Eye reflexes and their tests

Question 1

What is the pupillary light reflex?

Answer 1

Shrinking of the pupil (miosis) in response to light

Question 2

How is the pupillary light reflex tested?

Answer 2

• Shine a light into one eye (pen torch) and check the shrinking (ipsilateral miosis)
• Remove the light for 3 seconds
• Shine a light into the same eye and check the consensual shrinking of the pupil in the other eye (consensual miosis)
• Repeat with the other eye

Question 3

What conclusions are drawn in a healthy test for the pupillary light reflex?

Answer 3

If both ipsilateral and consensual reflexes are present, the reflex pathway is intact (healthy).

Question 4

You won’t have to do this in the OSPE but you must be able to recall the details of it, what is the test of the accommodation reflex?

Answer 4

Ask the patient to focus on a far object, such as a picture on a wall behind you
Then, with a short countdown, bring your finger 5-10cm in front of their eyes.
Their ability to re-adjust (accommodate) the near object from the far object is what is being tested

Question 5

What are the stops along the way of the afferent pathway for pupillary constriction?

Answer 5

1) Ganglion cells in the eye
2) Optic nerve (CN II), nasal/temporal fibres leave the eye and nasal fibres cross at optic chiasm
3) Optic tracts (post-optic chiasm)
4) Pretectal nucleus
5) Edinger-Westphal nucleus (processed here)

Question 6

What are the stops along the way of the efferent pathway for pupillary constriction?

Answer 6

1) EW nuclei
2) Parasympathetic fibres along oculomotor nerve (CN III)
3) Ciliary ganglion
4) Parasympathetic fibres along ciliary nerves (CN V1)
5) Sphincter pupillae - constriction

Question 7

How would you go about testing the corneal reflex? (You won’t have to do it in the OSPE but you must be able to recall the test)

Answer 7

Place some cotton wool on the sclera of the eyeball

• Should produce a rapid closure of the eye to protect itself
• you do need to know the afferent/efferent pathways

Question 8

What are the stops along the way of the afferent pathway of the corneal reflex?

Answer 8

Touch sensation sent as an impulse along the ophthalmic branch of the trigeminal nerve (CN V1)

Question 9

What are the stops along the way of the efferent pathway of the corneal reflex?

Answer 9

From facial motor nucleus along the facial nerve (CN VII), to orbicularis oculi (quickly shuts the eye, shuts the eyelids)