CPOA Spectacle Dispensing 5 — Questions and Answers
Question 1: What is the purpose of 'face form' (wrap) angle in spectacle frame fitting?
- It determines the pantoscopic tilt needed
- It curves the frame front to follow the contour of the patient's face (Correct answer)
- It adjusts the temple length for comfort
- It aligns the optical centers vertically
Correct answer: It curves the frame front to follow the contour of the patient's face
Face form (wrap) angle describes how the frame front curves to match the natural curvature of the patient's face for better fit and aesthetics.
Question 2: Which of the following describes a 'slab-off' (bicentric) grind, and when is it used?
- A high-plus lens ground to reduce center thickness, used in aphakic patients
- Prism ground into the lower segment of one lens to correct vertical imbalance in bifocals (Correct answer)
- A flat back curve on a high-minus lens for cosmetic thinning
- A fresnel prism added to reduce anisometropia
Correct answer: Prism ground into the lower segment of one lens to correct vertical imbalance in bifocals
Slab-off grinding removes base-up prism from the reading area of one lens to equalize vertical prism imbalance caused by anisometropia in bifocal wearers.
Question 3: A patient with a high minus prescription asks for the thinnest possible lenses. Which combination is best?
- CR-39 with a small eye-size frame
- High-index material with a small eye-size frame (Correct answer)
- Polycarbonate with a large frame
- Trivex with a large frame
Correct answer: High-index material with a small eye-size frame
High-index materials have a steeper refractive index (thinner profiles), and smaller frames require less edge thickness for minus lenses.
Question 4: When using a pupillary distance ruler to measure monocular PD, the optician should align the ruler's zero at:
- The temporal limbus of the right eye
- The center of the patient's nose bridge (Correct answer)
- The nasal limbus of the left eye
- The lateral canthus of the right eye
Correct answer: The center of the patient's nose bridge
The zero (reference point) is placed at the center of the nose bridge, and each pupil center is then measured to that midline.
Question 5: Which statement about polycarbonate lenses is correct?
- They have the highest Abbe value of all lens materials
- They are impact-resistant and meet ANSI Z87.1 safety standards (Correct answer)
- They are the thinnest available high-index material
- They require no additional scratch-resistant coating
Correct answer: They are impact-resistant and meet ANSI Z87.1 safety standards
Polycarbonate is inherently impact-resistant and is the standard material meeting ANSI Z87.1 for safety eyewear; it does require a scratch-resistant coating.
Question 6: A frame temple that ends with a plastic or metal curve that hooks behind the ear is called a:
- Comfort cable temple (Correct answer)
- Library temple
- Skull temple
- Convertible temple
Correct answer: Comfort cable temple
A comfort cable temple has a curved or coiled end that hooks behind the ear, providing extra security, commonly seen in sports and children's frames.
Question 7: To verify that a bifocal segment height has been placed correctly in finished glasses, the optician should measure from:
- The top of the frame to the top of the segment
- The lowest point of the lens to the top of the segment
- The pupil center to the top of the bifocal segment while the patient wears the frame (Correct answer)
- The optical center to the segment top
Correct answer: The pupil center to the top of the bifocal segment while the patient wears the frame
Segment height is verified by measuring from the pupil center (or lower lid margin, per office protocol) to the top of the bifocal segment while the patient wears the fitted frame.
CPOA Spectacle Dispensing 5
What is the purpose of 'face form' (wrap) angle in spectacle frame fitting?