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Glasses - what do you use?

Old 17th May 2016, 11:35
  #21 (permalink)  
 
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I was told when I did my initial medical over 20 years ago that photo chromatic lenses weren't allowed because of a heavy landing by a DC9 Captain. He had been flying in bright sunlight over 8/8 low cloud, when he descended the lenses didn't have enough time to clear before he touched down in a fairly dim environment, misjudging the landing because he couldn't see properly.

Are modern lenses better or is the prohibition still in effect ?
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Old 17th May 2016, 12:13
  #22 (permalink)  
 
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Photochromic lenses

20 years ago 95% of photochromic /photochromatic lenses were "Photogrey" brand and were glass made by Corning Glass Co.


They were indeed slow to change back to clear especially as they got older...but in the cockpit environment a certain percentage of UV light which made them go dark is filtered out by Perspex screens or even the heat treated glass screens of a DC9...its a bit hard to believe they would be so dark as to cause an accident...another myth perhaps?


Unfortunately the CASA guidelines were written about 20 yrs ago ...so this myth is perpetuated...the guidelines disappeared off the website about 2 yrs ago pending re-writing and have not made it back yet!!!


I quite happily wear my Transitions brand photochromic lenses flying day and night and only put sunglasses on if landing directly into a low western sun...the tinting brand is available across several different lens making companies and works best if combined with a good quality anti-reflection coating...the coating makes them go darker faster ,lighten up faster, and makes any residual tint virtually disappear completely indoors or at night.


"Transitions" [a registered brand] is a "treatment" for most types of plastic used in lenses including so called "hi-index" materials which reduce thickness and weight in modern lenses[ which are 99% plastic these days] .


In the cockpit they are about 50% tinted behind the Perspex and go to 85% within 36secs of stepping out into daylight.


My 2 cents worth.


Flopt

Last edited by Flopt; 17th May 2016 at 12:23. Reason: more info
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Old 17th May 2016, 16:22
  #23 (permalink)  
 
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Thanks for the info, much appreciated.
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Old 17th May 2016, 21:17
  #24 (permalink)  
 
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I'm also at the age where the old eyeballs are wearing out, I've needed reading glasses for the last 8 years or so. For work (I work in IT) I use prescription progressive lenses which cost a fortune (about $1k), they're excellent and I sometimes use them for flying, but they are wickedly expensive. They take getting used to - the area of good focus is a bit reduced and you need to move your head around a bit more - after a while it's not a problem.

My Class2 medical specifies bifocals must be worn - according to my LAME progressives meet this because they're really just bifocal with the line smoothed out. My headset bag includes a cheap pair of off-the-shelf clear bifocals and a pair of bifocal sunglasses.

The sunglasses I use most of the time - these are normal sunnies with add-on hydrotac lenses that I've fitted myself. These are excellent gel lenses that cost around $20 and you fit to the inside of ordinary (non-focal) glasses and can position them to where they're right for your vision. For flying, I've got them adjusted so that the top bifocal line lines up with the top of the aircraft panel - higher than for most bifocals, so I've got perfect vision both outside and towards the panel. I wouldn't be without them now.
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Old 18th May 2016, 07:14
  #25 (permalink)  
 
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As someone said earlier, this getting older is a right pain in the tailpipe. Had to chuckle a bit about the spare glasses thing though, I've had a couple of mishaps over the years between flying and sailing, such that I'm pretty careful about ensuring I have a second pair about now. Eg. prescription sunnies whipped off my face when I stuck my head out of a doorless Aerobat to check on line of sight below for an impending photo shoot, a weird wind tunnel effect behind a wraparound pair of non-prescription sunnies that whipped an old fashioned stiff contact lens clean off the eyeball in an open cockpit type and most recently, an older pair of glasses that fell apart after a stray reefing line gave me a wake up slap in the face. Trying to replace these with prescription sunnies didn't work well in the dark and I quickly relinquished the helm to someone who had a better chance of seeing the waves and then leading lights. The benefits of a multi crew environment.
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Old 19th May 2016, 23:59
  #26 (permalink)  
 
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Hi guys
I have had the medical requirement to where reading correction for a couple of years now. What I can add to this discussion is;

CASA require two pairs on deck, there are no restrictions on tinting so one can be sunnies.

I use graduated lenses and they take time to get used to, your brain has to learn how to read the signals from your eyes and it can be quite uncomfortable. Some people may never adapt and as such bi-focal may be your only choice.

Wrap around lenses will need to be of the highest quality to help reduce distortion at the peripherals. I have wrap around sunnies, to reduce light coming in from the sides, but not in my clear lenses that I wear at night. You can get some weird effects off these things especially at night.

If you want the clearest vision, do not buy polycarbonate lenses, you will need to use TRIVEX, CR39 or better still GLASS. You will need to go to one of the better quality outlets to get these. Believe it or not two of this countries most prominent and well regarded eyeglass suppliers do not supply the best stuff. The injection moulding process of polycarbonate lenses puts stress into the product basically distorts the vision and can create a slight milky look.

My sunglass lenses are made from TRIVEX (index 1.53) and have all the properties of polycarbonate however they have have a much better ABBE value of 45 Vs 29, i.e. they are virtually as clear as glass. CR39 is another option for good clarity but it may shatter if thrown at the concrete at high velocity. Glass will definitely shatter on contact with the hard stuff but is the best when it comes to scratch resistance.

About Trivex
http://www.x-celoptical.com/aris_tri...chFeatures.pdf


Serengeti sell prescription lenses in TRIVEX but you need to go to a Serengeti agent, and there are surprisingly few, and be sure to ask for genuine serengeti lenses. They are expensive, not much change from 1K! You can get TRIVEX from other good suppliers but when I worked it out the price was not much different, perhaps $100 cheaper with decent frames. I went for the serengeti, figured I wear then all day and want the best sun protection for my eyes and apparently the lenses are adapted best for the wrap around frames.

Choose AMBER, brown or if your completely obsessive about colour, grey lenses.

I can't believe they are not a TAX deduction for at least the sec on pair???

SN
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Old 20th May 2016, 13:00
  #27 (permalink)  
 
Join Date: May 2007
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Optical lens materials

Mmm ...not quite correct Soupy......

Virtually no optical outlet wants to make glass lenses these days as they are too dangerous and heavy . We used to either chemically toughen them or heat anneal them but they were still dangerous,caused polarised phenomena in heat treated screens in older cars and airliners and you only see them these days in "old" sunglasses brands ,usually from the USA.

Virtually all plastic lenses are injection moulded...stock lenses in single vision in the range+ or- 6.00/-2.00 usually come out of a packet at the optical lab. Doesn't matter if they are CR39 , Trivex, polycarbonate, or the latest 1.60 ,1.67, or 1.74 materials....all 'ground' i.e. individually made to your prescription lenses start as an injection moulded thick " blank".

The main difference in the cause of distortions and cloudy vision is the quality of manufacture , the quality of the research in the design of the curvatures and the quality of the coatings applied for scratch and reflection reduction.

With no-name brands coming out of China or other cheap labour countries ,for instance , you are taking pot luck ...and some chain groups repackage them with names that sound like quality.....surprised?

Companies like Zeiss, Rodenstock,Essilor , Shamir, Coburn,and a few others make lenses of roughly equal high quality probably also in China or Thailand but control and supervise their factories to 1st world standards.
I believe Serengeti lenses are made by Coburn.

I get to try all the materials at no charge and don't think Trivex is any better than polycarbonate except for slight colour dispersion at oblique angles....I can see a slight colour fringe on either side of a power line occasionally.
The newer 1.60 refractive index material is thinner, lighter than Trivex for the same power and has a similar Abbé number so less colour fringes than poly....probably better than Trivex....but I don't notice it much.
Lens design has improved rapidly in the last few years as computers have become more powerful so lens curves can be calculated to give clear vision as the eye looks obliquely through the edges of a lens.

We no longer lathe then grind with carborundum then polish with cerium oxide the way I was taught 43 years ago...now digital surfacing produces infinitely variable shapes for multifocals or "aspheric best form " peripheries....
I still need to go and see one of these machines.....$ 4.00 lenses from India are not of this standard...

My advice is find an optometrist who gives value by using good quality lenses ( they don't have to be the dearest)..
and takes the time to accurately take the optical centre measurements....like a broken record...
Cheers,

Flopt
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Old 21st May 2016, 07:19
  #28 (permalink)  
 
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Does anyone know where you can get a good set of clip on sun glasses to go over your prescription glasses? Ones that aren't Polaroid.......
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Old 21st May 2016, 07:53
  #29 (permalink)  
 
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I started using these in preference to clip-ons many years ago:
Pre-Made With "Extreme Glare" Custom Non-Rx Lenses | Zurich Rx and Non Prescription Sunglasses Out-Perform Polarized
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Old 21st May 2016, 09:23
  #30 (permalink)  
 
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There is an argument for not buying the most expensive lenses at the start as your eyes will deteriorate further before settling down.
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Old 21st May 2016, 09:38
  #31 (permalink)  
 
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Originally Posted by ACMS
Does anyone know where you can get a good set of clip on sun glasses to go over your prescription glasses?
Don't go the flip-up route... I proposed to some of our FAs that I get flip-ups and they all said they wouldn't speak to me again...

Looking for "Fitovers" myself; non-polarised ones are few and far between.
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Old 21st May 2016, 10:49
  #32 (permalink)  
 
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I see your problem, you proposed with a flip up and not a ring.......rookie mistake

Fitovers ey?

Mmmmmm ok
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Old 21st May 2016, 11:31
  #33 (permalink)  
 
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Good thread...

I was told back when I had excellent eyesight to expect a need for glasses around 45. Well at 46, I needed reading glasses and like others above got the half moon style that sat on the end of the nose or on a string around the neck when not required. Not long later further enhancements were required. Multifocals were not good in the cockpit for me. I tried Tri vocals for a while to read the panel above, but found it easier with the bi-foals and tilting the head back as mentioned above. I found it does not get any better as the years roll on, but that's the way it is!
My second pair has always been my "anti-glare" glasses. Used to be ok, but who knows now??
The danger now is screwing your old eyes trying to read your iPad or phone!!
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Old 21st May 2016, 13:41
  #34 (permalink)  
 
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Flopt
Glass is available you just have to specify it, remember we are the customer. Plenty of people still ask for glass which I'm sure frustrates those who dislike it with a passion. Yes it will shatter if smacked hard enough but then poly and other plastics will scratch just by looking at them. I've had glass sunnies for at least 10 years, broke a lens when I dropped them on a tile floor. That's the risk with glass, but it's a buyers choice, yes??? Yes they are heavier but not by much in the straight sunglasses, probably becomes a problem with a prescription I would imagine. Dangerous?, I try to take mine off before someone punches me in the eyeball.

My understanding is that injection moulding is done at medium temperatures and under high pressure then rapidly cooled, whereas the cast process (TRIVEX and probably others) is done without pressure so the material can conform to the mould shape at its own pace and Cool slowly. Less inbuilt stress in the product is the result but it does take longer to produce the blank and as such it is more expensive.

I did try the 1.6 index material but still found it not as sharp as the TRIVEX, but certainly much better than the poly, perhaps it was the coatings but when I'm paying I want what I want, right????

I would agree that you should find a good optometrist who will measure your optical centres although I'm pretty sure they all do that??? Perhaps not for the online optical shops, buyer beware, cheaper is not necessarily just as good. My centres were measured and confirmed 3 times by three separate people in the establishment. If that is not right it will undermine even the best lenses I believe.

Im not an expert or optometrist but I did a fair bit of research before I purchased, I could have pretty much got the same frames and TRIVEX lenses from another manufacturer but it was only about $100 cheaper than the Serengeti product. They may be as good or even better I'm not sure, but I didn't read too much bad about the Serengeti prescription product so that is what swayed me in the end. I'm not saying everyone should head out and by what I bought, I'm just adding my experience to the conversation.

SN
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Old 21st May 2016, 13:49
  #35 (permalink)  
 
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Originally Posted by Soup Nazi View Post
Flopt
Glass is available you just have to specify it, remember we are the customer. Plenty of people still ask for glass which I'm sure frustrates those who dislike it with a passion. Yes it will shatter if smacked hard enough but then poly and other plastics will scratch just by looking at them. I've had glass sunnies for at least 10 years, broke a lens when I dropped them on a tile floor. That's the risk with glass, but it's a buyers choice, yes??? Yes they are heavier but not by much in the straight sunglasses, probably becomes a problem with a prescription I would imagine. Dangerous?, I try to take mine off before someone punches me in the eyeball.

My understanding is that injection moulding is done at medium temperatures and under high pressure then rapidly cooled, whereas the cast process (TRIVEX and probably others) is done without pressure so the material can conform to the mould shape at its own pace and Cool slowly. Less inbuilt stress in the product is the result but it does take longer to produce the blank and as such it is more expensive.

I did try the 1.6 index material but still found it not as sharp as the TRIVEX, but certainly much better than the poly, perhaps it was the coatings but when I'm paying I want what I want, right????

I would agree that you should find a good optometrist who will measure your optical centres although I'm pretty sure they all do that??? Perhaps not for the online optical shops, buyer beware, cheaper is not necessarily just as good. My centres were measured and confirmed 3 times by three separate people in the establishment. If that is not right it will undermine even the best lenses I believe.

Im not an expert or optometrist but I did a fair bit of research before I purchased, I could have pretty much got the same frames and TRIVEX lenses from another manufacturer but it was only about $100 cheaper than the Serengeti product. They may be as good or even better I'm not sure, but I didn't read too much bad about the Serengeti prescription product so that is what swayed me in the end. I'm not saying everyone should head out and by what I bought, I'm just adding my experience to the conversation.

SN
Well there ya go Floppy one - any questions?

Dr
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Old 22nd May 2016, 05:44
  #36 (permalink)  
 
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Well I'm confused........

So what is it boys? Which ones should I be getting?

I'm off to OPSM to get my eyes tested again and will look ( pardon the pun ) into getting progressive.........
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Old 22nd May 2016, 07:43
  #37 (permalink)  

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ACMS,

I don't think anyone can tell you what YOU should be getting because it's such a subjective thing.

I don't doubt that the folks who say don't go multifocals have problems with them, but I don't. So my recommendation based on my experience is that they're great.

I use Hoya lenses because the optometrist said that they have the widest (lateral) field of view in multifocal lenses. Is this true? I don't know, it could be the optometrical equivalent of Airbus v Boeing. But on my 4th pair now, I've not had any problems adjusting and find them excellent.

The time I did try bi-focals, I couldn't get past the delineation between the two focal lengths and the subsequent bluring when I looked through the wrong lens. Yet with the multi-focals, and no delineating line, my brain/eyes have just naturally adapted and I automatically look with the subject in focus.

Welcome to spectacle world.
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Old 22nd May 2016, 10:58
  #38 (permalink)  
 
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Welcome to spectacle world.
Buggah, I've just entered the "can't comfortably see things up close when wearing glasses" brigade. It's not too bad right now but I imagine it will get worse with age.

My optometrist is an old salt who has handed the business down to his son but still works part time to help out. Lot's of things have changed since he started, with the dearth of bad/cheap prescriptions being the order of the day. One thing they no longer do is grind the lenses themselves.

The glasses I have are only for long distance only, they are plastic for light weight and coated with glass to prevent scratches. I have two pairs one with a brown tint for the day time and the other is clear for night time with an anti-glare coating which needs constant cleaning.

One thing I've noticed when holidaying in the country for months on end is that my long distance eyesight improves to the point that I don't need to wear glasses. This is I believe due to the eyes getting some long distance focus exercise that is just not possible in the city. That or there is something NOT in the water supply.

I guess it's only a matter of time that someone eventually develops a lens that quickly adapts to the object near or far being looked. This will be a godsend and will dispense with the need for bifocals altogether.
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Old 22nd May 2016, 11:41
  #39 (permalink)  

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Originally Posted by Soup Nazi
CASA require two pairs on deck, there are no restrictions on tinting so one can be sunnies.
My DAME told me the opposite of this, when he warned me that on my renewal in 2017 I'd have to present the second pair of specs as part of the medical renewal process.
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Old 22nd May 2016, 12:29
  #40 (permalink)  
 
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Thanks Clarrie:--- I've had glasses for reading for nearly 7 years now. I've had tri-focals made up for 2 years but I only used them when quite tired ( mainly for distance when tired ). I use the cheap chemist readers and look over the top for distance, but they no longer do the job as well as I now need. The trouble is that the expensive tri-focals are annoying me a bit ( can read the PFD clearly but not the ENG instruments ) , that's why I'm going to look at progressive glasses now.
I'm told they take a bit of getting used to..........especially in peripheral vision during landing?

It's all these different types of lens that's confusing that Flopt and Soup Nazi were talking about earlier in link 26 and 27.
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