i'am 55 and recently took up rifle shooting having not done it since school days. when i look through a diopter sight i see what looks like a ragged greyish bit of 'debris' on the left hand side of the sight picture. it looks exactly as if there's a bit of fluff in the sight. i've had my eye checked by two opticians who say they can't see anything wrong. i just wondered if anyone on here had ever come across anything like this before. my left eye's fine but of course i'am right handed!