Accommodation

Question 1

Structures involved in accommodation

Answer 1

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

Question 2

What kind of muscle is the ciliary muscle

Answer 2

Smooth muscle

Question 3

What kind of neural control is the ciliary body dominated by

Answer 3

PNS (short ciliary nerves)

Question 4

Sympathetic innervation to the ciliary body

Answer 4

Very little, thought to induce relaxation. Long ciliary nerve

Question 5

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

Answer 5

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

Question 6

What are the 3 muscle fibers of the ciliary body

Answer 6

• longitudinal
• radial
• annular (Circular)

Question 7

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

Answer 7

Longitudinal fibers

Question 8

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

Answer 8

Epichoroidal stars (outer surface of choroid)

Question 9

Where does the longitudinal muscle fiber of the ciliary body insert

Answer 9

Scleral spur

Question 10

During accommodation, what muscles contract

Answer 10

All 3 ciliary body muscle fibers

Question 11

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

Answer 11

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.

Question 12

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

Answer 12

Releasing resting tension on the zonular fibers during accommodation

Question 13

How does the scleral spur move during accommodation?

Answer 13

Posteriorly

Question 14

What type of flow pathway is increased during accommodation

Answer 14

Trabecular meshwork

Question 15

What kind of pathway decreases flow during accommodation

Answer 15

Uveoscleral pathway

Question 16

What kind of pathway increases flow during relaxation

Answer 16

Uveoscleral pathways

Question 17

What pathway decreases flow during relaxation

Answer 17

Trabecular meshwork

Question 18

How does the scleral spur move during relaxation

Answer 18

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

Question 19

Where do zonular fibers originate from

Answer 19

non pigmented epithelium of the ciliary body

Question 20

What are zonules made of

Answer 20

Elastic

Question 21

What are the zonules secreted by

Answer 21

The nonpigmented ciliary epithelium

Question 22

NPCE at tips of ciliary processes

Answer 22

Modified to secrete aqueous humor

Question 23

NPCE in the valleys between processes

Answer 23

Modified for producing the lens zonules and anchoring them

Question 24

Primary function of the zonules

Answer 24

Stabilize the lens

Question 25

What are all of the zonular fibers

Answer 25

``` Anterior zonules -anterior group -equatorial group -posteiror group Posterior zonules ```

Question 26

Where does the posteiror zonule originate

Answer 26

NPCE near ora serratta

Question 27

Where does the posterior zonule fiber insert

Answer 27

Pars plicata

Question 28

Posterior zonules

Answer 28

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

Question 29

Anterior zonules

Answer 29

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

Question 30

What is the driving force for accommodation

Answer 30

Elastic capsule

Question 31

Which zonules are relaxed during relaxation

Answer 31

Posterior zonules

Question 32

Which zonules are tight when relaxed

Answer 32

Anterior

Question 33

Which zonules are tight when accomodated

Answer 33

Posteiror zonules

Question 34

Which zonules are relaxed during accommodation

Answer 34

Anterior zonules

Question 35

What does the lens content do in accommodation

Answer 35

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

Question 36

Resting state has how much tonic accomodation

Answer 36

1.5D

Question 37

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

Answer 37

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

Question 38

Circuitry of the accommodative triad

Answer 38

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

Question 39

Age related loss of accommodation

Answer 39

Presbyopia

Question 40

When is presbyopia complete by

Answer 40

50 years of age

Question 41

What is presbyopia due to

Answer 41

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

Question 42

Correction for presbyopia

Answer 42

Bifocals and CL