CPOA Contact Lens Basics 2 — Questions and Answers
Question 1: Which contact lens parameter describes the curvature of the back surface of the lens?
- Base curve (Correct answer)
- Diameter
- Power
- Center thickness
Correct answer: Base curve
Base curve (BC) describes the curvature of the posterior lens surface and determines how the lens fits on the cornea.
Question 2: A patient's contact lens prescription reads: -2.50 -1.25 x 180. This lens is best described as:
- Spherical soft lens
- Toric soft lens (Correct answer)
- Multifocal lens
- Rigid gas-permeable lens
Correct answer: Toric soft lens
The presence of a cylinder power (-1.25) and axis (180) indicates a toric lens designed to correct astigmatism.
Question 3: What is the primary advantage of daily disposable contact lenses over monthly replacement lenses?
- Higher oxygen transmissibility
- Eliminated need for lens care solutions (Correct answer)
- Lower overall cost
- Thicker lens material
Correct answer: Eliminated need for lens care solutions
Daily disposable lenses are discarded after each use, eliminating the need for cleaning and storage solutions.
Question 4: Which material property of contact lenses is described by the term 'Dk/t'?
- Water content
- Oxygen transmissibility (Correct answer)
- Refractive index
- Lens flexibility
Correct answer: Oxygen transmissibility
Dk/t represents oxygen transmissibility, where Dk is oxygen permeability and t is lens center thickness.
Question 5: A patient reports their soft contact lenses feel dry by the end of the day. Which lens property most directly affects this complaint?
- Base curve radius
- Lens diameter
- Water content (Correct answer)
- Lens power
Correct answer: Water content
Higher water content lenses can evaporate moisture more readily, contributing to end-of-day dryness symptoms.
Question 6: Extended wear contact lenses are FDA-approved for continuous wear up to how many days?
- 3 days
- 7 days
- 14 days
- 30 days (Correct answer)
Correct answer: 30 days
FDA-approved silicone hydrogel extended wear lenses can be worn continuously for up to 30 days and nights.
Question 7: Which type of contact lens solution combines cleaning, rinsing, disinfecting, and storing in one product?
- Saline solution
- Hydrogen peroxide solution
- Multipurpose solution (Correct answer)
- Daily cleaner
Correct answer: Multipurpose solution
Multipurpose solutions (MPS) perform multiple lens care functions in a single convenient product.
CPOA Contact Lens Basics 2
Which contact lens parameter describes the curvature of the back surface of the lens?