Eyeglasses - a few unqualified remarks (1 Viewer)

[Alexis Powell]

For anyone reading this thread, my best advice is to use the posts here (and past threads devoted to eyeglasses in the BirdForum archive) as data or points to consider to accelerate your own thinking and exploration, but there is no substitute for finding what works best for you individually, and that may be quite different than what is recommended by me or others.

As for myself, readers of my past posts will know that I am a visually obsessive person, who feels blind when my vision drops below 20/15 acuity, who prefers to turn my eyes rather than move my head, who is constantly looking this way and that (I say that my eyes dart around the view), who is moderately myopic and with bad astigmatism in one eye, who has lost much focusing ability in recent years due to age (52 yrs), and who routinely in everyday outdoor and indoor life needs to or likes to look at things up-close (i.e. literally, held close to my eyes). I have a history of spending lots of time in dusty and sometimes dirty and wet field situations, where cleaning optics must be done carefully to avoid scratches but where careful cleaning is not always feasible, so scratch resistance is a virtue. I've played around with trying different types of glasses almost as much as I have different models of binoculars (and to a lesser extent scopes). My prescription for corrected distance vision and astigmatism has been extremely stable for the past 20+ years, which means that since I can use my old glasses indefinitely into the future, I've been able to use my insurance benefits every year to experiment with different frames, lens materials, and lens designs in new glasses without worrying about getting something worse than what I already like best for a given situation. At some points in the past, I've carried as many as six eyeglasses with me to wear in different situations. These days, most of the time, I only carry two (or three, when I absolutely need sunglasses, which is rare. I really don't like sunglasses).

Here's a very quick summary of the what and the why of my best eyeglasses solutions for my everyday life wear as well as for my birding/natural history needs and preferences.

FRAMES
For frames, I prefer high quality metal frames with spring hinges, individual nose pieces (with large silicone pads, not the dinky ones that I see are the default provided these days), and a twin bridge connection between the lenses to hold them rigidly aligned to one another and to resist breakage. The bridge just above the nose should bow forward to fit around the nose such that the lenses can be fit closer to the eyes than would otherwise be possible. High quality metal, whether steel or other, can be bent badly (e.g. in an unintended mishap) but can then be bent back into shape without the metal breaking or snapping at welds. The frame may not be as pretty afterward, but at least the glasses keep working when on a trip or in field situations far from an optical shop. These kind of frames are quite rare these days, in my experience--nearly all of my favorite frames (steel alloys) were made in Italy in the early to late 1990s, though a few years back I found some near equivalent quality frames from Korea. For my preferred frame shape...see below.

LENS SHAPE
I prefer big aviator or somewhat smaller modified (flatter-bottomed, or swept slightly upwards at the outer bottom corners) aviator type lenses for several reasons. I like lenses that allow me to see the whole view, without restricting my peripheral vision or cutting off my view as I rotate my eyes this way and that, left and right, up and down. So I especially like frame+lens designs that allow the glasses to wrap around my eyes to an extent, almost like covering them like goggles. They fit close to my eyes, I can see all around, and they protect my eyes from the merciless Kansas wind, esp. when bicycling, and from brush and spider webs etc (the only sometimes disadvantage is fogging when humidity is very high). Such lenses also work best for sunglasses, though that is a different topic. Another advantage of big lenses is that they allow lots of lee-way for bifocal and varifocal customization.

LENS MATERIAL
I don't usually consider myself as bothered as some people seem to be by chromatic aberration in binoculars, but I must say that I despise polycarbonate eyeglasses for their EXTREME levels of chromatic aberration. My favorite material for field glasses has been regular old uncoated glass (easiest to clean, unbeatable scratch and gouge resistance), but now that I seem to live a gentler life, I find that Trivex with all the latest coatings performs well optically and offers some advantages when scratch and gouge resistance aren't my top concern. Don't let any sales person or other joker, who hasn't directly compared the scratch and gouge resistance of plain glass to other materials with fancy coatings, tell you that anything performs in practice as well as plain glass when it comes to resisting scratches. No contest, glass wins.

LENS DESIGN
I still have a nice set of single vision eyeglasses that are unbeatable for any time that I don't need to see up-close, but since I always seem to want to examine things (and even read) at close range, I rarely use them nowadays. My preferred field glasses (and driving glasses) are bifocals with the line set lower than usual. Since I use large lenses, I still have lots of space for a good-sized near section even though it is set lower. I like the diopter set to allow me to look at objects comfortably that are ~30 cm away. Actually, I prefer to look at things even closer (in which case I take off my glasses to use my myopic eyes), but ~30 cm is the distance that works best for me as a compromise. With such bifocals, I get a high quality, almost unrestricted view of distant things, both on and off-axis, and I also get a nice view of objects in the hand, a combo that works great for most of my natural history exploring.

In regular everyday life, or especially when indoors in the lab, or sometimes in the field (e.g. when catching amphibians and reptiles by hand), it is nice to be able to focus sharply at any distance. In those cases, I more often use varifocal lenses. My current favorites are one of the latest and greatest models from Essilor, which work incredibly well for off-axis viewing in comparison to some older progressive lens designs, but they still can't match a single correction or the top of a bifocal for birding and driving, when I like to dart my eyes around. Since my preferred lenses are large, which allows room to spread out a steep diopter ramp, I am able to have these made such that I can sharply focus down to ~20 cm in low light (and even closer in bright light) and yet still work comfortably when typing at my computer and with things in the arm length and farther range, and yet still have a very generous distance vision section at the top. For me, these glasses work so intuitively for looking at everything at any distance that I feel like I have my young eyes again! They only fail when I start birding or butterflying, in which case their fleeting glimpse resolution for scanning and spotting things just isn't up to my standards, even though it is quite good for other purposes. Off-axis distance viewing across the top of the glasses is excellent but still requires very slight head adjustment for razor sharpness. Although I prefer my bifocals for naked-eye scanning, I don't have any trouble using my varifocal glasses with binoculars. In fact, I really don't notice any issues at all when using them with binoculars or camera (unless I am being very picky in side-by-side comparison). I think the negative experiences of others in those situations is a result if them using glasses with lenses that are too small.

I hope these thoughts are of help to others trying to navigate these choices,

--AP

 

[Doheth]

Use with binoculars:-
If one cannot see clearly at moderate distances with the naked eyes, due either to near-sightedness, advanced presbyopia or astigmatism, then one is going to need correction when birding,...

I'm very near-sighted, but my binoculars have plenty of adjustment and I can bring everything into focus without using correction. Is this actually sub-optimal? For example, if I wore contacts that corrected my vision to more-or-less normal, would there be an improvement when using binoculars?

Correction for far-sightedness with positive lenses effectively reduces eye relief, whereas negative lenses for the near-sighted increase it.

I did not know this. Is this a "technically" kind of thing, or is it noticeable?

I've been a contact wearer most of my adult life, but have switched back to glasses (mostly) in the last couple of years. This is an interesting thread, thanks!

 

[Binastro]

Hi and welcome.

If you have astigmatism, unless very minor, then glasses or contacts may help with a binocular.

Really one should try with and without glasses/contacts and use whatever you find most suitable.

Also the eye relief may determine what you decide to use.

Regards,
B.

 

[Lewis]

This is a great thread.

I have life-long farsightedness and astigmatism and can’t see anything without glasses. I am flummoxed by the fact I always have to adjust the separate right diopter when using binoculars. I just this past week got an updated prescription and still I have to adjust the right binocular lens away from the neutral setting to match the clarity of the left.

Do other people who wear corrective glasses experience this?

(Another related experience is that I am always able to confidently and quickly focus the right lens of binoculars, whereas I am perpetually fiddling with the right diopter, feeling like it is perhaps a little off.)

(As I write this, I am wondering if this is less of an optical issue and more of a psychiatric one 😮🙂)

L

 

[Binastro]

If you are talking about a zero setting on the binocular, this is not relevant as only the very best binoculars are set up at the factory accurately.

It might even depend on whether the technician has his own eye issues.

Also the opticians only work to loose standards, whereas I can easily see a difference of 1/8 dioptre and 2.5 degree mild astigmatism.
That is +/- 1/16 dioptre and +/-1.25 degrees.

Regards,
B.

 

[bsantini1]

Chiming in here casually, just like that 😁 not pretending I have the solution for everyone when it comes to spectacles.

Lately, I've been lurking around more here, but I must be cautious not to put in too much effort in order to preserve my sanity. But at the moment, optics are all the rage again for me, but I'm also out there birding more nowadays. After having given the Svbony scope to my son, and vainly looked for a substitute, I defied the vow to myself and ordered another 406P ED 80 mm. And what a scope! If the first sample was 95% of my Nikon ED82A due to a small amount of CA, this one is virtually indistinguishable from the Nikon. I'm considering to invest in a Pentax XW14 or one of those Nikon NAV eyepieces for it.

Almost always when I'm off work I use contact lenses. The latest iteration of them are so sharp it's surreal. This influences which binoculars I use. If the weather is fine, I prefer the 8x30 E II, so thanks to the contacts, it is no more the outlier and the exception in my collection, it's the preferred tool of the trade. Sometimes it's replaced by the Kite Lynx ED 8x30 due to precipitate and temperature issues. The EDG 7x42 is particularly fine in cold weather because its eye relief is so large that I can use wrap-style protective spectacles over my contacts to minimise excessive tearflow. The contacts are so insanely sharp that 7x and 8x deliver all there is to see. The Meopta 12x50 can accordingly often replace the scope now.
Obviously, I want to buy more, but I'm so happy with what I have that I can't find a base not covered. A Kowa 6,5x32 and a MHG 10x42 are desired, but not really more than just that - desired.

In general, it's my opinion that maximised visual acuity with corrective lenses is a prerequisite for good vision in binoculars. If you have a moderate myopia or hyperopia but no astigmatism, you can allow yourself to take the glasses off and focus with the binoculars.
I simply don't understand why people buy binoculars for two or three grand, when their uncorrected vision is so poor. A budget binocular allowing the use of spectacles can simply crush an NL Pure used w/o spectacles if you're unfortunate (read: stupid enough not to prioritise your eyes)

Varifocal lenses are "Jack of all trades, master of none". All spectacle lenses introduce distorsions, and most of us willingly adapt thanks to the brain's plasticity. In everyday life, varifocals can oftentimes be the most feasible solution. But the compromises of varifocals are a magnitude higher than the already distorting single vision lenses, and those compromises will show when used with top-of-the-line binoculars.
Immediately below pupil height, the progression channel begins. It is quite frankly narrow. And if the binocular's eye relief is on the tight side, so you're forced to raise your chin to let the eyeglass touch the eyecup even in the lowest part, you will be looking through the narrow progression zone.
So the almost-sharp-to the edge binocular will end up appearing mediocre.

I therefore recommend getting a pair of good single-vision distance spectacles for use with binoculars. Granted, this will also be fiddly for some who want to, or need to see at close range too. This is where contacts enter. With monovision, the bin's diopter can be used to even out the difference between the eyes while maintaining good reading acuity. With both contacts set to distance sharpness, you can use cheap reading glasses when necessary.

Frame materials, nose pads and such are a personal choice. What is one man's only possible alternative, won't fit the other. Stick to what makes you happy but make sure the binoculars have enough eye relief.

//L

No bifocals?

 

[looksharp65]

No bifocals?

Personally? In fact, I have a pair for a very specific use not related to birding. And while I encourage progressive lenses for ordinary users, in particular newbies, I have nothing against letting existing bifocal wearers go on with them.

Bifocals should be fine for many binocular users as well, provided the dividing line could be placed reasonably low. This is to avoid the reading glass to interfere with the straight-forward view if the eye relief is tight and you need to press the spectacles flat onto the eyepieces with your chin raised.

Unfortunately, mounting the bifocals lower down may introduce height diplopia, comparable to miscollimated binoculars. This occurs when the power difference between the right and the left lens is too big and/or the lenses are mounted excessively low.

//L

 

[Ted Y.]

In general, it's my opinion that maximised visual acuity with corrective lenses is a prerequisite for good vision in binoculars. If you have a moderate myopia or hyperopia but no astigmatism, you can allow yourself to take the glasses off and focus with the binoculars.
I simply don't understand why people buy binoculars for two or three grand, when their uncorrected vision is so poor. A budget binocular allowing the use of spectacles can simply crush an NL Pure used w/o spectacles if you're unfortunate (read: stupid enough not to prioritise your eyes)

Interesting

 

[Maljunulo]

If you have refractive error only, and it isn’t grotesquely large, there is absolutely no reason to “pre-correct” with glasses or contacts. (as far as looking through the binocular is concerned)

 

[Binastro]

Unless the binocular is corrected very carefully for one separation of the objectives and eyepieces.

This is unlikely in practice as binoculars are such poor telescopes anyway, and they work at close distance, although probably not optimally.

This is not the case with some photo lenses, which are strictly optimised for one distance, and in some cases one wavelength.

Regards,
B.

 

[GrampaTom]

Re-reading what I wrote in #5, what has followed since, and thinking about changes for myself, I’ve a comment or two re what some others have written to add.

I carry Sibley and Cornell/Merlin in my Iphone, use both for visual and sound identity as well as maintaining my personal list. Close vision is a must. Bifocals are my choice, for reasons discussed by others above. Since last winter’s Cataract surgery where I opted for single distant vision lens, they are a must. Post Cataract surgery I don't "need" eyeglasses to see beautifully through my binoculars. In fact the view is really best without. But its a drag to stop and get out glasses in order to read these phone apps. Perfection is the enemy of the good. So I mostly still bird with eyeglasses.

There’s lots of good advice posted here. There is though more to say and know about. A couple years ago, I experienced Detached Vitreous in both eyes. Not to be confused with Detached Retinas, DV though means there are now "scars" visible in the periphery of the view in each eye. My brain most of the time ignores. There was no material effect on the then current vision quality at the center, and no important effect while looking through binos, from this.

A year ago, 6 months before Cataract surgery, I’d just returned from birding, was staring through binos out across a couple hundred yards of cityscape at a structure on the roof of another building. As I stared, trying to discern the thing, I noticed I was seeing double. The initial single image drifted apart in to 2. Blinking, looking away seemed to help. I wrote it off as tiredness from the days activity.

Then surgery. Astigmatism gone, (Toric lens). Left eye a little fuzzy. Right eye spectacular. Happily that result aligned with eye dominance. Vision in both eyes is so good I now though see stuff I had not… good and bad. Attached to the Detached Vitreous scars, a bit of attached vitreous fold is now visible. There were many tiny specs, floaters, that have mostly more or less drifted away. With new very simplified prescription lens in my eyeglasses I kept having mixed results of vision quality especially in my main distance/bifocal equipped set. Out and about birding, while actively searching with my eyes and/or with the target moving, I wasn't noticing so much. Stopping to stare at stable objects here and there, I became aware that double vision was (and probably had been ) a thing. The term double vision is potentially misleading. An object would start to divide, became 1.25, 1.5, then 2. Now with new “prism” lens in my eyeglasses, things seem under control.

While I fundamentally agree we should all spend the time and money to make sure our eyes are as good as they can be before shelling out the bucks for binoculars. I would argue though if the center of vision is good, the money spent on good to great binos is not wasted. And the investment just improves as one learns through use there are issues and those get fixed.

 

[GrampaTom]

Unless the binocular is corrected very carefully for one separation of the objectives and eyepieces.

This is unlikely in practice as binoculars are such poor telescopes anyway, and they work at close distance, although probably not optimally.

This is not the case with some photo lenses, which are strictly optimised for one distance, and in some cases one wavelength.

Regards,
B.

Not sure how to read that first sentence. Can you help please?

Ive read the sentiment before about binoculars being poor telescopes. They're not though, (telescopes) are they? Binoculars used for the ranges designed, at 8-10X, handheld, are really quite spectacular near as I can tell.

 

[Maljunulo]

Yes Tom, a binocular is two telescopes, fixed together so that their optical axes are parallel.

 

[GrampaTom]

Yes Tom, a binocular is two telescopes, fixed together so that their optical axes are parallel.

Of course. I get that. We’re playing. Two telescopes tied together with a hinge or two and the required collimation makes it a binocular not a telescope. Since it’s designed to be handheld, deliver bifocal vision, providing depth of field, at shortish ranges it’s a different thing. Its a binocular not a telescope, even though it contains two of the latter... Should we judge optical quality the same for either? Would a binocular with the optics of a telescope used to look at Saturn's rings, be a better thing? Would it be cost effective?

 

[Tringa45]

Of course. I get that. We’re playing. Two telescopes tied together with a hinge or two and the required collimation makes it a binocular not a telescope. Since it’s designed to be handheld, deliver bifocal vision, providing depth of field, at shortish ranges it’s a different thing. Its a binocular not a telescope, even though it contains two of the latter... Should we judge optical quality the same for either? Would a binocular with the optics of a telescope used to look at Saturn's rings, be a better thing? Would it be cost effective?

Hi Tom,

As Maljunulo pointed out, they are all telescopes, mostly Keplerian refractors ranging from a Nikon 6x15M CF up to binocular telescopes with 150 mm aperture or larger, although double Newtonian reflectors exist with mirror diameters in excess of 18".

Btw, I think what Binastro meant by "separation of objectives and eyepieces" was the correction of the instrument for specific distances, i.e. for infinity in an astronomical telescope. Here, for corrected vision, the separation would be the sum of the focal lengths of objective and eyepiece, but for closer objects we would have to rack out the eyepiece(s), as on most Porro binoculars.
However I don't think it's as critical as he implies and have never noticed any image degradation at close focus with binoculars or birding scopes.
Macro camera lenses and enlarging lenses work satisfactorily over quite a large range of distances.
I have a 6x18 Zeiss monocular that achives 25 cm close focus by extending the objective by 40 mm. Here the magnification is about 9x and the edge sharpness is better than at infinity, although the AFoV is of course correspondingly smaller.

Regards,
John

 

[GrampaTom]

Hi Tom,

As Maljunulo pointed out, they are all telescopes, mostly Keplerian refractors ranging from a Nikon 6x15M CF up to binocular telescopes with 150 mm aperture or larger, although double Newtonian reflectors exist with mirror diameters in excess of 18".

Btw, I think what Binastro meant by "separation of objectives and eyepieces" was the correction of the instrument for specific distances, i.e. for infinity in an astronomical telescope. Here, for corrected vision, the separation would be the sum of the focal lengths of objective and eyepiece, but for closer objects we would have to rack out the eyepiece(s), as on most Porro binoculars.
However I don't think it's as critical as he implies and have never noticed any image degradation at close focus with binoculars or birding scopes.
Macro camera lenses and enlarging lenses work satisfactorily over quite a large range of distances.
I have a 6x18 Zeiss monocular that achives 25 cm close focus by extending the objective by 40 mm. Here the magnification is about 9x and the edge sharpness is better than at infinity, although the AFoV is of course correspondingly smaller.

Regards,
John

Thanks John,

How about my questions? Given the role a binocular mostly plays, does it need the optical quality of a telescope designed for looking at the heavens? Would it be cost (price) effective? If not therefore, should we disparage its optical performance?

Im chuckling. As you know, Im a simple birder.

The Birdforum, bino sub group contains a largish active group of bino collectors that tend to subvert the conversation away from actual field (birding) use, and create lots of heat. Then in the Spotting Scope and Tripod/Heads sub group there are folks, (no insult intended), who are celestial oriented and discuss telescopes with technical language far beyond my abilities and/or I suspect the needs of we terrestrial birders...

Keplerian Refractors? Is that better than those ol Abbe-Koenig thingies? How can I buy one o dose in a bino?

Tom

 

[Maljunulo]

“The optical quality of a telescope” can be anything from abysmal to superb.

There is nothing magical about a telescope that imbues it with “optical quality”.

Each side of a binocular is a telescope.

 

[MiddleRiver]

Back to thread title…

It is my understanding that diff patterns of varifocal lenses are avail. Is there an optician or ophthalmologist here that can tell us which product to look for if a lower section is needed for close reading but I want the biggest ‘ditch’ for distance correction an using bins?

 

[Patudo]

A budget binocular allowing the use of spectacles can simply crush an NL Pure used w/o spectacles if you're unfortunate (read: stupid enough not to prioritise your eyes)

I have to admit - I enjoy looksharp's posts, but this comment does not match my own experience. I use binoculars that require me to remove my glasses on a fairly regular basis, and once properly set up (assuming there is enough focus beyond infinity etc) image quality is excellent, certainly better than budget binoculars used with glasses. If the NL has enough focus beyond infinity for me to use without glasses I would expect it to be well ahead of anything budget, even if the latter was used with glasses. But fortunately I don't have significant astigmatism (just a little, in my left eye).

 

[GrampaTom]

looksharp65 said:
A budget binocular allowing the use of spectacles can simply crush an NL Pure used w/o spectacles if you're unfortunate (read: stupid enough not to prioritise your eyes)

I have to admit - I enjoy looksharp's posts, but this comment does not match my own experience. I use binoculars that require me to remove my glasses on a fairly regular basis, and once properly set up (assuming there is enough focus beyond infinity etc) image quality is excellent, certainly better than budget binoculars used with glasses. If the NL has enough focus beyond infinity for me to use without glasses I would expect it to be well ahead of anything budget, even if the latter was used with glasses. But fortunately I don't have significant astigmatism (just a little, in my left eye).

Me to. Confess though I had Looksharp65's above comment in mind when I went into all that in #31. I essentially agree with the sentiment, eyes should most of the time be prioritized before bino, but my experience suggests its not quite that straightforward for each of us.