HANDS ON - FIX AND FIT
Old Lenses New Frames
by Alex Yoho, ABOM

Dispensers are often asked if they can put patients' old lenses into new frames. Though the best move is to advise the patient to purchase a new pair of eyewear, it is possible to fill their request.

There are two ways to do so. You can reshape the frame, or you can find a similar frame and re-shape the lenses to fit the existing frame shape.

	Mui Mui style MU 13 BV from Luxottica

FRAME RESHAPING

To find a frame that can be reshaped, we must take several factors into consideration.

STEP 1. The DBL (distance between lenses) must be within tolerance. If the old frame has an 18 DBL and the new frame has a 22 DBL, the eyewear's optical centers will be off PD by 4mm.

This may be OK. If the patient is wearing a prescription of up to ±0.75 diopters in the horizontal meridian, we can use Prentice's rule and find that 0.75, times 4mm divided by 10 equals 0.3 diopters of prism in each eye horizontally, which is within ANSI tolerances. The higher the power, the more critical it is to find a frame with a matching DBL.

STEP 2. Look at how the frame is positioned vertically. If the frame is too high or low, it could cause problems with a multifocal fitting height. Hold the loose lenses up to the new frame while the patient is wearing it. As long as the multifocal is in the correct position with the lenses centered top to bottom, it should work.

One word of caution: Be sure the bridge fits well on the patient and the nasal edge of the lens matches it closely. When the nasal angle is changed on a plastic frame, it will fit differently and may change the height of the final product. This angle change could work to your advantage if the fit of the frontal angle is improved.

STEP 3. Work the lens into the frame. With a metal frame, find a frame size with the same circumference as the patient's old lenses. You can sometimes check this by measuring the old lens against the sample lens from the new frame.

If the C-sizes are close, insert the lens into the frame and draw the eyewire down with eyewire closure pliers. Take care not to draw down so tightly that the barrels on the eyewire bend, or there will be a gap at the closure point and the eyewire may gouge the lens.

Ideally, the eyewire will self-conform to the lens. It's also helpful to have a 180� line on the lenses to make sure you don't draw the eyewire down to a crooked lens. If there are gaps and the corners are different from the new frame, you will need to soften the corner or create a more squared corner by using various eyewire shaping pliers. A plastic frame will usually conform to the shape of a lens without too much difficulty, but care must be taken in either case to not roll the eyewire.

RE-EDGING LENSES

If you have decided that re-edging the lenses is the better option, most of the above problems can be eliminated. To begin, ensure that the DBL on the new frame is equal to or greater than the original frame. If it is greater, some of the lens can be edged off to maintain the PD.

As for the vertical placement, the same basic rules apply. When edging material away, you can edge more off the top or bottom to raise or lower the seg height. The most important thing is to make sure there is enough lens to fill in any sharp corners without changing the shape of the frame. A good way to accomplish this is to use the sample lenses from the new frame. Before removing them from the frame, be sure to put a 180� line on both the sample and old lenses so they will not be edged off-axis.

Lay the sample lens with the mark you made in alignment with the corresponding mark on the old lens and trace it. Before beginning, check that both horizontal and vertical are even, and double-check the seg height. Edge off all the high points until you have changed the shape of the lens right down to the traced mark while maintaining bevel placement. Next, reduce the size until you have a lens that will fit snugly in the frame. Now mount the lenses and check PD and seg height.

With a little practice, you will be able to offer this valuable service to your patients.

Questions or comments may be E-mailed to the author at ayoho@cox.net.