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Progresses in Chromovitrectomy

Eduardo B. Rodrigues¹, M. E. Farah², C. H. Meyer³, S. Mennel⁴, M. Maia²
(¹Florianopolis, ²Sao Paulo, ³Bonn, ⁴Marburg)

Background: Chromovitrectomy facilitated intra-operative identification of fine pre-retinal membranes and tissues. Progresses in chromovitrectomy may enable discovery of new dyes with better safety profile and with new tissue-affinity properties. In addition, improved techniques may enable minimization of concentration of dye in contact with the retina. Methods: 1. To evaluate the retina toxicity of two doses 0.05 % and 0.5 % of six novel dyes for chromovitrectomy in rabbits eyes: light green (LG), fast green (FG), evans blue (EB), brilliant blue (BriB), bromophenol blue (BroB) or indigo carmine (IC); 2. To evaluate the staining affinity of LG, FG, EB, BriB, and BroB to the ILM, ERM, and vitreous in animals and human donor eyes; 3. To investigate the overlap of light irradiance of vitrectomy light sources in comparison to light absorbance of vital dyes; 4. To analyze the osmolarity and pH of nine vital dyes; 5. To describe a technique to paint epiretinal membranes with vital dyes. Results: 1. Histology examination disclosed slight focal retinal changes in eyes exposed to 0.05% LG, IC, FG, BriB, and BroB, similar to the control. At the higher dose of 0.5 %, BroB, LG and EB promoted cellular edema and vacuolization within the ganglion and bipolar cells, whereas 0.5 % FG and IC caused slight retinal alterations similar to BSS injection. Intravitreal injection of 0.5 % EB caused significant loss of neuroretinal cell counts in comparison to control eyes (p<0.05). 2. BriB possesses best staining affinity to ILM, while BroB, EB and LG may also stain the ILM. Most vital dyes bind to vitreous and cellular ERM. 3. Spectrophometry analysis revealed that most vital dyes except ICG have remarkable overlap with every available vitrectomy light source at absorbance from 550nm to 680nm. Overlap of irradiance of endoillumination fiberoptics and absorbance of vital dyes was greater in Grieshaber GLS and Alcon Accurus H3. Photon 2 had the lower overlap area among all light sources; 4. Osmolarity of all nine dyes diluted in water decreased to very low value ranging from 0 to 54 mOsm, while dilution in BSS and glucose promoted small but clinically relevant changes in osmolarity and pH in ranges from 260 to 340mOsm. 5. The use of the VINCE may allow fine epiretinal painting. Conclusions: Novel vital dyes possess much variable properties in toxicity, staining affinity, osmolarity and pH, which may influence their retinal biocompatibility. Intra-operative light exposure during chromovitrectomy should be minimized. The progressive order of retinal biocompatibility of novel dyes, from safest to most toxic, was IC, FG, BriB, BroB, LG, EBs.

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