Fix and Fit
Back in plastic, part II
By Alex Yoho, ABOM

In part one of this series of working with zyl frames, we discussed adjusting bridges to attain correct frame fits. Here are pointers for mounting lenses and fitting temples in plastics.

When mounting lenses, I believe the best method is as follows: Heat the eyewire thoroughly with either hot air or a frame warming pan containing glass beads or salt, warming the eyewire but not the bridge and endpiece. If you're using beads or salt, they should be heated to about 350 degrees fahrenheit. Be sure to swish the frame around continuously to avoid pitting the frame and to facilitate mounting. Also, familiarize yourself with any cold mount frames since they will be ruined if placed in heat with the lenses out. Most of them may be heated a bit after the lenses are inserted for adjusting purposes.

When mounting lenses onto plastic frames, heat the eyewire thoroughly in a warming pan or with hot air, but exclude the bridge and endpiece

I prefer to mount the lenses from the front of the frame. Begin with the hot frame face up and the endpiece away from you. Hold the frame by the first two fingers of each hand just inside the top and bottom of the eyewire.

Suspending the lens just above the frame between your two thumbs, tuck the temporal side of the lens securely in the eyewire and begin to move your thumbs to the nasal side of the lens. While pushing firmly with your thumbs, begin sliding your index fingers along the lens toward the nasal point and lifting the eyewire onto the bevel of the lens. Finally, pop the lens in at the nasal corner. This up-and-around motion with the index fingers is very important to keep the eyewire from rolling.

ON A ROLL

Sometimes the eyewire rolls when you've tried your best to mount the lens correctly. This can be caused by a lens that is too large or because the lens was just popped in. Older frames often come in, rolled due to heat over long periods of time such as in a hot car. Regardless of the reason, the eyewire must be heated then gingerly rolled back (and just a bit further), or the lens will continually have retention problems.

Of course, aligning a plastic frame requires the same motions that any frame needs. We just need to use slightly different techniques to get there. Bridge alignment, for example, can be done quite easily when you are proficient at mounting lenses. As you mount both lenses quickly in succession, the eyewire near the bridge remains warm. Or, if the lenses have been mounted a while, you can heap up the beads or salt, or use hot air to warm the bridge and address the three planes of bridge alignment.

First check X-ing by using a light source reflecting off the front of the lenses. After warming the bridge area, untwist the frame until the light reflections are even vertically.

Next, take a look at face form by placing the temples on a table with the frame front hanging over and the endpieces touching the table. Observe the distance of each side of the bridge to the table's edge. They should each be about 1/8 inch to 1/4 inch away from the table and even, thus eliminating any skew.

You can also use the table's edge to check frontal skew by placing the top of the frame against the edge and making sure the sides of the bridge are even.

If the bridge on the patient's left side is higher, heat the bridge area, then while pushing on the bottom of the bridge, grasp the left eyewire and rotate it counter-clockwise a bit.

If more is needed, rotate the right side counter-clockwise too, but brace the top of the bridge with your finger. This will bring the right side of the bridge up.

When the lines of the bridge are running parallel to a straight-edge resting across the tops of the eyewires, (the table is handy again) the frontal skew is corrected.

	Mount the lenses from the front of the frame

ENDPIECE ADJUSTMENTS

Continuing our overall alignment, we find it's different to make endpiece adjustments to plastic frames. To adjust the balance, sometimes called the fitting triangle, we will need to adjust the head space in or out. Moving a temple inward requires rolling the eyewire, but only in the endpiece. Note that the endpiece itself should not be heated since the hinge could loosen.

To widen the head space, the endpiece can be rolled out the same way it was brought in. Or, some opticians simply file the butt of the temples to allow them to open up. There is a time and place for filing temples, but you should only do it when absolutely necessary.

One time to file a temple is when you want to add pantoscopic tilt, angling temples down, or retroscopic tilt, angling temples up. As the temples are angled, the hinge bends, and the temple butt now has a gap. This also causes the temple to move inward and, if left as is, would close up the gap and spoil the adjustment.

If the temples are raised, the front will move away from the face to clear the patient's cheeks. To maintain this adjustment, file the temple butt where it touches the frame front.

Try to take one or two strokes at a time, then open the temple up to check your progress. The goal is to file until the temple butt is once again parallel with the abutment on the chassis. This may necessitate moving the endpiece.

Customizing plastic frames would not be complete without discussing temples. Lengthening temples can be done by adding face form to the front. It is also possible to cut plastic off the temple leaving the core exposed, and adding temple tip extenders.

Cable-maker temple tips may also be added. Shortening temples of plastic frames is a matter of cutting to length, and smoothing the tips.

Comments or questions may be addressed to the author at ayoho@mindspring.com