VF - Ocular Accommodation 1 - Week 4

Question 1

By what age is accommodation fully developed?

Answer 1

6 months of age

Question 2

What are the three muscle types of a cilary body?

Answer 2

Sphincter
Radial
Longitudinal

Question 3

What kind of motion occurs when ciliary muscles contract?

Answer 3

Forward and inward

Question 4

What happens to the ora serrata during ciliary muscle contraction?

Answer 4

Moves anteriorly

Question 5

What happens to the anterior chamber during ciliary muscle contraction?

Answer 5

Narrows.

Question 6

On which surface does the lens become more curved during accommodation?

Answer 6

The anterior surface.

Question 7

Describe the parasympathetic pathway to ciliary muscles.

Answer 7

Begins at the Edinger-Westphal nucleus
Preganglionic fibres synapse to the ciliary ganglion.
Most postganglionic fibres travel via the short ciliary nerve. Some travel with the long ciliary nerve.

Question 8

Describe the sympathetic pathway to ciliary muscles.

Answer 8

Begins at the thalamus and hypothalamus.
Travels down to the cilio-spinal centre at T1 in the spinal cord.
Here second order neurons leave through ventral roots, up the cervical chain, and synapse at the cervical ganglion.
Third order neurons continue up into the sympathetic carotid plexus and enter the eye via the:
Trigeminal nerve, 1st division
Long/short ciliary nerves, passing through ciliary ganglions without synapse.

Question 9

What neurotransmitter mediates parasympathetic innervation?

Answer 9

Acetylcholine

Question 10

What neurotransmitter mediates sympathetic innervation?

Answer 10

Noradrenaline

Question 11

Is sympathetic innervation agonistic or antagonistic to parasympathetic innervation (to ciliary muscles)?

Answer 11

Antagonistic

Question 12

What is a possible purpose of sympathetic innervation to the ciliary muscles?

Answer 12

To reestablish distance focus after prolonged near activity.

Question 13

What is the trigger for the afferent pathway to ciliary muscles? Which part of the brain is it signalled to, and where is it transformed to?

Answer 13

Blur on the retina.
It signals in the lateral geniculate nucleus, and is transformed to the edinger westphal nucleus. This starts the efferent pathway.

Question 14

Which accommodative response is faster, far to near, or near to far?

Answer 14

Far to near is faster than near to far.

Question 15

What is the latency of accommodation, and does it depend on age?

Answer 15

400 ms, independent of age.

Question 16

Does response time of accommodation depend on age?

Answer 16

Yes

Question 17

Is latency of accommodative response slower with binocular or monocular viewing?

Answer 17

Monocular.

Question 18

Define microfluctuations in terms of accommodation.

Answer 18

When viewing a steady object, the accommodative response fluctuates slightly at ±0.25D.

Question 19

Define tonic accommodation and dark accommodation.

Answer 19

They are both the same thing.

It is the passive state of accommodation in the absence of stimulus.

Question 20

What state does the accommodative system adopt in complete darkness? What is this state called?

Answer 20

A myopic state of ~1.00D.

This is the tonic resting state.

Question 21

Is accommodative state in complete darkness consistent or does it depend on previous stimuli?

Answer 21

It depends on previous stimuli. The equilibrium level in the dark depends on the duration and magnitude of the previous stimulus.

Question 22

Accommodation is stimulated by what four factors? Which is the primary driver?

Answer 22

• Blur - the primary driver
• Proximal awareness
• All vergence movements
• Tonic accommodation

Question 23

Define accommodative convergence.

Answer 23

When accommodation occurs, a secondary convergence occurs, bringing the two eyes together to focus on the object being viewed.

Question 24

Define presbyopia.

Answer 24

Ages related physiological reduction in the amplitude of accommodation.

Question 25

Name 4 pre-presbyopic dysfunctions.

Answer 25

Accommodative insufficiency
Accommodative excess
Accommodative infacility
Accommodative spasm

Question 26

Name 8 factors that influence accommodation.

Answer 26

Blur
Target size
Depth/pupil size
Luminance
Target proximity
Convergence of eyes
Optical aberrations
Age