Ophthalmic Lenses and Materials Flashcards
6 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Ophthalmic Lenses and Materials flashcards as text
A patient who does a significant amount of night driving complains of distracting glare and halos from oncoming headlights. Which lens treatment would be most effective in addressing this specific complaint?
Answer: Anti-reflective coating
Anti-reflective (AR) coating is specifically designed to reduce reflections from the front and back surfaces of the lens. This allows more light to pass through to the eye and significantly decreases glare, halos, and ghost images, which are especially noticeable during night driving.
Which of the following lens material properties is most directly associated with the amount of transverse chromatic aberration a patient is likely to experience?
Answer: Abbe Value
The Abbe value is a measure of a lens material's chromatic dispersion. A lower Abbe value indicates higher dispersion, which causes more chromatic aberration (color fringing), especially when viewing off-axis. Materials with a higher Abbe value have less dispersion and therefore cause less chromatic aberration.
A patient has a prescription of R: -1.50 DS and L: -5.00 DS and complains of eye strain and occasional double vision when reading through their new bifocals. This vertical imbalance at the reading level is best corrected by which of the following?
Answer: Applying a bicentric grind (slab-off)
The significant difference in power between the two eyes (anisometropia) induces different amounts of vertical prism when the patient looks down to read. A bicentric grind, commonly called a slab-off, adds base-up prism to the lower portion of the most minus (or least plus) lens to counteract this induced imbalance and alleviate the patient's symptoms.
What is the primary optical advantage of an aspheric lens design compared to a standard spherical design, particularly in higher-powered prescriptions?
Answer: It reduces peripheral distortions and improves aesthetics.
Aspheric lenses have a more complex surface curvature that gradually changes from the center to the edge. This design reduces or eliminates spherical aberration, which causes distortion when looking away from the lens center. This results in a wider field of clear vision and also allows for flatter, thinner, and lighter lenses, which is more aesthetically pleasing.
Which of the following lens designs provides a continuous, seamless progression of power from distance to near vision without any visible lines?
Answer: Progressive addition lens
A progressive addition lens (PAL) is a multifocal lens that corrects for presbyopia by gradually and smoothly changing in power from the top (for distance vision) to the bottom (for near vision). This design allows for clear vision at all distances without the visible lines characteristic of bifocals or trifocals.
According to FDA regulations for standard "dress eyewear," what is the procedure used to test the impact resistance of a lens?
Answer: A 5/8 inch steel ball is dropped from 50 inches.
The FDA's "Drop Ball Test" for dress eyewear (non-safety) requires a 5/8 inch steel ball, weighing approximately 0.56 ounces, to be dropped from a height of 50 inches onto the horizontal outer surface of the lens. To pass, the lens must not fracture.