What causes an oddly shaped pupil?

A pupil which is not round, but looks as if it is leaking into the iris? Is this similar to a birthmark, or what?

sometime it's due to a genetic syndrome , and it's a sign of other abnormalities , sometimes it's a sign of previous intraocular inflammation and development of abnormal attachment of the iris and the lens [ usually ] , some times it's a disease in nerves , or due to trauma to the eye ball .

Coloboma of the iris.

The missing Madeline McCann girl also has it.

It's just a congenital condition, perhaps genetic; not really known. It can be mild with no effect whatsoever on a person, or depending on the shape, size, and placement, it can have an effect on someon's vision.

The pupil itself is just a hole in your iris. Lots of people think the pupil is a structure of its own. Your iris has an opening: through that opening, the doctor can see your retina (when using lighted magnification). To the rest of us, that opening just looks black, and we call that opening 'pupil'.

So it's actually the iris which has not formed a perfectly round hole.

The opening gets bigger and smaller based on different factors (light, trauma, etc), but that opening is contolled by iris muscles.

Because it is just an opening to the back of the eye, that's why people get red-eye effect in photos: it's the camera's flash that illuminates through the opening, and off the redness of the retina.

Mostly Genetic- although if this is something that causes discomfort, go to your Eye Dr ASAP! This anomly is more commonthan you might think- I went to school with a gal whose pupils were keyhole shaped and she never had any problems- was strange looking into her eyes-