recently I was struggling a little more than usual with a frequent occurrence during my sitting. I sit in medium daylight about two feet from some generic white woodchip wallpaper (not sure of the term, it's that grainy textured stuff) which after a few minutes of zazen tends to turn into swirling green and violet blots. A bit like being inside a lava lamp. If I ignore the dazzle my field of view will usually dim after another few minutes. If I blink or move my eyes the nuisance vanishes – together with my concentration.
The problem is less apparent in candle light and in the dim lit zendo. I read that a too tense meditation can lead to visual irritation or temporary loss of sight. So what to do? Change lighting, change wallpaper, change attitude, change nothing?
I'll keep an eye on the problem (haha), but maybe I can benefit from your experience.