Term
| What are four different ways to take visual acuities if the patient cannot see the Snellen chart? |
|
Definition
- walk up (10/400)
- finger count (FC @ 3 feet)
- light projection (can tell where light is coming from)
- light perception (LP @ 1 foot)
|
|
|
Term
| What will pinhole tell you about their vision? |
|
Definition
Improvement = at least part of the acuity loss is refractive
No Improvement = something other than their refraction is causing the acuity loss |
|
|
Term
| Is a lot of the refraction done in or out of the phoropter? |
|
Definition
a lot of the refraction is done out of phoropter
- especially with macular degeneration
- can do a task-specific exam
|
|
|
Term
sequence for low vision examination:
How might retinoscopy be different? |
|
Definition
- you may need to move closer to the patient to perform ret due to hazy media
- do NOT forget to alter working distance lens!
|
|
|
Term
sequence for low vision examination:
How will the refraction be altered? |
|
Definition
- open the entire acuity chart - put the smallest letter they can see on the bottom of the chart and bigger letters above this line
- you may want to later isolate lines to stop them from calling out entire chart each time
- find the best spherical lens (general spherical refraction)
- make big changes! (larger JND)
- find the best cylinder and axis (details to come)
- refine the spherical power (BSBVA)
- check acuities
NOTE: many are presbyopes, so do a task-specific exam, including near subjective
NOTE: don't forget about the tests you might not do as often (red/green, radial line, keratometry, etc.) |
|
|
Term
sequence for low vision examination:
How might obtaining the cylinder and axis be different? |
|
Definition
- try JCC first to see if they are sensitive to the test (most will be)
- add and subtract cylinder power keeping equivalent sphere until you find the best cylinder power (keep more minus cyl in place, initially)
- turn the axis dial to bracket the axis which creates the best visual acuity
- may have large range due to low BCVA, in whcih case put at midpoint of range OR have them turn dial themselves until best clarity is obtained
- add and subtract cylinder power keeping equivalent sphere to refine the cylinder power (leave more plus cyl in place)
|
|
|
Term
sequence for low vision examination:
What will you need to ensure during phoria and vergence testing? |
|
Definition
| make sure to use a target they can see with BOTH eyes |
|
|
Term
| What acuity do you want to give them? |
|
Definition
| give them the smallest acuity that allows them to see the letters |
|
|
Term
| How might their JND be different? |
|
Definition
they will have a large JND so make big changes for forced choice
- 20/50 = 0.50D lens changes
- 20/100 = 1.00D lens changes
- 20/200 = 2.00D lens changes
|
|
|
Term
| What do you want to do if you don't find a significant change in prescription? |
|
Definition
| do NOT change rx if little difference is found |
|
|
Term
example problem solving:
Your patient wants to see a newspaper (20/50 demand).
He can see 20/100 at 40cm with +2.50 add.
- how close does he need to bring the newspaper so he can see it?
- What add does he need to work at this distance?
|
|
Definition
- he must bring paper 20cm (half as close) to see it
- divide denominator of acuity demand by BCVA to determine how much the working distance must be altered by
- 50/100 = 0.50, and 40cm*0.5 = 20cm
- he needs a +5.00D add to see the newspaper
- divide denominator of BCVA by acuity they want to achieve to determine magnification requires
- 100/50 = 2x, and 2.50*2 = +5.00 add power
NOTE: if very task specific, have them bring in what they want to be able to read/see and do refraction sequence using this specific target |
|
|
