Edge Polish On Transition Lenses?

[medicalretina]

I Heard That It's Not Recommended To Edge Polish Transition Lenses.
What's Your Feed Back?

Gil

[CME4SPECS]

Why not? I do it all the time!

[drk]

Maybe this is it?

I recently had a -12.00 patient come inside for adjustment on her Silhouette Titan with Zeiss Gradal Brevity 1.67 Transitions, Zeiss Carat Gold with edge polish. (Yeah, I'm a little proud...) What was interesting is that, from the side, you could tell that anterior 95% of the lens was clear, and that the back had a thin layer of darkening. It looked interesting, but not unattractive.

What I couldn't figure out is why it looked like it was the back surface that was darkened, and not the front. Isn't the imbibing process on the front? Was I drunk (again), or was there an optical illusion?

[Jim Schafer]

I wrote this CS bulletin back in the early to mid 90's...


Some patients may notice a darker activated ring around the periphery of their Transitions Lenses. The darker ring will only be encountered under a very limited set of conditions. The conditions required are: open or rimless frames, exposed or polished lens edges, and certain activation (lighting) conditions.

This ring is NOT due to a defect in the lens or mishandling during surfacing and should not be cause for alarm.
The darker activated ring is only visible under certain conditions, typically initial activation in low daylight light (low UV conditions). It usually is not visible to the wearer but by someone observing the wearer. In most cases, the condition corrects itself the longer the wearer is outdoors (in 3-5 minutes).
The darker ring is caused by light rays entering through the thicker, polished edges of certain prescriptions. The light enters through the edge, is reflected off of the back surface of the lens and directed towards the front surface. On Transitions Lenses, this phenomenon results in the photochromic compounds being activated from both the front and the back area of the reflections. As a result, extra photochromic molecules are activated that would normally be shielded, resulting in the darker area. However, the longer the wearer is outdoors, the photochromics on the surface darken to the point the lens is evenly darkened.

This situation can occur on any photochromic lens.

For Best Results:
To minimize the occurrence of this condition, Transitions Optical recommends that labs polish to a satin finish rather than to polish to a high luster finish. This will minimize and diffuse the light entering the lenses and still provide the patient with a cosmetically appealing lens.

I hope this helps, Call if you have any questions
Jim