COA Contact Lens Fundamentals

Question 1

What does the base curve of a contact lens describe?

Accepted Answer

The curvature of the central posterior surface of the lens

Answer

The total diameter of the lens

Answer

The oxygen permeability of the lens material

Answer

The power of the lens in diopters

Question 2

What does 'Dk' represent in contact lens terminology?

Accepted Answer

The oxygen permeability of the lens material

Answer

The lens diameter in kilograms

Answer

The dioptric power of the contact lens

Answer

The dissolving constant of the cleaning solution

Question 3

A patient's contact lens shows a tight-fitting pattern on fluorescein evaluation with a rigid gas-permeable lens. Which of the following best describes this fit?

Accepted Answer

Steep fit with central pooling and minimal edge clearance

Answer

Flat fit with excessive edge lift

Answer

Alignment fit with uniform fluorescein pattern

Answer

Interpalpebral fit with superior bearing

Question 4

Which type of contact lens is most appropriate for correcting irregular astigmatism caused by keratoconus?

Accepted Answer

Rigid gas-permeable lens

Answer

Soft toric lens

Answer

Daily disposable spherical soft lens

Answer

Monovision soft lens

Question 5

What is the term for the measurement of the contact lens that describes its total width from edge to edge?

Accepted Answer

Overall diameter (OAD)

Answer

Base curve

Answer

Optical zone diameter

Answer

Back vertex power

Question 6

Which contact lens design uses alternating concentric zones to provide correction for both near and distance vision?

Accepted Answer

Concentric/annular multifocal

Answer

Monovision

Answer

Aspheric multifocal

Answer

Translating bifocal

Question 7

What is the primary advantage of silicone hydrogel contact lenses over conventional hydrogel lenses?

Accepted Answer

They have significantly higher oxygen transmissibility (Dk/t)

Answer

They are less expensive to manufacture

Answer

They provide better UV protection

Answer

They require no cleaning or disinfection