This was when I was working on a project where the drug in question was to be injected intravitreally. To be effective, it needed to get to the back of the retina. There are many membrane layers in the eye before you get to the back of the retina and the drug was a reasonably big protein. One of the big challenges in the first human trial was that you couldn't really confirm that the drug got to the target - sampling the vitreous fluid isn't really an option.
In later trials, FDA demanded a 'double-masked' study (for obvious reasons, the usual term 'double-blind' was deemed inappropriate). So we actually had to figure out how to give the placebo subjects a sham injection (or at least the impression that they had received an injection) with as little risk as possible. Conduct of the study was quite complicated.
The irony was, because of the mechanism of action of the drug, almost everyone receiving active drug regained a couple of lines vision on the eye chart within 24 hours. Which made it perfectly clear to all concerned who was getting active and who was on placebo.
But the eyeball was very cool, and if I got frustrated, I could always stick things in it and claim a valid reason for doing so.
That study sounds familiar--I used to work for an ophthalmology journal. Sadly, they never let us have tennis-ball-sized eyeball models (nor smaller ones) to stick things in--although we did get some tasty chocolate eyeballs a few times.