Detachment Volume Research Articles

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

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. Retinal detachments were made in Dutch rabbits by injecting autologous liquefied vitreous (albumin concentration 244.11 micrograms/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 Subretinal and vitreous fluid samples were withdrawn 0 to 4 hours later and analyzed for albumin concentration (by gel electrophoresis) and osmolality.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 micrograms/ml) of fluorescein isothiocyanate albumin. When the authors made detachments using autologous liquefied vitreous, the subretinal albumin concentration increased to 333.3 micrograms/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. 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.

Formation of ellipsoidal bubbles at a free-standing nozzle

When gas is injected at high velocity into liquid, the bubbles formed at the nozzle are elongated in the direction of gas flow due to the axial momentum of the gas. In this paper, the bubble is modelled as a prolate ellipsoid growing at a nozzle which projects vertically upwards into a body of inviscid liquid. The shape of the bubble is defined in terms of axial ellipticity, as determined by an energy balance on the gas jet enclosed by the expanding envelope. The time of growth and hence the free bubble volume is derived from the familiar inertial model of bubble motion in which the bubble hydrodynamic mass is presented as a function of axial ellipticity. Theoretical predictions of bubble shape and size at the detachment stage are presented in terms of the injection number, N I , a dimensionless representation of the gas dispersion forces. There is good agreement with experimental observation of air and helium injection into water. Over a range of N I from 0.17 to 1.5 which embraces the energetic injection conditions encountered commercially, bubble ellipticity at detachment increases parabolically whereas the dimensionless bubble volume decreases steadily. The bubble detachment volume under these conditions shows a linear relationship with the gas injection rate. The implications of these findings for gas-liquid contacting and for nozzle design are briefly considered.