(1a) Trial Frame vs Phoropter Flashcards
adjustments for trial frame
pupillary distance, temple length, pantascopic tilt, nose pad
auxiliary lenses
pinhole, occluder, prisms, slits, maddox rods, red/green filters
explain pinhole
used to determine whether reduced vision is caused by refractive error. if this is the case, pinhole will cause an improvement in visual acuity
position of lens in trial frame
sphere first, cylinder in front of sphere. auxiliary anywhere
advantages of trial frame
better for those with high rx (4D or higher) bc vertex distance can be maintained well (by placing lens closest to eye)
better for presbyopia px as frame similar to specs, can look down and simulates near reading vision better
phoropter advantages
- faster, convenient for examiner
- comfortable for px, no weight on nose
- lenses not greased
- greater axis accuracy during cylindrical correction
- addividity errors reduced
phoropter disadvantages
- hide patients face thus cannot observe px and their responses
- head tilt affects cylindrical axis
- difficult to control vertex distance
- need to check again with trial frame for px with high rx
- eff power at near different than in prescribed lens