Contact Lens Fitting and Dispensing Flashcards
7 cards from real NOCE 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 Lens Fitting and Dispensing flashcards as text
During an RGP lens follow-up, a lens rides superiorly and shows temporal lag with each blink. What is the most likely cause?
Answer: The lens is fitted too flat
A flat-fitting RGP lens has poor corneal alignment, causing it to decenter superiorly and exhibit excessive movement and temporal lag on the blink.
What is the purpose of performing an 'over-refraction' during a contact lens fitting?
Answer: To refine the contact lens power while the lens is on the eye
Over-refraction is performed with the trial contact lens in situ to determine what additional power is needed to achieve best corrected acuity with that specific lens.
A soft lens patient reports significant end-of-day dryness and discomfort. Which change would MOST likely improve comfort?
Answer: Switching to a silicone hydrogel lens material
Silicone hydrogel lenses provide higher oxygen transmissibility and tend to maintain better surface wettability throughout the day, reducing end-of-day dryness compared to conventional hydrogels.
What does 'limbal clearance' refer to in the context of contact lens fitting?
Answer: The space between the lens edge and the corneal limbus
Limbal clearance is the space between the edge of a contact lens and the corneal limbus (corneoscleral junction), which is important for limbal vessel health and comfort.
For a patient with a spectacle prescription of -2.50 -1.50 x 180, which contact lens type would provide BEST visual correction?
Answer: Toric soft contact lens
With 1.50 D of cylinder, a toric soft lens is the most appropriate choice since the residual astigmatism with a spherical lens would likely reduce visual acuity significantly.
What is the primary purpose of sodium fluorescein dye when fitting RGP contact lenses?
Answer: To visualize the tear layer distribution beneath the lens
Sodium fluorescein, illuminated with a cobalt blue light, reveals the tear film distribution beneath an RGP lens, allowing the practitioner to assess the fitting relationship.
What is the ideal movement of a correctly fitted soft contact lens following a blink?
Answer: 0.5 to 1.0 mm of movement
A well-fitted soft contact lens should exhibit approximately 0.5 to 1.0 mm of movement after a blink, indicating adequate tear exchange without excessive lens instability.