ABO Contact Lens Fitting 5

Question 1

Corneal topography showing an asymmetric bow-tie pattern with skewed radial axes (SRAX) is most suggestive of:

Accepted Answer

Keratoconus

Answer

SRAX on corneal topography, where the bow-tie axes are not aligned, is a hallmark early sign of keratoconus.

Question 2

A bifocal contact lens using an alternating (translating) design relies on which mechanism for near vision?

Accepted Answer

Lens translation downward on downgaze to position the near segment in front of the pupil

Answer

Translating bifocal lenses shift downward in downgaze so the near segment aligns with the visual axis, similar to an executive bifocal spectacle lens.

Question 3

The minimum recommended Dk/t for daily wear soft lenses to avoid significant corneal hypoxia is approximately:

Accepted Answer

24 × 10⁻⁹

Answer

Holden and Mertz established that a Dk/t of ≥24 × 10⁻⁹ is required for daily wear to limit chronic corneal edema to ≤4%.

Question 4

A patient wearing monthly replacement soft lenses is non-compliant with lens care. Which complication are they at GREATEST risk for?

Accepted Answer

Microbial keratitis, particularly Acanthamoeba

Answer

Poor lens hygiene and improper care (especially tap water use) dramatically increase risk of microbial and Acanthamoeba keratitis.

Question 5

When fitting a toric soft lens, the practitioner should evaluate lens axis stability after how many blinks?

Accepted Answer

After 10–15 minutes of adaptation and several blinks

Answer

Toric soft lens rotation should be assessed after at least 10–15 minutes of adaptation so the lens has settled into its stable position.

ABO - American Board of Optometry Practice Test

ABO - American Board of Optometry Practice Test

ABO Contact Lens Fitting 5