NVG - eye surgery for ageing eyes...
"Just a pilot"
Immediately after retiring, I had presbyopic lens exchange and I kick myself for waiting. From bifocals to 20/30 vision. I also had some cataract development, now I see colors better.
FB - a Hoffman Box is something that hangs on the wall and is used to check the setup of NVG - you use it in a darkened room and it has a very low light illuminated series of graduated circles and a series of Snellen charts in it.
The Snellen charts are a series of vertical and horizontal lines at different thicknesses that correspond to visual acuity - ones for 20/20, 20/25, 20/30, 20/35 etc up to about 20/50 I think (6/6, 6/9, 6/12 etc for Europe).
On a good pair of goggles, correctly adjusted, you should see 20/35 clearly.
The circles go from light to dark shading in sectors and the more sectors you can discern, the better the goggles.
I will take some photos tomorrow at work and post them.
Using the Hoffman Box sets a base level by which you can assess poor tubes and note excessive scintillation, honeycombing and black spots.
The Snellen charts are a series of vertical and horizontal lines at different thicknesses that correspond to visual acuity - ones for 20/20, 20/25, 20/30, 20/35 etc up to about 20/50 I think (6/6, 6/9, 6/12 etc for Europe).
On a good pair of goggles, correctly adjusted, you should see 20/35 clearly.
The circles go from light to dark shading in sectors and the more sectors you can discern, the better the goggles.
I will take some photos tomorrow at work and post them.
Using the Hoffman Box sets a base level by which you can assess poor tubes and note excessive scintillation, honeycombing and black spots.
I have worn specs for over 40 years and contacts for some 30, I looked into lens surgery about twelve months ago and even went to a full blown eye hospital explaining that I wanted to start flying again, after several visits the surgeon told me under no circumstances would they perform the operation as CAA regulations would not allow me to fly once it was done.
I wear multi focal contact lenses and as these cannot be worn I have had to buy varifoca glasses.
My AME at the time told me a BA pilot had had the surgery done and that my surgeon wasn't up to speed.
In the end I have stuck with the varifocals, but I would love to have the surgery if it would mean I can fly without specs or contacts! The CAA and other bodies across the globe would need to be in agreement of course, but if you know this is possible I'd love to hear back from you or anybody else that knows about this.
Ta very much!
Originally Posted by [email protected]
that’s helpful.
Evenso, we rely on the armed forces services for our equipment, it’s worth while looking into this
I have had new lenses fitted at age 77 and now have perfect eyesight - long and short distance. Talk to Mr Jonathan Luck at the Circle At Bath - actually in Peasdown St John.Costs £5800 and the best money I have ever spent.
We also use boards with the same snellen charts for adjustment but as the lighting level in the room dont get that precise you dont get a comparable value of the function of your goggles.
I have taken a newly serviced/checked pair of goggles tested in the Hoffman box and actually found them not really good and because of this, chosen another pair.
without the Hoffman Im quite sure I wouldnt noticed that they differed from others.
Both ways of setup are ok but it is a lot higher quality with the Hoffman box( not the actual tuning but the measureble performance of the goggle)
We actually did a ranking of around 25 sets of goggles ( had some years of use) with the Hoffman and found that only the top ten actually should be used by pilots in low light situations. All of them passed the annular checks.
Of course I have done a lot of flights just taking out the goggles on a job and checked the settings from the learned values, and it works fine. But you do not know if they perform as they should.
Glasses
Getting presbyopia and I find some problems with wearing glasses with NVG’s.
I always had the goggles close and quite high( not possible to adjust them higher).
Even if I adjust them further forward (without loosing FOV) the part of my progressive glasses I see below are to strong for a sharp view of the instrument panel/MFD’s.
Maps/plates/checklists in the lap is ok, but not the instrument panel.
The first fix was to use a set of glasses with lower strength, but the increasing presbyopia makes this a bad idea today.
Change of lenses is not an option due to regulations
( but after retirement is is).
I always had the goggles close and quite high( not possible to adjust them higher).
Even if I adjust them further forward (without loosing FOV) the part of my progressive glasses I see below are to strong for a sharp view of the instrument panel/MFD’s.
Maps/plates/checklists in the lap is ok, but not the instrument panel.
The first fix was to use a set of glasses with lower strength, but the increasing presbyopia makes this a bad idea today.
Change of lenses is not an option due to regulations
( but after retirement is is).
Thanks very much I've just had a look at the site and I'll give them a call this week. Much appreciated Georg1na.
Aakee, just read your reply and that was my take on it, I couldn't have it done if I wanted to fly. As mentioned previously my AME had said it was doable, but the eye surgeon said not. I'll speak to Jonathan Luck this week who georg1na had suggested and post back. If it's possible and does not impede flying this is great news. But if it buggers anything up I'll stick with specs.
Thanks for the guidance all.
Thanks for the guidance all.
FB - the Snellen charts visible inside the Hoffman Box
As AAKEE says, it is the ability to compare goggles to a standard to know which ones work best that is the one big advantage.
The other big plus is that you can teach people how to set their goggles up properly from the outset. When I was a Squadron Training Officer, I used to pick up pilots goggles that they had 'set up' and check them on the Hoffman box - the number that had used the rear, dioptre adjustments to get a good picture instead of the front adjustments was surprising and they were giving themselves eyestrain trying to get a good focus on an image that wasn't properly focused in the first place.
I know I have mine set up properly if I end up with the sharpest image I can get - usually 20/35 - and the dioptre scales at the back match my eyesight prescription for reading glasses - between +1.0 and +1.5.
The only slight downside is that the Hoffman Box gives you a set up with the focus on infinity which isn't much use for helicopter operations so you still make a real world adjustment once in the cockpit or on dispersal - but you are doing it from a known and correct setting.
There are no good solutions for presbyopia where refractive surgery is concerned. Your only choices are multifocal correction and monovision. Both really screw with your depth perception. You can try both by going to your eye doc and asking for contact lenses that do the same things.
.......
I've also tried progressive lenses. Again, I did not care for them, although I can understand how some might prefer that, especially with the FAA requirement for older pilots to demonstrate visual acuity at both 16 and 32 inches distance.
For flying I still very much prefer a set of plain old bifocals with a line set a little lower than what might be normal. I can easily meet the FAA requirement for 20/40 at 16 inches using the lower section, and 32 inches with the upper section. I've got bifocal sunglasses, too. They are the cat's meow and I wear them for everything, not just flying.
.......
I've also tried progressive lenses. Again, I did not care for them, although I can understand how some might prefer that, especially with the FAA requirement for older pilots to demonstrate visual acuity at both 16 and 32 inches distance.
For flying I still very much prefer a set of plain old bifocals with a line set a little lower than what might be normal. I can easily meet the FAA requirement for 20/40 at 16 inches using the lower section, and 32 inches with the upper section. I've got bifocal sunglasses, too. They are the cat's meow and I wear them for everything, not just flying.
On the question of degraded depth perception:
(Apologies, not a rotorhead or NVG user. Not sure about the etiquette here - I didn't think I should spawn a new thread)
I have presbyopia (my reading glasses are +2). My distance vision requires no correction but benefits from slight correction. I wear progressives to fly and they seem to work brilliantly, I have perfect acuity wherever in the field of view I need it. However, my landings are still pretty untidy and I wonder if my depth perception is screwed without me realising it. Is that a known thing? I thought progressives and varifocals were the same thing ? Is there any way to objectively measure depth perception (without causing alarm to the AME!) ? I used to drive with bifocal sunglasses, and I also found they were great. But I now wear the progressives as much as I can on the principal that I should train my brain to handle the input. Wondering now if I should try flying in the bifocal sunglasses and see if that's better - although I am reluctant to sacrifice the marginal improvement in distance acuity.
Last edited by double_barrel; 10th Nov 2019 at 11:06.
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@double_barrel: assuming you are in the US? My AME measures depth perception with his vision testing machine. There are tests for this. You can go to your local eye doc or eyeglass place and be tested (with your preferred vision correction) without "alarming your AME" 
That's what I do every year (Class II medical). In fact I've got my yearly eye exam set up to be one month before my medical is due every year. That way my prescription is tip top before I go in to see the AME.
Also, it's a very personal decision what works best for you. Like I wrote above, when presbyopia hit I tried pretty much everything. I went with what worked the best for me, which is plain old bifocals. By making them the right strength (and putting the split of the lens in the right place--I like it a little lower than most) I can see 16" 20/40 with the bottom part, and 32" 20/40 with the top part (and 20/20 distant vision, of course). I'm happy with that and it meets the US Class II requirements for old guys
That's what I do every year (Class II medical). In fact I've got my yearly eye exam set up to be one month before my medical is due every year. That way my prescription is tip top before I go in to see the AME.Also, it's a very personal decision what works best for you. Like I wrote above, when presbyopia hit I tried pretty much everything. I went with what worked the best for me, which is plain old bifocals. By making them the right strength (and putting the split of the lens in the right place--I like it a little lower than most) I can see 16" 20/40 with the bottom part, and 32" 20/40 with the top part (and 20/20 distant vision, of course). I'm happy with that and it meets the US Class II requirements for old guys
@double_barrel: assuming you are in the US? My AME measures depth perception with his vision testing machine. There are tests for this. You can go to your local eye doc or eyeglass place and be tested (with your preferred vision correction) without "alarming your AME" That's what I do every year (Class II medical). In fact I've got my yearly eye exam set up to be one month before my medical is due every year. That way my prescription is tip top before I go in to see the AME.
Also, it's a very personal decision what works best for you. Like I wrote above, when presbyopia hit I tried pretty much everything. I went with what worked the best for me, which is plain old bifocals. By making them the right strength (and putting the split of the lens in the right place--I like it a little lower than most) I can see 16" 20/40 with the bottom part, and 32" 20/40 with the top part (and 20/20 distant vision, of course). I'm happy with that and it meets the US Class II requirements for old guys
That's what I do every year (Class II medical). In fact I've got my yearly eye exam set up to be one month before my medical is due every year. That way my prescription is tip top before I go in to see the AME.Also, it's a very personal decision what works best for you. Like I wrote above, when presbyopia hit I tried pretty much everything. I went with what worked the best for me, which is plain old bifocals. By making them the right strength (and putting the split of the lens in the right place--I like it a little lower than most) I can see 16" 20/40 with the bottom part, and 32" 20/40 with the top part (and 20/20 distant vision, of course). I'm happy with that and it meets the US Class II requirements for old guys
Avoid imitations
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Can I check something with you Shy?
I have worn specs for over 40 years and contacts for some 30, I looked into lens surgery about twelve months ago and even went to a full blown eye hospital explaining that I wanted to start flying again, after several visits the surgeon told me under no circumstances would they perform the operation as CAA regulations would not allow me to fly once it was done.
I wear multi focal contact lenses and as these cannot be worn I have had to buy varifoca glasses.
My AME at the time told me a BA pilot had had the surgery done and that my surgeon wasn't up to speed.
In the end I have stuck with the varifocals, but I would love to have the surgery if it would mean I can fly without specs or contacts! The CAA and other bodies across the globe would need to be in agreement of course, but if you know this is possible I'd love to hear back from you or anybody else that knows about this.
Ta very much!
I have worn specs for over 40 years and contacts for some 30, I looked into lens surgery about twelve months ago and even went to a full blown eye hospital explaining that I wanted to start flying again, after several visits the surgeon told me under no circumstances would they perform the operation as CAA regulations would not allow me to fly once it was done.
I wear multi focal contact lenses and as these cannot be worn I have had to buy varifoca glasses.
My AME at the time told me a BA pilot had had the surgery done and that my surgeon wasn't up to speed.
In the end I have stuck with the varifocals, but I would love to have the surgery if it would mean I can fly without specs or contacts! The CAA and other bodies across the globe would need to be in agreement of course, but if you know this is possible I'd love to hear back from you or anybody else that knows about this.
Ta very much!
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Where refractive or lens replacement surgery is concerned, you can get a single correction or a multifocal correction (example). The multifocal approach requires the brain to do a lot of "image processing" for lack of a better term. This is, obviously, quite a bit different than a bifocal or varifocal (what us Yanks call "progressive") eyeglass lens.
Since they make multifocal contact lenses (this approach doesn't work in eyeglasses), you can experience the multifocal approach for yourself if you get a pair of multifocal contacts. I tried them and hated it with a passion. I even gave it a good three weeks to get used to them. Couldn't do it. Some people can. Don't know anyone that flies with them, and don't know anyone that has had multifocal refractive surgery, either.
Avoid imitations
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I think you are confusing refractive surgery or lens replacement surgery terminology with eyeglass terminology. If I'm reading things correctly, I think Shy is saying he had lens replacement surgery.
There are separate rules for cataract surgery. As already mentioned above.