The only thing I can think of is that you may be experiencing the phenomenon of 'floaters' which are bits of flotsam and jetsam in the eyeball itself. I've seen them myself. The laser beam itself shouldn't have any effect per se.
Take a look at http://www.allaboutvision.com/conditions/spotsfloats.htm and see if this is relevant to your experience.
LeeH
I would guess another phenomenon, although it would help to have a little better picture of what you're seeing. Laser reflections often show an oddly undulating blotchy dark-light pattern. The pattern moves in a strange way as you move your head. This results from coherent interference between the laser light scattered off different things. The light reaching some part of our eye can consist of light following slightly different paths, with the wave-fronts either accidentally adding up or accidentally canceling. An ordinary light source would show a similar effect, but its pattern is changing so rapidly that you just see the blurred-out average, with all the blotches removed. Mike W.
(published on 04/26/2008)