Four short lines set up what feels like an experiment. The word "participants" and the title "Thesis 11" suggest a study or a set of propositions, so the poem sounds cool and clinical, as if someone is reporting on a procedure. Everyone is blindfolded, which is simple enough. Then the last two lines turn strange: "one is denied / the world within."
The poem seems to say that losing sight is one thing, but losing your inner world is another. The sentence is also ambiguous. It's unclear who does the denying, or how, and that vagueness is unsettling. Maybe the blindfold shuts out the outer world while one person is also cut off from imagination or private thought.
The speaker doesn't state any feeling. The detached tone hides whatever emotion might be there, and that restraint is what creates the mood: cold, uneasy, a little ominous. It leaves you wondering who is in control, and what it would mean to lose your own mind's landscape.