Increased release of tumour necrosis factor-alpha in human tear fluid after excimer laser induced corneal wound

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Abstract
AIMS To measure the pre- and postoperative tear fluid tumour necrosis factor-α (TNF-α) concentration and release in patients undergoing excimer laser photorefractive keratectomy (PRK). METHODS Tear fluid samples from 18 PRK patients were collected with scaled microcapillary tubes preoperatively (day 0), on the second (day 2), and on the seventh (day 7) postoperative days. The TNF-α concentration was measured using a double antibody radioimmunoassay, and the TNF-α release was calculated by multiplying the concentration by the tear fluid flow in the collection capillary. RESULTS The mean tear fluid flow in the capillary was 22.5 μl/min (range 1.5–93.2) on day 0, 80.7 μl/min (3.0–219, p = 0.0002) on day 2, and 14.6 μl/min (1.8–41.7, NS) on day 7. The mean TNF-α concentration and release values were: day 0, 358 ng/l (110–680) and 9.5 pg/min (0.2–37.5, NS); day 2, 417 ng/l (< 5–750, NS) and 28.6 pg/min (0.6–81.5; p = 0.003); and day 7, 320 ng/l (< 5–735, NS) and 4.8 pg/min (0–25.4, NS), respectively. CONCLUSION TNF-α appears to be a component of normal tear fluid. In spite of hypersecretion caused by the corneal wound, TNF-α concentrations remain constant during wound healing. TNF-α release increases significantly during the 2 postoperative days following PRK, suggesting a role in corneal wound healing.