VF - Ocular Accommodation 1 - Week 4 Flashcards

1
Q

By what age is accommodation fully developed?

A

6 months of age

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2
Q

What are the three muscle types of a cilary body?

A

Sphincter
Radial
Longitudinal

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3
Q

What kind of motion occurs when ciliary muscles contract?

A

Forward and inward

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4
Q

What happens to the ora serrata during ciliary muscle contraction?

A

Moves anteriorly

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5
Q

What happens to the anterior chamber during ciliary muscle contraction?

A

Narrows.

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6
Q

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

A

The anterior surface.

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7
Q

Describe the parasympathetic pathway to ciliary muscles.

A

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.

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8
Q

Describe the sympathetic pathway to ciliary muscles.

A

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.

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9
Q

What neurotransmitter mediates parasympathetic innervation?

A

Acetylcholine

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10
Q

What neurotransmitter mediates sympathetic innervation?

A

Noradrenaline

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11
Q

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

A

Antagonistic

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12
Q

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

A

To reestablish distance focus after prolonged near activity.

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13
Q

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?

A

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

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14
Q

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

A

Far to near is faster than near to far.

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15
Q

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

A

400 ms, independent of age.

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16
Q

Does response time of accommodation depend on age?

A

Yes

17
Q

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

A

Monocular.

18
Q

Define microfluctuations in terms of accommodation.

A

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

19
Q

Define tonic accommodation and dark accommodation.

A

They are both the same thing.

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

20
Q

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

A

A myopic state of ~1.00D.

This is the tonic resting state.

21
Q

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

A

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

22
Q

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

A
  • Blur - the primary driver
  • Proximal awareness
  • All vergence movements
  • Tonic accommodation
23
Q

Define accommodative convergence.

A

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

24
Q

Define presbyopia.

A

Ages related physiological reduction in the amplitude of accommodation.

25
Q

Name 4 pre-presbyopic dysfunctions.

A

Accommodative insufficiency
Accommodative excess
Accommodative infacility
Accommodative spasm

26
Q

Name 8 factors that influence accommodation.

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