Accommodation Flashcards Preview

PPO2 > Accommodation > Flashcards

Flashcards in Accommodation Deck (38):
1

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

Normal Accommodation (consensual and equal)

2

List the components of the near triad

convergence, accommodation, miosis

3

What are the two types of accommodation

Positive accommodation (focus) and Negative accommodation (defocus)

4

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

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

5

What 3 things occur in negative accommodation

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

6

What are the 4 types of NORMAL accommodation

reflex, tonic, convergence, and psychic/near

7

What stimulates reflex accommodation

the quality of retinal images (blurred or defocused signals)

8

What does tonic accommodation depend on

the tone of the ciliary body

9

What is convergence accommodation (aka: relative accommodation)

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

10

What are strong drivers for near work induced myopia

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

11

How can you measure accommodation

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

12

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

(1/.05m) = 20D

13

List three standards for push-up method

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

14

What is psychic accommodation

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

15

Why is accuracy of accommodation not perfect

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

16

What two things did Donder suggest about normal amplitude of accommodation

it decreases with age and biological variation

17

What is lag for majority of normal people

+0.50D

18

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

maximal accommodation is reached

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?

tonic accommodation

20

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

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

21

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

convergence stimulus of accommodation (NRA)

22

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

no... not Perfect

23

describe intermittent accommodation

5-8" for short periods of time

24

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

2 hours

25

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

40 and 75

26

Average expected accommodative amplitue

18.5-(0.30)(age)

27

maximum expected accommodative amplitude

25-(0.40)(age)

28

minimum expected accommodative amplitude

15-(0.25)(age)

29

what is accommodative facility?

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

30

how is accommodative facility tested?

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

31

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

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

32

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

4 cpm for each eye

33

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

5 cpm binocularly
7 cpm monocularly

34

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

10 cpm binocularly
11 cpm monocular

35

how is accommodative insufficiency measured?

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

36

accommodative excess

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

37

accommodative spasms

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)

38

accommodative infacillity

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)