Peter wrote:
much better still, buy surgeon’s loupes
Or one of those things that make you look like Locutus of the Borg.
I have an optical correction note on my medical.
I cover the “second pair” requirement by having a pair of “thinoptics” in a case stuck to my phone case, or on my key ring.
The text regarding a second pair has recently disappeared from the CAA rubric. However it is still a good idea. I use prescription sunglasses as my primary pair, with my usual glasses as a back-up pair. When flying at night, I carry a second pair of “normal” glasses. I have broken a pair in flight, so have never regretted this policy.
I went to varifocals too. But with a caveat…
First of all, I requested the reading zone and transition zone to be lower than usual. To read I need to shift my gaze to the bottom part of the lenses conscientiously. Not a problem (at least for me). Like said before, I invested in expensive lenses. (Essilor Highest end possible. They provide a clear field of vision and no distortion.
Secondly, I had the lenses treated to have behind the windshield chromatic lenses.
They work beautifully. While driving or flying they change color. Not too dark, just enough to avoid eye fatigue or being blinded by luminosity. (The brand of the surface coating is Transition Drivewear)
So, I can read a chart, look away for traffic, my eyes are protected from the sun, but I can fly at dawn, dusk, and night with the same glasses. I only use one pair of glasses for all and don’t have pockets on my shirts!
Hope this helps…
Emmanuel
Interesting you got photochromic lenses to work “indoors”, @EDavidson. They need UV and IME are almost useless. But maybe Transitions actually work? How clear do they go? It would be great to have a pair of glasses which work for both day and night.
Essilor are very good. I once bought an unusual titatium sunglass frame (Lindberg) and only Essilor could make the lenses fit. Nowadays there are others who can do it, but nobody is cheaper than the very pricey Essilor 
Multiple threads on spectacles merged.
The newer Essilor Transitions XTRActive are activated by lower light frequencies so still work behind car windows. Transitions Drivewear are polarised.
Most lens substrates absorb UV whereas Essilor’s newest coating, Crizal Prevencia, reflects it. This has the undesired effect of UV reflecting off the back of the lenses into the eyes so it’s worth asking the lab to put a different coating on the back.
Transitions Lenses and Blue Light Technical Notes (link). local copy
The newer Essilor Transitions XTRActive are activated by lower light frequencies so still work behind car windows.
That’s a great find! I will look into it. However I fly with complicated bifocals, with a +0.50 insert which only one company in the US does.
Transitions Drivewear are polarised.
That’s no good for flying and I am surprised it would be ok for driving due to (a) satnav etc LCD screens and (b) some instrument panels.
it’s worth asking the lab to put a different coating on the back
I would be amazed if they would do that. One might be able to get an additional coating though.
As I posted further back, following a hunt for lenses with extra good UV attenuation, there is a fair bit of it out there (it’s a bit of a fashion right now too, but for good reasons) but none of the companies seem to be doing bifocals. They do just plain lenses (single prescription) or the expensive varifocals. Varifocals are difficult for many people, so the stick-on reading inserts are the only option and actually they work well if you get good quality ones. The fresnel lens ones are horrible…
The Prevencia coating appears to reduce reflected UV to a negligible amount by destructive interference.
“On the back side, the interferential layers have been created to minimise the reflection of UV rays into the eye.” (link).
“Studies suggest that up to 50% of UV exposure can come from reflections off of the back surface of the lens.[ 1] Crizal® UV lenses reduce the backside UV reflections to 4% ….” (link). [ 1] Citek, Karl. Anti-reflective coatings reflect ultraviolet radiation. Optometry. 2008 Mar;79(3):143-8. DOI: 10.1016/j.optm.2007.08.019. (link).
alioth wrote:
Or one of those things that make you look like Locutus of the Borg.
Now we need to debate if it is a good thing or a bad thing… Especially when being inspected ;-)
