It makes sense to give the police every bit of information you can. Does it make sense to publicise that information world-wide? I would be guided by the police on that. I think they often keep details about crimes back, so when people confess they can check if they know those details. if they don't, they're giving a wrong confession.
The coloboma/eye defect/fleck may have proved useful as a check when people reported sightings, had it not been publicised so widely. I find it quite astonishing what Kate Mccann told Piers Morgan, when every poster and appeal made a huge thing about the eye;
MORGAN: Madeleine had a very distinctive eye pattern, didn't she? Tell me about that, Kate, in case people see somebody they think may be Madeleine. Tell me about her eye.
K. MCCANN: If I'm honest,
we haven't put too much emphasis on her eye, because I think you have to be very close to her to see it. But her eyes are slightly different colors, and one of them has this brown fleck in it. But you do notice, particularly on photographs, but --
http://transcripts.cnn.com/TRANSCRIPTS/1105/11/pmt.01.html