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Ophthalmology > Reflexes of the Eye > Flashcards

Reflexes of the Eye Flashcards

1
Q

What division of the trigeminal nerve does the supraorbital nerve belong to?

A

CN V1 = ophthalmic

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2
Q

Where does CN V1 supply on the face?

A

Upper eyelid, cornea, conjunctiva

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3
Q

Where does CN V2 supply on the face?

A

Skin of lower eyelid and over the maxilla

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4
Q

Where does CN V3 supply on the face?

A

Skin over mandible and TMJ (except the angle of the mandible)

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5
Q

What is the sensory limb of the blink reflex?

A

Action potentials conducted from the cornea via CN V1 branches to the trigeminal ganglion, then along CN V to pons

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6
Q

What nerves are the central CNS connections between in the blink reflex?

A

CN V and CN VII

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7
Q

What is the motor limb of the blink reflex?

A

Action potentials conducted via CN VII to eyelid part of orbicularis oculi

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8
Q

What are the autonomic reflexes of the eye?

A

Wide eye opening of fight/flight, pupillary light reflex, accommodation reflex, lacrimation reflex, vestibulo-ocular reflex, oculocardiac reflex

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9
Q

What is the vestibulo-ocular reflex?

A

Turns eye in opposite direction to head movement and stabilises gaze on object during head movement

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10
Q

What nerves are involved in the vestibulo-ocular reflex?

A

CNS connections between CN VII and CN III/IV/VI

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11
Q

What is the oculocardiac reflex?

A

Reflex bradycardia in response to tension on extra-ocular muscles or pressure on eye

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12
Q

What nerves are involved in the oculocardiac reflex?

A

CNS connections between CN V1 and CN X

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13
Q

What are the sympathetic reflexes of the eye?

A

Opens eyes wider, get more light in, focus on far objects, emotional lacrimation

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14
Q

What are the parasympathetic reflexes of the eye?

A

Get less light in (protect retina from bright light/when asleep), focus on near objects, reflex lacrimation (to clean eye)

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15
Q

Which muscles opens the eye wider?

A

Levator palpebrae superioris = contains skeletal and smooth muscle, Mueller’s muscle, sympathetic innervation

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16
Q

What do post-synaptic sympathetic fibres travel via to open the eyes wider?

A

Superior cervical sympathetic ganglion, internal carotid nerve, internal acoustic meatus, axons carried on ophthlamic artery and on its branches to orbital structures

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17
Q

What nerves modality constricts the pupils during rest and digest, and in bright light?

A

Parasympathetic system

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18
Q

What is a non-physiologically constricted pupil classed as?

A

A miotic pupil (e.g Horner’s syndrome)

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19
Q

Are fixed pin point or dilated pupils normal?

A

No = are often serious pathological signs (ie of opiates or CN III pathology respectively)

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20
Q

Which structure is responsible for constricting the pupils?

A

Sphincter pupillae fibres = encircle pupil around the internal circumference of the iris

21
Q

Which nerve modality is responsible for pupillary dilation?

A

Sympathetic system

22
Q

What is a non-physiologically dilated pupil classed as?

A

A mydriatic pupil (e.g mydriatic drugs)

23
Q

What structure is responsible for dilating the pupils?

A

Dilator pupillae fibres = radially arranged, originate around external circumference of iris (fixed) amd insert around internal circumference of iris (mobile)

24
Q

What is the special sensory limb of the pupillary light reflex?

A

Ipsilateral CN II

25
Q

Where do the CNS connections for the pupillary light reflex occur?

A

In the midbrain

26
Q

What is the motor limb of the pupillary light reflex?

A

Bilateral CN III

27
Q

How does the stimulation of the eye affect the pupillary light reflex?

A

Direct light reflex occurs in stimulated eye

Consensual light reflex occurs in non-stimulated eye

28
Q

How many neurons make up the chain in the pupillary light reflex?

A

4

29
Q

What is the first neuron in the pupillary light reflex?

A

Retinal ganglion cell = pass via ipsilateral optic nerve, decussate in optic chiasm, synapse in pretectal nucleus in midbrain

30
Q

What is the second neuron in the pupillary light reflex?

A

Bilateral = located entirely in midbrain and connect pretectal nucleus to next synapse in Edinger-Westphal nucleus

31
Q

What is the Edinger-Westphal nucleus?

A

Location of cell bodies of parasympathetic axons of CN III

32
Q

What is the third neuron in the pupillary light reflex?

A

Bilateral = pass from Edinger-Westphal nucleus via CN III then its inferior division to synapse in ciliary ganglion

33
Q

What is the fourth neuron of the pupillary light reflex?

A

Bilateral = course in short ciliary nerves to sphincter pupillae muscles

34
Q

What do the suspensory ligaments of the lens connect?

A

The circumference of the lens and the ciliary body

35
Q

What is the ciliary body?

A

Both muscular and vascular = smooth muscle like sphincter around circumference

36
Q

What happens to the ciliary muscle during far vision?

A

Relaxes = no parasympathetics, ligament tightens and lens flattens to focus on object in distance

37
Q

What happens to the ciliary muscle during near vision?

A

Contracts = parasympathetic control, ligament relaxes and lens becomes spherical to focus on near objects

38
Q

What does the lens accommodation reflex occur in response to?

A

Near vision

39
Q

What are the three elements of the lens accommodation reflex?

A

Bilateral pupillary constriction
Bilateral convergence of both eyes towards midline
Bilateral relaxation of lens

40
Q

What nerve innervates all three aspects of the lens accommodation reflex?

A

CN III

41
Q

What causes bilateral pupillary constriction during the lens accommodation reflex?

A

Parasympathetic constrictor of sphincter pupillae

42
Q

What causes the bilateral convergence of both eyes towards the midline during the lens accommodation reflex?

A

Medial rectus muscle

43
Q

What causes the bilateral relaxation of the lens during the lens accommodation reflex?

A

Contraction of ciliary muscles

44
Q

What is the purpose of basal tears?

A

Corneal health = cleans/nourishes and hydrates avascular cornea, contains lysozyme (hydrolyses bacterial cell walls)

45
Q

What causes reflex tears?

A

Chemical or mechanical stimulation

46
Q

What is the sensory limb of reflex tears?

A

CN V1 from the cornea and conjunctiva

47
Q

What is the motor limb of reflex tears?

A

Parasympathetic axons from CN VII

48
Q

What emotions can cause lacrimation?

A

Happiness, fear or sadness

Ophthalmology (20 decks)

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