ABO Industry Standards Flashcards

Prentice's rule states that induced prism equals:

Answer: Power (D) × decentration (cm)

Prentice's rule: Prism (Δ) = Power (diopters) × decentration (centimeters), used to calculate induced prism from lens decentration.

What is the base curve of an ophthalmic lens?

Answer: The curve specifically designated as the reference or 'base' from which other curves are measured

The base curve is the reference surface curve (usually the front curve) from which the lens prescription is built and other curves are calculated.

Under ANSI Z80.3, sunlens luminous transmittance categories range from Category 0 to Category 4. What does Category 4 indicate?

Answer: Very dark lenses (3-8% transmittance) not suitable for driving

Category 4 sunlenses have very dark tints with only 3-8% luminous transmittance and are not recommended for use while driving.

In frame standards, the 'boxing system' is used to:

Answer: Provide a standardized method for measuring lens and frame dimensions

The boxing system is a standardized method using a rectangle (box) around the lens aperture to measure frame and lens dimensions such as A, B, DBL, and ED.

What is the 'effective diameter' (ED) of a lens in the boxing system?

Answer: The diameter of the smallest circle that will encompass the entire lens shape

The effective diameter (ED) is the diameter of the smallest circle centered on the boxing center that completely encloses the lens shape.

According to ANSI Z80.1, what is the cylinder power tolerance for lenses with cylinder powers greater than 2.00D?

Answer: ±5% of the specified cylinder

For cylinder powers exceeding 2.00D, ANSI Z80.1 allows a tolerance of ±5% of the specified cylinder power.

Which of the following correctly describes 'wrap angle' (face-form tilt) in frame fitting?

Answer: The angle at which the frame front curves horizontally to follow the face

Wrap angle (face-form tilt) is the horizontal curvature of the frame front that follows the contour of the patient's face.