ABO Practical Exam Questions and
Answers10
Single Vision - ANSWERS-corrects for one distance
Multifocal - ANSWERS-Corrects with two or more prescriptions (or 'powers')
Bifocal - ANSWERS-lens having two focus strengths
Trifocal - ANSWERS-pertaining to having three focus strengths
Calculating Prismatic Effects - ANSWERS-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 - ANSWERS-BI & BI
BO & BO
BU & BD
Cancelling Prism - ANSWERS-BI & BO
BD & BD
BU & BU
Prentice's Rule - ANSWERS-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 - ANSWERS-The difference in vertical prism power at the reading level in a
pair of lenses.
OC Height's by lens - ANSWERS-SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
Vertex Compensation - ANSWERS-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 - ANSWERS-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 - ANSWERS-PD
Vertical Centration - ANSWERS-OC
Horizontal & Vertical Centration Formula - ANSWERS-Given PD/OC - Human PD/OC= mm moved
Answers10
Single Vision - ANSWERS-corrects for one distance
Multifocal - ANSWERS-Corrects with two or more prescriptions (or 'powers')
Bifocal - ANSWERS-lens having two focus strengths
Trifocal - ANSWERS-pertaining to having three focus strengths
Calculating Prismatic Effects - ANSWERS-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 - ANSWERS-BI & BI
BO & BO
BU & BD
Cancelling Prism - ANSWERS-BI & BO
BD & BD
BU & BU
Prentice's Rule - ANSWERS-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 - ANSWERS-The difference in vertical prism power at the reading level in a
pair of lenses.
OC Height's by lens - ANSWERS-SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
Vertex Compensation - ANSWERS-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 - ANSWERS-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 - ANSWERS-PD
Vertical Centration - ANSWERS-OC
Horizontal & Vertical Centration Formula - ANSWERS-Given PD/OC - Human PD/OC= mm moved
