NOCE Lens Treatments and Coatings

Question 1

What is the primary purpose of an anti-reflective (AR) coating applied to ophthalmic lenses?

Accepted Answer

To reduce glare and surface reflections, improving visual clarity and cosmetic appearance

Answer

AR coatings reduce light reflections off lens surfaces, which minimizes glare, improves light transmission, and gives lenses a more cosmetically appealing clear appearance.

Question 2

A patient asks why their CR-39 lenses need a UV-protective treatment. Which statement is most accurate?

Accepted Answer

CR-39 requires a UV-absorbing treatment to achieve UV400 protection because it transmits significant UV radiation on its own

Answer

Standard CR-39 does not inherently block UV radiation adequately, so a UV-absorbing additive or coating must be incorporated to achieve UV400 (blocks up to 400nm) protection.

Question 3

Which mechanism causes photochromic lenses to darken when the wearer moves outdoors?

Accepted Answer

Exposure to ultraviolet (UV) radiation triggers a molecular change in the photochromic compounds

Answer

Photochromic lenses contain UV-sensitive molecules (such as naphthopyrans) that undergo a reversible structural change when exposed to UV radiation, causing the lenses to darken.

Question 4

What is the main functional benefit of applying a scratch-resistant (hard) coating to ophthalmic lenses?

Accepted Answer

It reduces surface micro-abrasions that degrade optical clarity over time

Answer

Scratch-resistant coatings harden the lens surface to minimize micro-abrasions from everyday cleaning and handling, which preserves optical clarity over the life of the lens.

Question 5

Which cleaning method is recommended for lenses with an anti-reflective coating?

Accepted Answer

Clean with a fresh microfiber cloth and an appropriate lens-cleaning solution or water

Answer

AR-coated lenses should be cleaned with a clean microfiber cloth and a lens-safe cleaning solution to avoid scratching the coating with abrasive materials or damaging it with harsh chemicals.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE Lens Treatments and Coatings