A case of massive uveal effusion showed typical secondary retinal detachments with shifting fluid, retinal exudates, and total retinal detachments. Analysis of the subretinal fluid revealed a protein content more than three times that in plasma, and predominantly consisting of albumin. It seems reasonable to assume that the protein-rich fluid explains the phenomenon of "shifting fluid." The subretinal fluid showed no cells, low potassium content, and only plasma acid phophatase isoenzyme, indicating that the subretinal fluid was not an inflammatory exudate.
Brockhurst RJ, Lam K. Uveal EffusionII. Report of a Case With Analysis of Subretinal Fluid. Arch Ophthalmol. 1973;90(5):399-401. doi:10.1001/archopht.1973.01000050401015