Sir,
We wish to add our comments to the recent review article describing the use of trypan blue (TB) in anterior segment surgery.1 To understand its potential uses, we need some knowledge of its biochemistry. TB (C34H23N6O14S4Na4) is a negatively charged, water soluble bis-axo dye that is used in cell biology to confirm cell viability. The selectively permeable cell membrane of viable cells does not allow this ‘foreign’ chemical to enter and hence appear colourless while the uptake in dead cells results in a blue discolouration. Similarly, TB will delineate collagen type IV-rich membranes. Both these properties are utilized in ophthalmology, the former in highlighting viable cells after conjunctival brush cytology, the latter in staining the anterior lens capsule (as well as ILM and ERM tissue).2 Permanent discolouration is avoided by dilution with balanced salt solution. TB also stains poorly hydrated tissues better than well-hydrated ones explaining the contrast seen between the acellular lens capsule and the water-rich cells of the cortical lens.
Unmentioned risks include potential teratogenicity (has been associated with encephalocoele formation in animal models) and carcinogenicity (lymphoma in the rat model); both models, however, used subcutaneous injections of TB. Similarly, ocular abnormalities have been described in the pregnant murine model.3 As a cautionary measure, the risk benefit ratio should be properly assessed before proceeding with TB-assisted ophthalmic surgery in pregnant or nursing women.
References
Jhanji V, Chan E, Das S, Zhang H, Vajpayee RB . Trypan blue dye for anterior segment surgeries. Eye 2011; 25 (9): 1113–1120.
Martinez-Osorio H, Calonge M, Corell A, Reinoso R, López A, Fernández I et al. Characterization and short-term culture of cells recovered from human conjunctival epithelium by minimally invasive means. Mol Vis 2009; 15: 2185–2195.
Hoshino K, Nakane K, Kameyama Y . Influences of teratogenic agents on the manifestation of genetic malformations—effects of the maternal administration of trypan blue during pregnancy on the manifestation of genetic microphthalmia (mc) in mice. Annu Rep Res Inst Environ Med Nagoya Univ 1972; 19: 85–87.
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Khan, K., Khan, R. Why we get a blue stain. Eye 26, 335–336 (2012). https://doi.org/10.1038/eye.2011.287
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DOI: https://doi.org/10.1038/eye.2011.287