ABO NOCE Basic Opticianry Ophthalmic Lenses and Materials 3

Question 1

When dispensing lenses with anti-reflective (AR) coating, why must a hard coat be applied beneath the AR coating?

Accepted Answer

To provide a smooth, durable surface for the AR layers to adhere to

Answer

Hard coat creates a smooth, durable surface that allows the thin vacuum-deposited AR layers to adhere properly and reduces microabrasions that would compromise coating performance.

Question 2

A photochromic lens darkens when exposed to UV radiation because of which mechanism?

Accepted Answer

UV radiation activates silver halide or organic molecules embedded in the lens, causing a color change

Answer

Photochromic lenses contain silver halide crystals or organic photochromic molecules that undergo a reversible chemical reaction when exposed to UV radiation, causing the lens to darken.

Question 3

What is the main advantage of Trivex over polycarbonate as an impact-resistant lens material?

Accepted Answer

Trivex has a higher Abbe value providing better optical clarity

Answer

Trivex has an Abbe value of approximately 45 compared to polycarbonate's 30, giving Trivex significantly better optical clarity and less chromatic aberration while maintaining excellent impact resistance.

Question 4

In a progressive addition lens, where is the distance optical power measured?

Accepted Answer

In the fitting cross or distance reference point (DRP)

Answer

The distance power of a PAL is measured at the distance reference point (DRP) or fitting cross, which is positioned in front of the patient's pupil for distance viewing.

Question 5

Which type of lens segment shape in a bifocal provides the widest near field of view?

Accepted Answer

Executive (E-style) full-width segment

Answer

The Executive (E-style or Franklin-style) bifocal extends the near segment across the full width of the lens, providing the widest possible near field of view.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Ophthalmic Lenses and Materials 3