PC - Binocular Vision 1 Accommodation - Week 2

Question 1

By what age is accommodation thought to be fully developed?

Answer 1

6 months of age.

Question 2

Name the 4 major stimulators of accommodation in order of strength.

Answer 2

Blur - primary driver
Proximal awareness
Vergence
Tonic accommodation

Question 3

Name 6 factors that influence accommodation.

Answer 3

Blur
Luminance
Proximity
Chromatic aberration
Convergence of eyes
Age

Question 4

What are 5 features of accommodation that can be measured clinically?

Answer 4

Posture (lag/lead)
Amplitude (NPA)
Accommodative facility
Relative accommodation (NRA/PRA)
Convergence accommodation (A/AC)

Question 5

Describe Monocular Estimate Method - Near Retinoscopy for measuring accommodation.

Answer 5

The target and observer are at the same distance, so the reflex is a measure of the stability and accuracy of the accommodative response.

Question 6

What are two advantages of doing MEM?

Answer 6

Objective and can be done in free space

Question 7

What are the expected values for a MEM finding, and keeping this in mind, what value would raise suspicion?

Answer 7

Expected - +0.25 - 0.50

Minus findings, or above +0.75 should raise suspicion

Question 8

Consider binocular cross cylinder. Is it subjective or objective?

Answer 8

Subjective

Question 9

Can the binocular cross cylinder be done in free space?

Answer 9

No, requires a phoropter.

Question 10

Name a disadvantage of the binocular cross cylinder.

Answer 10

Not close enough to a reeal life near task, and can be influenced by a lack of proximal cues.

Question 11

What are the expected values for the binocular cross cylinder?

Answer 11

+0.50 with a standard deviation of +0.50.

Question 12

Describe the pushup method to measure amplitude of accommodation. Is it subjective or objective?
What are the expected values?

Answer 12

Near point accommodation technique.
Is a subjective test.
Amplitude = 18 - (age/3)
or
Minimum amplitude = 15 - (age/4)
SD = +/-2.00D

Question 13

Consider the reverse pushup method. Explain why this method overestimates the accommodative amplitude.

Answer 13

Due to the magnification effect of bringing the target closer and improving VA.

Question 14

Describe the refractor head and portable near point rule.

Answer 14

A variation of the monocular pushup method, allowing you to measure blur using the refractor head attachment.

Question 15

Name a disadvantage of doing the pushup method when the patient is behind a phoropter.

Answer 15

It interferes with proximal cues and may give a different result.

Question 16

Describe the minus lens to blur technique.

Answer 16

Minus lens are added to a target at 33cm until it can no longer be seen.

Question 17

Compare the expected results of the pushup method to minus lens to blur, and explain why the difference, if any.

Answer 17

Minus lens to blur typically less than pushup method by 2.00D. This is due to the lack of the magnification effect of moving the target closer to the patient.

Question 18

Define accommodative facility.

Answer 18

The speed and efficiency at which accommodation takes place.

Question 19

How is accommodative facility measured?

Answer 19

Using near accommodative facility flippers.

Question 20

Describe how accommodative facility is performed.

Answer 20

The patient is given a near fixation target. The flippers are + and - lenses. Beginning with the + side, the lenses are flipped, and the patient is timed on how long it takes for them to regain focus.

Question 21

What is accommodative facility measured in, and what are the expected adult values?

Answer 21

Cycles per minute

Average is 8 cycles per minute

Question 22

Define 3 characteristic signs of accommodative insufficiency.

Answer 22

High lag
Low amplitude
Poor facility

Question 23

Define 3 characteristic signs of accommodative excess.

Answer 23

Variable VA
No lag/lead
Fails + facility

Question 24

Define 2 characteristic signs of accommodative spasm.

Answer 24

Reduced VA
Reduced lead
Fails + facility

Question 25

Define 2 characteristic signs of ill-sustained accommodation.

Answer 25

High variable lag

Slow facility

Question 26

Define 2 characteristic signs of in-facility accommodation.

Answer 26

Slow facility + and -