Increased release of tenascin in tear fluid after photorefractive keratectomy

Extracellular matrix protein tenascin (TN) is expressed in the anterior stroma during corneal wound healing. In this study we analysed TN release in tear fluid after photorefractive keratectomy (PRK). Tear fluid TN concentrations of ten PRK patients were measured with an immunoassay. Tear fluids were collected preoperatively and 1, 2 and 7 days after PRK. The tear fluid collection time and the volume of tears collected were registered. Because tear fluid flow was greatly increased postoperatively, tear fluid flow-corrected release (TN flux) was calculated. The tear fluid flow was 4.50 +/- 0.94 microliters/min (mean +/- SEM) preoperatively, 55.48 +/- 16.70 microliters/min (P < 0.01) on the 1st, 33.91 +/- 7.91 microliters/min (P < 0.01) on the 2nd, and 13.79 +/- 5.49 microliters/min (P > 0.05) on the 7th postoperative day. The preoperative TN concentration was 0.85 +/- 0.20 microgram/ml. On the 1st postoperative day it decreased to 0.37 +/- 0.17 microgram/ml (P > 0.05), most likely due to the dilution effect caused by hypersecretion after PRK. The TN concentration was 0.67 +/- 0.12 microgram/ml (P > 0.05) on the 2nd and 0.78 +/- 0.15 micrograms/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 14.40 +/- 4.99 ng/min (P < 0.05) and 22.66 +/- 6.12 ng/min (P < 0.05), respectively. On the 7th postoperative day a tendency towards decreased flux (14.00 +/- 6.02 ng/min, P > 0.05) was observed. Although there is 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 the follow-up visit on postoperative day 7.