Trityl dyes patent blue V and brilliant blue G - clinical relevance and in vitro analysis of the function of the outer blood-retinal barrier.
The use of vital dyes during vitrectomy allows easier removal of less recognizable structures like epiretinal membranes or the internal limiting membrane (ILM). In recent years, numerous studies have investigated the use of indocyanine green (ICG), trypan blue (Membrane Blue), triamcinolone, autologous blood and presently trityl dyes such as patent blue V (PBV, Blueron), crystal violet and brilliant blue G (BBG, Brilliant Peel) in chromovitrectomy. Reports on potential risks of these dyes, especially ICG, such as reduced visual acuity, possible visual field defects or alterations of the retinal pigment epithelium (RPE) limited their application. A systematic review of the literature up to July 2007 was performed using Medline (http://www.ncbi.nlm.nih.gov/ PubMed/) where we specifically searched for relevant information regarding the laboratory as well as clinical use of PB and BBG. To evaluate the effect of PB and BBG on the RPE, PB and BBG have been added to an in vitro model of the outer blood-retinal barrier to assess dye-associated barrier properties. Two concentrations of PB (2.4 and 1.2 mg/ml) and BBG (0.25 and 2.4 mg/ml) were investigated. To simulate in vivo conditions of a fluid-filled eye and an air-filled eye the dyes were added either to the culture medium or directly to the RPE cells where they remained for 2.5 min. To determine barrier properties, transepithelial resistance (TER) was measured at 3 days of follow-up. Ultrastructural integrity of RPE cells was evaluated by transmission electron microscopy. Following application of PB, barrier properties in the fluid- as well as in the air-filled eye showed only mild, transient and no significant decrease in TER. BBG did not cause a breakdown of the outer bloodretinal barrier at the concentration of 0.25 mg/ml in the model of the fluid-filled eye. The concentration of 2.4 mg/ml in the model of the fluid-filled eye as well as both concentrations in the model of the air-filled eye showed a minor decrease after 1.5 h, which was no longer observed after 24 h. Transmission electron microscopy did not show any dye-associated ultrastructural alterations to the RPE cells. In clinical use, PB showed only mild staining of epiretinal membranes and moderate staining of the ILM. Although BBG did not stain epiretinal membranes, it represents an appropriate candidate for the future, as BBG has a high affinity for the ILM. The use of trityl dyes in the posterior eye segment seems to be safe concerning damage to the RPE and its barrier function, especially when the dye is applied to the fluid-filled eye.
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