My 10 y/o doggy seems to have an eye problem.

He keeps getting mucous like goobies in his L eye (not so much in his right)

His L eye is a tiny bit red. We took him to the vet awhile ago andthey gave us eye drops Prednefrin Forte which kind of cleared it up but im thinking maybe the eye is dry? I dunno

Any thoughts?

I might take him back to the vet this week but I thought I'd ask you wonderful girls