ABO Practical
Single Vision - CORRECT ANSWER-corrects for one distance
Multifocal - CORRECT ANSWER-Corrects with two or more prescriptions (or
'powers')
Bifocal - CORRECT ANSWER-lens having two focus strengths
Trifocal - CORRECT ANSWER-pertaining to having three focus strengths
Calculating Prismatic Effects - CORRECT ANSWER-obtained at the center of an
optical lens by producing a difference in edge thickness, either by grinding the
back surface at an angle to the front surface during lens surfacing or, if the lens
has sufficient power, de-centering the optical center of the lens
Compounding Prism - CORRECT ANSWER-BI & BI
BO & BO
BU & BD
Cancelling Prism - CORRECT ANSWER-BI & BO
BD & BD
BU & BU
Prentice's Rule - CORRECT ANSWER-P=hcm x D
P=amount of prism created
h= number of cm OC moved
cm= centimeters (convert to mm, divide by 10)
D= power in meridian with error
Vertical Imbalance - CORRECT ANSWER-The difference in vertical prism power
at the reading level in a pair of lenses.
OC Height's by lens - CORRECT ANSWER-SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
, Vertex Compensation - CORRECT ANSWER-A plus lens when moved farther
from the eye gains in plus power
Distance is 0 with CL because they are on the eye
Vertex compensation Formula - CORRECT ANSWER-De= Dl/(1 + d xDl)
De= diopter effective value of error created
D/= lens power (given power)
d= amount in METERS lens moved from refracted position to position lens is
worn
Keep sign for what it is (+/-)
- to d means moves away
Horizontal Centration - CORRECT ANSWER-PD
Vertical Centration - CORRECT ANSWER-OC
Horizontal & Vertical Centration Formula - CORRECT ANSWER-Given PD/OC -
Human PD/OC= mm moved
Frame PD is found by adding A+DBL
Power in Oblique Meridians - CORRECT ANSWER-Dt= (sina)²x Dc +Ds
Dt= Total Power we need
(sina)²= degree we have degree we need
Dc= cylinder power
Ds= sphere power
Lensmeter - CORRECT ANSWER-is an ophthalmic instrument. It is mainly used
by optometrists and opticians to verify the correct prescription in a pair of
eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct
mounting of lenses in spectacle frames. (also known as a focimeter or
vertometer)
Lens Measurement Devices - CORRECT ANSWER-lens clock, calipers,
millimeter ruler, circumference gauge
Single Vision - CORRECT ANSWER-corrects for one distance
Multifocal - CORRECT ANSWER-Corrects with two or more prescriptions (or
'powers')
Bifocal - CORRECT ANSWER-lens having two focus strengths
Trifocal - CORRECT ANSWER-pertaining to having three focus strengths
Calculating Prismatic Effects - CORRECT ANSWER-obtained at the center of an
optical lens by producing a difference in edge thickness, either by grinding the
back surface at an angle to the front surface during lens surfacing or, if the lens
has sufficient power, de-centering the optical center of the lens
Compounding Prism - CORRECT ANSWER-BI & BI
BO & BO
BU & BD
Cancelling Prism - CORRECT ANSWER-BI & BO
BD & BD
BU & BU
Prentice's Rule - CORRECT ANSWER-P=hcm x D
P=amount of prism created
h= number of cm OC moved
cm= centimeters (convert to mm, divide by 10)
D= power in meridian with error
Vertical Imbalance - CORRECT ANSWER-The difference in vertical prism power
at the reading level in a pair of lenses.
OC Height's by lens - CORRECT ANSWER-SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
, Vertex Compensation - CORRECT ANSWER-A plus lens when moved farther
from the eye gains in plus power
Distance is 0 with CL because they are on the eye
Vertex compensation Formula - CORRECT ANSWER-De= Dl/(1 + d xDl)
De= diopter effective value of error created
D/= lens power (given power)
d= amount in METERS lens moved from refracted position to position lens is
worn
Keep sign for what it is (+/-)
- to d means moves away
Horizontal Centration - CORRECT ANSWER-PD
Vertical Centration - CORRECT ANSWER-OC
Horizontal & Vertical Centration Formula - CORRECT ANSWER-Given PD/OC -
Human PD/OC= mm moved
Frame PD is found by adding A+DBL
Power in Oblique Meridians - CORRECT ANSWER-Dt= (sina)²x Dc +Ds
Dt= Total Power we need
(sina)²= degree we have degree we need
Dc= cylinder power
Ds= sphere power
Lensmeter - CORRECT ANSWER-is an ophthalmic instrument. It is mainly used
by optometrists and opticians to verify the correct prescription in a pair of
eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct
mounting of lenses in spectacle frames. (also known as a focimeter or
vertometer)
Lens Measurement Devices - CORRECT ANSWER-lens clock, calipers,
millimeter ruler, circumference gauge
