A few months ago, I started having optical illusions—seeing things that weren’t there. For instance, when I was reading, images of flowers or vines or little colored feathery things would show up on the page exactly as though they were illustrations; in fact they looked like illustrations from a child’s picture book. They didn’t interfere with my reading, they just looked pretty, but they weren’t really there. Was this a new and fearsome stage of my glaucoma? I didn’t really think I was going crazy, but what was going on?

Then I started seeing the images in other places too. I might see a life-sized vine growing up from a planter on my deck, climbing the wall, coming through the picture window into the living room, winding around light fixtures and draping over the television set—and sometime later I would realize it was gone. And almost always, whenever I’m reading or writing, whole gardens of plants or vines will be on the page at least part of the time. In fact, there is a ferny plant of some kind in front of me right now as I type: lush green leaves, pinkish-white stems, all waving in a breeze that I can’t feel.

There was never anything alarming about the images—except, of course, their existence. Where were they coming from? What was the matter with my eyes, with my brain? Nothing I found on line about glaucoma mentioned anything like this.

Finally the other day I asked Google a different question. Without mentioning glaucoma, I asked What does it mean when I see things that aren’t there?

I was instantly rewarded with an explanation by the Discovery Eye Foundation, in the form of an interview between an eye doctor and a patient asking this same question. The patient was hesitant, afraid his hallucinations were a symptom of early dementia. But the doctor assured him they were not. Instead they were something called Charles Bonnet Syndrome after the doctor who had first identified it many years ago, and it is relatively common (between 10 and 40 percent) among patients who have “low vision” such as from macular degeneration (which I have had for many years).

The doctor listed six characteristics that will tell the patient it is this syndrome: (1) The images occur when you are fully conscious and wide awake, often during broad daylight; (2) You are aware that they are not real; (3) They occur in combination with normal perception; for example, you may see a sidewalk clearly but find it covered with dots, flowers, or faces; (4) They are visual only and do not occur with any sounds or other sensations; (5) They appear and disappear without obvious cause; and (6) They are amusing or annoying but not grotesque.

After all my anxiety, I couldn’t have made up a better, happier, more satisfactory answer for myself! I can’t imagine why I had never heard of this syndrome before in all my years of going to eye doctors. In the first place, how can this phenomenon happen? And in the second place, when something seems so miraculous, why isn’t it common knowledge?

Anyway, I’m just going to enjoy these lovely and surprising pictures that decorate my life these days. They remind me that every now and then, there’s nothing to worry about.