PRA/NRA Flashcards
What kind of patient would we test PRA/NRA for?
52 y/o
Near vision blur though current reading glasses
Old spectacles
Initially when he first received them, his near vision was clear, but gradually over the past 6 months he cannot see as well up close anymore.
What is the purpose of PRA/NRA?
To increase and relax accommodation while maintaining a constant vergence
Help determine near Rx
What is the mechanism of NRA?
Uses plus lenses which relaxes accommodation
What is the mechanism of PRA?
Using minus lenses which increases the accommodative response
What is the lighting and correction for PRA/NRA?
Bright illumination
Proper distance refraction in phoropter
What is the target for NRA/PRA?
One line of letter larger than near V/A set at 40cm
(Near V/A 20/20, use 20/30 letters)
Should NRA or PRA be performed first?
NRA
What should be done before testing?
Monocularly check for 20/20
Make sure phoropter is converged
How is NRA performed?
Add plus lenses binocularly until point of first blur
Total amount added is the NRA
Set lenses back to distance Rx
How is PRA performed?
Add minus lenses binocularly until point of first blur
Total amount added is equal to PRA
When should a suppression check be performed?
If results reach expected values (+/- 2.50)
Place pen between patient and chart
Have patient focus on chart then report how many pens they see (should be 2)
add minus lenses until chart is blurry or only one pen is seen
When should we end the test?
If results are greater than +/- 3.00
Describe a near base for presbyopia patients.
Tentative add placed before performing NRA/PRA
What is the normal result for non presbyopes?
+/- 2.50 on non-presbyopia patients
Describe how to record results for NRA/PRA with suppression check and for a near base.
NRA/PRA +2.75/-1.50 c suppression check
NRA/PRA >+3.00/-2.50 c suppression check
Near base: +1.00, NRA/PRA +2.00/-1.00
