The Scientific Basis of the EYTEX™ System

Abstract

The EYTEX™ system is an in vitro method for predicting in vivo ocular irritation via a target biomacromolecular approach. EYTEX™ uses changes of relevant macromolecules upon exposure to chemicals and formulations to predict in vivo irritancy and toxicity endpoints.The EYTEX™ system is based on alterations in the conformation and hydration of an ordered macromolecular matrix. An oligomeric protein with a molar mass of approximately 300,000g/mol is the major active component of the reagent. This oligomer, characterised by 12 subunits, associates itself into strands which are then incorporated into a gel network. This network also includes smaller proteins, peptides, amino acids, aminoglycans and mucopolysaccharides, which contribute to the overall response of the macromolecular matrix to a diverse array of test compounds, such as acids, bases, salts, solvents, surfactants, lubricants, preservatives, emulsions, dyes, amines, amides and many others. The method has been extensively evaluated using chemicals and formulations from diverse classes and with different ranges of toxicity, representing various mechanisms of ocular toxicity. Results using the in vitro test correlate broadly with the Draize in vivo eye irritancy test results. Quantification of the EYTEX™ method is based on measurement of changes in optical density of the matrix, which are sensitive to the conformation and hydration of protein, as well as the order in the matrix. These changes, which occur when the matrix is exposed to chemicals and formulations, can be used to predict in vivo ocular irritancy. Calibrators and controls provide assay standardisation with a 4–8% coefficient of variation. Multiple dose and time variables relating to irritancy potential can be assessed and compared with Draize in vivo results. The EYTEX™ system provides a comprehensive set of four protocols suitable for analysing chemicals and formulations with varying degrees and mechanisms of ocular irritancy.