My eye doctor diagnosed me with posterior blepharitis, I have been doing warm compresses and lid massages. Yet my vision is still blurry. Why?

It takes time. Posterior blepharitis takes time to improve. The quality of the tear lake, which is composed of meibomian gland secretions (the part you are treating), mucin layer, ; aqueous layer, aides the ocular surface to be as clear ; smooth as possible. Use artificial tears like refresh™ tears to help with part of the blurry vision, but continue with the compresses/massages. Eye doc can also rx doxycycline.