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

To block ultraviolet radiation from reaching the eye

Answer

To increase the impact resistance of the lens material

Answer

To reduce the overall weight of the lens

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

CR-39 naturally blocks 100% of UV radiation up to 400nm without any treatment

Answer

CR-39 can block UVB but requires treatment only for UVA radiation

Answer

UV coatings are optional for CR-39 because patients never receive sufficient UV exposure indoors

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

Increased visible light intensity activates the heat-sensitive dye layers

Answer

Infrared radiation from sunlight activates silver halide crystals in the lens

Answer

Decreased temperature outdoors causes the chromic molecules to contract and absorb light

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

It makes the lens completely impervious to all surface damage

Answer

It increases the flexibility of the lens material to resist cracking

Answer

It eliminates the need for an anti-reflective coating on the same 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

Dry wipe with disposable paper towels using firm pressure to remove debris

Answer

Use undiluted ammonia-based household glass cleaner for best results

Answer

Rinse with very hot water to dissolve oils, then air dry without wiping

Question 6

UV400 protection on ophthalmic lenses means the lens blocks all ultraviolet light up to which wavelength?

Accepted Answer

400 nm

Answer

350 nm

Answer

380 nm

Answer

420 nm

Question 7

Which combination of lens materials inherently blocks UV radiation up to 400nm without requiring an additional UV coating or treatment?

Accepted Answer

Polycarbonate and Trivex

Answer

Crown glass and CR-39 plastic

Answer

CR-39 plastic and high-index 1.67

Answer

High-index 1.74 and crown glass