Spectacle Dispensing Procedures Flashcards
6 cards from real NOCE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Spectacle Dispensing Procedures flashcards as text
A patient wearing new progressive addition lenses complains that they must lift their chin excessively to read clearly. What is the most likely cause of this issue?
Answer: The segment height was measured too low.
If the fitting cross (segment height) of a progressive lens is positioned too low, the patient must look further down through the lens to access the full reading power in the near zone. This forces them to compensate by lifting their chin to bring the near zone into their line of sight.
What is the primary optical purpose of applying an appropriate amount of pantoscopic tilt to a pair of spectacle frames?
Answer: To better align the lens's optical axis with the eye's visual axis as it rotates downward for near vision.
Pantoscopic tilt angles the bottom of the lenses toward the cheeks. This adjustment is crucial because as the eye rotates downward to read, the tilt helps keep the visual axis perpendicular to the lens surface, which maintains the prescribed optical correction and reduces aberrations.
According to ANSI Z80.1 standards for prescription ophthalmic lenses, which of the following represents the acceptable tolerance for the cylinder axis of a lens with a power of +3.00 -1.25 x 090?
Answer: ± 3 degrees
The ANSI Z80.1 tolerance for cylinder axis depends on the magnitude of the cylinder power. For a cylinder power greater than 0.75 D and up to 1.50 D, the standard tolerance for the axis is ±3 degrees. The cylinder in this prescription (-1.25 D) falls within this range.
A patient is fitted with their first pair of flat-top 28 (FT-28) bifocals and complains that the floor seems blurry and 'jumps' when they walk, particularly on stairs. This common adaptation issue is most likely caused by:
Answer: The segment height being measured too high.
When the bifocal segment is set too high, the patient's line of sight inadvertently passes through the near-vision portion of the lens when they look down at the floor or stairs. This causes the ground to be out of focus and induces a prismatic effect (image jump), creating a sensation of instability.
When selecting a frame for a patient with a high myopic prescription (e.g., -10.00 D), which frame characteristic is MOST critical for minimizing lens thickness and weight?
Answer: A small, round eye size that centers the patient's pupils well within the lens aperture.
High minus lenses are thinnest at the optical center and thickest at the edges. Choosing a small, round frame that requires minimal decentration (i.e., the patient's PD is very close to the frame's geometric center distance) allows the optician to use the thinnest central portion of the lens blank, drastically reducing the final edge thickness and weight.
An optician is fitting a patient with an Executive (Franklin-style) bifocal. What is the standard anatomical landmark used to determine the correct segment height for this type of lens?
Answer: The upper margin of the patient's lower eyelid.
Due to the highly visible line that spans the entire width of the lens, the standard fitting protocol for an Executive or Franklin-style bifocal is to place the top of the segment line directly at the patient's lower eyelid margin. This provides a wide field of view for near tasks while minimizing the line's interference with distance vision.