I don't have that many details on two of the clients, but the other two got the procedure done at Toronto Western Hospital. I believe the doctor was Dr. Robert Devenyi.

I don't know the cost, but I know it was expensive. Two of them had to get funds through church donations to fund the operation, not sure about the other two.

As for how effective... I'm sorry to report it wasn't that effective. While it was useful for some things to come up in contrast, it was easily overwhelmed and difficult to use in real life conditions. For example, it was helpful to locate a dark door along a white wall, or following a white line along the black asphalt while crossing the street. However, most things are not arranged in such a high contrast manner, and the lighting can sometimes play tricks. For example, a shadow cast by a light fixture might appear dark enough that it looks like a door.