PLATELET-DERIVED GROWTH FACTOR-BB (PDGF-BB) IN TEAR FLUID - A POTENTIAL MODULATOR OF CORNEAL WOUND-HEALING FOLLOWING PHOTOREFRACTIVE KERATECTOMY

Purpose. To measure the pre- and postoperative tear fluid platelet-der ived growth factor-BE (PDGF-BB) concentrations of patients undergoing excimer laser photorefractive keratectomy (PRK). Methods. Tear fluid s amples from PRK patients were collected with scaled microcapillary tub es preoperatively (Day 0, N = 23), on the second (Day 2, N = 24) and o n the seventh (Day 7, N = 14) postoperative days. The PDGF-BB concentr ation was measured using a sandwich enzyme immunoassay, and the PDGF-B B release was calculated by multiplying the concentration by the tear fluid flow in the collection capillary. Results. The mean tear fluid f low in the capillary was 17.4 mu l/min (range 1.4-55.0) on Day 0, 62.6 mu l/min (4.3-125.0, p = 0.0000) on Day 2, and 15.5 mu l/min (1.2-50. 0, NS) on Day 7. Seventeen percent (4/23) of the Day 0 samples contain ed detectable concentrations of PDGF-BB (range 95-1330 ng/l). On Day 2 all (24/24) tear samples showed significantly increased concentration s (mean 507 ng/l, range 45-2280 ng, p = 0.0001) and releases (mean 27. 6 pg/min, range 1.0-98.0; p 0.0000). On Day 7 PDGF-BB was still measur able in 9/14 samples (mean concentration 194 ng/l, range <5-925 ng/l, and mean release 1.9 pg/min, range 0.04-6.8 pg/min). Conclusions. PDGF -BB is an inducible component of tear fluid. In spite of hypersecretio n caused by the corneal wound, PDGF-BB concentrations raised significa ntly during the initial wound healing. Increased PDGF-BB release durin g the two postoperative days following PRK suggests a role in corneal wound healing.