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P. B. Henrich, S. Priglinger, T. Josifova, P. C. Cattin; Staining of the Internal Limiting Membrane With Brilliant Blue G Yields Lower Contrasts Than Staining With Indocyanine Green. A Quantitative Assessment. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3599.
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© ARVO (1962-2015); The Authors (2016-present)
To describe an objective method for the measurement of contrast strengths as they appear to the surgeon's eye during vitreo-retinal surgery and to report that Brilliant Blue G provides weaker contrasts during Chromovitrectomy than Indocyanine Green.
In a retrospective pilot study, we analyzed the intra-operative videos of 13 consecutive chromovitrectomies, recorded on a Medlife Trio Digital Camera and a Medlife Mind Stream Digital Recorder attached to an Opmi Visu 200 Ophthalmic Microscope (all Carl Zeiss Meditec, Jena, Germany). At the beginning of each intervention, exposure and color calibration alignments were performed (XpoBalance®, Lastolight Ltd., Coalville, Leics, United Kingdom). For intra-operative staining of the ILM, either Indocyanine Green (ICG, 1.25mg/ml) or Brilliant Blue G (BBG, 0.25mg/ml) had been applied at the surgeon’s discretion (BBG in 6, ICG in 7 cases). Main outcome measure was the recognizability of ILM staining strength compared to remaining retina. The perceived color contrast in the videos was determined in the CIE 1976 (L*,a*,b*) color space. This color space is perceptually uniform, i.e. the MacAdam ellipses have a uniform circular shape, and changes of the same visual importance produce the same amount (Euclidean distance) in the color space. To ensure invariance to different lighting, caused for example by the vignetting artifact, the Euclidean distance was only calculated over the chromaticity components a* and b*, neglecting the lightness L*. The perceived color difference was averaged over regions of interest defined by the surgeon. Statistical analyses was performed with the software package R. Normality of the distributions was tested with the Kolmogorof-Smirnov test and a p-value <0.05 was considered statistically significant.
Chromaticity diagram analysis showed a significantly (p<0.05) higher contrast recognizability for ILMs stained with ICG than for those stained with BBG. The chromaticity difference in the CIE LAB color space between stained ILM and the unstained retina was 7±5 for BBG and 19±7 ICG.
BBG is the only approved vital dye which selectively stains the ILM. While both BBG and ICG provide reproducible and clinically useful staining of the ILM, ICG yields a significantly more well-discernible contrast between the ILM and the unstained retina.
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