
- coordination of the vestibulo-ocular system
1. PPRF: Horizontal gaze center
2. riMLF/INC: Vertical gaze center
3. Vestibular nucleus: VO reflex
4. Motor nuclei of III, IV and VI
INFRANUCLEAR
1. Oculomotor, Trochlear and Abducens nerves
2. Neuromuscular junctions
3. EOMs
What are the components of the motility test?
- Examine in primary gaze
- Examine binocular (version) movement in the horizontal, vertical and oblique gazes
- note for deviations, under- or overshooting
- if with noted abnormalities, may test
monocular (duction) movements individually - Check for vergence
- Check for both saccades (fast movements) and pursuits (slow tracking movements)
What are the ancillary tests used to examine strabismus patients?
- done when a misalignment or deviation is observed in the motility exam
- Hirschberg’s/Corneal Light Reflex Test
- qualitative assessment of eye deviations - Cover and Uncover Test
- diagnose tropias and uncover phorias - Prisms Tests
- quantify angle of deviations in a tropic or phoric eye - Red Glass Test
- diagnose diplopia - Bielschowsky Three Step Test
- isolate and localize the paretic muscle causing a cyclovertical eye deviation - Forced Duction Test
- toothed forceps or cotton-tipped applicator is used to grasp the conjunctiva and passively move the anesthetized eye towards a particular gaze direction
- if no movement or if resistance is noted: RESTRICTIVE strabismus
