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 analysed TN release in tear fluid after photorefractive keratectomy (PRK). • Methods: 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. • Results: The tear fluid flow was 4.50±0.94 μl/min (mean±SEM) preoperatively, 55.48±16.70 μl/min (P 0.05) on the 7th postoperative day. The preoperative TN concentration was 0.85±0.20 μg/ml. On the 1st postoperative day it decreased to 0.37±0.17 μg/ml (P>0.05), most likely due to the dilution effect caused by hypersecretion after PRK. The TN concentration was 0.67±0.12 μg/ml (P>0.05) on the 2nd and 0.78±0.15 μg/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) was observed. • Conclusion: 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.