Mechanical properties of the rabbit cornea during wound healing after treatment with epidermal growth factor

To determine whether epidermal growth factor (EGF) accelerates the healing of corneal tissue, we measured the tensile strength, ductility (total deformation at rupture) and toughness of 60 rabbit corneas with 7-mm perforating wounds after topical treatment with EGF or saline for 8, 13 or 23 days. The three mechanical properties were measured using corneal strips mounted on an Instron tensometer. A traction speed of 5 cm/min was chosen from speed-response curves for the three measures of interest. Since the values for eyes of a single rabbit were correlated, we used the data for one eye, selected at random, from each animal in the data analysis. EGF enhanced tensile strength (p = 0.003) and toughness (p = 0.03) of corneas without reducing ductility. The difference in tensile strength and toughness between EGF- and saline-treated corneas was more striking at 8 and 13 days than at 23 days. Histologic studies at 13 and 23 days supported these observations: at 13 days the healing process was more advanced in EGF-treated corneas, whereas at 23 days no histologic differences were noted. We conclude that EGF accelerates wound healing in rabbit corneas with perforating wounds without reducing ductility of the corneal tissue.