Huh? Seeing crisp vitreous floaters while using microscope

[djfontaine]

TL;DR Summary

Looking to understand the optics of how I can be repeatably seeing a crisp virtual image of my vitreous floaters while using microscope at high power

This seems crazy, but I've discovered that when using my microscope at high power - a 10x eyepiece and 40x objective for 400x magnification - and a plain bright field I can get a clear virtual image of my own vitreous floaters. The images are crisp, in a tight focal plane, move in that sluggish "gelatinous" way with my eye movements, and are readily repeatable. It appears that the light rays are somehow projecting a focused shadow of the floaters onto my retina.

Obviously, I can't photograph what I'm seeing with my own eyes in my own eyes, but I've attached a rough approximation of what I'm seeing - only it's MUCH sharper and well-defined in the scope.

Can anyone provide an optical explanation for how this could be occurring? Is this something that could be diagrammed or modeled with ray tracing software? Can anyone else with floaters and a microscope duplicate my experience?

I'd love to know what some of you with deep optics backgrounds might have to say about this.

dj

 

[Nugatory]

Your experience isn’t unusual.
They’re in the path from light source to retina so always imaged on the retina. Whether we’re aware of them or not depends on how the brain processes the signals from the retina; you’ve found lighting conditions in which your brain isn’t editing them out.

 

[OmCheeto]

After spending half an hour googling, I could not find any reasonable explanations.
My complete and utter guess is that it is related to Schlieren photography, where the light source converges to a point somewhere along its path.
I've long wondered why I could see my eyelashes, seemingly in focus, when they got bent between my eyeball and the eyepiece looking into my microscope. It simply made no sense to me at all.

I think @Andy Resnick is well versed in microscopy. He might know.

 

[Gleb1964]

To observe the floaters you need to limit the entrance pupil to the minimum possible size and look against evenly illuminated bright background. The pin-point entrance pupil would produce the best visibility of in eye imperfections. Using high magnification microscope or telescope does provide a very small exit pupil which helps to highlight the floaters. That would be limiting factor for observers with floater to use a small exit pupil (high magnification).

 

[djfontaine]

Thanks for your inputs, all.

Regarding the exit pupil, it appears 400x must provide a bit of a sweet spot. At lower magnification (100x), I do not see them. At higher magnification (1000x), I see them larger, but naturally with a much smaller field of view and depth of field, providing a jumpier view and less "context".

The reference to exit pupil also got me down a different web search path, where I came across this similar post on a microscopy forum - https://www.microbehunter.com/microscopy-forum/viewtopic.php?t=7058

I will add that this isn't just scientific curiosity. I've got reason to believe they're actually pathogenic, not the usual collagen tangles, as I've been told by 2 previous retinologists in 2 years. In fact, what I see actually lines up perfectly with online micrographs of the suspect organism (fungal). It's a worsening problem for me, so I wanted to have firmer footing before going to see specialist #3 to avoid further gaslighting.

Thanks for confirming I'm not nuts. Well, not about that anyway!

 

[Andy Resnick]

TL;DR Summary: Looking to understand the optics of how I can be repeatably seeing a crisp virtual image of my vitreous floaters while using microscope at high power

This seems crazy, but I've discovered that when using my microscope at high power - a 10x eyepiece and 40x objective for 400x magnification - and a plain bright field I can get a clear virtual image of my own vitreous floaters. The images are crisp, in a tight focal plane, move in that sluggish "gelatinous" way with my eye movements, and are readily repeatable. It appears that the light rays are somehow projecting a focused shadow of the floaters onto my retina.

I have not seen this phenomena specifically, but I have seen similar optical effects.

My suspicion is that in the microscope's 'image space' (where your eyeball is located), the numerical aperture is very low- approaching zero- meaning the light entering your eye consists of plane waves (off-axis image points are created by tilted plane waves). This increases contrast created by floaters and dirt on the sensor, so they are more visible.

That's just my guess...

 

[sophiecentaur]

My suspicion is that in the microscope's 'image space' (where your eyeball is located), the numerical aperture is very low- approaching zero- meaning the light entering your eye consists of plane waves (off-axis image points are created by tilted plane waves). This increases contrast created by floaters and dirt on the sensor, so they are more visible.

That makes sense. If the direction of light passing through each of the parts of the floaters then they will 'throw distinct shadows' on parts of the retina - looking better defined.

There is a similar effect when you compare photographs taken with small and large apertures. I vaguely remember reading about this. Small apertures give better depth of focus for the wanted object but dust on the surface of the sensor makes stronger imperfections with a small aperture but the light ariving from the whole area of the lens comes from a variety of directions and blurs the dust. I think I have actually seen this, in the past. Does this make sense?

 

[Orthoceras]

... it's MUCH sharper and well-defined in the scope.

Can anyone provide an optical explanation for how this could be occurring? Is this something that could be diagrammed or modeled with ray tracing software? Can anyone else with floaters and a microscope duplicate my experience?

It is a shadow image. In my experience the easiest way to view floaters is looking through a pinhole at a bright surface. The smaller the pinhole the better, but not too small. I got the sharpest view of my floaters with a 0.2 mm pinhole, made by poking a very tiny hole in a piece of aluminium foil.
When using a microscope, the exit pupil of the microscope is comparable to the pinhole. A microscope I used yesterday had an exit pupil diameter of about 1 mm at a magnification of 400x. My floaters appeared about as crisp as when looking through a simple 1 mm pinhole.