Hi,
How are you? Are there other symptoms present aside from the vision problems? You may benefit from imaging studies and from another evaluation by a neuro-opthalmologist, which specializes or deals with portions of the nervous system related to the eyes. Take care and do keep us posted.
I have exact same experience two days ago. It started with a small dot (2-3mm at 30cm distance). Soon it became a circular (prismatic, more like a C letter covering from 11 o'clock to 4 o'clock). Later it became whole spread on the right side of the vision. Lastly it just disappeared.