INCREASED RELEASE OF TENASCIN IN TEAR FLUID AFTER PHOTOREFRACTIVE KERATECTOMY

Background: Extracellular matrix protein tenascin (TN) is expressed in the anterior stroma during corneal wound healing. In this study we an alysed TN release in lear fluid after photorefractive keratectomy (PRK ). Methods: Tear fluid TN concentrations of ten PRK patients were meas ured with an immunoassay. Tear fluids were collected preoperatively an d 1, 2 and 7 days after PRK. The tear fluid collection time and the vo lume of tears collected were registered. Because tear fluid flow was g reatly increased postoperatively, tear fluid flow-corrected release (T N flux) was calculated. Results: The tear fluid flow was 4.50+/-0.94 m u l/min (mean+/-SEM) preoperatively, 55.48+/-16.70 mu l/min (P<0.01) o n the 1st, 33.91+/-7.91 mu l/min (P<0.01) on the 2nd, and 13.79+/-5.49 mu l/min (P>0.05) on the 7th postoperative day. The preoperative TN c oncentration was 0.85+/-0.20 mu g/ml. On the 1st postoperative day it decreased to 0.37+/-0.17 mu g/ml (P>0.05), most likely due to the dilu tion effect caused by hypersecretion after PRK. The TN concentration w as 0.67+/-0.12 mu g/ml (P>0.05) on the 2nd and 0.78+/-0.15 mu g/ml (P> 0.05) on the 7th postoperative day. The preoperative TN flux was 5.23/-1.88 ng/min. On the 1st and 2nd postoperative days the TN flux was 1 4.40+/-4.99 ng/min (P<0.05) and 22.66+6.12 ng/min (P<0.05), respective ly. On the 7th postoperative day a tendency towards decreased flux (14 .00+/-6.02 ng/ min, P>0.05) was observed. Conclusion: Although there i s a minor decrease in TN concentration after PRK due to increased tear fluid flow, a significant increase in TN flux was observed. Complete reepithelialization of the ablated area was observed in all eyes at th e follow-up visit on postoperative day 7.