i would have is checked out by a vet. Squishy had that when she was little the vet said it was allergies and to keep it clean it would go away. It did an she has beautiful eyes now. But it could be infection. best to have it checked out
what color is it and is it always basically consistant in color and amount? If it is its normal and nothing to worry about. If you notice sneezing or watery eyes/runny nose, etc... then I would have your cat taken to the vet to be treated. But cats, just like all animals, get eye boogers