Chemical and Physical Stability of Perfluorocarbons with Laser Treatment

Giant retinal tears

A giant retinal tear (GRT) is a full-thickness neurosensory retinal break that extends circumferentially around the retina for three or more clock hours in the presence of a posteriorly detached vitreous. Its incidence in large population-based studies has been estimated as 1.5% of rhegmatogenous retinal detachments, with a significant male preponderance, and bilaterality in 12.8%. Most GRTs are idiopathic, with trauma, hereditary vitreoretinopathies and high myopia each being causative in decreasing frequency. The vast majority of GRTs are currently managed with a pars plana vitrectomy; the use of adjunctive circumferential scleral buckling is debated, but no studies have shown a clear anatomical or visual advantage with its use. Similarly, silicone oil tamponade does not influence long-term outcomes when compared with gas. Primary and final retinal reattachment rates are achieved in 88% and 95% of patients, respectively. Even when the retina remains attached, however, visual recovery may be limited. Furthermore, fellow eyes of patients with a GRT are at higher risk of developing retinal tears and retinal detachment. Prophylactic treatment under these circumstances may be considered but there is no firm evidence of its efficacy at the present time.

Polar application of test substances in an organotypic environment and under continuous medium flow: a new tissue-based test concept for a broad range of applications in pharmacotoxicology

We have established a new test concept for in vitro pharmacological trials. Our model employs tissue explants to test compounds for toxicity which arises with the metabolic interactions among different cell types. Microsurgical preparation of tissue explants avoids the destruction of the organ-specific tissue architecture. Explants were mounted in tissue carriers to improve nutrition and handling of the sample. To allow for the omission of serum supplementation of the culture medium, explants were cultured under continuous medium flow. Test substances are applied considering the polar architecture of most tissues in vivo, for example, covering the apical aspect of epithelia. In principal, all tissues obtained from any species, including man, can be used in this system. A trial application was performed with vitreous body substitutes, substances used in ophthalmology. One compound had passed cell culture tests, but caused massive blood vessel deterioration in vivo. Using our test system based on the developing renal vessel system, we could confirm, within 24 hours, severe vessel damage which resembles the injury suffered by the rabbit retina. We demonstrate that an improved tissue culture assay is a suitable tool for the detection of toxicity that remained unidentified in cell culture tests.