Contact Lenses Flashcards
7 cards from real ABO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Contact Lenses flashcards as text
Which contact lens solution component is most associated with Acanthamoeba keratitis when patients use homemade saline or tap water?
Answer: Sodium chloride contaminated with Acanthamoeba cysts
Tap water and homemade saline may harbor Acanthamoeba cysts; contact of lenses or cases with these sources is the primary risk factor for Acanthamoeba keratitis.
When evaluating a fluorescein pattern for an RGP lens fit, a 'with-the-rule' corneal astigmat fitted with a spherical RGP will show:
Answer: Bearing centrally and pooling superiorly/inferiorly
In with-the-rule astigmatism, the vertical meridian is steeper; a spherical lens bears centrally along the flat horizontal meridian and shows pooling (fluorescein) along the steep vertical meridian.
A patient's keratometry readings are 44.00/47.00 @ 090. What type of corneal astigmatism is present?
Answer: With-the-rule astigmatism
With-the-rule astigmatism means the vertical meridian (90°) is steeper; here 47.00 D at 090 confirms the steeper vertical meridian.
Orthokeratology (ortho-K) lenses are fitted to achieve what primary effect?
Answer: Temporarily flatten the cornea to reduce myopia
Orthokeratology uses reverse-geometry RGP lenses worn overnight to temporarily reshape (flatten) the central cornea, reducing myopia for daytime clear vision without spectacles.
What is the recommended maximum time a conventional soft contact lens patient case should go before replacement?
Answer: 3 months
Contact lens cases should be replaced every 3 months (or sooner if damaged) to reduce biofilm accumulation and contamination risk.
A presbyopic patient who wears monovision contact lenses has the dominant eye corrected for distance. What is the typical approach for the non-dominant eye?
Answer: Correct for near vision
In monovision, the dominant eye is corrected for distance and the non-dominant eye is corrected for near, allowing the brain to suppress the blurred image as needed.
Which parameter most directly influences the tear exchange beneath a rigid gas-permeable contact lens?
Answer: Edge lift (axial edge clearance)
Edge lift determines the amount of clearance at the lens periphery, directly controlling how freely tears can pump beneath the lens with each blink.