This eye took all day

kw: local events, observations, photographs, medicine

Behold my dilated eye. If you look at your own eye in the mirror, close-up (this is easier if one has myopia, as I do), you'll see that the pupil is normally about one-third this size, or about 2mm. This was taken two hours after the dilation drops were put in, and at maximum the opening was 8mm; in this image it is about 6mm. Even in very dim light, for a man my age, the eye won't open more than 5mm or 5.5mm, though a young person's eye can open to 7mm. That is why "night vision" binoculars are designed to have an "exit pupil" opening of 7mm.

I saw a retina specialist to get an angiogram of the retina. I've had a dim spot, way off to the side, for a few months. I am prone to retinal hemorrhages, and I am used to them being absorbed and vanishing in less than one month. Because this one lasted so long, I sought a specialist's opinion.


This is the angiogram, on the left, with a "white light" image of the retina on the right. Though this is the "bad" eye, the doctor says it all looks very healthy (whew!). The spot, which is only partly in view to the lower right, below the yellow optic nerve, is indeed a hemorrhage, but is dissolving more slowly than they did in the past. At this point, it is mostly gone already. Fortunately, there is no apparent damage or separation of the retina.

A bit of geography. The center of the field is the macula, where vision is the keenest. It looks dim because there is some pigment there. In this eye, the optic nerve is to the right, on the side next to the nose. This is the "blind spot", where there is no retina. That is why it is brighter, because the retina is very dark red, so as to absorb the most light for keen vision: the most abundant visual pigment absorbs green and blue=green light, while the next one absorbs most of the red, but a little of that bounces back (thus "red-eye" in flash photos). The winding things are the blood supply to the retina. This is how they look in a normal eye. The gray areas at the edges are areas where the camera couldn't quite send enough light. This is a pretty wide-angle image, after all.

The way the angiogram was made was that a nurse injected fluorescein into a vein, then took a series of pictures using a blue-green flash. The camera had a yellow filter, because the dye fluoresces yellow-orange. That is what is behind the grayscale image above. It really shows the vein network.

So I am to be checked every couple of months to be sure this hemorrhage vanishes, but I also have to reduce my blood pressure, to help prevent future bleeds. Guess that'll help other things also. I spent the afternoon sleeping off the dilation, because I can't do much with the poor vision such dilation induces. What a way to spend my day off!