ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 4 — Questions and Answers
Question 1: A patient returns complaining of headaches only when using their new progressive lenses for near work. The most likely cause is:
- Incorrect distance PD
- Segment addition is too high
- The reading zone is not being accessed due to incorrect fitting height (Correct answer)
- Excessive base curve on the lens
Correct answer: The reading zone is not being accessed due to incorrect fitting height
If the progressive fitting height is too low, the patient cannot comfortably access the near zone, causing them to strain through an intermediate corridor region.
Question 2: The term 'effective diameter' of a spectacle lens refers to:
- The largest circle that fits within the lens shape
- The smallest circle centered on the optical center that will encompass the entire frame shape (Correct answer)
- The distance from the optical center to the closest frame edge
- The total width of the lens blank
Correct answer: The smallest circle centered on the optical center that will encompass the entire frame shape
Effective diameter is the diameter of the smallest circle centered on the optical center that contains the entire edged lens shape, used to determine the minimum blank size needed.
Question 3: When fitting a child with spectacles, which consideration is MOST critical compared to fitting an adult?
- Using only glass lenses for durability
- Ensuring sufficient vertex distance for magnification
- Proper pupillary distance and fitting height due to rapid facial growth (Correct answer)
- Avoiding anti-reflective coatings
Correct answer: Proper pupillary distance and fitting height due to rapid facial growth
Children's faces grow rapidly, so PD and fitting height must be accurate and the frame must be appropriately sized for their current facial dimensions.
Question 4: A plano lens fitted 14 mm in front of the eye has an effective power at the cornea of:
- +0.25 D
- Plano (0.00 D) (Correct answer)
- -0.25 D
- Depends on the base curve
Correct answer: Plano (0.00 D)
A plano (zero power) lens has no vergence-altering effect regardless of vertex distance — it transmits light without convergence or divergence.
Question 5: Which of the following frame materials is MOST resistant to corrosion and is commonly used for patients with metal allergies?
- Monel
- Beryllium alloy
- Titanium (Correct answer)
- Nickel silver
Correct answer: Titanium
Titanium is highly corrosion-resistant and hypoallergenic, making it the preferred choice for patients with nickel or metal allergies.
Question 6: A patient's prescription reads OD -3.50 -1.25 x 090. The principal meridians of power are:
- -3.50 D at 090 and -4.75 D at 180 (Correct answer)
- -3.50 D at 180 and -4.75 D at 090
- -4.75 D at 180 and -3.50 D at 090
- -2.25 D at 090 and -3.50 D at 180
Correct answer: -3.50 D at 090 and -4.75 D at 180
The sphere power (-3.50) acts at the axis meridian (090) and the combined sphere+cylinder power (-3.50 + -1.25 = -4.75) acts 90° away at 180.
Question 7: An interpupillary distance of 64 mm is measured on a patient, but the selected frame has a frame PD of 72 mm. The required decentration per lens is:
- 8 mm total, 4 mm per lens inward (Correct answer)
- 8 mm total, 4 mm per lens outward
- 4 mm total, 2 mm per lens inward
- 4 mm total, 2 mm per lens outward
Correct answer: 8 mm total, 4 mm per lens inward
The difference of 8 mm (72 - 64) must be split equally, requiring 4 mm of inward decentration per lens to align optical centers with the pupils.
ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 4
A patient returns complaining of headaches only when using their new progressive lenses for near work.
The most likely cause is: