Eye muscles - Intrinsic

Question 1

What is the overall function of the intrinsic muscles

Answer 1

Control the pupil diameter and helps alter the lens curvature to enable us to see near objects

Question 2

What is the three intrinsic muscles in the eye

Answer 2

Ciliaris muscle

Constrictor pupillae

Dilator pupillae

Question 3

Where is the cillaris muscle found

Answer 3

In the ciliary body

Question 4

What is the constrictor pupillae found

Answer 4

In the iris at the pupillary boarder

Question 5

Where is orientation of the dilator pupillae and where is it found

Answer 5

Radially running muscle in the iris

Question 6

What innervates the ciliaris muscle

Answer 6

Parasymapthetic component of the Oculomotor CNIII

Question 7

What innervates the constrictor pupillae

Answer 7

Parasymapthetic component of the Oculomotor CNIII

Question 8

What innervates the dilator pupillae

Answer 8

Sympathetic from the plexus around the blood vessels

Question 9

What is the pupillary reaction to increased illumination

Answer 9

Parasympathetic innervates the constrictor pupillae muscle and both pupils constrict

Question 10

What is the pupillary reaction to decreased illumination

Answer 10

Sympathetic innervates dilator pupillae muscle and both pupils dilate

Question 11

What is the steps in examining pupillary reflex

Answer 11

Start in dimly lit room - with pupils dilated

Pen torch in front of one eye check for both pupils constricting (Direct and consensual reflex)

Swing light to other side should remain both pupils constricted

Question 12

What is the pathway if the pupillary reflex differ to the light pathways

Answer 12

Light falls on retina and follow normal path to optic tract, fibres then destined to active pupillary reflex leave optic tract and travel to the midbrain to the Oculomotor nucleus

Question 13

What part of the occulomotor nucleus (IIIn) does the parasympathetic fibres travel

Answer 13

Edinger- Westphal nucleus

Question 14

What side of the EWN does pupillary reflex fibres go

Answer 14

Both sides

Question 15

Where does the preganglionic parasympathetic fibres from the EWN travel and synapse in the efferent pathway of the pupillary reflex

Answer 15

Pass into the orbit and synapse in the ciliary ganglion

Question 16

Where do postganglionic fibres travel and what do the stimulate in the pupillary reflex

Answer 16

Travel through short ciliary nerves to constrictor pupillae and cause pupil constriction of both sides

Question 17

What is is called when pupils size may be different

Answer 17

Anisocoria

Question 18

What occurs in an abnormal light reflect

Answer 18

Pupils may look normal but react abnormally to light

Question 19

What are common causes of abnormal/absent pupillary reflex

Answer 19

Any abnormality of the afferent limb/ centre / efferent limb of the reflex

Diseases of the retina – detachment/ degenerations or dystrophies

Diseases of the optic nerve – such as in optic neuritis (frequently seen in MS)

Diseases of the III cranial nerve (efferent limb)

Question 20

Why is it important to check pupillary reflex if you see a patient with CNIII

Answer 20

As in conditions of diabetes CNIII palsy, there is usually no damaged to parasympathetic fibres

Question 21

What is suspected in a diabetic patient if they have CNIII palsy and pupillary reflex is absent

Answer 21

Suspected cerebral artery aneurysm

Question 22

How does anisocoria occur in Horners syndrome

Answer 22

Anisocoria due to damage to the sympathetic innervation to the pupil affecting the dilation of the pupils

Question 23

What are additional signs of Horners syndrome

Answer 23

You might also see ptosis
(drooping of the eyelid) on the affected side

anhidrosis (loss of sweating on the affected side)

Question 24

What is the paths of sympathetic innervation to the eye

Answer 24

Thoracolumbar outflow of the sympathetic goes down the sympathetic chain and cervical ganglia and the postganglionic sympathetic fibres travel along the blood vessel

Question 25

Where can horners syndrome occurs

Answer 25

occur any point of sympathetic pathway