Something strange is going on with my vision. Is this a symptom of preeclampsia?
One of the tricky things about preeclampsia is that many of the symptoms could be preeclampsia but could also be other things, including normal pregnancy symptoms. There are different types of visual disturbances and phenomena, some of them normal, some concerning.
What is normal?
Floaters. Floaters are small black, grey, or white, blurry shapes floating in your field of vision. These are literal bubbles and debris floating in your eye jelly. Everyone has them, but most of the time our brains do a good job of ignoring them. They become more noticeable during pregnancy and as we age. They are usually nothing to worry about, unless you very suddenly have a lot of them to the point that they are interfering with your ability to see.
Blue Entoptic Phenomenon. When you stare at the bright blue sky, you may notice small white spots streaking around your vision. These are white blood cells moving through your optical veins and arteries. Again, our brains usually filter them out, but we can often see them when we stare at the sky.
Visual snow. This can be a little like watching an old fashioned TV or old video recording. You can see everything, but the background is just flickering a little. I notice this more when looking at something dark in bright light, or something bright in dim light, or when my eyes are tired. (Personal story from our admin Jen: In my third preeclamptic pregnancy, my visual snow got very noticeable. At first I thought it was the preeclampsia visual disturbances. I was hospitalized and put on the induction schedule. But when I had no other symptoms of brain swelling and stayed stable overnight, they decided to wait. I had snow the whole final three weeks. When my brain started to swell an hour post partum, the visual disturbances were obviously different.)
Phosphenes. These are the stars you might see for a few seconds if you hit your head, shave your armpits, or stand up too quickly, or the colors and shapes you see when rubbing your eyes. As long as they fade away quickly, they are normal.
Here is a video explaining these four common phenomena and showing what they look like:
Changes to your vision prescription. Pregnancy does a lot to our bodies. With shifting hormones and increased fluid, the shape of our eyes/lenses may change a little, making our vision a little blurry. We may need glasses when we did not before, or our previous prescription does not work as well. Sometimes our vision might even improve a bit!
What is concerning?
Flashing lights, tunnel vision, fishbowl vision, blank spots covering large areas of your vision that do not fade away. See examples and further descriptions below.
Flashing lights, which are different from "visual snow" in the background, that are right up front blocking you from seeing everything. They may flicker and change color. (This is called "scintillating scotoma" if you want to look up more examples.)
Tunnel vision, where you cannot see the periphery.
"Fishbowl" vision is like seeing everything through the distortion of water. Things may look longer or wider than they should.
Blank spots, like flashing lights, block you from seeing everything.
Here is where it gets tricky. Some of these same visual disturbances can also happen with migraine headache. You can also get ocular migraines without headache with the same visual issues. But if it is being caused by a migraine, it usually fades away within a half hour or so.
The preeclampsia visual disturbances are caused by brain swelling. The excess fluid puts pressure on your optic nerve, causing it to send signals to the brain “seeing” things that are not actually there. This cerebral edema is an end stage symptom that requires delivery soon after appearing. Other symptoms of brain swelling include severe, unresponsive headache, hyper reflexes, and clonus.
We will occasionally see people who had brain swelling without a headache. If you have flashing lights, tunnel vision, fishbowl vision, blank spots, with or without headache, that are not fading away, you should get checked. If it turns out to be just a migraine, great. You can get treatment for it. If it is brain swelling, you should be prepared to deliver.