ABO Practical Exam
Single Vision - ANSWER corrects for one distance
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
Frame PD is found by adding A+DBL
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
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)
Lens Measurement Devices - ANSWER lens clock, calipers, millimeter ruler,
circumference gauge
Lens Clock - ANSWER is used to measure the surface powers base curve of a lens
Lens Calipers - ANSWER Measures thickness of lenses in mm
Millimeter ruler - ANSWER measures interpupillary distance, or seg heights, or OC
heights
Circumference gauge - ANSWER For quick and accurate measurements of lenses
or patterns.
Corneal reflex Pupilometer - ANSWER for precisely measuring and digitally
recording pupillary distances. Used for measuring of monocular and binocular
Hand Tools - ANSWER Screwdrivers, needle-nose pliers, tweezers, files
scratchless screwdriver - ANSWER for working on drill mount or facetted lenses
pickup screwdriver - ANSWER jaws with spring tension to hold screws while you put
them in place, available with either type blade
Big Brass screwdriver - ANSWER unscrew most screw, with a large brass handle
plastic top screwdriver - ANSWER most popular and most dangerous
Pad Popper - ANSWER used to remove snap-in nosepads without changing the
alignment of the adjustable guard arms. the prongs are inserted behind the nosepad
and in front of the nosepad box. a simple twist removes the pad
Single Vision - ANSWER corrects for one distance
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
Frame PD is found by adding A+DBL
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
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)
Lens Measurement Devices - ANSWER lens clock, calipers, millimeter ruler,
circumference gauge
Lens Clock - ANSWER is used to measure the surface powers base curve of a lens
Lens Calipers - ANSWER Measures thickness of lenses in mm
Millimeter ruler - ANSWER measures interpupillary distance, or seg heights, or OC
heights
Circumference gauge - ANSWER For quick and accurate measurements of lenses
or patterns.
Corneal reflex Pupilometer - ANSWER for precisely measuring and digitally
recording pupillary distances. Used for measuring of monocular and binocular
Hand Tools - ANSWER Screwdrivers, needle-nose pliers, tweezers, files
scratchless screwdriver - ANSWER for working on drill mount or facetted lenses
pickup screwdriver - ANSWER jaws with spring tension to hold screws while you put
them in place, available with either type blade
Big Brass screwdriver - ANSWER unscrew most screw, with a large brass handle
plastic top screwdriver - ANSWER most popular and most dangerous
Pad Popper - ANSWER used to remove snap-in nosepads without changing the
alignment of the adjustable guard arms. the prongs are inserted behind the nosepad
and in front of the nosepad box. a simple twist removes the pad
