From the fact that a study allowed participants to continue receiving an experimental medication, it does not follow that the medication is accepted. It may be that a medication is unacceptably dangerous, but with the ill effects usually appearing relatively quickly, so that people who are on it can stay on it. It may be that a condition requires careful monitoring to stabilize it, and is badly destabilized by any changes in medication -- even the removal of a medication that in itself is entirely harmful. It may be that a condition responds well to placebo effects, which are lost when treatment is changed.

I can't say whether any of those apply to glaucoma. But I can say that "don't study that, or you'll have to consider it accepted" is a lousy policy.