Optical microscope tips: I want to see with both eyes!

May 11, 2009 3:24 AM

How do I get better at using an binocular compound optical microscope? I'd like to hear hints and tips I'm also interested in theories as to why I find this such a challenge, as it seems to come naturally to most people.

I have difficulties using a binocular optical microscope - no problems on focusing on the specimen etc, more with the vision-related stuff. I adjust the distance between the eyepieces, but still find it hard to achieve a single image. Am I supposed to smoosh my eyes close into the eye-pieces, or keep them a few cm away?

I'm fairly happy using monocular models, though I never did learn the oft-recommended trick of keeping both eyes open - I can't see the specimen at all this way, it disappears and my vision just shows me the non-magnified view. Perhaps this is related?

I have myopia (short-sightedness) in both eyes (-10 dioptres in both eyes), and a small degree of astigmatism and I wear contacts most days, and spectacles occasionally. The contacts don't correct my vision completely, they are just the closest prescription that comes in daily disposable versions.

posted by Tapioca to science & nature (12 answers total)

I have the same problem and find my very long eyelashes exacerbate it. Not that that helps, just an observation that may inform. (I have short sight and an astigmatism and wear glasses.)
posted by taff at 4:35 AM on May 11, 2009

Do you have similar problems using binoculars?
posted by odinsdream at 5:11 AM on May 11, 2009

I'm not sure if I have any great advice on how to help, but I can assure you that it doesn't come easily to everybody. I still struggle, especially if I switch to a new microscope. Definitely keep playing with the distance between the eyepieces, and your distance from the eyepieces. For the latter, I recommend not smooshing in close; maybe 1cm away? Or maybe even 1.5-2cm since I wear glasses and they tend to feel in the way.
posted by dormouse at 5:12 AM on May 11, 2009

Also, do you have trouble seeing "magic eye" type 3D illustrations?

If so, you may be crossing your eyes too much, making the angle formed by your eyes and the vanishing point too large. You want that angle to be as close to zero as possible. You can practice this by looking out to the horizon and bring an object up in front of your eyes. Continue focusing on the horizon - kind of ignoring the object. Feel that eye muscle configuration and try to do that very same thing on the microscope.
posted by odinsdream at 5:16 AM on May 11, 2009

Thanks for all the responses so far...

Odinsdream, I don't own a pair of binoculars to check, and the last time I used binoculars was years ago but I don't recall problems. I can't do magic eye pictures, gave myself headaches as a child trying, back when they were all the rage.
posted by Tapioca at 5:27 AM on May 11, 2009

Are you looking through the microscope with your left eye or your right eye? If you're using your left eye switch to your right. If you're using the right eye switch to your left eye. Why?

"keeping both eyes open - I can't see the specimen at all this way, it disappears and my vision just shows me the non-magnified view."

That means you're not using your dominant eye to look through the microscope and it sounds like that's the cause of your problem.
posted by I-baLL at 6:06 AM on May 11, 2009

I had trouble at first, but managed to overcome the strangeness by moving back from the eye-pieces ... way back at first.

Just as an experiment, try moving back a few inches away, and look 'down into' the eyepieces as though you were looking into two wells. Lock onto the image down at the 'bottom', and then bring your head closer bit by bit. I now usually never actually get close enough to touch the rims of the eyepieces at all.
posted by woodblock100 at 7:05 AM on May 11, 2009

One of the two eyepieces should have a diopter adjustment to help balance any difference between the two eyes. Have you tried tweaking it?

One way to adjust it is to close the eye without the diopter adjustment and then adjust focus. Then switch eyes and adjust the diopter to get focus in the other eye.
posted by exogenous at 8:22 AM on May 11, 2009

Sometimes I have trouble with this when switching to a new microscope. What works for me is closing one eye, getting the image 'centered' in that field of view, then closing the other eye (while opening the first eye) and getting the same image 'centered' in the second field of view. Then open both eyes, and presto- single image.

Sometimes I have to do a few iterations of this, while adjusting the width of the eyepieces. My eyes are widely spaced, so microscopes are almost never set up with the eyepieces set to an appropriate distance for me when I sit down to use one.
posted by u2604ab at 12:28 PM on May 11, 2009

I also have myopia with astigmatism, switch between glasses and contacts, can't do magic eye puzzles at all, and sometimes have the trouble you're describing. To make it worse I too have long lashes, can't do it with my glasses on at all, my eyes are different prescriptions and I can only wink on one side (so can't close my right eye without also closing my left eye). But with some practise and effort I can make it work properly.

First make sure the seat is the right height and distance out so you're comfortable, you should be able to just lean in causally rather than crane or strain your neck. Then do what exogenous is describing, having both eyes correctly focussed from the start will make a huge difference. Then place your eyes next to the eyepiece to line up, adjust the distance to about right, then pull back a bit, you don't want them smooshed in. You should be able to find a place between 1 and 2 cm out where the images line up. You may need to tweak the distance again at this point to get it right. Also let your eyes relax, trying too hard definitely makes it worse. Probably what happens when you relax is your dominant eye takes over so you're mostly looking through one anyway, you just need to adjust the other one so it's not obstructing the view. Oh start at a low magnification, it's easier to get it right somehow when it's not so focussed in. Once you get it right a few times you'll get a feel for it and be able to get into position faster next time, plus you'll be less tense. It does get easier!

When they do line up and everything goes all clear and 3d-ish it's cool. But I think lots of us struggle to get there so don't feel bad if it takes some time.
posted by shelleycat at 4:38 PM on May 11, 2009

I just realized my description above is wrong. First focus using the normal focus control and while closing the eye with the diopter adjustment. Then close the first eye and focus using the diopter.
posted by exogenous at 5:26 AM on May 12, 2009

Thanks for all the great answers! I had a bit of a play with the dioptre adjuster (never even noticed it was there before!). That combined with moving a little further back from the eyepieces seems to have done the trick. Much improved viewing.
posted by Tapioca at 2:22 AM on May 13, 2009