Accommodation Flashcards
Heath’s components of accommodation are:
- tonic
- proximal
- voluntary
- vergence
- reflex (defocus)
tonic accommodation accounts for about ____ D of accommodation
1-1.5 D of accommodation
CA/C ratio is
the convergence accommodation per unit of convergence
which is more clinically significant: CA/C or AC/A?
AC/A ratio is more clinically significant
reflex accommodation is driven by
retinal defocus or blurring of the retinal image
closed-loop negative feedback control
depth of focus number averages at
0.62 D
depth of field ____ with decreasing pupil diameter
increases
absolute presbyopes can measure about ____ D of accommodation
1 D
depth of focus is measured clinically as the:
difference between the accommodative stimulus and the response
lag= ____ accommodation
under
lead= ___ accommodation
over
what is more common: under-accommodation (lag) or over-accommodation (lead)?
under-accommodation (lag)
amplitude of accommodation is the
total amount of accommodation available, measured in diopters
amplitude of accommodation is the inverse of the:
near point of accommodation in meters
do hyperopes gain or lose amplitude through their spectacle rx?
lose
do myopes gain or lose amplitude through their spectacle rx?
gain
push up amps measure _____ than minus lens amps
higher
Donders push up or minus lens method:
-retinal image size increases greatly (up to 400%)
Donders
Donder’s push up or minus lens method:
-retinal image size decreases slightly (up to 10%)
Minus lens
Donder’s push up or minus lens method:
-proximal stimulation increases
Donders
Donder’s push up or minus lens method:
-proximal stimulation is constant
Minus Lens
Donder’s push up or minus lens method:
-target change is more natural
Donders
Donder’s push up or minus lens method:
-stimulus change is continuous
Donders
Donder’s push up or minus lens method:
-stimulus change is discrete
Donder’s push up or minus lens method:
Donder’s push up or minus lens method:
-overestimates amplitude
Donders
Donder’s push up or minus lens method:
-underestimates amplitude
Minus Lens
push up test expected values for age 14, 50, and 75
14 D at age 10
2.5 D at age 50
0 D at age 75
Hofstetter formula for average amplitude
18.5 D - (0.3 x age)
Hofstetter formula for minimum amplitude
15 D - (0.25 x age)
why are binocular measures almost always higher for accommodative amplitude
amplitude is increased with convergence
reflex accommodation + vergence accommodation
