ABO-NCLE PRACTICAL TEST EXAM 2025 ACTUAL EXAM COMPLETE 180+ QUESTIONS WITH
DETAILED VERIFIED ANSWERS (100% CORRECT ANSWERS) ALREADY GRADED A+
Question 1
What is the primary purpose of a lensometer (focimeter)?
A) To measure interpupillary distance
B) To determine the base curve of a lens
C) To measure the power of an ophthalmic lens
D) To verify prism in a spectacle frame
E) To adjust temple length
Correct Answer: C) To measure the power of an ophthalmic lens
Rationale: A lensometer (focimeter) is the instrument used by opticians to accurately measure
the spherical power, cylindrical power, axis, and prism of a spectacle lens.
Question 2
When neutralizing a lens on a manual lensometer, what indicates a spherical lens?
A) The mire lines appear clear and focused in all meridians simultaneously.
B) The mire lines become clear at two distinct positions 90 degrees apart.
C) There is a noticeable jump in the mires when rotating the lens.
D) The prism reference dot moves significantly.
E) The lens causes excessive magnification.
Correct Answer: A) The mire lines appear clear and focused in all meridians simultaneously.
Rationale: For a spherical lens, there is only one focal point, so both sets of mire lines (usually
thin and thick lines) will come into clear focus at the same time and in the same position.
Question 3
What is the correct procedure for finding the optical center of a lens using a manual
lensometer?
A) Align the mires, then mark the center of the lens.
B) Rotate the lens until the axis is zero, then center the mires.
C) Move the lens until the target is centered on the reticle's crosshairs.
D) Focus the mires, then adjust the frame.
E) Measure the diameter of the lens.
Correct Answer: C) Move the lens until the target is centered on the reticle's crosshairs.
Rationale: The optical center of a lens is the point through which light passes undeviated. On a
lensometer, this is found by positioning the lens so that the center of the mire target aligns
with the center of the lensometer's reticle (crosshairs).
Question 4
If a lensometer reading shows -2.00 -1.00 x 090, what is the power in the 180 meridian?
A) -2.00 D
B) -1.00 D
,C) -3.00 D
D) +1.00 D
E) -0.50 D
Correct Answer: A) -2.00 D
Rationale: The first number (-2.00 D) is the spherical power. The cylinder power (-1.00 D) is
applied at the axis (090). To find the power at the 180 meridian, we only consider the sphere
power, as the cylinder has no effect at 90 degrees away from its axis. Therefore, the power at
180 is -2.00 D.
Question 5
When measuring prism on a lensometer, what does a displacement of the target indicate?
A) Excessive cylinder power
B) Improper lens mounting
C) The presence of prism
D) An incorrect axis
E) A scratched lens
Correct Answer: C) The presence of prism
Rationale: Prism displaces the image of the mire target away from the optical center of the
lensometer's reticle. The amount and direction of displacement correspond to the amount
and base direction of the prism.
Question 6
What is the standard tolerance for spherical power up to +/- 6.50 D?
A) +/- 0.06 D
B) +/- 0.12 D
C) +/- 0.25 D
D) +/- 0.50 D
E) +/- 1.00 D
Correct Answer: B) +/- 0.12 D
Rationale: According to ANSI Z80.1 standards, the tolerance for spherical power up to +/- 6.50
D is +/- 0.13 D, often rounded to +/- 0.12 D in practice or for MCQ options. This reflects the
acceptable deviation from the prescribed power.
Question 7
When verifying a progressive addition lens (PAL) with a lensometer, where should the distance
power be measured?
A) At the geometric center of the lens
B) Through the prism reference point
C) At the engraving marks above the fitting cross
, D) At the fitting cross
E) In the reading area
Correct Answer: C) At the engraving marks above the fitting cross
Rationale: The distance reference point (DRP) on a PAL is typically located at specific engraving
marks (often small circles or lines) usually found 4mm above the fitting cross. This is the
designated point for verifying the full distance prescription.
Question 8
What is the primary benefit of CR-39 lens material?
A) High refractive index
B) Excellent impact resistance
C) Low specific gravity (lightweight) and good optical clarity
D) UV protection without coating
E) Very thin profile
Correct Answer: C) Low specific gravity (lightweight) and good optical clarity
Rationale: CR-39 is a plastic polymer known for its excellent optical properties, being relatively
lightweight compared to glass, and having good clarity. Its impact resistance is better than
glass but not as high as polycarbonate.
Question 9
Which lens material offers the best impact resistance?
A) Glass
B) CR-39
C) Polycarbonate
D) Trivex
E) High-index plastic (1.67)
Correct Answer: C) Polycarbonate
Rationale: Polycarbonate is a thermoplastic material renowned for its superior impact
resistance, making it the material of choice for safety eyewear and children's glasses. Trivex is
also excellent but polycarbonate generally holds the top spot for impact resistance.
Question 10
What is the purpose of tinting spectacle lenses?
A) To increase overall lens power
B) To reduce glare and increase comfort
C) To improve peripheral vision
D) To make the lenses thinner
E) To change the refractive index
Correct Answer: B) To reduce glare and increase comfort
DETAILED VERIFIED ANSWERS (100% CORRECT ANSWERS) ALREADY GRADED A+
Question 1
What is the primary purpose of a lensometer (focimeter)?
A) To measure interpupillary distance
B) To determine the base curve of a lens
C) To measure the power of an ophthalmic lens
D) To verify prism in a spectacle frame
E) To adjust temple length
Correct Answer: C) To measure the power of an ophthalmic lens
Rationale: A lensometer (focimeter) is the instrument used by opticians to accurately measure
the spherical power, cylindrical power, axis, and prism of a spectacle lens.
Question 2
When neutralizing a lens on a manual lensometer, what indicates a spherical lens?
A) The mire lines appear clear and focused in all meridians simultaneously.
B) The mire lines become clear at two distinct positions 90 degrees apart.
C) There is a noticeable jump in the mires when rotating the lens.
D) The prism reference dot moves significantly.
E) The lens causes excessive magnification.
Correct Answer: A) The mire lines appear clear and focused in all meridians simultaneously.
Rationale: For a spherical lens, there is only one focal point, so both sets of mire lines (usually
thin and thick lines) will come into clear focus at the same time and in the same position.
Question 3
What is the correct procedure for finding the optical center of a lens using a manual
lensometer?
A) Align the mires, then mark the center of the lens.
B) Rotate the lens until the axis is zero, then center the mires.
C) Move the lens until the target is centered on the reticle's crosshairs.
D) Focus the mires, then adjust the frame.
E) Measure the diameter of the lens.
Correct Answer: C) Move the lens until the target is centered on the reticle's crosshairs.
Rationale: The optical center of a lens is the point through which light passes undeviated. On a
lensometer, this is found by positioning the lens so that the center of the mire target aligns
with the center of the lensometer's reticle (crosshairs).
Question 4
If a lensometer reading shows -2.00 -1.00 x 090, what is the power in the 180 meridian?
A) -2.00 D
B) -1.00 D
,C) -3.00 D
D) +1.00 D
E) -0.50 D
Correct Answer: A) -2.00 D
Rationale: The first number (-2.00 D) is the spherical power. The cylinder power (-1.00 D) is
applied at the axis (090). To find the power at the 180 meridian, we only consider the sphere
power, as the cylinder has no effect at 90 degrees away from its axis. Therefore, the power at
180 is -2.00 D.
Question 5
When measuring prism on a lensometer, what does a displacement of the target indicate?
A) Excessive cylinder power
B) Improper lens mounting
C) The presence of prism
D) An incorrect axis
E) A scratched lens
Correct Answer: C) The presence of prism
Rationale: Prism displaces the image of the mire target away from the optical center of the
lensometer's reticle. The amount and direction of displacement correspond to the amount
and base direction of the prism.
Question 6
What is the standard tolerance for spherical power up to +/- 6.50 D?
A) +/- 0.06 D
B) +/- 0.12 D
C) +/- 0.25 D
D) +/- 0.50 D
E) +/- 1.00 D
Correct Answer: B) +/- 0.12 D
Rationale: According to ANSI Z80.1 standards, the tolerance for spherical power up to +/- 6.50
D is +/- 0.13 D, often rounded to +/- 0.12 D in practice or for MCQ options. This reflects the
acceptable deviation from the prescribed power.
Question 7
When verifying a progressive addition lens (PAL) with a lensometer, where should the distance
power be measured?
A) At the geometric center of the lens
B) Through the prism reference point
C) At the engraving marks above the fitting cross
, D) At the fitting cross
E) In the reading area
Correct Answer: C) At the engraving marks above the fitting cross
Rationale: The distance reference point (DRP) on a PAL is typically located at specific engraving
marks (often small circles or lines) usually found 4mm above the fitting cross. This is the
designated point for verifying the full distance prescription.
Question 8
What is the primary benefit of CR-39 lens material?
A) High refractive index
B) Excellent impact resistance
C) Low specific gravity (lightweight) and good optical clarity
D) UV protection without coating
E) Very thin profile
Correct Answer: C) Low specific gravity (lightweight) and good optical clarity
Rationale: CR-39 is a plastic polymer known for its excellent optical properties, being relatively
lightweight compared to glass, and having good clarity. Its impact resistance is better than
glass but not as high as polycarbonate.
Question 9
Which lens material offers the best impact resistance?
A) Glass
B) CR-39
C) Polycarbonate
D) Trivex
E) High-index plastic (1.67)
Correct Answer: C) Polycarbonate
Rationale: Polycarbonate is a thermoplastic material renowned for its superior impact
resistance, making it the material of choice for safety eyewear and children's glasses. Trivex is
also excellent but polycarbonate generally holds the top spot for impact resistance.
Question 10
What is the purpose of tinting spectacle lenses?
A) To increase overall lens power
B) To reduce glare and increase comfort
C) To improve peripheral vision
D) To make the lenses thinner
E) To change the refractive index
Correct Answer: B) To reduce glare and increase comfort
