Abstract
Purpose :
Subretinal perfluorcarbon liquid (PFCL) bubbles have been described as adopting an omega-shape. The purpose is to understand why they all do it. The hypothesis is that the shape is determined by contact angle of 3 phases in contact with one another namely, PFCL, retina and subretinal fluid. This hypothesis in turn predicted that the surface energy of the bubbles should be associated with certain structural changes within the neurosensory retina. We further speculated that these structural changes might be exploited for a novel means of removal of PFCL from under the retina.
Methods :
In vitro experiments were carried out to examine the contact angle with droplets of PFCL of 6 different volumes resting on a surface modified PMMA under water. The aspect ratios (width/height) of the droplet profiles were measured. We also analysed all published OCT images of subretinal PFCL bubbles. A novel way of removing subretinal PFCL was tested in an ex-vivo eye-cup model using porcine retina. Three clinical cases intended for removal of subretinal PFCL are also described.
Results :
In vitro, the contact angles inside all 6 cases volumes of PFCL were obtuse. The aspect ratios of the 10,20,40,60,80 and 100 microlitres in vitro bubbles were 1.3,1.4,1.7, 1.9, 2.0 and 2.2 respectively. The aspect ratios strongly correlated with the size of the bubble, R2 being 0.976. For the published images, the mean contact angle was 127 degrees (+/-SD 11, range 108 to 145); the aspect ratios varied greatly from 0.3 to 2.5. In all cases, the retina overlying the bubble is thinned. In one clinical case, the subretinal PFCL was expelled into the vitreous cavity before removal and for the other two, perforating the retina alone enabled the bubbles to escape without aspiration. In the ex vivo retina eye cup, the use of placing PFCL in front of the retina facilitated removal of subretinal PFCL using needle puncture and without aspiration.
Conclusions :
The omega shape is determined by the contact angles of the bubbles in the suberetinal space. As the subretinal fluid is absorbed, the retina stretches and thins over the bubble putting the bubble under tension. These observations with the ex-vivo model suggest that the removal of subretinal PFCL might be facilitated by placing a large bubble of PFCL in front of the retina and a small puncture in the retina overlying the bubble without the need to use aspiration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.