What Does A Blister On Sclera Of Eye Indicate?

I woke up this morning with a blister on the sclera of my right eye. No pain, just red, itchy, and vision was blurred. Then during day vision affected more in that my depth perception was off. Then around 6pm tonight my pupil in that eye is dilated to its full extent and left pupil pin point. The blister appears to have gone down but around where it was is still red. What could it be?