ABO PRACTICAL UPDATED ACTUAL QUESTIONS WITH
CORRECT ANSWERS
Question 1.
Single Vision
ANSWER
corrects for one distance
Question 2.
Multifocal
ANSWER
Corrects with two or more prescriptions (or 'powers')
Question 3.
Bifocal
ANSWER
lens having two focus strengths
Question 4.
Trifocal
ANSWER
pertaining to having three focus strengths
Question 5.
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 6.
Compounding Prism
ANSWER
BI & BI BO & BO BU & BD
1
,Question 7.
Cancelling Prism
ANSWER
BI & BO BD & BD BU & BU
Question 8.
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 9.
Vertical Imbalance
ANSWER
The difference in vertical prism power at the reading level in a pair of lenses.
Question 10.
OC Height's by lens sation
ANSWER
SV = 1/2 of B Progressive = Fitting cross FT = 5mm above segment 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
2
, 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
Question 18.
Lens Calipers
ANSWER
Measures thickness of lenses in mm
Question 19.
Millimeter ruler
ANSWER
measures interpupillary distance, or seg heights, or OC heights
Question 20.
Circumference gauge
ANSWER
For quick and accurate measurements of lenses or patterns.
3
CORRECT ANSWERS
Question 1.
Single Vision
ANSWER
corrects for one distance
Question 2.
Multifocal
ANSWER
Corrects with two or more prescriptions (or 'powers')
Question 3.
Bifocal
ANSWER
lens having two focus strengths
Question 4.
Trifocal
ANSWER
pertaining to having three focus strengths
Question 5.
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 6.
Compounding Prism
ANSWER
BI & BI BO & BO BU & BD
1
,Question 7.
Cancelling Prism
ANSWER
BI & BO BD & BD BU & BU
Question 8.
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 9.
Vertical Imbalance
ANSWER
The difference in vertical prism power at the reading level in a pair of lenses.
Question 10.
OC Height's by lens sation
ANSWER
SV = 1/2 of B Progressive = Fitting cross FT = 5mm above segment 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
2
, 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
Question 18.
Lens Calipers
ANSWER
Measures thickness of lenses in mm
Question 19.
Millimeter ruler
ANSWER
measures interpupillary distance, or seg heights, or OC heights
Question 20.
Circumference gauge
ANSWER
For quick and accurate measurements of lenses or patterns.
3
