Uveal effusion in nanophthalmic eyes probably is the result of choroidal congestion secondary to imparied vortex venous drainage through the thick sclera that is characteristic of nanophthalmos. Ten eyes with nonrhegmatogenous retinal detachment, occurring in nanophthalmic eyes, were treated by vortex vein decompression and, in some cases, drainage of choroidal and/or subretinal fluid with air injection into the vitreous cavity. Eight of the ten eyes showed reattachment of the retina after this procedure. There results support the hypothesis that choroidal congestion is the basic mechanism of nanophthalmic uveal effusion.