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 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.
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.