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MBChB YR2: Opthalmology > Anatomy: Reflexes of the Eye > Flashcards

Anatomy: Reflexes of the Eye Flashcards

1
Q

Name the muscle fibres responsible for pupillary dilation in response to sympathetic stimulation

A

Dilator pupillae fibres

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2
Q

What is the oculocardiac reflex?

A

Reflex bradycardia in response to tension on extraocular muscles or pressure on the eye

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3
Q

Name the muscle fibres responsible for pupillary constriction in response to parasympathetic stimulation

A

Sphincter pupillae fibres

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4
Q

In the corneal (blink) reflex, the central CNS connections are between CN V and CN ____

A

CN VII

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5
Q

Name the cranial nerve which is responsible for sensory innervation of the face

A

Branches of CN V (trigeminal nerve)

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6
Q

What is the function of basal tears?

A

Involved in corneal health - clean/nourish and hydrate cornea, involved in corneal health

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7
Q

Name the muscle which alters the change of the lens in the lens accommodation reflex

A

Ciliary body

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8
Q

What is the function of the lens accommodation reflex?

A

Change in the shape of the lens to focus on a near or further away object

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9
Q

What is the vestibulo-ocular reflex?

A

Turns the eyes in the opposite direction to a head movement to stabilise gaze on an object during head movement

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10
Q

What is the function of reflex tears?

A

Extra tears in response to mechanical or chemical stimulation

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11
Q

Where do CNS connections occur in the pupillary light reflex?

A

Midbrain in a 4 neurone chain

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12
Q

In ‘far vision’, how does the shape of the lens change?

A

Ciliary muscle relaxes, ligament tightens and lens flattens

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13
Q

Which cranial nerve is responsible for the motor (efferent) limb of the pupillary light reflex?

A

Bilateral via CN III → bilateral constriction

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14
Q

What is a ‘fixed-dilated (‘blown’) pupil?

A

Often a serious pathological sign (e.g. of CN III pathology)

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15
Q

In the pupillary light reflex, a _____ light reflex occurs in the non-stimulated eye

A

Consensual

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16
Q

Name the muscle responsible for the wide eye opening of fight or flight

A

Mueller’s muscle of LPS (involuntary - sympathetic innervation)

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17
Q

How would you clinically assess the lens accommodation reflex?

A

Clinically assess all 3 components of the reflex:

  • Bilateral pupillary constriction (parasympathetic constriction of sphincter pupillae)
  • Bilateral convergence of both eyes towards midline (medial rectus)
  • Bilateral relaxation of the lens (lens becomes spherical due to contraction of the ciliary muscles)
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18
Q

Describe the effect of parasympathetic stimulation on the eye

A

Get less light into into eyes (to protect the retina from bright light or when asleep), focus on near objects, reflex lacrimation (to wash away stimulant foreign body and clean the cornea)

19
Q

What is a mydriatic pupil?

A

A non-physiologically enlarged pupil (e.g. from mydriatic drugs which induce dilation of the pupil)

20
Q

Which cranial nerve is responsible for the sensory (afferent) limb of the pupillary light reflex?

A

Ipsilateral CN II

21
Q

The ciliary muscle ____ in ‘near vision’

A

Contracts

22
Q

Which regions of the face are given sensory innervation by CN V2 (maxillary nerve)?

A

Skin of the lower eyelid, skin over the maxilla

23
Q

Describe the pathway of postsynaptic sympathetic fibres from the superior cervical sympathetic ganglion to the orbit

A

Superior cervical sympathetic ganglion → internal carotid nerve → internal carotid plexus → axons carried on ophthalmic artery and on its branches to orbital structures

24
Q

What is the function of the corneal (blink) reflex?

A

Protective function - protects the eyes from foreign bodies and bright lights

25
Q

In the pupillary light reflex, a _____ light reflex occurs in the stimulated eye

A

Direct

26
Q

In ‘near vision’, how does the shape of the lens change?

A

Ciliary muscle contracts, ligament relaxes and lens becomes spherical

27
Q

Which cranial nerves are responsible for the sensory (afferent) limb of the corneal (blink) reflex?

A

Action potentials conducted from cornea via CN V1 branches

To trigenimal ganglion, then along CN V to pons

28
Q

What is the corneal (blink) reflex?

A

Involuntary blinking of the eyelids elicited by stimulation of the cornea

29
Q

Name the nerves involved in the oculocardiac reflex

A

CN V1 and CN X

30
Q

Which regions of the face are given sensory innervation by CN V3 (mandibular nerve)

A

Skin over mandible and TMJ, except over angle of mandible

31
Q

What is a miotic pupil?

A

Non-physiologically constricted pupil (e.g. a component of Horner’s syndrome)

32
Q

Describe the effect of sympathetic stimulation on the eye

A

Eyes open wider to get more light into eyes, may help focus on far objects, emotional lacrimation

33
Q

Which cranial nerves are responsible for the motor (efferent) limb of the corneal (blink) reflex?

A

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

34
Q

What is a fixed ‘pin point’ pupil?

A

Often a serious pathological sign (e.g. opiate drugs)

35
Q

Describe the arrangement of the sphincter pupillae fibres

A

Encircle pupil around the internal cicumference of iris

36
Q

The ciliary muscle ______ in ‘far vision’

A

Relaxes

37
Q

Which regions of the face are given sensory innervation by CN V1 (ophthalmic nerve)?

A

Upper eyelid, cornea, conjunctiva

38
Q

The ___________ division of the ANS is responsible for contraction of the ciliary muscle to accommodate the lens in near vision

A

Parasympathetic

39
Q

Which branch of the ANS is responsible for emotional tears?

A

Sympathetic

40
Q

Describe the arrangement of the dilator pupillae fibres

A

Radially arranged - fixed origin around external circumference of iris, mobile insertion around internal circumference

41
Q

Name the cranial nerves responsible for the efferent limb of the lacrimation reflex

A

Parasympathetic axons originating from CN VII

42
Q

Name the cranial nerves responsible for the afferent limb of the lacrimation reflex

A

CN V1 from cornea/conjunctiva

43
Q

Name the nerves involved in the vestibulo-ocular reflex

A

CN VIII and CNs III, IV and VI

MBChB YR2: Opthalmology (20 decks)

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