Midterm II Flashcards
What optical property does Remole’s Method use to calculate induced prism?
Dynamic spectacle magnification
Is is more accurate than Prentice’s rule for plus lenses, but not minus lenses.
Freeform lens design for PALs can compensate for a lot of lens features. What feature can it no fully compensate for?
Peripheral abberations
The near zone of a PAL is specified to begin at at ___% of the near add
95%
PALs are great, but many people are not good candidates, including…
1) Satisfied users of other near focus spectacle lenses (SV readers, Tri/Bi-Focals)
2) Occulomotor imbalances
3) >3D Anisometropia
4) High Rx
5) High Add
6) Large Pupils
7) “Type A” patients, like Larry
According to Dr. Sheedy’s research, the largest area of the near zone of any PAL offers ____% of the area provided by a FT-28 segment
50%
Which bifocal design includes add power on the back surface of the lens?
Cemented
If a multi-focal has cyl, it is always ground into the opposite surface as the add segment
Free Card
What is slab off prism used for, and in what quantities is it available?
Slab off removes vertical prism from a lens. It’s available in up to 6pd, and in 0.5pd increments. It begins for bifocals at the start of any flat topped near segment. This is also true for trifocals; the slab off starts below the intermediate segment, starting with the near segment.
Why can’t we use Prentice’s rule to determine the prism induced by plano sunglasses?
The base curve is not flat
What type of lens will cause diplopia while reading for a patient with a high anisometropic correction?
Segmented bifocals
Can safety factor differ if the lens is resolved in plus or minus cyl form?
Yes! It can differ!
OC location of Executive/Franklin
0mm
OC location of FT-40/45
0mm
OC location of FT-25/28
5mm
OC location of R-Seg (Ribbon)
7mm
