ABO Practical Exam Questions And Correct Answers,
With Complete Verified Solution. Updated 2024
Single Vision
corrects for one distance
Multifocal
Corrects with two or more prescriptions (or 'powers')
Bifocal
lens having two focus strengths
Trifocal
pertaining to having three focus strengths
Calculating Prismatic Effects
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
BI & BI
BO & BO
BU & BD
Cancelling Prism
BI & BO
BD & BD
BU & BU
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
Vertical Imbalance
The difference in vertical prism power at the reading level in a pair of lenses.
OC Height's by lens
SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
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
Vertex compensation Formula
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
PD
Vertical Centration
OC
Horizontal & Vertical Centration Formula
Given PD/OC - Human PD/OC= mm moved
Frame PD is found by adding A+DBL
Power in Oblique Meridians
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
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)
Lens Measurement Devices
lens clock, calipers, millimeter ruler, circumference gauge
Lens Clock
is used to measure the surface powers base curve of a lens
Lens Calipers
Measures thickness of lenses in mm
Millimeter ruler
measures interpupillary distance, or seg heights, or OC heights
Circumference gauge
For quick and accurate measurements of lenses or patterns.
Corneal reflex Pupilometer
for precisely measuring and digitally recording pupillary distances. Used for measuring
of monocular and binocular
Hand Tools
Screwdrivers, needle-nose pliers, tweezers, files
scratchless screwdriver
for working on drill mount or facetted lenses
pickup screwdriver
jaws with spring tension to hold screws while you put them in place, available with either
type blade
Big Brass screwdriver
unscrew most screw, with a large brass handle
plastic top screwdriver
most popular and most dangerous
Pad Popper
With Complete Verified Solution. Updated 2024
Single Vision
corrects for one distance
Multifocal
Corrects with two or more prescriptions (or 'powers')
Bifocal
lens having two focus strengths
Trifocal
pertaining to having three focus strengths
Calculating Prismatic Effects
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
BI & BI
BO & BO
BU & BD
Cancelling Prism
BI & BO
BD & BD
BU & BU
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
Vertical Imbalance
The difference in vertical prism power at the reading level in a pair of lenses.
OC Height's by lens
SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
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
Vertex compensation Formula
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
PD
Vertical Centration
OC
Horizontal & Vertical Centration Formula
Given PD/OC - Human PD/OC= mm moved
Frame PD is found by adding A+DBL
Power in Oblique Meridians
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
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)
Lens Measurement Devices
lens clock, calipers, millimeter ruler, circumference gauge
Lens Clock
is used to measure the surface powers base curve of a lens
Lens Calipers
Measures thickness of lenses in mm
Millimeter ruler
measures interpupillary distance, or seg heights, or OC heights
Circumference gauge
For quick and accurate measurements of lenses or patterns.
Corneal reflex Pupilometer
for precisely measuring and digitally recording pupillary distances. Used for measuring
of monocular and binocular
Hand Tools
Screwdrivers, needle-nose pliers, tweezers, files
scratchless screwdriver
for working on drill mount or facetted lenses
pickup screwdriver
jaws with spring tension to hold screws while you put them in place, available with either
type blade
Big Brass screwdriver
unscrew most screw, with a large brass handle
plastic top screwdriver
most popular and most dangerous
Pad Popper
