Neuro-Ophthalmology Flashcards
Pupillary Disturbances
- Abnormal reaction to light or dark
- 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)
Anisocoria
interrupt Parasymp
Interrupt Symp
Interrupt parasymp: mydriatic pupil (abnormally dilated), poorly responsive to light
Interrupt symp: miotic pupil (abnormally constricted); poorly responsive to dark
Clinical evaluation of anisocoria
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.
Determining cause of anisocoria
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
Small pupil with poor reaction to dark
–>sympathetic dysfunction–>dilation lag, ptosis +/- anhidrosis= Horner syndrome
Large pupil with poor reaction to light
Either:
1. abnormal structure=iris damage
- Parasymp dysfunction:
a. ) tonic dilation, segmental palsy, light-near dissoc= Tonic
b. )ptosis, EOM paresis=3rd n palsy
Horner Syndrome
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
Tonic pupil
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
How do we know visual field loss is neurologic?
- will affect vertical or horizontal meridian
- homonymous visual field defect (same side, both eyes)
- or combination of 1 and 2
Lesion location and field loss
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
Retinotopy
1,2,5,6,9,10 –> right calcarine sulcus
3,4,7,8,11,12 –> left calcarine sulcus
Neurologic Visual Pathway
optic nerve–>chiasm–>optic tract–> lateral geniculate nucleus in thalamus–>optic radiations–>occipital cortex.
Optic Nerve dysfunction
Complaints:
- monocular vision loss (blurred, missing, dim)
- 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)
APD: afferent pupillary defect
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
Diplopia
- 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)
questions for diplopia
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?
Oscillopsia
- appearance of movement of the visual world
- Nystagmus-involuntary eye movements
- Nystagmoid movements–don’t meet nystagmus definition
Nystagmus
2 phases (slow or fast), 3 types:
pendular: slow slow
jerk: fast slow
mixed: slow slow, fast slow
Direction: horizontal, vertical, torsional,mixed
Downbeat nystagmus example. Why?
-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.
