ABO ADVANCED PRACTICE EXAM
QUESTIONS AND ANSWERS 100%
VERIFIED. JUST RELEASED
1. A patient is wearing a -12.00 D sphere lens at a 14mm vertex distance. If the new frame sits
at a 10mm vertex distance, what is the effective power of the lens required?
A. -11.45 D
B. -12.61 D
C. -12.00 D
D. -13.25 D
Answer: B
Conceptual Explanation: Using the formula F_new = F / (1 - dF), where d is the change in
meters (0.004m closer). Since the lens moves closer, a minus lens becomes effectively
weaker, so a stronger minus power is needed. F = -12 / (1 - (-0.004 * -12)) = -12 / (1 -
0.048) = -12.605 D.
2. Calculate the slab-off (bicentric grinding) required for the following Rx at a 10mm reading
level: OD: +3.00 -1.00 x 180, OS: -1.00 -0.50 x 180, Add: +2.00 OU.
A. 1.5 prism diopters BU OS
B. 3.5 prism diopters BU OS
,C. 2.5 prism diopters BD OD
D. 4.0 prism diopters BU OS
Answer: B
Conceptual Explanation: Calculate power in the 90th meridian: OD is +2.00, OS is -1.50.
Differential at 10mm (1cm): OD prism = 1 * 2 = 2.0 BD; OS prism = 1 * 1.5 = 1.5 BU. Net
imbalance = 3.5 prism diopters. Slab-off is traditionally placed on the most minus (or least
plus) lens as Base Up: 3.5 BU OS.
3. According to ANSI Z80.1 standards, what is the cylinder axis tolerance for a lens with a
cylinder power of 1.75 D?
A. plus or minus 5 degrees
B. plus or minus 2 degrees
C. plus or minus 3 degrees
D. plus or minus 7 degrees
Answer: B
Conceptual Explanation: For cylinder powers greater than 1.50 D but less than or equal to
5.00 D, the ANSI Z80.1-2015 standard specifies an axis tolerance of plus or minus 2
degrees.
4. Which of the following lens materials has the highest chromatic aberration?
A. Crown Glass (Abbe 59)
, B. Polycarbonate (Abbe 30)
C. CR-39 (Abbe 58)
D. Trivex (Abbe 45)
Answer: B
Conceptual Explanation: Chromatic aberration is inversely proportional to the Abbe
value. Polycarbonate has the lowest Abbe value (30) among common lens materials,
resulting in the highest chromatic aberration.
5. A +10.00 D lens is tilted 15 degrees pantoscopically. What is the new sphere and induced
cylinder power?
A. Sphere +10.65, Cyl +0.50 x 180
B. Sphere +10.00, Cyl +0.25 x 090
C. Sphere +10.22, Cyl +0.71 x 180
D. Sphere +10.15, Cyl +1.15 x 090
Answer: C
Conceptual Explanation: Using Martin’s Formula: New Sphere = F(1 + (sin^2 theta / 3n)).
Induced Cyl = F * tan^2 theta. For a +10.00 lens at 15 degrees, the sphere increases slightly
and a cylinder with axis 180 (for pantoscopic tilt) is induced.
6. What is the refractive index of Trivex?
A. 1.498
QUESTIONS AND ANSWERS 100%
VERIFIED. JUST RELEASED
1. A patient is wearing a -12.00 D sphere lens at a 14mm vertex distance. If the new frame sits
at a 10mm vertex distance, what is the effective power of the lens required?
A. -11.45 D
B. -12.61 D
C. -12.00 D
D. -13.25 D
Answer: B
Conceptual Explanation: Using the formula F_new = F / (1 - dF), where d is the change in
meters (0.004m closer). Since the lens moves closer, a minus lens becomes effectively
weaker, so a stronger minus power is needed. F = -12 / (1 - (-0.004 * -12)) = -12 / (1 -
0.048) = -12.605 D.
2. Calculate the slab-off (bicentric grinding) required for the following Rx at a 10mm reading
level: OD: +3.00 -1.00 x 180, OS: -1.00 -0.50 x 180, Add: +2.00 OU.
A. 1.5 prism diopters BU OS
B. 3.5 prism diopters BU OS
,C. 2.5 prism diopters BD OD
D. 4.0 prism diopters BU OS
Answer: B
Conceptual Explanation: Calculate power in the 90th meridian: OD is +2.00, OS is -1.50.
Differential at 10mm (1cm): OD prism = 1 * 2 = 2.0 BD; OS prism = 1 * 1.5 = 1.5 BU. Net
imbalance = 3.5 prism diopters. Slab-off is traditionally placed on the most minus (or least
plus) lens as Base Up: 3.5 BU OS.
3. According to ANSI Z80.1 standards, what is the cylinder axis tolerance for a lens with a
cylinder power of 1.75 D?
A. plus or minus 5 degrees
B. plus or minus 2 degrees
C. plus or minus 3 degrees
D. plus or minus 7 degrees
Answer: B
Conceptual Explanation: For cylinder powers greater than 1.50 D but less than or equal to
5.00 D, the ANSI Z80.1-2015 standard specifies an axis tolerance of plus or minus 2
degrees.
4. Which of the following lens materials has the highest chromatic aberration?
A. Crown Glass (Abbe 59)
, B. Polycarbonate (Abbe 30)
C. CR-39 (Abbe 58)
D. Trivex (Abbe 45)
Answer: B
Conceptual Explanation: Chromatic aberration is inversely proportional to the Abbe
value. Polycarbonate has the lowest Abbe value (30) among common lens materials,
resulting in the highest chromatic aberration.
5. A +10.00 D lens is tilted 15 degrees pantoscopically. What is the new sphere and induced
cylinder power?
A. Sphere +10.65, Cyl +0.50 x 180
B. Sphere +10.00, Cyl +0.25 x 090
C. Sphere +10.22, Cyl +0.71 x 180
D. Sphere +10.15, Cyl +1.15 x 090
Answer: C
Conceptual Explanation: Using Martin’s Formula: New Sphere = F(1 + (sin^2 theta / 3n)).
Induced Cyl = F * tan^2 theta. For a +10.00 lens at 15 degrees, the sphere increases slightly
and a cylinder with axis 180 (for pantoscopic tilt) is induced.
6. What is the refractive index of Trivex?
A. 1.498
