ABO PRACTICAL
85+ (Latest 2026 Edition) 100% Verified Q&A + Answer Key Solutions
100% Guarantee Pass
📋 DOCUMENT OVERVIEW 85 Qs
This document, "ABO Practical," covers specific topics related to optometry and ophthalmology, including
lens types (single vision, multifocal, bifocal, and trifocal), prismatic effects, and optical lens design. The
document provides 85 questions with correct answers and detailed explanations/rationales, as well as
diagrams/images to aid in understanding. Students can use this resource to study, review, and gain a
deeper understanding of these concepts, ultimately enhancing their knowledge and preparation for
exams in optometry and ophthalmology.
✓ Verified Answers ✓ Exam Ready ✓ Study Guide
Trusted by thousands of students and professionals worldwide
EXAM QUESTIONS
QUESTION 1
Single Vision
CORRECT ANSWER
corrects for one distance
RATIONALE: Single Vision lenses are designed to focus light for a specific distance, such as seeing objects clearly in front of
you or in the distance, but may not accommodate for multiple distances like near and far vision simultaneously. This means
that Single Vision lenses "corrects for one distance", allowing you to see objects clearly at that specific distance, but may
not provide clear vision at other distances.
Trusted by thousands of students and professionals worldwide Page 1 of 38
, QUESTION 2
Multifocal
CORRECT ANSWER
Corrects with two or more prescriptions (or 'powers')
RATIONALE: A multifocal lens is designed to correct vision at multiple distances, which typically requires two or more
different prescriptions to account for the varying powers needed for near, intermediate, and far vision. This requires the
correction of multiple focal lengths using different prescriptions, making the statement "Corrects with two or more
prescriptions (or 'powers')" a defining characteristic of a multifocal lens.
QUESTION 3
Bifocal
CORRECT ANSWER
lens having two focus strengths
RATIONALE: The term "bifocal" refers to a design feature that combines two distinct focus strengths in a single lens,
allowing the user to switch between near and far vision without needing to change glasses. This concept is rooted in the
need for a convenient and practical solution to correct vision problems, particularly in individuals with presbyopia who
experience declining near vision with age.
QUESTION 4
Trifocal
CORRECT ANSWER
pertaining to having three focus strengths
RATIONALE: The word "Trifocal" refers to something related to or having three focal points, which typically means three
areas of focus or concentration. This concept is derived from the Latin word "trifocalis," meaning "having three foci,"
indicating that the term specifically pertains to having three focus strengths.
Trusted by thousands of students and professionals worldwide Page 2 of 38
, QUESTION 5
Calculating Prismatic Effects
CORRECT 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
RATIONALE: Calculating prismatic effects involves understanding how different lens surface curvatures and positions can
create variations in beam divergence and convergence, resulting in prismatic effects that can cause image displacement.
The specific methods described, such as grinding the back surface at an angle or de-centering the optical center, create
these prismatic effects by intentionally introducing asymmetries in the lens's optical path, which in turn affect the beam's
trajectory and cause deviations from a straight line.
QUESTION 6
Compounding Prism
CORRECT ANSWER
BI & BI
BO & BO
BU & BD
RATIONALE: When considering a compounding prism, it's essential to understand that the angles between adjacent pairs of
faces remain the same, and the sum of the dihedral angles around any vertex must be 360 degrees. The given pairs
represent opposite, congruent dihedral angles, which satisfy these conditions, making them a valid arrangement for a
compounding prism.
QUESTION 7
Cancelling Prism
CORRECT ANSWER
BI & BO
BD & BD
BU & BU
RATIONALE: In the context of a "Cancelling Prism" question, the correct answer "BI & BO BD & BD BU & BU" reflects the
process of eliminating or cancelling out like terms in an algebraic expression by factoring, where BI, BD, and BU represent
different terms that can be factored. This allows the expression to be simplified and solved by canceling out common
factors, resulting in a more manageable and solvable form.
Trusted by thousands of students and professionals worldwide Page 3 of 38
, QUESTION 8
Prentice's Rule
CORRECT 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
RATIONALE: Prentice's Rule is based on the principle that the amount of prism created in a meridian is directly proportional
to the power in that meridian and the distance the cover test (OC) is moved, which is then converted from centimeters to
millimeters by dividing by 10. This relationship is established by considering how the movement of the cover test affects the
position of the images on the retina and how it relates to the optical power in the system.
QUESTION 9
Vertical Imbalance
CORRECT ANSWER
The difference in vertical prism power at the reading level in a pair of lenses.
RATIONALE: Vertical imbalance in a pair of lenses refers to the unequal distribution of weight or power, which can cause
the lenses to rotate or shift when worn, disrupting their intended position on the eyes. The difference in vertical prism
power at the reading level in a pair of lenses measures this imbalance by quantifying the disparity in prism power between
the two lenses, allowing for precise correction and alignment.
QUESTION 10
OC Height's by lens
CORRECT ANSWER
SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
RATIONALE: The correct answer is based on established optical principles where the Seg height (SV), Pupillary Distance
(PD), and Focal Point (FT) are interrelated, and the given values represent the relationships between these key concepts.
Specifically, the SV being 1/2 of the Bridge (B) ensures proper alignment of the lens with the wearer's face, while the
Progressive and Fitting Cross (FT) values help determine the optimal lens design and positioning for optimal vision.
Trusted by thousands of students and professionals worldwide Page 4 of 38
85+ (Latest 2026 Edition) 100% Verified Q&A + Answer Key Solutions
100% Guarantee Pass
📋 DOCUMENT OVERVIEW 85 Qs
This document, "ABO Practical," covers specific topics related to optometry and ophthalmology, including
lens types (single vision, multifocal, bifocal, and trifocal), prismatic effects, and optical lens design. The
document provides 85 questions with correct answers and detailed explanations/rationales, as well as
diagrams/images to aid in understanding. Students can use this resource to study, review, and gain a
deeper understanding of these concepts, ultimately enhancing their knowledge and preparation for
exams in optometry and ophthalmology.
✓ Verified Answers ✓ Exam Ready ✓ Study Guide
Trusted by thousands of students and professionals worldwide
EXAM QUESTIONS
QUESTION 1
Single Vision
CORRECT ANSWER
corrects for one distance
RATIONALE: Single Vision lenses are designed to focus light for a specific distance, such as seeing objects clearly in front of
you or in the distance, but may not accommodate for multiple distances like near and far vision simultaneously. This means
that Single Vision lenses "corrects for one distance", allowing you to see objects clearly at that specific distance, but may
not provide clear vision at other distances.
Trusted by thousands of students and professionals worldwide Page 1 of 38
, QUESTION 2
Multifocal
CORRECT ANSWER
Corrects with two or more prescriptions (or 'powers')
RATIONALE: A multifocal lens is designed to correct vision at multiple distances, which typically requires two or more
different prescriptions to account for the varying powers needed for near, intermediate, and far vision. This requires the
correction of multiple focal lengths using different prescriptions, making the statement "Corrects with two or more
prescriptions (or 'powers')" a defining characteristic of a multifocal lens.
QUESTION 3
Bifocal
CORRECT ANSWER
lens having two focus strengths
RATIONALE: The term "bifocal" refers to a design feature that combines two distinct focus strengths in a single lens,
allowing the user to switch between near and far vision without needing to change glasses. This concept is rooted in the
need for a convenient and practical solution to correct vision problems, particularly in individuals with presbyopia who
experience declining near vision with age.
QUESTION 4
Trifocal
CORRECT ANSWER
pertaining to having three focus strengths
RATIONALE: The word "Trifocal" refers to something related to or having three focal points, which typically means three
areas of focus or concentration. This concept is derived from the Latin word "trifocalis," meaning "having three foci,"
indicating that the term specifically pertains to having three focus strengths.
Trusted by thousands of students and professionals worldwide Page 2 of 38
, QUESTION 5
Calculating Prismatic Effects
CORRECT 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
RATIONALE: Calculating prismatic effects involves understanding how different lens surface curvatures and positions can
create variations in beam divergence and convergence, resulting in prismatic effects that can cause image displacement.
The specific methods described, such as grinding the back surface at an angle or de-centering the optical center, create
these prismatic effects by intentionally introducing asymmetries in the lens's optical path, which in turn affect the beam's
trajectory and cause deviations from a straight line.
QUESTION 6
Compounding Prism
CORRECT ANSWER
BI & BI
BO & BO
BU & BD
RATIONALE: When considering a compounding prism, it's essential to understand that the angles between adjacent pairs of
faces remain the same, and the sum of the dihedral angles around any vertex must be 360 degrees. The given pairs
represent opposite, congruent dihedral angles, which satisfy these conditions, making them a valid arrangement for a
compounding prism.
QUESTION 7
Cancelling Prism
CORRECT ANSWER
BI & BO
BD & BD
BU & BU
RATIONALE: In the context of a "Cancelling Prism" question, the correct answer "BI & BO BD & BD BU & BU" reflects the
process of eliminating or cancelling out like terms in an algebraic expression by factoring, where BI, BD, and BU represent
different terms that can be factored. This allows the expression to be simplified and solved by canceling out common
factors, resulting in a more manageable and solvable form.
Trusted by thousands of students and professionals worldwide Page 3 of 38
, QUESTION 8
Prentice's Rule
CORRECT 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
RATIONALE: Prentice's Rule is based on the principle that the amount of prism created in a meridian is directly proportional
to the power in that meridian and the distance the cover test (OC) is moved, which is then converted from centimeters to
millimeters by dividing by 10. This relationship is established by considering how the movement of the cover test affects the
position of the images on the retina and how it relates to the optical power in the system.
QUESTION 9
Vertical Imbalance
CORRECT ANSWER
The difference in vertical prism power at the reading level in a pair of lenses.
RATIONALE: Vertical imbalance in a pair of lenses refers to the unequal distribution of weight or power, which can cause
the lenses to rotate or shift when worn, disrupting their intended position on the eyes. The difference in vertical prism
power at the reading level in a pair of lenses measures this imbalance by quantifying the disparity in prism power between
the two lenses, allowing for precise correction and alignment.
QUESTION 10
OC Height's by lens
CORRECT ANSWER
SV = 1/2 of B
Progressive = Fitting cross
FT = 5mm above segment
RATIONALE: The correct answer is based on established optical principles where the Seg height (SV), Pupillary Distance
(PD), and Focal Point (FT) are interrelated, and the given values represent the relationships between these key concepts.
Specifically, the SV being 1/2 of the Bridge (B) ensures proper alignment of the lens with the wearer's face, while the
Progressive and Fitting Cross (FT) values help determine the optimal lens design and positioning for optimal vision.
Trusted by thousands of students and professionals worldwide Page 4 of 38
