On Friday afternoon I was sitting in the sunny kitchen reading an article written by a man who emigrated to the US from Ireland early in this century. Then a cloud passed over my eyes. All the contrast ran out of the page like the type was dissolving into the liquid white around it. The room was turning into the blurred fade of an old photograph. And I thought, "This is it. I am going blind. These are the last words I'll ever read."

It was a poignant moment, savoring the fading sight of the room and the resonant effect of those last printed lines. There might be no more surfing the web, no more lingering eye contact, and I would likely be out of job. I wondered what small explosion inside the soft machinery of my brain was causing this system failure. So much, it seemed, was about to change because of that inaudible, meaty blast. I remembered reading an article by a man who one day drove home through a thickening gray fog only to find when he arrived that the darkness was inside his own eyes. Something irretrievable had ruptured within him. Veils were falling forever between him and that familiar landscape. All this rushed through me like water, too fast to really grasp.

Then, of course, the clouds tore back from the sun and color flooded into the room. Oh, I thought, I'm not blind -- it's just the skies. I wonder exactly how many times clouds have obscured the sun shining through windows of a room in which I was reading, and why on this occasion I was beguiled into a fantasy of blindness by a mere change in light. There have been other similarly hypochondriacal moments. Standing at the bathroom mirror, I thought I saw the exposed root of a tooth peeking through my gum, like the flesh of my mouth was scraping back to expose the wet skull inside. That turned out to be a piece of corn.

There is a puzzle here, and many ways to decode it. I could conclude that working at an ambulance again is reminding me of the inherent breakability of the body. Preparing to meet moments of desperation in others' lives tends to remind that I'm not immune to them myself.

Or I could accept that these are omens, and that their message must be derived to be useful. Perhaps it's hidden in the messengers of those fearful moments: corn and clouds. Perhaps the importance is to be found in the fragility of eyes and teeth, or in their capacity to do the same things. Eyes and teeth begin to break down that which enters the body, reducing light and nutrition to a more consistent medium for appropriation, initiating the digestion of vital inputs.

Teeth. Sometimes when angry I get the strong urge to bite. I want to latch on to the world and tear off a hank of it, shake it around in my jaws a little. Perhaps my vegetarian teeth miss the ancestral texture of flesh. They just want a little of the old action.

Eyes. Recently I've been playing a game with myself in which I try to see how fast I can connect a stream of visual images in my mind. Each image can be connected to the previous one, but there can be no planning, no anticipation, and above all, no conscious control. I find sustaining such visual cacophony to be nearly as difficult as blanking my mind for any period of time. Keeping up a nearly-random stream of mental sights can leave me feeling exhausted and nauseated.

As ridiculous as this sounds, I originally played with this process as a kind of jamming signal in case anyone ever tried to read my mind. I figured that mind-reading must be like most kinds of human cognition: involving the integration and interpretation of stimuli in the individual's own mind. In other words, you "read" a mind the same way you "read" a book -- viewing the information provided and forming your own thoughts based on that information. The reader's mind is thus every bit as important as the mind of the person being read. They're not just getting a direct download; they're interpreting a stream of information using heuristics to collapse the raw input into usable chunks. I figured a stream of random images would prove maddeningly difficult to digest and might be so unpleasant that they would be forced to abandon the attempt. Increasing the speed would make the experience like flashing pages of text in front of someone who was slow reader: hopeless.

The only problem is that while running the visual stream, I'm every bit as incapacitated as the reader. But the exercise might have the unintended benefit of practicing faster overall cognition, enabling me to foil would-be mind readers by outpacing them.

But that isn't really about eyes at all -- it's about mind, and confusing them is like talking to your dentist about gastrointestinal problems. As for my eyes, they are slightly red but functioning normally. They are omnivorous, and if they destroy flesh with their gaze as teeth do, they are only marginally aware of it.