NRA \PRA ..Orthoptics evaluation

1. NRAPRA
Jyoti shah
Optometrist

2. Overall
The primary objective of these tests is to determine whether the patient requires an
add for near work.
The NRA can also be used to determine whether a patient has been overminused
during the subjective examination.
Indirect measure of accommodation
Binocular procedure

3. Negative Relative Accommodation and
Positive Relative Accommodation
Measurement
EQUIPMENT NEEDED
Phoroptertrial frame, plus and minus lenses
Reduced Snellen chart @ 40 cm
SETUP
1. Seat the patient comfortably behind the phoropter with trial frame with the patient’s
distance correction in place.
2. Place the near point card at a 40-cm distance from the patient, with good illumination

4. PROCEDURE
Instruct the patient to look at the target and keep it clear and single.
Instructions: “I will be changing the lenses in front of your eyes. Try to keep the line of letters
clear and single for as long as you can. Tell me as soon as the letters become blurry or double.”
 Add plus lenses in +0.25 D increments until the patient reports the first sustained blur or
diplopia.
 Record the amount of plus added above the distance prescription as the NRA.
 Remove the plus lenses and return to the distance prescription.
 Add minus lenses in −0.25 D increments until the patient reports the first sustained blur or
diplopia.
 Record the amount of minus added above the distance prescription as the PRA.
Stop the PRA test when you reach −2.50 D above the distance prescription.

5. Expected values :The expected values for NRA are +2.00, ±0.50; for PRA, the
expected values are −2.37, ±1.00.