'Black Disc' Observations (Science).

[Jimford]

I've so far had three 'Eylea' injections for my AMD. After two of them I had the 'Black Disc' syndrome.

My observations were that the discs appeared at the bottom of my vision, and were of a dark bluish-black colour with a slightly lighter centre.

As the injecting nurses stated, these are air bubbles. So why are they 'black'?

When light passes between two transparent mediums, it's path is bent (refracted). In this case it happens twice - from water to air (into the bubble) and back out into water. The angle to which the light is bent depends on the angle at which it is incident (hits) the change of medium. I suspect that the bubbles are very small - maybe pinhead size - therefore the bending of the light as it passes though most of the bubble would be quite acute (because of the acute curvature of the bubble surface) and the emerging light may miss the retina entirely, making the bubble appear black. The lighter centre of the disc is because the light that hits nearer the middle of the bubble is scarcely bent, and passes through to the retina.

Now here's the part that came to me in a 'light bulb' moment in the shower - I find it quite exciting!

'My' Black Discs appear at the _bottom_ of my vision, and I suspect others may also find this to be so. So why at the bottom, when air bubbles should float to the top? The bubbles _have_ floated to the top of the eye, but appear to be at the bottom because the image on the retina of our eyes is inverted - upside down. Our brains invert this image such that up is up and down is down, but in doing so places the image of the bubbles at the bottom of our vision.

(There is an analogy for this in modern 'mirrorless' digital cameras (those without a 'hump' on top). The image is inverted on the sensor, but the camera 'computer' turns it the right way up on the viewing screen.)

I hope the above is clear. I would welcome comments and criticism.

Jim

[Eyelet]

Oh what fun you have had Jim ....interesting. I just think of them as a tribe of Mickey Mouse ears. 👁

[rosyG]

agree with your point- I have an inferior retinal vein occlusion but sight is affected in the upper quadrant- I've wondered if this is for the same reason

[Rosalyn-helpline Partner]

Dear Jimford,

I will do some research on this and come back to you.

Kind regards,

Macular Society helpline

0300 3030 111.

[e-mail]

[Jimford]

Also, the 'Black Disc' effect can be seen in a microscope, when small bubbles are trapped in the water under a cover slip.

[Rosalyn-helpline Partner]

Dear Jimford,

I have just consulted with a well respected ophthalmologist via email. This was their reply to your post:

"You’re nearly there!

The bubbles float up, but are seen in the lower field of view, because the images are thrown on the superior retina which sees things in the lower field."

I hope that helps,

Kind regards,

Macular Society helpline

[Jimford]

Thanks for the reply. I thought that the above was what I basically said - so I was 100% there. (You can tell me I'm wrong!) 😉

[Yeso]

I have the black disc since I got the injection yesterday afternoon, nearly 24 hours.. when will it go?

Thank you