Purchase this article with an account.
Gerd Geerling, Julie T. Daniels, John K. G. Dart, Ian A. Cree, Peng T. Khaw; Toxicity of Natural Tear Substitutes in a Fully Defined Culture Model of Human Corneal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2001;42(5):948-956.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. Serum and saliva have recently been advocated as natural tear
substitutes for intractable aqueous-deficient dry eyes, but the effects
of these fluids on corneal epithelium have not been well characterized.
A laboratory study was performed in a defined test model to compare the
toxicity of natural and pharmaceutical tear substitutes and to identify
potentially toxic factors in natural tear substitutes, such as amylase,
hypotonicity, and variations in preparation.
methods. Primary human corneal epithelial cells were cultured with defined
keratinocyte serum-free medium. The cells were incubated with
hypromellose (hydroxypropylmethylcellulose 0.3%) with and without
benzalkonium chloride 0.01%, saliva with differing osmolalities, 100%
serum, and 50% serum (1:1 vol/vol with chloramphenicol 0.5%) for
varying times and concentrations. Toxicity was examined in four ways.
Microvillous density was assessed with scanning electron microscopy.
Cell membrane permeability and intracellular esterase activity were
analyzed after staining with fluorescent calcein-AM/ethidium homodimer
and cellular adenosine triphosphate (ATP) was quantified using a
results. The toxicity ranking of the tear substitutes correlated in all assays.
The ATP assay was the most sensitive, followed by ethidium cell
permeability, and finally the esterase activity. Preserved hypromellose
was more toxic than the unpreserved preparation. Among natural tear
substitutes, natural saliva was most toxic. Isotonic saliva and 50%
serum were of similar toxicity, and 100% serum was least toxic.
Natural tear substitutes were—except for natural saliva—less toxic
than unpreserved hypromellose. Hypotonicity, but not amylase, was the
major toxic effect associated with saliva. The dilution of serum with
chloramphenicol induced toxicity.
conclusions. This is the first toxicity study using human primary corneal epithelial
cells cultured under fully defined conditions as an in vitro model.
Cellular ATP is a sensitive parameter for quantifying toxicity.
Isotonic saliva and serum offer greater therapeutic potential for
severely aqueous-deficient dry eyes than do pharmaceutical tear
This PDF is available to Subscribers Only