Purchase this article with an account.
Y Guo, C Begley, D Renner, G Wilson; Methods for Quantifying Minor Irritancy To The Human Corneal Surface . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1684.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Traditional methods of assessing eye irritancy rely on animal models and alternative in vitro methods. We assessed the ability of two in vivo techniques to quantify the response of human corneas to minor irritancy. Method: Two different insults to the corneal surface of 10 normal human subjects were investigated: local surface drying produced by voluntarily holding the eye open, and the instillation of benzalkonium chloride (0.01% BAC). Sodium fluorescein staining of the cornea was monitored and surface cells were collected using soft contact lensed with four insertions and removals. Both nucleated cells and cell structures without stainable nuclei (ghosts cells) were counted using acridine orange and Hoechst. The percent of corneal surface staining was quantified by image analysis of individual video frames using a MATLAB program. Results: Corneal surface staining with fluorescein ranged from 0% to 5% of the corneal surface. Image analysis of even small amounts of surface fluorescein staining was possible over the entire corneal surface in a single image. The technique was limited by (1) potential errors in calculating the percent staining using a flat image of a curved surface, (2) autofluorescence of the crystalline lens. Greater amounts of fluorescein nucleated cells were higher initially, but decreased with time. Nucleated cell counts (total for four collections) varied from 10 to 157 in BAC eyes, and from 82 to 256 for the eyes that were held open. Cell ghosts were always present, however, their number was not correlated with the number of nucleated cells. Conclusion: BAC and exposure produced corneal fluorescein staining and increased cell counts, which can be used to quantify the minor irritancy of surface drying or slight toxicity. The non-invasive techniques of image analysis of fluoresein staining and cell counts may be useful for assessing minor eye irritancy to the corneal surface of human eyes.
This PDF is available to Subscribers Only