NOCE Ophthalmic Products and Materials 3 — Questions and Answers
Question 1: What does the refractive index of a lens material determine?
- The lens's resistance to impact
- How much the lens bends light relative to its thickness (Correct answer)
- The UV protection level of the material
- The Abbe value of the lens
Correct answer: How much the lens bends light relative to its thickness
The refractive index measures how much a material bends light; a higher index allows a thinner lens to achieve the same optical power.
Question 2: Which frame material is known for its hypoallergenic properties and is most commonly used for patients with metal allergies?
- Monel
- Beryllium
- Titanium (Correct answer)
- Nickel silver
Correct answer: Titanium
Titanium is highly biocompatible and hypoallergenic, making it the preferred metal frame material for patients with nickel or other metal sensitivities.
Question 3: A blue light filtering lens coating is designed to block light primarily in which wavelength range?
- 200–280 nm
- 380–500 nm (Correct answer)
- 550–650 nm
- 700–800 nm
Correct answer: 380–500 nm
Blue light filtering lenses target the 380–500 nm range (high-energy visible light), which includes the violet and blue wavelengths associated with digital screen exposure.
Question 4: Which type of multifocal lens design eliminates visible segment lines while providing a smooth progression of power?
- Flat-top bifocal
- Round segment bifocal
- Progressive addition lens (Correct answer)
- Executive bifocal
Correct answer: Progressive addition lens
Progressive addition lenses (PALs) provide a gradual, seamless change in power from distance to near without visible dividing lines.
Question 5: Zyl (cellulose acetate) frame material is best adjusted using which method?
- Cold bending
- Salt pan or hot air heating (Correct answer)
- Hydraulic press
- Ultrasonic welding
Correct answer: Salt pan or hot air heating
Zyl frames are thermoplastic and must be heated with warm salt or a frame warmer before adjustment to avoid cracking or breaking the material.
Question 6: What is the purpose of a lens's UV 400 designation?
- It blocks all light above 400 nm
- It blocks UV radiation up to 400 nm wavelength (Correct answer)
- It indicates the lens transmits 400 lux
- It certifies the lens meets ANSI impact standards
Correct answer: It blocks UV radiation up to 400 nm wavelength
UV 400 means the lens blocks all ultraviolet radiation up to 400 nanometers, covering both UVA and UVB ranges completely.
Question 7: Which lens design feature in a progressive lens is responsible for the distortion or 'swim' experienced in peripheral vision?
- The reading zone corridor
- Peripheral astigmatic aberration (Correct answer)
- The distance zone curvature
- The fitting cross height
Correct answer: Peripheral astigmatic aberration
Progressive lenses have unavoidable astigmatic aberration zones in the peripheral areas due to the mathematically complex surface required to blend power changes.
NOCE Ophthalmic Products and Materials 3
What does the refractive index of a lens material determine?