Ophthalmic Products and Materials Flashcards

What does the refractive index of a lens material determine?

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.

Which frame material is known for its hypoallergenic properties and is most commonly used for patients with metal allergies?

Answer: Titanium

Titanium is highly biocompatible and hypoallergenic, making it the preferred metal frame material for patients with nickel or other metal sensitivities.

A blue light filtering lens coating is designed to block light primarily in which wavelength range?

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.

Which type of multifocal lens design eliminates visible segment lines while providing a smooth progression of power?

Answer: Progressive addition lens

Progressive addition lenses (PALs) provide a gradual, seamless change in power from distance to near without visible dividing lines.

Zyl (cellulose acetate) frame material is best adjusted using which method?

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.

What is the purpose of a lens's UV 400 designation?

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.

Which lens design feature in a progressive lens is responsible for the distortion or 'swim' experienced in peripheral vision?

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.