Some may be individual red blood cells swollen due to osmotic pressure. Others may be chains of red blood cells stuck together; diffraction patterns can be seen around these. Others may be "coagula of the proteins of the vitreous gel, to embryonic remnants, or the condensation round the walls of Cloquet's canal" that exist in pockets of liquid within the vitreous.
That's a different phenomenon from the picture. The picture shows a body in the vitreous jelly. The article you linked is a "brain filling in gaps" phenomenon.
Still, very cool article. I had never read about that.