Relative Accommodation Flashcards
What does relative accommodation test the ability of?
The ability for your patient to both relax (NRA) and stimulate (PRA) accommodation while maintaining single, binocular vision.
What do you do to find NRA? What does this cause?
You add plus lenses by 0.25D steps until the patient reports sustained blur of the target at 40 cm. It causes decreased accommodation and subsequently affects accommodative and fusional vergence.
For a presbyope, what must you begin with when doing NRA?
You must begin with a near control lens that is the total of MR and bifocal add as the beginning point since the presbyope will be blurred at 40 cm through manifest refraction.
What sign does a net NRA always have?
Positive sign
What sign does a net PRA always have?
Negative sign
On NRA, the patient will need to employ _____________ vergence to counter the reduction in accommodation and accommodative convergence (which leads to a shift toward _________)
positive fusional; exophoria
On PRA, the patient will need to employ _____________ vergence to counter the increase in accommodation and accommodative convergence (which leads to a shift toward _________)
negative fusional; esophoria
For NRA, what lenses do you use? Does accommodation increase or decrease? Does positive fusional vergence increase or decrease?
For NRA, use plus lenses, decrease accommodation, increase PFV
For PRA, what lenses do you use? Does accommodation increase or decrease? Does negative fusional vergence increase or decrease?
For PRA, use minus lenses, increase accommodation, increase NFV
The amount of the net NRA is determined by two factors:
1) The amount of accommodation that was relaxed for the test stimulus
2) The amount of Positive Fusional Vergence available to the patient, as measured by the Base Out vergence
How much does the depth of focus add?
0.50D
When can a problem arise when testing negative accommodation?
1) If the patient is highly exophoric with a normal AC/A, the patient may go diplopic before the blur point. If this happens, record the point at which the diplopia occurs and note the value was diplopia.
2) If more than 3.00D of plus is added over the manifest refraction, the patient could be over minused on the manifest refraction.
Exophoric patient usually have ___ AC/A.
Low
What does NRA measure?
measures the amount of accommodation that can be relaxed relative to convergence (increase in NAV and subsequent need for more PFV)
The amount of the net PRA is determined by two factors:
1) The accommodative amplitude of the patient.
2) The amount of negative fusional vergence available to the patient, as measured by the Base In vergence
Problem that can occur with positive relative accommodation
If the patient is highly esophoric, the patient may go diplopic before the blur point. If this happens, record the point at which the diplopia occurs and note the value was diplopia.
Highly esophoric patients usually have ___ AC/A.
high
When does the blur occur for PRA?
the blur occurs when accommodation is fully stimulated or when the patient runs out of NFV.
When does the blur occur for NRA?
the blur occurs when accommodation is fully relaxed or when the patient runs out of PFV.
If tests are run monocularly, what is the only thing being tested?
Accommodation
Doing PRA testing for a bino exophore, would the patient like or not like the minus given?
Exo would like the minus given in PRA because it helps relax exophoria.
Doing PRA testing for a bino esophore, would the patient like or not like the minus given?
Not like. It would make the esophoria worse.
Doing PRA testing for a monocular esophore, would the patient like or not like the minus given?
Help if the results were limited by NFV instead of accomodation.
Doing NRA testing for a monocular esophore, would the patient like or not like the plus given?
No change
Doing NRA testing for a monocular exophore, would the patient like or not like the plus given?
They would like it. It would help if their eyes were limited by PFV instead of accomodation.
Doing NRA testing for a binocular esophore, would the patient like or not like the plus given?
They would like it because it helps their eso. They would have higher number.
Doing NRA testing for a binocular exophore, would the patient like or not like the plus given?
Not like the plus and take less. It makes exophoria worse
For PRA, an exophore has to become _______ before running out of the predicted AC/A endpoint
esophoric
For PRA, a __________ is more likely to run out of accommodation amplitude than negative fusional vergence.
exophore
For NRA, what values do you use and look at for near testing?
Use PFV, BO testing.
For PRA, what values do you use and look at for near testing?
Use NFV, BI vergence testing
What is always the predicted accommodative amplitude for NRA testing?
+ 2.50 D
How to find the predicted accommodation endpoint for PRA testing?
Accommodation amplitude - 2.50D (from stimulus)
