COA Contact Lens Fundamentals 2

Question 1

A patient complains of giant papillary conjunctivitis (GPC) after months of soft contact lens wear. What is the most likely cause?

Accepted Answer

Mechanical irritation and immune response to lens deposits or the lens edge

Answer

GPC (also called contact lens-induced papillary conjunctivitis, CLPC) is caused by repeated mechanical trauma from the lens edge and immune reaction to protein deposits on the lens surface, leading to papillae on the upper tarsal conjunctiva.

Question 2

What does 'Dk/t' represent in contact lens science?

Accepted Answer

Oxygen transmissibility, calculated as permeability divided by lens thickness

Answer

Dk/t is oxygen transmissibility, which accounts for both the material's oxygen permeability (Dk) and the actual thickness (t) of the lens, providing a measure of how much oxygen reaches the cornea.

Question 3

During a soft contact lens over-refraction, what is the primary purpose of this procedure?

Accepted Answer

To determine the final contact lens power needed by refracting over a trial lens

Answer

Over-refraction determines the residual refractive error remaining while the patient wears a trial contact lens, allowing the practitioner to calculate the correct final lens power.

Question 4

What is orthokeratology (ortho-k)?

Accepted Answer

Use of specially designed rigid lenses worn overnight to temporarily reshape the cornea

Answer

Orthokeratology involves wearing specially designed rigid contact lenses overnight to temporarily flatten the cornea, reducing myopia during the day without lenses.

Question 5

Which fluorescein staining pattern is commonly associated with a poorly fitting rigid gas-permeable lens causing 3 and 9 o'clock staining?

Accepted Answer

Desiccation of the corneal epithelium at the 3 and 9 o'clock limbal positions due to inadequate tear coverage

Answer

Three and 9 o'clock staining results from desiccation of the cornea at the nasal and temporal limbus, where the RGP lens edge causes inadequate blinking and tear film coverage.

COA - Certified Ophthalmic Assistant Practice Test

COA - Certified Ophthalmic Assistant Practice Test

COA Contact Lens Fundamentals 2