Accommodation

Question 1

Where is the posterior chamber located?

Answer 1

Posterior to the iris and anterior to the lens and lens zonules.

Question 2

Where does the primary innervation for increased accommodation originate?

Answer 2

The parasympathetic nervous system.

Question 3

Why does stress interfere with accommodation?

Answer 3

Stress is indicative of sympathetic nervous system activation, which also decreases or inhibits accommodation.

Question 4

What is the near triad?

Answer 4

It is an explanation of the relationship between accommodation between accommodation, convergence, and pupil diameter.
Increased accommodation increases convergence and decreases pupil diameter.
Increased convergence increases accommodation and decreases diameter.
Decreased pupil diameter does NOT affect accommodation or convergence.

Question 5

Which factor of the near triad is the strongest?

Answer 5

Accommodation.

Question 6

How big is the human lens?

Answer 6

About 9 mm in diameter and 3.6 mm thick.

Question 7

During accommodation, how much thicker does the lens get?

Answer 7

About .5 mm.

Question 8

What is presbyopia?

Answer 8

Normal age-related loss of ability to accommodate and thus see close targets clearly.

Question 9

What are some common symptoms of accommodative dysfunction?

Answer 9

Reduced accommodative facility, blurry vision (especially with near targets), asthenopia.

Question 10

How do added minus lenses affect accommodation?

Answer 10

They stimulate accommodation and increase accommodative demand. Minus lenses partially diverge the light, increasing the accommodative demand on the lens.

Question 11

How do added plus lenses affect accommodation?

Answer 11

They relax accommodation. The plus lenses partially focus light, reducing the accommodative demand on the lens.

Question 12

What three factors must be measured to accurately assess accommodation?

Answer 12

Amplitude, facility, and posture.

Question 13

How can you measure accommodative amplitude?

Answer 13

You can increase accommodative demand by decreasing the target distance until the patient notices prolonged blur. This is called the Donders push-up test for NPA and is performed monocularly.
You can also add minus lenses of increasing magnitude to increase the accommodative demand until the patient notices prolonged blur.

Question 14

What is Hofstetter’s equation for maximum amplitude?

Answer 14

25.0-(0.40 x age in years)

Question 15

What is Hofstetter’s equation for average amplitude?

Answer 15

18.5-(0.33 x age in years)

Question 16

What is Hofstetter’s equation for minimum amplitude?

Answer 16

15.0-(0.25 x age in years)

Question 17

What is the primary stimulus to accommodation?

Answer 17

Retinal image blur.

Question 18

What is PRA and how is it measured?

Answer 18

Positive Relative Accommodation. It is a test to measure the amount that accommodation can be increased (via the near triad) at a target distance of 40cm before vergence is affected.

Question 19

What lenses would you use to measure PRA?

Answer 19

Minus lenses to stimulate the POSITIVE response in the eyes.

Question 20

Why is PRA not a true measure of accommodative amplitude?

Answer 20

Since the test is performed binocularly, the vergence system is in play as well as accommodation.

Question 21

What is NRA and how is it measured?

Answer 21

Negative Relative Accommodation. It is a test to measure the amount that accommodation can be decreased (via the near triad) at a target distance of 40cm before vergence is affected.

Question 22

What lenses would you use to measure NRA?

Answer 22

Plus lenses to stimulate the NEGATIVE response in the eyes.

Question 23

What is meant by the terms “accommodative lag” and “accommodative lead?”

Answer 23

They are the difference between the calculated accommodative demand of a given target distance and the amount of accommodation that the individual responds.

Question 24

What two tests can be used to measure accommodative posture?

Answer 24

Cross grid technique (subjective test) and dynamic retinoscopy (objective).

Question 25

In dynamic retinoscopy, how would you interpret the light going with movement?

Answer 25

This would mean there is too little accommodation, which means there is some lag. This is normal.

Question 26

In dynamic retinoscopy, how would you interpret the light going against movement?

Answer 26

This would mean there is too much accommodation, which means there is some lead. This is abnormal.

Question 27

When administering the Developmental Eye Movement (DEM) Test, what would a poor score on parts A and B indicate?

Answer 27

An issue with visual-verbal automaticity.

Question 28

When administering the DEM Test, what would a poor score on part C indicate?

Answer 28

An issue with saccadic-fixation eye movement ability.

Question 29

What test would be used for accommodative amplitude?

Answer 29

NPA, or using added minus lenses.

Question 30

What test would be used for accommodative facility?

Answer 30

Lens rock.

Question 31

What test would be used for accommodative posture?

Answer 31

Cross grid technique or dynamic retinoscopy.