Oh, wow.....
Our son (now 3 yrs old) started Tobi a few months ago. He had the same thing....redness in the eye, in the inner corner, first one eye, later the other, later also in the outer corner. At first I thought it was the Tobi irritating the eyes (because of the mask leaking or something). I even contacted the clinic about it, but they didn't know why....
We were not able to eridicate the PA after 2 months of Tobi, but the pulmonologist was really surprised about that, he could hardly believe he had PA, because the lungs were completely clear. So he said he thought it might be in the sinuses and Tobi didn't reach it. That's when a light bulb went off..... if it was in the sinuses, maybe it was sort of pushed out by the Tobi through the tear ducts, than ended up in the eye and infected/irritated the eye. He later went on IV's for two weeks, and oral cipro for 4 weeks and hasn't cultured it the last 3 months.... =)
This is my personal explanation, it has not been confirmed by the doctor, though he did say it was possible. However, he is very 'evidence based', if there is no scientific research, he is not convinced of anything.
Good luck.