ABO ABO Industry Standards 3 — Questions and Answers
Question 1: In ophthalmic lens standards, what is the 'optical center' of a single vision lens?
- The geometric center of the lens blank
- The point on the lens where prismatic effect is zero (Correct answer)
- The thinnest point of the lens
- The point on the lens aligned with the pupillary distance
Correct answer: The point on the lens where prismatic effect is zero
The optical center is the point on a lens through which light passes without being deviated (zero prismatic effect).
Question 2: What is the standard pupillary distance measurement method used when fitting progressive addition lenses?
- Monocular PD measured from each pupil to the bridge (Correct answer)
- Binocular PD measured across both pupils simultaneously
- PD measured from the dominant eye only
- PD estimated from the frame's total width
Correct answer: Monocular PD measured from each pupil to the bridge
For PALs, monocular PD is the preferred method, measuring from the center of each pupil to the bridge of the nose independently.
Question 3: According to FDA regulations, which lens material is exempt from the standard dress impact (drop-ball) test requirement?
- Polycarbonate
- CR-39 plastic
- Trivex
- Glass lenses over 3mm thick (Correct answer)
Correct answer: Glass lenses over 3mm thick
FDA regulations exempt glass lenses that are at least 3mm thick at their thinnest point from the drop-ball impact test.
Question 4: What does the 'Abbe value' of a lens material indicate?
- The material's scratch resistance
- The degree of chromatic aberration (color dispersion) (Correct answer)
- The UV transmittance of the material
- The material's resistance to chemical damage
Correct answer: The degree of chromatic aberration (color dispersion)
The Abbe value (V-number) measures chromatic aberration; a higher value means less color fringing and better optical clarity.
Question 5: Which organization publishes the ANSI Z80 series of ophthalmic standards in the United States?
- The Vision Council of America
- The American Optometric Association
- The American National Standards Institute (Correct answer)
- The FDA Center for Devices and Radiological Health
Correct answer: The American National Standards Institute
ANSI (American National Standards Institute) publishes and maintains the Z80 series, which includes standards for ophthalmic lenses, frames, and instruments.
Question 6: Under ANSI Z80.1, the distance power tolerance for lenses with power greater than ±6.50D is:
- ±0.13D
- ±0.25D
- ±2% of the power (Correct answer)
- ±0.50D
Correct answer: ±2% of the power
For lenses with powers greater than ±6.50D, ANSI Z80.1 specifies a tolerance of ±2% of the specified power.
Question 7: What is the primary purpose of an anti-reflective (AR) coating on ophthalmic lenses?
- To increase the lens's scratch resistance
- To reduce surface reflections and improve light transmission (Correct answer)
- To block UV radiation
- To reduce lens weight
Correct answer: To reduce surface reflections and improve light transmission
AR coatings use thin-film interference to cancel surface reflections, increasing visible light transmission and reducing glare.
ABO ABO Industry Standards 3
In ophthalmic lens standards, what is the 'optical center' of a single vision lens?