Pupils Flashcards
What are the 4 fundamental rules of pupils?
- Pupils are equal members of a team
- The pupil control system has two “managers”
- Pupils are subject to a near triad or synkinesis
- The pupils reflect the body in which they live
Pupils do what to allow better focus?
Constrict
How is pupillary constriction achieved?
By the pupillary light reflex
What percent of the population has physiological anisocoria?
20%
If anisocoria is physiological, does the level of illumination change the amount of anisocoria?
No
What are the two “pupil managers”?
Para-sympathetic system
Sympathetic system
What is the (pupil) target of the para-sympathetic system?
Iris sphincter
What is the neurotransmitter for the system responsible for miosis of the pupil?
Acetylcholine
What is the afferent pathway of the pupillary light reflex?
Light on the retina ->
Signals carried to the brain ->
About half of the fibers cross over at the optic chiasm ->
Pupil fibers leave the optic tract and enter the brachium of the superior colliculus->
Enter the pretectal nucleus in the midbrain
Which fibers cross over at the optic chiasm in the afferent pathway of the pupillary light reflex?
Nasal fibers
What is the efferent pathway of the pupillary light reflex?
Info starts at the pretectal nucleus ->
Goes to the Edinger-Westphal nuclei on both sides ->
Travels back to the eye along CN III ->
Fibers synapse at the ciliary ganglion ->
Destination is the iris sphincter
What are the neurotransmitters for the sympathetic system?
Preganglionic: acetylcholine
Postganglionic: norepeinephrine
What is the (pupil) target of the sympathetic system?
Iris dilator
If there is a lesion at the optic chiasm, what visual fields will be lost?
Temporal visual fields
If there is a lesion at the optic tract, what visual fields will be lost?
The same side in both eyes (Lesion on right side, lose temporal of left eye, medial of right)
If there is a lesion at the lateral geniculate nucleus, what visual fields are impaired?
The same side in both eyes (Lesion on right side, lose temporal of left eye, medial of right), but with macular sparing
Where is a 1st order lesion found in the sympathetic system to the eye?
Begins at hypothalamus, goes to the center of Budge (C8-T1,2)
What is the most likely cause of a 1st order lesion of the sympathetic pathway?
Cerebro-vascular accident
- MS
- Neck trauma
Where is a 2nd order lesion found in the sympathetic system to the eye?
Center of Bugde (C8-T1,2), jumps the apex of the lung, and goes to the cervical ganglion
What are the most likely causes of a 2nd order lesion of the sympathetic system to the eye?
Pancoast's tumor (smokers) TB Cancer Trauma Throid
Where is a 3rd order lesion found in the sympathetic system to the eye?
Cervical ganglion
What is the sympathetic pathway to the eye from the cervical ganglion?
Follows the internal carotid artery ->
Splits into nasociliary and ophthalmic artery branches
What is a lesion on the nasociliary branch of the sympathetic system to the eye probably caused by?
Aneurysm
Nasopharyngeal carcinoma
What is a lesion on the ophthalmic artery branch of the sympathetic system to the eye most likely caused by?
Migraines
What type of fibers make up the optic chiasm?
Nasal fibers only
What is hippus?
The unstable equilibrium between the sympathetic and parasympathetic systems in the iris sphincter and dilator
What are the three events that occur in the near triad?
Accommodation
Convergence
Miosis
Which pathway/system is responsible for accommodation?
Parasympathetic
The near triad is independent of what two things?
Illumination
Decreased accommodative ability (presbyopia)
What occurs in light-near dissociation?
Can have accommodation, but absent pupil reaction
What demographics have smaller pupils?
Old people
Diabetics
Chronic alcoholics
Those with pain or ocular inflammation
When should the accommodative response be checked?
Only if the direct light response is abnormal/absent
What is anisocoria?
Pupil size difference of more then 0.5 mm, may have lid involvement
What is an amaurotic pupil?
Blind pupil
No direct light reflex
What is Hutchinson’s pupil?
Fixed, dilated pupil
Unilateral
If anisocoria is more noticeable in the dark, what isn’t working well?
Iris dilator muscle
What things may cause anisocoria?
Miotic drops Iritis Horner's syndrome Argyll Robertson pupil Long standing Adie's pupil
The sympathetic pathway to the eye is a ___ neuron arc
3
Anhydrosis will occur in Horner’s syndrome only when the lesion occurs before ___.
Carotid bifurcation and superior cervical ganglion
With what is herterchormia associated?
Congenital Horner’s syndrome
Why does congenital Horner’s syndrome occur?
Brachial plexus injury during birth
In children under 5, why might acquired Horner’s syndrome occur?
Neuroblastoma in the sympathetic chain of the chest and neck
How do we rule out neuroblastoma in children?
Refer to pediatrician
What are the symptoms of Adie’s Tonic Pupil?
80% unilateral Dilated pupil Poor reaction to light Slow tonic re-dilation De-nervated ciliary ganglion Sectoral palsy of the iris sphincter
Which pupil disorder becomes bilateral at a rate of 4% per year?
Adie’s Tonic pupil
What happens to a longstanding Adie’s pupil?
It will become constricted
What is light-near dissociation?
When the response to accommodation is stronger than the light response
In light-near dissociation, what is the ratio of accommodation fibers to pupil fibers?
30:1
What causes light-near dissociation?
Midbrain lesions that are close to the pretectal synapse
When is light-near dissociation diagnostically valuable?
If the direct light reflex is absent or abnormal
In which syndromes/diseases is the light-near dissociation phenomenon seen?
Adie's tonic pupil Argyll-Robertson pupil Diabetes Dorsal midbrain syndrome Aberrant regeneration of CN III: miosis with Adduction Amyloidosis
What is seen in Argyll-Robertson pupils?
Both pupils are constricted and irregular
Light-near dissociation
Dilate poorly in the dark
Respond poorly to dilating agents
In which diseases is Argyll-Robertson pupil commonly seen?
Syphilis Diabetes Chronic alcoholism Multiple sclerosis Sarcoidosis
APD is an asymmetry in which pathway?
Afferent pathway
What is usually the cause of APD?
Massive retinopathy or optic neuropathy
What does APD stand for?
Afferent Pupillary Defect
How is APD detected?
By the swinging flashlight test
Is APD present in functional amblyopia?
Nope
APD is also known as what?
Marcus-Gunn pupil
Can eyes with 20/20 acuity and normal visual fields have APD?
Yes
What does PERRLA(-) stand for?
Pupils are Equal, Round, Reactive to light, Accommodation, no APD
