Monday, July 29, 2013

seeing spots

phosphenes aplenty these past few days, and a headache since saturday (mid-monday now), but no aura. i'll spend this post describing the phosphenes, which are interesting.

the phosphenes are always exactly foveal, less than a degree across. they are never noticeable for more than a few tens of seconds. the sensation is very similar to the very beginning of the typical aura. their appearance is very subtle, as though there is a smudge over the central view. it's comparable to having looked at the sun glinting off a surface and having a bright foveal afterimage. sometimes it seems that i can close my eyes and see a floating spot, like an afterimage, which easily fades from view; sometimes i can't see anything.

another sensation that the phosphene is similar to is lustre or shimmering as from interocular conflict. earlier today i found myself gazing into the distance above my desk, thinking about something, and thought i was seeing a spot; then after a few seconds i realized that my left eye was seeing a mark on the underside of a plywood shelf, where a screw pokes out, with my left eye, while the same view by the right eye was occluded by a hanging piece of paper. once i understood what i was seeing, the sensation seemed to change; it is as though i am strongly sensitized to the onset of the aura, and when i think i am seeing it, or seeing these blippy phosphenes, i feel that i know i'm seeing it, which turns back around and affects the way it feels to see it.

a third way of describing the sensation is as scotoma-like, but there is never any scotoma, or at least not any so large or stable that i can see it. it's more like what is seen is interfered with; maybe it's a scotoma in the confluence? mostly in V2/V3?

anyways, the foveal spots are always brief. in the past few days i've noticed them a dozen times. during the same period, i've repeatedly noticed the familiar difficulty with reading text, especially in the morning. i look at black text on a white background, and it's very difficult to read, as though the letters are jumbled. i think what's happening is that the afterimages aren't being properly suppressed, and that it's only noticeable with the high-contrast stimulus of black-on-white text, especially on a computer screen where the white is really bright. at other times i've noticed problems with afterimages, especially of textures, seeming to 'stick' from fixation to fixation, thinking that i see something in one location when it's actually carried over from the previous fixation. these sensations aren't afterimages in the common sense of light impressed in the retinas, which have their characteristic slow fuzzy fade; they are clearer and sharper at the same time that they are less substantial.

a headache started saturday sometime, then disappeared, then reappeared yesterday, subtle - only noticed it when changing posture - and remains today, where it was slightly excruciating earlier and mostly gone now. right trigeminal nerve, felt it above the right eye at the supraorbital nerve, and above my upper right teeth.

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