WHEN VITREOUS ENTERS THE SUBRETINAL SPACE - IMPLICATIONS FOR SUBRETINAL FLUID PROTEIN

Purpose: Vitreous enters the subretinal space in rhegmatogenous detach ments, but the protein concentration in subretinal fluid from clinical detachments is much higher than in vitreous. These experiments were d esigned to study short-term changes in subretinal albumin concentratio n after vitreous enters the subretinal space. Methods: Retinal detachm ents were made in Dutch rabbits by injecting autologous liquefied vitr eous (albumin concentration 244.11 mu g/mL) into the subretinal space through a micropipette. Subretinal and vitreous fluid samples were wit hdrawn 0 to 4 hours later and analyzed for albumin concentration (by g el electrophoresis) and osmolality. The authors also made detachments with Hanks' balanced salt solution containing an approximate vitreal l evel (294.8 mu g/mL) of fluorescein isothiocyanate albumin. Results: W hen the authors made detachments using autologous liquefied vitreous, the subretinal albumin concentration increased to 333.3 mu g/mL 4 hour s after detachment, by which time the detachment volume had fallen to 65% of its initial level. The total amount of albumin in the subretina l space did not change significantly. Subretinal fluid osmolality rema ined within the range of 292 to 294 mOsm/kg despite the steady absorpt ion of fluid from the detachment. The results were essentially the sam e when detachments were made with saline and fluorescein isothiocyanat e albumin rather than vitreous itself. Conclusions: The subretinal con centration of albumin increases as water in subretinal fluid is absorb ed across the retinal pigment epithelium. If liquefied vitreous contin ues to enter the subretinal space, as occurs in clinical cases of rheg matogenous retinal detachment, this mechanism may cause albumin to acc umulate.