ABO Contact Lens Fitting 2

Question 1

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

Accepted Answer

Rigid gas-permeable (RGP) lens

Answer

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

Question 2

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

Accepted Answer

Add 15° to the prescribed axis

Answer

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

Question 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

The lens power needs to be adjusted by −0.75 D

Answer

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

Question 5

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

Accepted Answer

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

Answer

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

ABO - American Board of Optometry Practice Test