ABO Practical Exam with Correct Answers 2026
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)
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)
