POISON singer BRET MICHAELS is suffering through yet another health issue.  This time, it's a corneal ulcer, which is also referred to as an eyesore.  It's unclear how serious it is.

Bret tells the "Birmingham News", quote, "I got a shot in my eye yesterday.  They numb your eye completely.  They don't even have a remedy for what's wrong with my eye.  They're using this crazy stuff in my eye that they invented."

Apparently, the eyesore was caused by an eye infection, which happened after fans "accidentally hit him with a glass" during an appearance at a nightclub in Panama City, Florida.

Bret explains, quote, "[When I was leaving the club] someone said, 'Bret, you rock!,' and this glass filled with vodka and Red Bull fell on my head, and something in the glass scratched my eye.  It was this comedy of errors that I survived through."

(That "comedy of errors" could also apply to the incident at the 2009 Tonys, when Bret was hit in the head by a set piece that was being lowered from the ceiling.  Here's video of that.)

(Bret is currently suing the Tonys... claiming that the accident played a significant role in the near-fatal brain hemorrhage he suffered last year.)