ABO NOCE Basic Opticianry Ophthalmic Products and Materials 2

Question 1

Which lens material has the highest Abbe value among commonly used ophthalmic plastics?

Accepted Answer

CR-39 (Allyl diglycol carbonate)

Answer

CR-39 has an Abbe value of approximately 58, the highest among common ophthalmic plastic materials, indicating the least chromatic aberration.

Question 2

A patient reports their anti-reflective coated lenses show a persistent colored sheen even after cleaning. This most likely indicates:

Accepted Answer

A delaminating or deteriorating AR coating

Answer

A persistent or irregular colored sheen after cleaning suggests the AR coating is delaminating or degrading and the lenses should be replaced.

Question 3

What is the primary purpose of a hard coat applied to plastic ophthalmic lenses?

Accepted Answer

Improve scratch resistance

Answer

Hard coats are applied to plastic lenses to improve scratch resistance, since most plastics are inherently softer than glass.

Question 4

Which frame material is most commonly associated with nickel allergy reactions in patients?

Accepted Answer

Monel

Answer

Monel, a nickel-copper alloy widely used in eyewear frames, is the most common source of nickel contact dermatitis in optical patients.

Question 5

High-index lenses with an index of 1.74 compared to CR-39 (1.50) will produce lenses that are:

Accepted Answer

Thinner but heavier

Answer

While high-index 1.74 lenses are significantly thinner, the denser material makes them heavier than CR-39 lenses of equivalent prescription.

ABO NOCE Basic Opticianry Practice Test