Pupil Responses Flashcards
Indications for examining pupil responses
- Routine examination
- Symptoms of neurological disease
- Symptoms of changed pupil size/shape
- Head trauma
Neurological symptoms linked with pupil responses:
• Sudden onset reduced vision
• Reduced vision affecting one eye only
• Headaches
• Changes in the appearance of colours
• Ocular pain- worse on eye movement
Pathway for afferent pupil pathway:
Retina
Optic nerve
Optic Chiasma:
• Nasal fibres swap (contralateral)
• Temporal fibres remain (ipsilateral)
Optic Tract
Pretectal Nucleus
• Go to each side of edinger-westphal nucleus
What are the two autonomic nervous system pathways involved in the efferent pathway?
- Sympathetic - Fight or flight - Iris dilator muscle
- Parasympathetic - rest and recover - iris sphincter muscle
Parasympathetic pupil pathway:
To eye from brain:
1. Edinger-Westphal nucleus
2. Cranial nerve 3 (oculomotor)
3. Iris sphincter muscle
Sympathetic pupil pathway:
To eye from brain:
1. Hypothalamus
2. Ciliospinal centre
3. Iris dilator muscle
How do we record pupils during clinical assessment?
• PERRLA
Pupils, equal, round and reactive to light + accommodation?
• Direct + consensual
What is anisocoria?
• Unequal pupil sizes
• Up to 25% of patients, the majority are physiological
Describe physiological anisocoria
• Small (<1mm)
• Constant
- Especially under different illumination levels, bright and dark
• No change in level of anisocoria suggests physiological
Describe pathological anisocoria
• Impairment of efferent pathway
Absent direct :
• Significant ocular or neurological disease
• Either afferent or efferent pathway
Absent consensual:
• If direct response is present, afferent pathway must be functional
• Must be impaired parasympathetic efferent pathway to affected eye
How is swinging flashlight test done?
• Right Eye- Direct response
Transfer light as quickly as possible to the left eye
• Left Eye- Direct response
Transfer light as quickly as possible back to the right eye
Describe horners syndrome
• Impaired sympathetic efferent innervation
• Iris dilator
• Anisocoria
- Eye effected has smaller pupil
• Greater anisocoria in dim light
- action of iris dilator muscle
• Normal direct + consensual, no RAPD
How does 3rd nerve palsy affect pupils:
Impaired parasympathetic efferent innervation:
• Iris sphincter muscle
• Anisocoria
• Which eye is affected?
- Larger pupil
• Impaired direct response (affected eye)
• Impaired consensual response (affected eye)
• Diplopia, ptosis and ocular motility abnormal
