NRA PRA
negative relative accommodation - answer decrease in accommodative demand while
the vergence stimulus is held constant
positive relative accommodation - answer increase in accommodative demand while the
vergence stimulus remains constant
NRA is measured clinically by - answer introducing positive lenses while the patient
views a near target at 40 cm
PRA is measured clinically by - answer introducing negative lenses while the patient
views a near target at 40 cm
endpoint of test - answer when patient reports first slight sustained blur even after being
encouraged to clear the target
value of PRA and NRA - answer amount of additional spherical power which has been
added to the distance correction
represents the magnitude of accommodation
DO NOT factor in target distance
PRA flow - answerincrease in blur driven accommodation
increase in accommodative convergence
decrease in disparity divergence (diverge)
decrease in convergent accommodation
NRA flow - answerdecrease in blur driven accommodation
decrease in accommodative convergence
increased disparity convergence (converge)
increase in convergent accommodation
low PRA caused by difficulty increasing blur driven accommodation - answerpresbyopia,
accommodative insufficiency
low PRA caused by difficulty with disparity divergence - answeresotropia, convergence
excess
low NRA caused by difficulty decreasing blur driven accommodation -
answeraccommodative excess, pseudomyopia, latent hyperopia
negative relative accommodation - answer decrease in accommodative demand while
the vergence stimulus is held constant
positive relative accommodation - answer increase in accommodative demand while the
vergence stimulus remains constant
NRA is measured clinically by - answer introducing positive lenses while the patient
views a near target at 40 cm
PRA is measured clinically by - answer introducing negative lenses while the patient
views a near target at 40 cm
endpoint of test - answer when patient reports first slight sustained blur even after being
encouraged to clear the target
value of PRA and NRA - answer amount of additional spherical power which has been
added to the distance correction
represents the magnitude of accommodation
DO NOT factor in target distance
PRA flow - answerincrease in blur driven accommodation
increase in accommodative convergence
decrease in disparity divergence (diverge)
decrease in convergent accommodation
NRA flow - answerdecrease in blur driven accommodation
decrease in accommodative convergence
increased disparity convergence (converge)
increase in convergent accommodation
low PRA caused by difficulty increasing blur driven accommodation - answerpresbyopia,
accommodative insufficiency
low PRA caused by difficulty with disparity divergence - answeresotropia, convergence
excess
low NRA caused by difficulty decreasing blur driven accommodation -
answeraccommodative excess, pseudomyopia, latent hyperopia
