aligning frames Flashcards
The tool you’ll reach for the most
an optical screwdriver
When you work with frames, you’ll use what?
When you work with frames, you’ll use several different optical screwdriver blade sizes.
Knowing the correct blade width to use is very important, why?
Knowing the correct blade width to use is very important, because the screws are so small that you can easily ruin a frame or strip the screw slot.
When you’re working with frames, here’s a good rule of thumb:
When you’re working with frames, here’s a good rule of thumb: Always select the widest screwdriver blade you can use without scratching a frame. It’s best to hold the shaft of the screwdriver between your fingers and press the top of the screwdriver to the palm of your hand while you twist the screwdriver.
And here’s another tip.
And here’s another tip. Eyeglass screws can occasionally loosen, especially in the hinge as the temples are opened and closed. We sometimes put a tiny drop of Loctite or clear fingernail polish on the end of a screw before inserting it to help prevent it from backing out.
lens axis pliers
To turn the lens so it’s aligned correctly in the frame, we use lens axis pliers like the pair shown below. They grab the lens on the front and back so we can rotate it.
Hot salt pans
Hot salt pans, contain heated table salt. Other types of hot pans use small glass beads. I personally don’t have a preference, but the salt is less expensive.
Forced hot air warmers
Forced hot air warmers allow you to adjust the temperature of the heat and to apply a more direct stream of hot air evenly to the area of a frame needing adjustment. This is a more modern, cleaner way to heat frames, so many people no longer use the pans.
pans using hot salt or glass beads have some additional drawbacks
pans using hot salt or glass beads have some additional drawbacks. For example, they can damage certain frame materials and lens coatings. That’s another reason why we often choose to use hot air instead.
lens caliper
lens caliper, which you’ll use to measure the center thickness of a lens. For instance, you’ll use this tool to determine whether you’re working with a regular lens that’s two millimeters thick or a safety lens that should be a minimum of three millimeters thick.
distometer
distometer to measure vertex distance.
pantoscopic tilt
the downward angle of a frame
In general, we aim for a pantoscopic tilt of what?
In general, we aim for a pantoscopic tilt of about 10 degrees. When we’re dealing with lenses that have a reading portion such as a bifocal portion at the bottom of the lens, or when we’re giving customers lenses that are custom-designed, we shoot for 5 to 15 degrees of tilt.
Every two degrees of pantoscopic tilt added to a frame front effectively lowers the optical center of the lens by how much?
one millimeter.
2° of pantoscopic tilt = optical center ↓1 mm
retroscopic tilt.
retroscopic tilt. Here, the upper portion of the frame is closer to the eyes than the lower part of the frame, Frames with this type of tilt look odd—and worse yet, people can’t see well with them. As you learned in today’s reading, you can often fix this problem using your hands and optical pliers.
orthoscopic tilt.
orthoscopic tilt. This means that the lenses are the same distance from the eye at the top and bottom of the frame.
face form,
face form how a pair of glasses wraps around a person’s face.
positive face form.
positive face form. This means that the frames curve slightly to follow the contours of the face. In this form, the bridge of the glasses will be slightly forward from the endpieces.
typically we aim for this face form
positive face form.
Vertex
Vertex, as you learned earlier, is the distance between the cornea and the back of an eyeglass lens.
Short vertex (too close to eye) =
More minus power
Long vertex (too far from eye =
Long vertex (too far from eye = More plus power
you’ll want your client’s glasses to sit at about the same distance from the eye—
—12 millimeters.
If the vertex distance is too close to or too far from the eyes, what will happen?
If the vertex distance is too close to or too far from the eyes, the power of the lenses will be too strong or too weak. We call this altered power the effective power of the lenses.
a perfectly aligned frame
a trued frame
alingeing the frame
Your first step will be to check the four-point touch of the frame.
to check the four-point touch of the frame.
to do this, you’ll place the frame upside-down with the temples open on a flat surface. When you do this, you should see that the frame touches the surface in four places: both tops of the earpieces and both endpieces of the eyewire. If it does, your alignment won’t be far off. (Be aware, however, that your client’s ears may not be level—so one temple may need to be higher than the other for the frame to look straight on the person’s head. We’ll talk more about this in the next lesson.)
