ABO PRACTICAL BOARD EVALUATION Questions with Correct
Answers (Grade A+)
Question 1: Multifocal.
Answer: Corrects with two or more prescriptions (or 'powers')
Question 2: Bifocal.
Answer: lens having two focus strengths
Question 3: Trifocal.
Answer: pertaining to having three focus strengths
Question 4: 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
Question 5: Compounding Prism.
Answer:
1. BI & BI
2. BO & BO
3. BU & BD
Question 6: Cancelling Prism.
Answer:
1. BI & BO
2. BD & BD
3. BU & BU
Question 7: 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
Question 8: Vertical Imbalance.
Answer: The difference in vertical prism power at the reading level in a pair of lenses.
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, Question 9: OC Height's by lens.
Answer:
1. SV = 1/2 of B
2. Progressive = Fitting cross
3. FT = 5mm above segment
Question 10: 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
Question 11: 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
Question 12: Horizontal Centration.
Answer: PD
Question 13: Vertical Centration.
Answer: OC
Question 14: Horizontal & Vertical Centration Formula.
Answer: Given PD/OC - Human PD/OC= mm moved Frame PD is found by adding A+DBL
Question 15: Power in Oblique Meridians.
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
Question 16: Lensmeter.
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)
Question 17: Lens Measurement Devices.
Answer: lens clock, calipers, millimeter ruler, circumference gauge
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Answers (Grade A+)
Question 1: Multifocal.
Answer: Corrects with two or more prescriptions (or 'powers')
Question 2: Bifocal.
Answer: lens having two focus strengths
Question 3: Trifocal.
Answer: pertaining to having three focus strengths
Question 4: 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
Question 5: Compounding Prism.
Answer:
1. BI & BI
2. BO & BO
3. BU & BD
Question 6: Cancelling Prism.
Answer:
1. BI & BO
2. BD & BD
3. BU & BU
Question 7: 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
Question 8: Vertical Imbalance.
Answer: The difference in vertical prism power at the reading level in a pair of lenses.
Page 1
, Question 9: OC Height's by lens.
Answer:
1. SV = 1/2 of B
2. Progressive = Fitting cross
3. FT = 5mm above segment
Question 10: 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
Question 11: 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
Question 12: Horizontal Centration.
Answer: PD
Question 13: Vertical Centration.
Answer: OC
Question 14: Horizontal & Vertical Centration Formula.
Answer: Given PD/OC - Human PD/OC= mm moved Frame PD is found by adding A+DBL
Question 15: Power in Oblique Meridians.
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
Question 16: Lensmeter.
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)
Question 17: Lens Measurement Devices.
Answer: lens clock, calipers, millimeter ruler, circumference gauge
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