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Ocular Block 7 > Accommodation > Flashcards

Accommodation Flashcards

1
Q

Structures involved in accommodation

A 
Ciliary body
-ciliary muscle 
Choroid
Iris
Anterior and posterior zonules
Crystalline lens 
-lens capsule
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2
Q

What kind of muscle is the ciliary muscle

A

Smooth muscle

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3
Q

What kind of neural control is the ciliary body dominated by

A

PNS (short ciliary nerves)

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4
Q

Sympathetic innervation to the ciliary body

A

Very little, thought to induce relaxation. Long ciliary nerve

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5
Q

Why is there both PNS and SNS innervation to the ciliary body

A

For smooth accommodative tracking and ciliary muscle acts as its own antagonist

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6
Q

What are the 3 muscle fibers of the ciliary body

A
  • longitudinal
  • radial
  • annular (Circular)
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7
Q

What muscle fibers of the ciliary body pull the ciliary body anteriorly and inward, causing the circumlental space to decrease in size

A

Longitudinal fibers

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8
Q

Where do the longitudinal muscle fibers of the ciliary body originate from

A

Epichoroidal stars (outer surface of choroid)

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9
Q

Where does the longitudinal muscle fiber of the ciliary body insert

A

Scleral spur

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10
Q

During accommodation, what muscles contract

A

All 3 ciliary body muscle fibers

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11
Q

Which lens fibers have the greatest contribution to changing the lens shape and why?

A

Circular (annular) fibers. As constriction occurs, there is a gradual rearrangement of the fibers to transition into annular fibers at the expense of the longitudinal and radial fibers.

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12
Q

Contraction of the entire ciliary muscle pulls the anterior choroid forward giving the ciliary muscle the primary function of

A

Releasing resting tension on the zonular fibers during accommodation

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13
Q

How does the scleral spur move during accommodation?

A

Posteriorly

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14
Q

What type of flow pathway is increased during accommodation

A

Trabecular meshwork

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15
Q

What kind of pathway decreases flow during accommodation

A

Uveoscleral pathway

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16
Q

What kind of pathway increases flow during relaxation

A

Uveoscleral pathways

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17
Q

What pathway decreases flow during relaxation

A

Trabecular meshwork

18
Q

How does the scleral spur move during relaxation

A

Returns to the anatomical postion and decreases flow across TM by closing flow channels which decrease the effective filtration area

19
Q

Where do zonular fibers originate from

A

non pigmented epithelium of the ciliary body

20
Q

What are zonules made of

21
Q

What are the zonules secreted by

A

The nonpigmented ciliary epithelium

22
Q

NPCE at tips of ciliary processes

A

Modified to secrete aqueous humor

23
Q

NPCE in the valleys between processes

A

Modified for producing the lens zonules and anchoring them

24
Q

Primary function of the zonules

A

Stabilize the lens

25
Q

What are all of the zonular fibers

A 
Anterior zonules
-anterior group
-equatorial group
-posteiror group 
Posterior zonules
26
Q

Where does the posteiror zonule originate

A

NPCE near ora serratta

27
Q

Where does the posterior zonule fiber insert

A

Pars plicata

28
Q

Posterior zonules

A

Attached to the ILM covering the NPCE near ora serrata. Enter valleys between ciliary processes and insert into the NPCE either in the valleys or walls of the ciliary processes. The posteiror zonules aid in pulling the ciliary muscle back to tis unaccommodated state postion after accommodation has ceased

29
Q

Anterior zonules

A

Attach at the anterior capsule surface (zonular lamella), equator, and posteiror capsule. Few fibers actually penetrate the capsule

30
Q

What is the driving force for accommodation

A

Elastic capsule

31
Q

Which zonules are relaxed during relaxation

A

Posterior zonules

32
Q

Which zonules are tight when relaxed

33
Q

Which zonules are tight when accomodated

A

Posteiror zonules

34
Q

Which zonules are relaxed during accommodation

A

Anterior zonules

35
Q

What does the lens content do in accommodation

A

Acts to reduce the rate of capsule movement as well as retard the extend of change in lens configurations

36
Q

Resting state has how much tonic accomodation

37
Q

What are the 3 physiological responses in the accommodative process (accommodative triad)

A
  1. Pupillary constriction
  2. Convergence of the eyes (medial rectus, dyscugate)
  3. Accommodation
38
Q

Circuitry of the accommodative triad

A

EW nucleus sends out preganglionic parasympathetics that travel in CN III that synapse in the ciliary ganglion to become post gang. Parasympathetics that travel in short posterior ciliary nerve

39
Q

Age related loss of accommodation

A

Presbyopia

40
Q

When is presbyopia complete by

A

50 years of age

41
Q

What is presbyopia due to

A

It’s is multifactorial. Due to global deterioration of the accommodative apparatus, no single factor is the cause

42
Q

Correction for presbyopia

A

Bifocals and CL

Ocular Block 7 (9 decks)

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