ABO Practical Exam Review Questions and
Revised Answers Graded A+
1. Single Vision: corrects for one distance
2. Multifocal: Corrects with two or more prescriptions (or 'powers')
3. Bifocal: lens having two focus strengths
4. Trifocal: pertaining to having three focus strengths
5. Calculating Prismatic Effects: obtained at the center of an optical lens by producing a ditterence in
edge thickness, either by grinding the back surface at an angle to the front surface during lens surfacing or, if the lens has suflcient
power, de-centering the optical center of the lens
6. Compounding Prism: BI & BI
BO & BO
BU & BD
7. Cancelling Prism: BI & BO
BD & BD
BU & BU
8. Prentice's Rule: 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
9. Vertical Imbalance: The ditterence in vertical prism power at the reading level in a pair of lenses.
10. OC Height's by lens: SV = 1/2 of B
Progressive = Fitting cross FT =
5mm above segment
11. Vertex Compensation: A plus lens when moved farther from the eye gains in plus power
Distance is 0 with CL because they are on the eye
12. Vertex compensation Formula: De= Dl/(1 + d xDl) De=
1/7
, diopter ettective 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
13. Horiẓontal Centration: PD
14. Vertical Centration: OC
2/7
Revised Answers Graded A+
1. Single Vision: corrects for one distance
2. Multifocal: Corrects with two or more prescriptions (or 'powers')
3. Bifocal: lens having two focus strengths
4. Trifocal: pertaining to having three focus strengths
5. Calculating Prismatic Effects: obtained at the center of an optical lens by producing a ditterence in
edge thickness, either by grinding the back surface at an angle to the front surface during lens surfacing or, if the lens has suflcient
power, de-centering the optical center of the lens
6. Compounding Prism: BI & BI
BO & BO
BU & BD
7. Cancelling Prism: BI & BO
BD & BD
BU & BU
8. Prentice's Rule: 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
9. Vertical Imbalance: The ditterence in vertical prism power at the reading level in a pair of lenses.
10. OC Height's by lens: SV = 1/2 of B
Progressive = Fitting cross FT =
5mm above segment
11. Vertex Compensation: A plus lens when moved farther from the eye gains in plus power
Distance is 0 with CL because they are on the eye
12. Vertex compensation Formula: De= Dl/(1 + d xDl) De=
1/7
, diopter ettective 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
13. Horiẓontal Centration: PD
14. Vertical Centration: OC
2/7
