NRA/PRA/BAF/MAF Flashcards
relative accommodation
ability to sustain fusion and clarity under varying accommodative conditions
tentative add (using NRA/PRA)
FCC + ((NRA +PRA)/2)
Negative Relative Accommodation
adding plus (think negative= relaxing accommodation)
Positive Relative accommodation
adding minus (think positive=stimulating accommodation)
PRA indirectly measures
NFV (divergence)
because accommodation is stimulated and converged eyes must try to diverge to maintain clear single image
NRA indirectly measures
PFV (convergence)
because accommodation is relaxed and diverged eyes must try to diverge to maintain clear single image
Is NRA or PRA performed first
NRA
when is NRA/PRA performed
immediately before minus lens amps (non-presbyopes) OR during add-determination
NRA/PRA purpose
to determine accommodative ability under binocular conditions
“range of focusing system”
NRA/PRA starting point
habitual rx (non-presbyopes) or tentative add (presbyopes)
NRA/PRA target
“read these words letter by letter” or 2 lines above BCVA of poorer seeing eye if not 20/20
why would a patient see a target after a PRA greater than -3.00 D?
most likely suppressing (per NBEO)
Expected NRA results
+2.00 (+/-0.50) D
+1.50 - +2.50
Expected PRA results
- 2.37 (+/-1.00)D
- 1.37 - -3.37
binocular accommodative facility
measures the interaction between accommodation and vergence
monocular accommodative facility
measures only accommodative facility
accommodative facility
to evaluate the stamina and dynamics of the accommodative response when switching between plus and minus lenses
“flexibility of your focusing system”
accommodative infacility
sluggish or difficult accommodative response to change in stimulus of fixation distance
accommodative facility target
20/40 single letter rock card at 40 cm, polaroid strips vertical over card for binocular
how long do you test accommodative facility for?
60s
things to note/record during BAF
cycles completed; plus or minus more difficult; any suppression/diplopia
ex: 6 cpm, (-) more difficult
1 cycle in BAF/MAF
2 boxes (cleared 1 plus and 1 minus)
expected adult BAF results
10 cpm
expected child BAF results
5 cpm
