Effects of subretinal and systemic osmolality on the rate of subretinal fluid resorption.

Small norhegmatogenous retinal detachments (blebs) were made in Dutch rabbit eyes by injecting solution into the subretinal space. There was no difference in resorption time between blebs made with isotonic, hypertonic or hypotonic sodium chloride. However, blebs made with sucrose solution took longer to resorb than those made with Hanks' solution, regardless of whether the sucrose was hypotonic or hypertonic. Intravenous injection of hyperosmotic solution (mannitol) accelerated the resorption of Hanks'-filled blebs but the injection of hypoosmotic solution (water) had no clear effect. The authors conclude that osmotic differences between the subretinal space, and the vitreous and/or choroid, are rapidly equilibrated by the surrounding tissues; but the rate of bleb resorption will be affected by the size and membrane permeability of the molecules within the subretinal space. The effects of increased serum osmolality may involve not only osmotic pressure but an opening of the tight junctions of the RPE.