Ophthalmic Products and Frames 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 Ophthalmic Products and Frames flashcards as text
A client selects a frame made from a titanium alloy known for its ability to return to its original shape after being bent or twisted. This material is an excellent choice for active individuals or children. Which material is being described?
Answer: Memory Metal
Memory metal is a titanium alloy, typically composed of about 50% titanium and 50% nickel, known for its superelastic properties. This allows frames made from it to withstand significant deformation and return to their original shape, making them ideal for children or those with an active lifestyle.
When identifying a progressive addition lens (PAL), permanent markings are etched onto the lens surface. What information is typically found on the temporal side of the lens?
Answer: The add power
Progressive addition lenses have permanent, semi-visible engravings for identification. The engraving on the temporal side of the lens indicates the add power (e.g., '2.00'). The nasal side typically contains a symbol or logo identifying the lens manufacturer and design.
A patient with a high myopic prescription (-9.50 D) is being fitted for new glasses. The refraction was performed at a vertex distance of 14 mm, but the new frames will sit at a vertex distance of 10 mm. How does this change in vertex distance affect the lens power required?
Answer: The effective power becomes more plus, requiring a weaker minus lens.
When a minus lens is moved closer to the eye, its effective power decreases (becomes less minus/more plus). Therefore, to compensate for the shorter vertex distance (from 14 mm to 10 mm), a slightly weaker minus power will be needed to provide the same visual correction as the original refraction.
According to the ANSI Z80.1-2020 tolerance standards, what is the allowable tolerance for sphere power for a prescription of -4.75 D?
Answer: ±0.13 D
The American National Standards Institute (ANSI) Z80.1-2020 standards provide guidelines for prescription ophthalmic lenses. For a single vision lens with a spherical power between +6.50 D and -6.50 D, the tolerance is ±0.13 D.
An optician is fitting a patient with a new pair of glasses and needs to increase the pantoscopic tilt. Which of the following adjustments would achieve this?
Answer: Angling the temples downward from the hinge point.
Increasing pantoscopic tilt means the bottom of the lens front moves closer to the patient's cheeks. This is achieved by angling the temples downward at the hinge or endpiece. This adjustment helps ensure the optical axis of the lens is correctly aligned with the eye's visual axis, especially for progressive lenses.
A reverse slab-off is used to compensate for vertical imbalance in a patient with anisometropia. On which lens is a reverse slab-off applied?
Answer: The lens with the most plus or least minus power in the vertical meridian.
A reverse slab-off creates base-down prism in the reading area of the lens. It is applied to the lens that naturally induces the most base-up prism, which is the lens with the most plus power or the least minus power in the 90-degree meridian. This contrasts with a conventional slab-off, which adds base-up prism to the most minus lens.