When vitreous enters the subretinal space - Implications for subretinal fluid protein

Purpose: Vitreous enters the subretinal space in rhegmatogenous detachments, but the protein concentration in subretinal fluid from clinical detachments is much higher than in vitreous. These experiments were designed to study short-term changes in subretinal albumin concentration after vitreous enters the subretinal space. Methods: Retinal detachments were made in Dutch rabbits by injecting autologous liquefied vitreous (albumin concentration 244.11 mu g/mL) into the subretinal space through a micropipette. Subretinal and vitreous fluid samples were withdrawn 0 to 4 hours later and analyzed for albumin concentration (by gel electrophoresis) and osmolality. The authors also made detachments with Hanks' balanced salt solution containing an approximate vitreal level (294.8 mu g/mL) of fluorescein isothiocyanate albumin. Results: When the authors made detachments using autologous liquefied vitreous, the subretinal albumin concentration increased to 333.3 mu g/mL 4 hours after detachment, by which time the detachment volume had fallen to 65% of its initial level. The total amount of albumin in the subretinal space did not change significantly. Subretinal fluid osmolality remained within the range of 292 to 294 mOsm/kg despite the steady absorption of fluid from the detachment. The results were essentially the same when detachments were made with saline and fluorescein isothiocyanate albumin rather than vitreous itself. Conclusions: The subretinal concentration of albumin increases as water in subretinal fluid is absorbed across the retinal pigment epithelium. If liquefied vitreous continues to enter the subretinal space, as occurs in clinical cases of rhegmatogenous retinal detachment, this mechanism may cause albumin to accumulate.