Contact Lens Fitting 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 Lens Fitting flashcards as text
What is the primary purpose of the edge lift in an RGP contact lens design?
Answer: Allow tear exchange and lens movement
Adequate edge lift creates a reservoir beneath the lens periphery, facilitating tear exchange and preventing lens adherence.
A scleral lens is most indicated for which of the following conditions?
Answer: Severe dry eye with irregular corneal surface
Scleral lenses vault completely over the cornea and land on the sclera, providing a fluid reservoir that benefits both irregular corneas and severe dry eye.
Which finding during a slit-lamp evaluation of a soft contact lens wearer suggests giant papillary conjunctivitis (GPC)?
Answer: Papillae greater than 0.3 mm on the upper tarsal conjunctiva
GPC is characterized by papillae ≥0.3 mm (often ≥1 mm in advanced cases) on the superior tarsal conjunctiva.
When assessing soft contact lens fit, acceptable lens movement after a blink should be approximately:
Answer: 0.2–0.4 mm
Optimal soft lens movement is 0.2–0.4 mm on primary gaze blink, indicating neither a too-tight nor too-loose fit.
A patient wearing silicone hydrogel lenses develops superior epithelial arcuate lesions (SEALs). The most appropriate initial management is:
Answer: Refit with a flatter base curve or thinner lens
SEALs are caused by mechanical trauma from a stiff lens edge; refitting with a flatter base curve or thinner lens reduces this mechanical effect.
What does the term 'sagittal depth' describe in contact lens fitting?
Answer: The vertical distance from the chord diameter to the back surface of the lens
Sagittal depth (sag) is the depth of the 'bowl' of the lens, determined by both base curve and diameter, and it dictates how the lens vaults the eye.
Which corneal staining pattern is most characteristic of solution toxicity from contact lens care products?
Answer: Diffuse punctate epithelial staining across the entire cornea
Solution toxicity typically presents as diffuse superficial punctate keratitis spread across the entire corneal surface.