Contact Lens Practice Flashcards
6 cards from real AOA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Contact Lens Practice flashcards as text
Which contact lens material parameter describes the amount of oxygen that actually reaches the cornea?
Answer: Dk/t (oxygen transmissibility)
Dk/t (oxygen transmissibility) is the measure of oxygen flux through a specific lens thickness and determines how much oxygen reaches the corneal epithelium.
Extended wear contact lenses are most associated with which serious complication?
Answer: Microbial keratitis
Extended (overnight) wear dramatically increases the risk of microbial keratitis, particularly from Pseudomonas aeruginosa and Acanthamoeba.
Orthokeratology (ortho-K) lenses work primarily by:
Answer: Reshaping the corneal epithelium during overnight wear
Ortho-K uses reverse geometry RGP lenses worn overnight to temporarily flatten the central corneal epithelium, reducing myopia during the day.
Giant papillary conjunctivitis (GPC) in contact lens wearers is best managed by:
Answer: Switching to daily disposable lenses and reducing wear time
GPC is an immunological response to lens deposits and mechanical trauma; daily disposables eliminate deposit accumulation and reduce antigenic load.
Which fitting relationship describes a rigid gas-permeable (RGP) lens that is steeper than the corneal curvature?
Answer: Steep (vaulting) fit
When a RGP lens base curve is steeper than the flattest corneal meridian (K), the lens vaults the cornea and causes apical clearance.
What is the FDA oxygen transmissibility threshold for extended-wear soft contact lenses?
Answer: Dk/t ≥ 87 ISO units
The FDA requires a minimum Dk/t of 87 ISO units for extended-wear (up to 30 nights) soft contact lens approval to support adequate corneal oxygenation.