Accommodation

Question 1

Process by which the dioptric power of lens changes to maintain a focused image on fovea

Answer 1

Normal Accommodation (consensual and equal)

Question 2

List the components of the near triad

Answer 2

convergence, accommodation, miosis

Question 3

What are the two types of accommodation

Answer 3

Positive accommodation (focus) and Negative accommodation (defocus)

Question 4

What 4 things occur in positive accommodation with parasympathetic nervous system (PSNS) stimulation

Answer 4

ciliary muscle contraction, ciliary body moves forward, ligament tension is released, and lens becomes more convex (increased dioptric power)

Question 5

What 3 things occur in negative accommodation

Answer 5

tension on ciliary muscle is released, capsule flattens, and dioptric power decreases

Question 6

What are the 4 types of NORMAL accommodation

Answer 6

reflex, tonic, convergence, and psychic/near

Question 7

What stimulates reflex accommodation

Answer 7

the quality of retinal images (blurred or defocused signals)

Question 8

What does tonic accommodation depend on

Answer 8

the tone of the ciliary body

Question 9

What is convergence accommodation (aka: relative accommodation)

Answer 9

as the convergence angle is changed the accommodation must increase to see a target nearer and nearer

Question 10

What are strong drivers for near work induced myopia

Answer 10

low illumination and low CA/C ratio (convergence-accommodation /convergence

Question 11

How can you measure accommodation

Answer 11

push-up method, minus lens induction, or plus lens relaxation

Question 12

If your patient reports blur at 5cm what is the amplitude of accommodation

Answer 12

(1/.05m) = 20D

Question 13

List three standards for push-up method

Answer 13

monocularly, habitual Rx, target 1-2 lines larger than best near acuity

Question 14

What is psychic accommodation

Answer 14

accommodation induced by the awareness of nearness of targets (microscopes, auto-refractor, eyestrain, charts less than 20ft away

Question 15

Why is accuracy of accommodation not perfect

Answer 15

the stimulus is not always equal to the response of accommodation (lead/more than needed and lag/less than needed)

Question 16

What two things did Donder suggest about normal amplitude of accommodation

Answer 16

it decreases with age and biological variation

Question 17

What is lag for majority of normal people

Answer 17

+0.50D

Question 18

if a patient reports blur, what type of accommodation are they experiencing?

Answer 18

maximal accommodation is reached

Question 19

what type of accommodation is strongly controlled by convergence and fusion? And also somewhat controlled by the shift of spectral sensitivity and chromatic aberration?

Answer 19

tonic accommodation

Question 20

when measuring accommodation with minus lenses when would you stop introducing minus lenses to the patient, while they are maintaining convergence at distance?

Answer 20

until the patient first reports blur (PRA= positive accommodation relative to convergence)

Question 21

with plus lenses, what signals the limit when accommodation is relaxed?

Answer 21

convergence stimulus of accommodation (NRA)

Question 22

Is the stimulus to accommodation always equal to the response in accommodation?

Answer 22

no… not Perfect

Question 23

describe intermittent accommodation

Answer 23

5-8” for short periods of time

Question 24

for how long should a person be able to sustain reading at 40 cm?

Answer 24

2 hours

Question 25

according to donders table at what age does a person experience 4.5 D of accommodation and 0 D of accommodation respectively?

Answer 25

40 and 75

Question 26

Average expected accommodative amplitue

Answer 26

18.5-(0.30)(age)

Question 27

maximum expected accommodative amplitude

Answer 27

25-(0.40)(age)

Question 28

minimum expected accommodative amplitude

Answer 28

15-(0.25)(age)

Question 29

what is accommodative facility?

Answer 29

the ability to “rock” back and forth accommodation from a distance to a near target

Question 30

how is accommodative facility tested?

Answer 30

using +/- 2.00 D Flippers and polaroid lenses. Done binocularly and reading bar is used to check for suppression

Question 31

during accommodative facility test, when would you test the eyes monoculary?

Answer 31

if patient records less than 8 cycles per minute. (in monocular test you dont use bar reader nor polaroid glasses)

Question 32

what range should monocular reading fall under during the accommodative facility test?

Answer 32

4 cpm for each eye

Question 33

expected results for children 8-12 in accommodative facility test?

Answer 33

5 cpm binocularly

7 cpm monocularly

Question 34

expected results for adults 13-30 in accommodative facility test?

Answer 34

10 cpm binocularly

11 cpm monocular

Question 35

how is accommodative insufficiency measured?

Answer 35

the “push up” method (near point accommodation). Record: blur/break/recovery

Question 36

accommodative excess

Answer 36

abnormally high lead (ex. 5D accommodation required, yet the accommodative response is more 5.75D). see this in younger patients

Question 37

accommodative spasms

Answer 37

inability to relax from the accommodative lead, some of which is experienced by the patient as an interference with distance vision (near-to-far-blur)

Question 38

accommodative infacillity

Answer 38

facility of accommodation may be reduced so that focusing from near to distance may cause blur that last more than a few seconds or a sustained blur after reading for 20 mins (difficult or blur at distance after reading)