CPOA Spectacle Dispensing 2 — Questions and Answers
Question 1: Which frame measurement represents the distance between the two lenses at the closest point?
- Bridge size (DBL) (Correct answer)
- Eye size
- Temple length
- Effective diameter
Correct answer: Bridge size (DBL)
The DBL (distance between lenses) measures the bridge width between the two lens openings at their closest point.
Question 2: A patient's prescription reads OD: -3.00 -1.00 x 090. What type of lens power does the '-1.00' represent?
- Sphere power
- Cylinder power (Correct answer)
- Add power
- Prism power
Correct answer: Cylinder power
The second value in a prescription (preceded by the axis) is the cylinder power, which corrects astigmatism.
Question 3: When adjusting nose pads to eliminate red marks on the patient's nose, the optician should:
- Widen the pad spread (Correct answer)
- Increase pad angle inward
- Raise the pad arms higher
- Tighten the pad screws
Correct answer: Widen the pad spread
Widening the pad spread distributes weight over a larger skin area, reducing pressure and marks.
Question 4: Anti-reflective (AR) coating primarily benefits patients by:
- Darkening lenses in sunlight
- Reducing glare and improving light transmission (Correct answer)
- Hardening the lens surface
- Adding UV protection
Correct answer: Reducing glare and improving light transmission
AR coating reduces surface reflections, allowing more light to pass through and minimizing glare for the wearer.
Question 5: Which lens material has the highest Abbe value (least chromatic aberration)?
- Polycarbonate
- Trivex
- CR-39 plastic (Correct answer)
- High-index 1.74
Correct answer: CR-39 plastic
CR-39 has an Abbe value of about 58, the highest among common ophthalmic lens materials, meaning less color fringing.
Question 6: A frame with a 52-18-140 measurement has a temple length of:
- 52 mm
- 18 mm
- 140 mm (Correct answer)
- 70 mm
Correct answer: 140 mm
In the standard frame notation eye-bridge-temple, the third number (140) is the temple length in millimeters.
Question 7: When a patient complains that their new progressive lenses make the floor appear to 'swim,' what is the most likely cause?
- Incorrect pupillary distance
- Incorrect add power
- Peripheral distortion inherent to progressive lenses (Correct answer)
- Incorrect base curve
Correct answer: Peripheral distortion inherent to progressive lenses
Progressive lenses have unavoidable peripheral aberration zones that can cause spatial distortion, especially during adaptation.
CPOA Spectacle Dispensing 2
Which frame measurement represents the distance between the two lenses at the closest point?