What is actually stained by rose bengal?
R. P. Feenstra and S. C. Tseng
Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, FL 33101.
It has been believed that 1% rose bengal does not stain normal, healthy
cells but rather stains degenerated or dead cells and mucous strands. In
contrast to this conventional knowledge, we discovered that both commercial
additive-containing and additive-free rose bengal solutions stained four
different types of healthy cultured cells, including rabbit corneal
epithelial cells. Rose bengal staining was rapid, dose dependent,
predominantly nuclear, and detectable with the naked eye at concentrations
as low as 0.05% and 0.025% for the commercial additive-containing or
additive-free solutions, respectively, and with the fluorescence microscope
at a concentration of 0.001%. It is surprising to discover that rose bengal
is not a vital dye; after staining, cells actually lost vitality, as
evidenced by instant morphologic changes, subsequent loss of cellular
motility, cell detachment, and cell death. Such an intrinsic toxic effect
was augmented by light exposure. The rose bengal staining of live as well
as detergent-treated (Triton X-100) cells could be blocked by such tear
components as mucin and albumin, suggesting that normally negative rose
bengal staining is due to the protective function of the preocular tear
film, ie, staining is not dictated by lack of cell vitality. These data
indicate that rose bengal staining ensues whenever there is poor protection
of surface epithelium by the preocular tear film; this represents a new
interpretation for rose bengal stains seen in various ocular surface
disorders.
