Hi, I was adjusting a patient's old glasses (zyl frame with ou -8.00 -3.50 x175) I used my little heater on the frame and pushed the temporal area on the front back to normal alignment. (They were slipping terribly). Let the frame air cool and what did I see? both lenses had vertical lines that looked similar to crazing execpt they were vertical instead of mosaic patterned. I removed the lens from the frame, and also noticed the inside curve had a warped look. It's almost as if the lens was too thin in the center. I did caliper the centers: 1.2mm and 1.3mm respectively. The lenses were some type of high index plastic. I have never in 25 years seen this happen and wonder if anyone might have an explanantion or theory as to what happened. Just a side note: I did take to a colleague, he said they felt like "jello" and thought they were casted lenses.........Any thoughts?
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See this often in high minus lenses. Sometimes it happens from stress, sometimes from age, sometimes from heat, and a occasionally a combination. Seems a little more likely in 166 index (but then a lot of high minus lenses are 166 index). I also see lenses that no longer fit the frame because the lens has warped usually side to side and sometimes uniformly as though the lens had been ground bi-toric. Sometimes you can rectify the problem by heating lens (in air) and placing it concave down on a flat surface and applying hand pressure 'til it appears more symetrical.
Chip -
Strange warpage in lenses
Chip,
Thank you, if the lenses hadn't been crazed in the center, I would have done as you suggest. The lenses were rendered unusable. I have kept them however, as I am determined to find out what or why it happened. Happy Holidays!
Marcie PattenComment
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