TEAR FLUID CELLULAR FIBRONECTIN LEVELS AFTER PHOTOREFRACTIVE KERATECTOMY

BACKGROUND: Fibronectin is supposed to have an important role in wound healing. The extradomain A-containing cellular fibronectin (EDAcFn) r efers to fibronectin, which instead of being a hepatocyte derived comp onent of blood plasma or body fluids, is produced locally. The present study was undertaken to clarify the possible changes in excretion of EDAcFn in tears following excimer laser photorefractive keratectomy (P RK). METHODS: An immunoassay was used to determine EDAcFn concentratio ns in human tear fluid samples of 11 eyes after PRK. Tear fluids were collected with scaled microcapillaries preoperatively as well as 1, 2, and 7 days after PRK. The time used to collect a known volume of tear s was registered. This was done to estimate the dilution effect relate d to the hypersecretion of tears after PRK. RESULTS: The mean preopera tive tear fluid EDAcFn concentration was 0.28 +/- 0.07 ng/mul with a w ide range (0.05 to 0.63). The tear fluid flow-corrected excretion of E DAcFn was 1.36 +/- 0.35 ng/min (range, 0.145 to 3.50). There was a sig nificant increase in both postoperative tear fluid flow and excretion of EDAcFn on days 1 and 2. The elevation of the mean EDAcFn concentrat ion did not decrease in spite of reflex tearing. The mean excretion of EDAcFn in tears was 28-fold on the first and 17-fold on the second po stoperative day. Normal level was reached by day 7. CONCLUSION: There is a rapid increase in excretion of EDAcFn in tears following PRK. Thi s seems to last only as long as an epithelial defect persists. The epi thelium of all eyes healed in 3 to 4 days in spite of wide interindivi dual variation in both tear fluid flow and EDAcFn excretion.