Black dot in the left eye when closing the iris

[AlesCZ]

Hello,
I have a weird problem. If I close nearly an iris on the condenser, in the left eye I see a black dot. I thought it was a defect in the eyepiece, but it is not. Left eye I see the same black dot in the right eyepiece and even in the second microscope. I noticed that the distance of the eye from the eyepiece, I can see the different layers of my eye (if iris almost closed). For me it is a strange phenomenon. The black dot is somewhere deeper in my eye (But when looking into a microscope to see this black spot sharp).
I have glaucoma, but I do not treat with it . It may be a problem with my eye? In normal situations, no black dot sight.

Thank you!

(sorry for my bad english)

[75RR]

Sounds like it could be Eye Floaters

"Looking like cobwebs or squiggly lines or floating bugs, floaters become apparent when you look at something evenly bright, such as white paper or a blue sky, and are more evident when you move your eyes. They are especially noticeable on looking through an optical instrument, such as a microscope or binoculars."

https://en.wikipedia.org/wiki/Floater

[JimT]

Check this site to see if it sounds like what you are experiencing:

https://nei.nih.gov/health/vitreous/vitreous

I have had two occurrences (happily none in the last 15 years). No big deal but you should get your eye checked.

Good luck.

[billbillt]

I think this condition is real common.. I see all kinds of weird particles also..."Floaters"..

BillT

[AlesCZ]

Thanks for the feedback folks. I have a theory. I have the dirt between the retina and lens of the eye. It probably works just like the lens of the camera. If there is dirt on the lens is visible only at high aperture number. If there is dirt on the sensor is always visible. This means that the retina would be ok.

By the way, let me introduce myself. My name is Aleš, I'm 35 years old and I'm from Czech Republic. I have two very old Meopta microscopes. It's one of my hobbies.

[kit1980]

If there is dirt on the sensor is always visible.

I learned the hard way that dirt on the sensor is much more visible with higher numerical aperture (or F-number).
That's because dirt is not really on the sensor, but on the glass that on the sensor, and visible dirt is really shadow of the dirt. With lower numerical aperture, more light comes from different angles under the dirt particle, so it's much less visible.

The same should be true for human retina problems, so check up with an eye doctor is probably a good idea.