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Magnifying visors: eyes crossed!


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I got a cheap magnifying visor recently. It was junk for a variety of reasons, and I returned it. I wanted to see if a visor would give me some stereoscopic vision that my clip on loupe doesn't. They seem popular.

Anyway, I noticed that at any magnification at all, I was cross eyed trying to focus on a movement. It seems to me the standard would have some degree of parallax between the lenses so that stereoscopy were possible, but this is the first such tool I've ever seen in person. Is it the norm that at 3.5X (the highest power in the box), you'd be totally cross eyed by the time you're close enough to see a movement? Am I missing something thinking that there should be some sort of compensation in the lenses to accommodate the distance/eye distance?

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I wear glasses daily. It looks like the Donegan visors have prismatic lenses, which is the word I was looking for when I said "parallax between the lenses". These were definitely not prismatic. They were $8.88 to my door. and when I returned them, the said don't bother sending them back and just gave me a refund. I ordered a Donegan visor last night, so we'll see in a week or two how they compare.

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In my experience this type works the best. I use them all the time and I'm very happy with them. Sometimes I combine two lenses to get even stronger magnification (use two rubber bands to tie the lenses together). Even Bergeon sell them (crazy price though). You can find them on eBay as well. In my experience the Donegan visors don't work well when working with watches as they get in the way of screwdrivers and tweezers. Personally I just couldn't motivate myself to get used to an eye glass. It takes quite a bit of practice to put tweezers and screwdrivers in the right place without stereo vision.

I had a little problem with becoming cross eyed too, especially in the beginning. Now it rarely happens but when it does I blink a few times and look at something in the distance and then try again. That said, we're all different, so maybe an eye glass is your best option, and it is a good option once you've practiced enough with it.

Forgot to mention that I consider my stereo microscope my most important "tool" alongside tweezers and screwdrivers.

Edited by VWatchie
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On 4/6/2021 at 10:17 PM, spectre6000 said:

I wear glasses daily. It looks like the Donegan visors have prismatic lenses, which is the word I was looking for when I said "parallax between the lenses". These were definitely not prismatic. They were $8.88 to my door. and when I returned them, the said don't bother sending them back and just gave me a refund. I ordered a Donegan visor last night, so we'll see in a week or two how they compare.

When you tested the magnifying visors, did you wear them over your prescription glasses or did you remove them?

If your uncorrected vision is unable to focus at a near object simultaneously, you have to wear your prescription lenses under the visor. Or else you'll end up with images that are in focus at different working distances and with different image sizes. This is probably why you felt "crossed eyed".

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When I was working as a watch/clock maker I just used eyeglasses even though I wore glasses I always took them off. I had what's called a lazy eye which is my right eye so I used my left eye for the watch and clock work which has excellent vision. Now because of age and diabetes vision in both is not so good. Please look after your eyes, you might not realise how much strain you put on them by using bad or poor magnification and it will affect your sight in years to come.   

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14 hours ago, HectorLooi said:

When you tested the magnifying visors, did you wear them over your prescription glasses or did you remove them?

If your uncorrected vision is unable to focus at a near object simultaneously, you have to wear your prescription lenses under the visor. Or else you'll end up with images that are in focus at different working distances and with different image sizes. This is probably why you felt "crossed eyed".

I was wearing my regular glasses. That was the whole point of the visor for me. I'm back at my computer post-surgery, and see the Donegan visor has shipped... from China. Pretty sure they're supposed to be made in Kansas. This might get interesting.

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Magnification is a personal preference item Everyone's eyes are different and personally I have tried visors,clip on the glasses systems but I always go back to various strength eye glasses. For really fine and close work I use a binocular microscope. 

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I have several conventional eye loupes which I use with a wire frame. I also have the stereo lens visor type that you tried but I never really got used to them. Then I also have a couple of clip on ones which I use regularly.

I also have several dental binocular loupes, which I use in my clinic but don't use them for watch repair because of their weight.

I also have a stereo microscope which I used for my dental labwork, but I brought it home last year. I still haven't adapted my working style to working from a microscope eyepiece. It just feels unnatural. 

I guess you'll have to try them all to find what works for you.

Several years ago I came across a digital stereo microscope with a 3D monitor at a dental trade show. It uses 3D tv technology that reqires the use of special lcd glasses that toggle the left and right lenses in sync with images displayed on the screen. I found it quite user friendly and there was hardly any learning curve.

The only problem was the price. The manufacturer wouldn't tell me the price as it was a prototype. I found a link in their website if anyone is interested. 

https://www.renfert.com/int-en/PM/Products/Equipment/Dental-Microscopes/EASY-view-3D

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I bought a relatively cheap stereoscopic visor similar to the Donegan. I do have to wear my prescription glasses as well at the same time as the correction on my eyes is not the same. If I left my glasses off, I would have differing focus distances as well. I have found the visor ok to work with so far. The biggest issue that I have with it is the headband which is vinyl in the front makes you sweat quickly where it touches your forehead. The sweat then runs down and in my case straight onto my glasses lenses.

I am going to make a couple of material covers with velcro attached to them to put over it.

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I'm still trying to find the perfect magnification.  I've nearly tried everything but as of yet nothing is very comfortable or practical for me.

I tried these https://www.aliexpress.com/item/4000770215571.html which are actually really good for the price.  Very versatile with being able to mount 2 magnifying lenses.  The light is removable to reduce weight.  The screw adjustment at the back presses in to lock it so that it doesn't loosen during use.

However, it doesn't suit me for watchmaking.  Sigh.

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28 minutes ago, spectre6000 said:

 Both eyes were magnified 3.5X (I assume), but the focus was not in the same place.

What do you mean by the focus is not in the same place?  You mean the image in both eyes do not converge into one coherent image? Or do you mean the focal distance is different for each eye? 

Did you try the other lenses that came with your visor? 

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On 4/10/2021 at 10:34 AM, HectorLooi said:

What do you mean by the focus is not in the same place?  You mean the image in both eyes do not converge into one coherent image? Or do you mean the focal distance is different for each eye? 

Did you try the other lenses that came with your visor? 

When the focal length is short enough (i.e. with the 3.5X lens), if both lenses are arranged in parallel, the lenses are focused a few cm apart. 

image of lens arrangement

If you look at the above image (it's an image from an Amazon review complaining about what may prove to be a counterfeit Donegan visor like I might be about to receive, so it's not the most perfect example), you'll see the lenses are positioned so that they meet in the middle and the object being focused on is in focus for both eyes. The ultra cheap lenses that came with the $8.88 visor I got had them totally parallel, so there was no way to be looking at the same thing at the short focal distance.

Edited by spectre6000
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Ok. I understand now. That "toe-in" angle is called the convergence angle.

The visor loupe that I have has a built in convergence angle. Even though the two lenses appear flat, if you look at the left and right edges of the lens, they are thicker than the middle where the lenses meet.

But then, with a simple, non-adjustable setup like this, it doesn't suit everyone. If you are lucky and the distance between  your eyes (inter pupillary distance) is the same as that of the visor, then all is good.

Even if you get an expensive surgical binocular loupe, you have to adjust the inter pupillary distance to suit you. And in my case, even the convergence angle didn't suit me. After using it for five years, squinting through slightly skewed lenses, I decided to do what the factory warned against doing. I loosened the lock screws and set my own convergence angle. And I have been using them for the last fifteen years.

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I have the Donegan visor, and a Bausch and Lomb Magna visor.  The Magna Visor has 2.6, 2.2, and 1.8 mag lenses. I find myself using the Magna Visor more often, usually with the 1.8x 12" focal length lens. I'm not even sure where the Donegan is ? . If I want something stronger, I generally use a 4x or greater single loupe with a wire holder on my left eye. 

Works for me.

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