ABO NOCE Basic Opticianry General Practice 3 — Questions and Answers
Question 1: Compared to CR-39 (index 1.50), a lens with a refractive index of 1.67 will be:
- Thinner and lighter for the same prescription (Correct answer)
- Thicker and heavier
- Same thickness but lighter
- Thicker but lighter
Correct answer: Thinner and lighter for the same prescription
Higher refractive index materials bend light more efficiently, allowing lenses to be made thinner for the same prescription power.
Question 2: The distance from the back surface of the spectacle lens to the front of the cornea is called the:
- Vertex distance (Correct answer)
- Pantoscopic tilt
- Back focal length
- Optical center height
Correct answer: Vertex distance
Vertex distance is clinically important for high prescriptions (typically ±4.00 D and above) because changes affect effective power.
Question 3: Which multifocal lens type has no visible dividing line between distance and near zones?
- Progressive addition lens (Correct answer)
- Flat-top bifocal
- Executive bifocal
- Round-top bifocal
Correct answer: Progressive addition lens
Progressive addition lenses provide a gradual power transition without a visible segment line.
Question 4: A patient is prescribed base-in prism. The perceived image will be displaced toward:
- The apex (temporally) (Correct answer)
- The base (nasally)
- Superiorly
- Inferiorly
Correct answer: The apex (temporally)
Light bends toward the base of a prism, but the perceived image is always displaced toward the apex.
Question 5: Anti-reflective coatings reduce reflections using the principle of:
- Destructive interference (Correct answer)
- Constructive interference
- Total internal reflection
- Diffraction
Correct answer: Destructive interference
AR coatings use thin film layers whose reflected waves are out of phase and cancel each other through destructive interference.
Question 6: Which measurement ensures the optical center of a lens aligns vertically with the patient's pupil?
- Optical center height (fitting height) (Correct answer)
- Pupillary distance
- Pantoscopic tilt
- Vertex distance
Correct answer: Optical center height (fitting height)
Optical center height (fitting height) is measured from the lowest point of the frame to the pupil center while the patient looks straight ahead.
Question 7: Polycarbonate lenses are recommended for safety eyewear primarily because of their:
- Superior impact resistance (Correct answer)
- Highest refractive index
- Best scratch resistance
- Superior optical clarity
Correct answer: Superior impact resistance
Polycarbonate has very high impact resistance, making it the preferred material for safety and children's eyewear.
ABO NOCE Basic Opticianry General Practice 3
Compared to CR-39 (index 1.50), a lens with a refractive index of 1.67 will be: