Contact Lens Fitting Flashcards

A patient with keratoconus is best managed with which contact lens modality?

Answer: Rigid gas-permeable (RGP) lens

RGP lenses vault the irregular cornea and provide a smooth refracting surface, making them the preferred option for keratoconus.

When fitting a soft toric lens, the lens consistently rotates 15° clockwise. What axis adjustment should be made?

Answer: Add 15° to the prescribed axis

Using the LARS rule (Left Add, Right Subtract), clockwise rotation means you add degrees to the axis.

Which base curve selection guideline is most appropriate when fitting a standard soft lens?

Answer: Choose a base curve 0.5–1.0 mm flatter than flat K

Soft lenses are typically fit 0.5–1.0 mm flatter than the flat K to allow appropriate drape and movement.

A patient's over-refraction with a trial RGP lens yields −0.75 D sphere. What does this most likely indicate?

Answer: The lens power needs to be adjusted by −0.75 D

A spherical over-refraction result is simply added to or subtracted from the trial lens power to determine final lens power.

Which fluorescein pattern indicates an appropriately fitted RGP lens on a normal cornea?

Answer: Feather touch or minimal apical clearance with even mid-peripheral bearing

An alignment fit shows slight apical touch or minimal clearance, even mid-peripheral bearing, and adequate edge lift.

Which parameter primarily determines the oxygen transmissibility (Dk/t) of a contact lens?

Answer: Center thickness and material Dk

Dk/t is calculated by dividing the material's oxygen permeability (Dk) by the lens center thickness (t).

A presbyopic patient with low myopia wants to try monovision contact lenses. Which eye is typically corrected for distance vision?

Answer: Dominant eye

In monovision, the dominant eye is corrected for distance and the non-dominant eye for near.