ABO PRACTICAL EXAM ACTUAL TEST
QUESTIONS AND CORRECT ANSWERS
◉ Multifocal.
Answer: Corrects with two or more prescriptions (or 'powers')
◉ Bifocal.
Answer: lens having two focus strengths
◉ Trifocal.
Answer: pertaining to having three focus strengths
◉ Calculating Prismatic Effects.
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.
Answer: BI & BI
BO & BO
BU & BD
,◉ Cancelling Prism.
Answer: BI & BO
BD & BD
BU & BU
◉ Prentice's Rule.
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.
Answer: The difference in vertical prism power at the reading level
in a pair of lenses.
◉ OC Height's by lens.
Answer: SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
, ◉ Vertex Compensation.
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.
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.
Answer: PD
◉ Vertical Centration.
Answer: OC
◉ Horizontal & Vertical Centration Formula.
Answer: Given PD/OC - Human PD/OC= mm moved
QUESTIONS AND CORRECT ANSWERS
◉ Multifocal.
Answer: Corrects with two or more prescriptions (or 'powers')
◉ Bifocal.
Answer: lens having two focus strengths
◉ Trifocal.
Answer: pertaining to having three focus strengths
◉ Calculating Prismatic Effects.
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.
Answer: BI & BI
BO & BO
BU & BD
,◉ Cancelling Prism.
Answer: BI & BO
BD & BD
BU & BU
◉ Prentice's Rule.
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.
Answer: The difference in vertical prism power at the reading level
in a pair of lenses.
◉ OC Height's by lens.
Answer: SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
, ◉ Vertex Compensation.
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.
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.
Answer: PD
◉ Vertical Centration.
Answer: OC
◉ Horizontal & Vertical Centration Formula.
Answer: Given PD/OC - Human PD/OC= mm moved
