Tear Turnover (TT) and corneal epithelial permeability (Pdc)

J. D Nelson, Patricial Williams

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Abstract

Purpose: TT is a measure of the affects of tear secretion, evaporation and drainage on the tear film. Pdc is a measure of the integrity of intracellular junctions and cellular membranes. TT and Pdc were determined in a group of normal subjects and in patients with keratoconjunctivitis sicca. Methods: TT and Pdc were determined simultaneous using a novel fluorophotometric method for a group of 13 normal subjects and 13 patients with keratoconjunctivitis sicca (KCS). Disodium fluorescein (DSF) was instilled into one eye and carboxy fluorescein (CF) into the fellow eye of each subject. Results: Mean TT rates for normal subjects were 21.27 ±9.15 and 21.78 ±8.88% for DSF and CF respectively. Mean Pdc values in normal subjects were 0.1868 ±0.855 and 0.1710 ±0.2509 nm/sec for DSF and CF respectively. Mean TT rates for the KCS group were 13.15 ±6.28 and 11.78 ±10.61%/min for the DSF and CF groups respectfully. Mean Pdc values in normal subjects were 0.7385 ±0.5429 and 0.4996 ±0.7590 nm/sec for DSF and CF respectively. TT rates were not correlated with age or with Pdc values. Pdc was found to increase with age and with increased corneal punctate staining. Conclusions: The mean Pdc value was 3-4 higher and the TT 38-46% lower in KCS subjects compared to normal subjects. Because individuals with KCS have a low TT and a high Pdc, they are doubly at risk for the therapeutic and toxic effects of substances introduced into their tearfilm.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996

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