Selective ILM Staining and Safety of Two Vital Dyes During a Human-Like Pars Plana Vitrectomy Ex Vivo in Porcine Eyes

Purpose: An ideal dye for intraocular use should effectively stain the target tissue while being easy to apply and remove. Additionally, it should not have any adverse effects resulting from prolonged contact with the retinal tissue. Recently, concerns have been raised about the safety of some vital dyes during surgical procedures as they may cross the internal limiting membrane and deposit on the retina. In this study, we aimed to investigate whether commercially available vital dyes, VIEW-ILM (R) and TWIN (R) (AL.CHI.MI.A. S.r.l., Ponte San Nicolo, Padova, Italy), have the potential to cross the internal limiting membrane during vitreoretinal surgery and deposit on the retina. Furthermore, we evaluated their safety in vitro and in vivo. Methods: A human-like pars plana vitrectomy was performed on porcine eyes ex vivo, with VIEW-ILM (R) or TWIN (R) used to stain the internal limiting membrane either with or without subsequent internal limiting membrane peeling. The two dyes were then extracted from retinal punches with or without internal limiting membrane, and quantified using high performance liquid chromatography. Safety was evaluated through in vitro cytotoxicity tests and in vivo skin sensitization and irritation tests according to ISO standards. Results: High performance liquid chromatography analyses demonstrated that VIEW-ILM (R) and TWIN (R) effectively stained the internal limiting membrane without crossing the membrane. No residual dyes were found in the retinal layers after internal limiting membrane removal. Furthermore, both in vitro and in vivo safety tests confirmed the absence of cytotoxicity, skin sensitization, and irritation. Conclusion: The results of this study support the safety and efficacy of VIEW-ILM (R) and TWIN (R) for internal limiting membrane staining. The experimental protocol described in this study could be utilized to gain a comprehensive understanding of the characteristics of vital dyes.