ABO NOCE Basic Opticianry Lens Coatings and Treatments 3

Question 1

What is the purpose of an anti-static coating applied to ophthalmic lenses?

Accepted Answer

To prevent static electricity from attracting dust and particles to the lens surface

Answer

Anti-static coatings reduce the build-up of static electrical charge on lens surfaces, which would otherwise attract airborne dust, lint, and particles, making lenses harder to keep clean.

Question 2

A patient reports that their AR-coated lenses have developed 'crazing' — a network of fine cracks in the coating. What is the most likely cause?

Accepted Answer

Exposure to heat, such as leaving glasses in a hot car

Answer

Heat causes the lens substrate and the AR coating to expand at different rates (different coefficients of thermal expansion), leading to stress and crazing or micro-cracking of the coating.

Question 3

In a standard gradient tint used in fashion eyewear, how is the tint distributed across the lens?

Accepted Answer

Darkest at the top, gradually lightening toward the bottom

Answer

Standard gradient tints are darkest at the top and gradually lighten toward the bottom, shielding the eyes from overhead sunlight while allowing relatively clear vision through the lower reading portion.

Question 4

What does the term 'blooming' refer to when describing anti-reflective coated lenses?

Accepted Answer

The characteristic residual color visible in the reflection from an AR-coated lens surface

Answer

'Blooming' refers to the characteristic residual reflection color (often green, blue, or purple) visible on AR-coated lenses, which results from the thin-film interference design of the multilayer coating stack.

Question 5

Brown/amber tinted lenses are particularly preferred for which visual task or activity?

Accepted Answer

Driving and outdoor sports in variable lighting conditions requiring enhanced contrast

Answer

Brown/amber tints enhance contrast and depth perception by selectively filtering blue light and transmitting warmer wavelengths, making them excellent for driving and variable outdoor lighting conditions.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Lens Coatings and Treatments 3