Dispensing Instrumentation Questions and Answers Flashcards
7 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 7 Dispensing Instrumentation Questions and Answers flashcards as text
When verifying a prism prescription with a lensometer, the prism amount is read by:
Answer: Observing how far the target is displaced from the reticle center in prism diopters
Prism is measured by decentering the lens until the target centers, with the displacement from center indicating the prism power in prism diopters.
The purpose of a seg height measuring tool or ruler is to:
Answer: Determine the vertical placement of the bifocal segment relative to the pupil
A seg height tool measures the distance from the segment top to the lowest part of the frame to ensure proper bifocal placement for the patient.
Which of the following best describes the function of a Geneva lens clock on a minus-powered meniscus lens?
Answer: It measures both front and back surface curvatures to derive the base curve
The Geneva lens clock measures the sag of each surface separately; by knowing the lens index, the front and back curves can confirm the base curve selection.
Frame pantoscopic tilt is measured using a:
Answer: Frame protractor or frame aligner with degree markings
A frame protractor or frame aligner with degree scale measures how many degrees the frame front is tilted forward from the vertical plane.
A lensometer target that shows a starburst or radiating spoke pattern when the lens is placed on the stage most likely indicates:
Answer: Lens warpage, aberrations, or a highly irregular lens surface
Irregular or distorted target patterns suggest the lens has surface irregularities, warpage, or optical defects rather than a clean prescription.
The effective diameter of a frame is determined by measuring:
Answer: The longest chord through the geometric center of the lens opening
The effective diameter (ED) is the longest chord across the lens shape through its geometric center, used for minimum blank size calculations.
Axis determination on the lensometer is most accurate when the dispenser:
Answer: Rotates the axis wheel until one set of lines is sharpest, then reads the axis scale
Accurate axis reading requires rotating the axis wheel to sharpen one focal line completely before noting the axis value on the scale.