Neuro-Ophthalmology

Question 1

Pupillary Disturbances

Answer 1

1. Abnormal reaction to light or dark
2. Anisocoria (diff sized pupils)

Normal pupils:
Anisocoria 0-1mm
Anisocoria must be the same in all levels of light
React normal to light and dark

Anisocoria is NEVER the result of vision loss.
-Due to parasympathetic or sympathetic damage.
Parasympathetic (norm): constriction–sphincter constricts
Sympathetic: dilation–radial dilates (occurs in dark; w/ fear)

Question 2

Anisocoria
interrupt Parasymp
Interrupt Symp

Answer 2

Interrupt parasymp: mydriatic pupil (abnormally dilated), poorly responsive to light

Interrupt symp: miotic pupil (abnormally constricted); poorly responsive to dark

Question 3

Clinical evaluation of anisocoria

Answer 3

Determine which pupil is the abnormal pupil, the smaller one or the larger one.
Step 1: Observe the size of the pupils in the light and the dark and
Step 2: Observe pupillary response to light

If the anisocoria is greater in dark and both pupils have a normal light response, then the smaller pupil is the abnormal pupil, and this finding is likely due to sympathetic dysfunction, which can be due to a Horner syndrome

If the anisocoria is greater in the light and the larger pupil has a poor response to light, then the larger pupil is the abnormal pupil.

Question 4

Determining cause of anisocoria

Answer 4

Light-near dissociation:Better pupillary constriction to a near target than to light

Tonic dilation to a distant target

Segmental palsy (iris sphrincter with partial constriction in some areas

If these 3 are present, pt has a tonic pupil due to parasymp dysfunction. If not, look for structural abnormality (if present, cause is damage to iris)–not nervous system.

If none of these: look for ptosis and extraocular muscle paresis: 3rd nerve palsy

Question 5

Small pupil with poor reaction to dark

Answer 5

–>sympathetic dysfunction–>dilation lag, ptosis +/- anhidrosis= Horner syndrome

Question 6

Large pupil with poor reaction to light

Answer 6

Either:
1. abnormal structure=iris damage

2. Parasymp dysfunction:
   a. ) tonic dilation, segmental palsy, light-near dissoc= Tonic
   b. )ptosis, EOM paresis=3rd n palsy

Question 7

Horner Syndrome

Answer 7

disruption of sympathetic fibers resulting in ptosis, miosis, anhidrosis

Anisocoria will be greater in the dark; normal pupillary response to light, dilation lag of miotic pupil.

First order: hypothal to cervical spinal cord
Second order: cervical spinal cord to superior cervical ganglion
third order: superior cervical ganglion to the iris sphincter muscle and eyelid

Question 8

Tonic pupil

Answer 8

disruption of parasympathetic fibers at and beyond ciliary ganglion.

• Anisocoria greater in light, large (abnorm) pupil will have poor response to light
• segmental constriction to light is present.
• better constriction to near target viewing during accommodation will be present compared to the constriction that occurs with light stimulus

Common cause: diabetes

Question 9

How do we know visual field loss is neurologic?

Answer 9

1. will affect vertical or horizontal meridian
2. homonymous visual field defect (same side, both eyes)
3. or combination of 1 and 2

Question 10

Lesion location and field loss

Answer 10

chiasm: field loss in outer right and outer left vertical meridian

left optic radiations (Meyer’s loop): vertical meridian/slice of pie homonymous defect

left inferior occipital: horizontal and vertical, punched out, homonymous

Question 11

Retinotopy

Answer 11

1,2,5,6,9,10 –> right calcarine sulcus

3,4,7,8,11,12 –> left calcarine sulcus

Question 12

Neurologic Visual Pathway

Answer 12

optic nerve–>chiasm–>optic tract–> lateral geniculate nucleus in thalamus–>optic radiations–>occipital cortex.

Question 13

Optic Nerve dysfunction

Answer 13

Complaints:

1. monocular vision loss (blurred, missing, dim)
2. decreased brightness or color vision impaired

Exam:
1. vision loss (acuity, field, or both)
*2. Afferent pupillary defect (APD) (problems getting light to brain, not actually a problem with pupil)
3. Color vision loss
*4. Abnormal optic nerve
(edema, pallor)

Question 14

APD: afferent pupillary defect

Answer 14

afferent– occurs w/ defect of pathway prior to synapse of retinal ganglion in LGN (thal)

hallmark of optic nerve or optic tract disturbance

Use swinging flashlight test to detect APD:
If one of the pupils dilates each time the light is shined in that eye after swinging from the other, then afferent dysfunction is present

Question 15

Diplopia

Answer 15

• double vision
• binocular? if yes, misalignment (neurogenic or mechanical)

Localize ocular misalignment:
nerve (3,4,6)
eye (displaced)
junction, neuromuscular (myasthenia)
muscle (thyroid assoc opthalmopathy, rare myopathies)

Question 16

questions for diplopia

Answer 16

1. is it binocular (goes away when either eye is closed) or monocular?
If binocular: then ocular misalignment
2. is it horizontal or vertical?
3. is it worse left right up or down?
4 . is it worse near or distance?

Question 17

Oscillopsia

Answer 17

• appearance of movement of the visual world
• Nystagmus-involuntary eye movements
• Nystagmoid movements–don’t meet nystagmus definition

Question 18

Nystagmus

Answer 18

2 phases (slow or fast), 3 types:

pendular: slow slow
jerk: fast slow
mixed: slow slow, fast slow

Direction: horizontal, vertical, torsional,mixed

Question 19

Downbeat nystagmus example. Why?

Answer 19

-localizable to cervical medullary junction
-Arnold Chiari malformation
(cerebellar flocculus normally inhibits anterior( not posterior) semicirc canals; when disinhibited the eyes drift up then fast corrective downward strokes.