ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting 5 — Questions and Answers
Question 1: The primary purpose of the distance between lenses (DBL or bridge size) measurement is to:
- Determine lens blank diameter
- Ensure the frame fits the patient's nose bridge (Correct answer)
- Calculate the progressive corridor length
- Set the pantoscopic tilt angle
Correct answer: Ensure the frame fits the patient's nose bridge
The DBL (distance between lenses) corresponds to the bridge size and ensures the frame fits comfortably and correctly on the patient's nose.
Question 2: Induced prism resulting from a patient looking through a point other than the optical center is calculated using:
- Snell's Law
- Prentice's Rule (Correct answer)
- Lensmaker's Equation
- Fick's Principle
Correct answer: Prentice's Rule
Prentice's Rule states that prism (in prism diopters) = decentration (cm) × lens power (diopters), and is the standard formula for calculating induced prism.
Question 3: A patient with a +3.00D right lens and +3.00D left lens has their glasses slide down 4mm on the nose. How much vertical prism is induced in each lens?
- 0.6Δ base down each eye
- 1.2Δ base up each eye
- 0.6Δ base up each eye
- 1.2Δ base down each eye (Correct answer)
Correct answer: 1.2Δ base down each eye
Using Prentice's Rule: 0.4cm × 3.00D = 1.2Δ; when plus lenses slide down, the pupil is above OC, inducing base-down prism — wait, the OC drops below pupil inducing base-up... actually when glasses slide down, pupil is above OC for plus lens = base-down. Re-checking: P = cF = 0.4 × 3 = 1.2Δ base-down in each eye.
Question 4: Which frame adjustment corrects a frame that sits too close to the eyelashes on one side?
- Decrease vertex distance on that side
- Bend the nose pad arm to move the pad outward on the opposite side
- Increase the splay angle of the nose pad on the affected side (Correct answer)
- Tighten the temple on the affected side
Correct answer: Increase the splay angle of the nose pad on the affected side
Increasing the splay (flare) angle of the nose pad on the side where lashes touch pushes that side of the frame away from the face.
Question 5: For a patient requiring a flat-top 35 bifocal, which minimum B measurement is generally recommended for the frame?
- 25mm
- 30mm
- 35mm (Correct answer)
- 40mm
Correct answer: 35mm
A flat-top 35 bifocal is 35mm wide and requires a frame with a B measurement of at least 35mm to accommodate the segment properly.
Question 6: When a patient reports that their new single vision glasses cause objects to appear tilted or slanted, the most likely cause is:
- Incorrect sphere power
- Cylinder axis error (Correct answer)
- Wrong pupillary distance
- Excessive base curve
Correct answer: Cylinder axis error
Cylinder axis errors cause objects to appear tilted or slanted because the corrective meridian does not align with the patient's astigmatic axis.
Question 7: The term 'face form' or 'wrap angle' refers to:
- The tilt of the lens from top to bottom
- The curvature of the frame front as it wraps around the face horizontally (Correct answer)
- The angle between the temples and the frame front
- The curve on the back surface of the lens
Correct answer: The curvature of the frame front as it wraps around the face horizontally
Face form (wrap angle) describes how much the frame front curves horizontally to follow the contour of the face, typically 5–10 degrees.
ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting 5
The primary purpose of the distance between lenses (DBL or bridge size) measurement is to: