Good news for a friend we've known since 1990. We've mentioned our interest in algae. This kind of photography is the most difficult we've ever tried. It is clearly difficult. Many turtles will tolerate a close approach, but macro photography of just an eye requires a large housed camera and flash to be just inches away from a turtle.
Humans are uncomfortable with such intrusion and turtles are no different.
Still, the results are worth it. Here is an example of Uwapo's left eye, which had a tumor in it in 1997. 48K JPEG Uwapo is a regression case. More of the same.