A fish-eye is a reflection just inside the table of girdle (on the opposite side). If the girdle is not polished and is thick the effect looks like a BIG circular inclusion, and can be as bad as an I3 (P3).

Fish-eyes are more apparent if the pavilion is shallow 39.5°, the table is large; the girdle is thick and not polished. Combinations of these factors worsen the effect.

Fish-eyes occur proportionately between the following pavilion depths and table sizes:

41 degree pavilion and 72.2% table
39 degree pavilion and 58.4% table

These fish-eyes require no tilt to see them. If the table gets 1% bigger you see a 1% fish-eye. Fiish-eyes are rated with a negative value that treats the effect like an inclusion, because that is what it looks like. No tilt required is the worst fisheye, and should be accompanied with a warning, "do not buy this diamond under any circumstances as it is a fish-eye."

A small amount of tilt to see a fish-eye is acceptable because these diamonds have a very good spread and look very big for the money.