Flashcards in quizes 2 Deck (55)
Which of these lenses can be made the thinnest?
Which of these lens options is best for a school bus driver?
Which of these materials has a refractive index of 1.523?
Which of these lenses acts a little like a venetian blind, stopping horizontal light rays from entering the eye?
A polarizing lens.
Which of these lenses would you recommend for a skier?
A mirrored lens.
What is a prism diopter?
The power of a prism to produce a one-centimeter deviation in a ray of light at a distance of one meter.
According to ANSI regulations, what is the prism power tolerance for a complete pair of glasses in the horizontal meridian?
.67 prism diopters.
What is decentration?
The displacement of the optical center in a lens to create a prismatic effect.
If a client’s pupillary distance is 70 and the frame’s GCD is 76, what is the required decentration in millimeters for each eye?
When Sally’s glasses arrive from the lab, you discover that the GCD is 66 mm. Sally’s pupillary distance is only 62 mm. Here is her prescription:
OD +1.00 sph
OS +3.00 sph
What is the induced prism in each lens?
.2 OD and .6 OS.
In which type of lens aberration will your client see a comet-shaped image?
When you use Vogel’s formula, you will first need to determine the spherical equivalent of the lens. What is this number?
Half the cylinder amount added to the sphere.
What is a slab-off?
A process in which the lab cuts off the lower part of the most minus-powered lens on the back side.
Which of these lenses helps prevent aberrations and is a good choice if you want a flat base curve?
An aspheric lens.
Which of these is a good rule of thumb when you’re selecting a base curve for a lens?
If the difference between lenses is greater than two diopters, it’s better to use the individual base curve selections.
Which of these frames is an optimal choice for a standard progressive lens?
Rectangular frames that are not very shallow.
Which of these features will you see in progressive lenses designed for computer use?
A larger-than-normal intermediate vision area.
What will you use a centration card for?
Determining where the reading portion will fall on a progressive lens and whether a lens will fit in a specific frame.
Which of these is another name for progressive lenses?
Which of these is an accurate statement about progressive lenses
They must be measured very accurately.
What is a mire line?
A line you’ll see through the eyepiece of a lensometer.
What does the spectacle table lever of a lensometer do?
It raises or lowers the glasses so they’re in the right position.
Which power will you calculate first when you’re using a lensometer to find the power of a lens?
The sphere power.
What’s one good reason for learning how to use a manual lensometer?
Some states require proficiency at this task as part of a practical exam for licensing.
What is the first step in using a manual lensometer?
Focus the eyepiece.
The eyesize of a frame is 50, and the DBL is 20. The person’s PD is 60. How much should the lens be decentered?
If the monocular PD of a right lens is 30, the eyesize is 50, and the DBL is 20, what is the decentration of the lens
If the MRP of a lens needs to be 30 mm, and the frame B measurement is 45, what is the MRP raise?
How many millimeters are there in 3.5 centimeters?