ABO Ophthalmic Dispensing 5

Question 1

A patient requires 2Δ base-down prism OD and 2Δ base-up prism OS. This is an example of:

Accepted Answer

Compensating prism

Answer

Compensating prism uses opposite bases in each eye to correct a vertical phoria, as opposed to yoked prism where both eyes receive the same base direction.

Question 2

Slab-off (bicentric grinding) is most commonly used to correct:

Accepted Answer

Vertical imbalance at the near zone in high anisometropic prescriptions

Answer

Slab-off creates a prism difference at the near zone to compensate for the vertical prismatic imbalance caused by anisometropia when reading through bifocals.

Question 3

The vertex distance significantly affects the effective power of lenses with power greater than approximately:

Accepted Answer

±5.00 D

Answer

Vertex distance compensation becomes clinically significant for powers of ±5.00 D or higher, where small changes in distance materially change the effective power at the eye.

Question 4

Which lens treatment absorbs UV radiation below 400 nm and is built into the lens material rather than applied as a coating?

Accepted Answer

UV inhibitor (UV absorber)

Answer

A UV inhibitor is incorporated into the lens monomer during manufacturing, providing UV400 protection as an inherent lens property, not a surface treatment.

Question 5

When dispensing a frame to a patient with a high nose, which bridge adjustment is most appropriate?

Accepted Answer

Increase the splay angle of the nose pads

Answer

Increasing the splay (flare) angle of the nose pads spreads them wider to accommodate a higher nose bridge and raise the frame on the face.

ABO - American Board of Optometry Practice Test

ABO - American Board of Optometry Practice Test

ABO Ophthalmic Dispensing 5