Human tear fluid PDGF-BB, TNF-alpha and TGF-beta 1 vs corneal haze and regeneration of corneal epithelium and subbasal nerve plexus after PRK

The aim was to determine the association of tear fluid cytokine levels and post-PRK corneal haze evaluated by in vivo confocal microscopy, In addition , the possible association between subbasal neural regeneration and haze fo rmation, or epithelial regeneration were investigated. Twenty eyes of 20 pa tients (16 women and four men, age 30.7 +/- 7.5 years, range 21-48 years) u nderwent a myopic PRK. The spherical equivalent (SE) of the intended correc tion was -4.7 +/- 1.5 D (range -2.75 to -9.00 D). ELISA-methods were used t o assess tear fluid concentrations of TGF-beta1, PDGF-BB and TNF-alpha pre- operatively, and post-operatively on day 2 and at 3 months. Tear fluid flow in the collection capillary was recorded, and rates of cytokine release (= tear fluid now-corrected concentrations) were calculated. In vivo confocal microscopy was performed at 3 months to evaluate the corneal morphology an d to determine numerical haze estimate. There was wide interindividual vari ation between pre-operative and post-operative concentrations and rates of release of TGF-beta1, PDGF-BB and TNF-alpha. Subepithelial haze was observe d in all corneas and the mean haze estimate was 506 +/- 401 U (100-1410 U). However, no association was found between tear fluid cytokine levels and p ost-PRK haze. Regenerating subbasal nerve plexus was found in 18 out of 20 corneas; in two corneas it was absent or could not be visualized due to sub epithelial haze. The density of the subbasal nerve fiber bundles had a posi tive correlation with the epithelial thickness (Pearson correlation, r = 0. 56, P = 0.011), but not with the haze estimate or the thickness of the haze area. At 3 months post-PRK, haze could be observed in all patients. The re sults suggest that tear fluid cytokine analysis, Bs measured, may not be su itable for screening the potential candidates for haze formation. We did no t find any correlation between haze and regeneration of subbasal nerve plex us, but we demonstrated that the regeneration of subbasal nerve plexus migh t have significant influence on regulation of epithelial healing. (C) 2001 Academic Press.