|Title||DIURNAL VARIATION AND VIABILITY OF CORNEAL SURFACE CELLS COLLECTED USING A SOFT CONTACT LENS|
|Author, Co-Author||Jie Zhou, Carolyn Begley, Graeme Wilson|
|Abstract|| PURPOSE: Previous investigators have demonstrated a diurnal variation in the numbers of ocular surface cells shed from the human cornea using an irrigation chamber. This investigation utilized soft contact lenses to collect corneal surface cells from both eyes of subjects to examine total numbers and cell viability.
METHODS: Corneal cells were collected from 6 subjects using NewVues lenses worn for 10 minutes, every 3 hours during one day. Viability counts were performed on a portion of the sample using two fluorescent probes, calcein AM and ethidium homodimer, viewed by epi-fluorescence microscopy. Calcein AM fluoresces green, indicating intracellular esterase activity in living cells. Ethidium homodimer is a nucleic acid stain that does not penetrate intact plasma membranes, and thus damaged or dead cells show red nuclear fluorescence. The remaining sample was filtered, stained with 1% toluidine blue, and counted using light microscopy.
RESULTS: Corneal cell collection using soft contact lenses demonstrated a statistically significant diurnal variation in total (p=0.0093), living (p=0.0279), and dead (p=0.0079) cell counts. The largest number of cells were collected in the morning and evening, and the lowest at mid-day. Total cell counts ranged from 38-324 cells/sample. On the average, living cells constituted 16% of the total sample, and dead cells 49%. 35% of cells showed red nuclear and green cytoplasmic fluorescence indicating metabolic activity in conjunction with membrane permeability. There was also a high correlation between the eyes in total (r=0.863;p=0.0001), living (r=0.615;p=0.0004), and dead cell (r=0.702;p=0.0001) counts.
CONCLUSIONS: This technique allows the collection of large numbers of corneal cells which could be used as a 'biopsy' of the cornea in disease conditions. In addition, the high correlation between the eyes in corneal cell shedding rates, and the diurnal variation in cell numbers, suggest a biological control of cel
|Affiliation of Co-Authors|