Refraction of the Low Vision Patient Flashcards
When are objective evaluations used in low vision?
With children from birth to 4 years old or for individuals that are unable to respond subjectively
What is the first step in low vision refraction?
retinoscopy (usually non-cycloplegic)
What are 3 benefits to using an auto refractor?
1) gives starting point
2) provides K-reading
3) saves time
What are some reasons that an auto-refractor might not be reliable?
nystagmus, poor fixation, Eccentric Viewing, media opacities
What are some reasons to use a trial frame for retinoscopy?
The patient wears PALs; lenses in the patients glasses are excessively scratched or the frame is broken
Does the sphere or cyl lens go in the back well closest to the eye?
sphere
How do you resolve a cylinder axis discrepancy when retinoscopy findings don’t match the spectacle Rx axis?
Lensometry
How is refraction used to decide ocular disease management?
BCVA gives insight into potential progression/ stabilization of disease and guides the treatment plan
What are some challenges/ assumptions that lead to a young patient with congenital disease not having proper refraction?
1) assumption that correction will not help
2) poor cooperation from young patients
3) surgical and medical management take priority
Individuals with vision loss are less/more sensitive to small refraction shifts
less
Eccentric viewing is trained in patients with central/peripheral vision loss
central
What are some conditions that may lead to significant refractive errors?
albinism, aphasia, cataracts, corneal scarring, keratoconus, degenerative myopia, Marfan’s syndrome, retinitis pigments, retinopathy of prematurity
What are some instances where a patient would benefit from trial frame refraction?
patients with nystagmus, torticollis, gaze palsies or are wheel chair bound might benefit from trial frame refraction because they may not be able to align their eyes in the phoropter
What are 3 advantages to trial frame refraction?
1) enables eccentric viewing
2) enables head positions that promote better vision
3) large lens changes are easier to present
When would you prescribe the auto refraction to a patient?
never, but useful for finding astigmatism and axis
What are the 3 possible starting points for setting up the trial frame?
1) autorefraction
2) retinoscopy findings
3) habitual prescription
what are the expected results from changing the pantoscopic tilt on the trial frame?
decrease vertex and decrease glare
Why might you use a (+) lens to blur a patient with nystagmus rather than occluding an eye?
occlusion often induces latent nystagmus and will result in a significant decrease in VA
Which method is more common in low vision refraction: JND or Bailey?
JND
How do we calculate JND?
divide the 20-ft Snellen denominator by 100, then divide that by 2 to find the lens to use.
Example: 20/400; JND = 4, show +/-2.00
What are the 4 steps for refining the best sphere using the JND method?
1) finding the midpoint
2) visual impairment consideration: using larger increments between choices
3) patient communication
4) verifying the best sphere
What happens to the JND as acuity improves?
it decreases
JND Method
What is the end point for a patient that has accommodation?
The maximum plus lens that keeps the best vision
What are the 4 steps to the Bailey Method?
- Broad Bracketing
- Refine Increments
- Compare and Choose
- Minimize Blur
