adverb/a ˌoxos ˈbistas/
visibly; for all the world to see.
“La enfermedad se ha acentuado. Su Majestad decae a ojos vistas.” — The disease has accentuated. His Majesty is withering away before our eyes.
Apparently, short for "a ojos [las cosas] vistas", hence the disagreement between "ojos" (masculine plural) and "vistas" (feminine plural)