Endothelial wound-healing of monkey cornea: fluorophotometric and specular microscopic studies

Abstract

The process of wound-healing in the corneal endothelium after transcorneal freezing was studied in the monkey, using the techniques of fluorophotometry, pachymetry and specular microscopy. After intramuscular injection of fluorescein, the dye exchange between the cornea and aqueous humor was studied by fluorophotometry and the results were analyzed on the basis of a two-compartment model: the transfer coefficient (kac) and the distribution ratio of the dye between the aqueous humor and the cornea (rac) were calculated, and the endothelial permeability coefficient (Kac) was computed using the thickness of the corneal stroma. The corneal thickness was measured at its center (CT) with a modified pachymeter. The endothelial cell morphometry was carried out at the central cornea using a wide-field contact-type specular microscope and a computerized image analyzer: the mean cell size (CS) was calculated. The values of Kac, kac, rac, CT and CS in 16 normal uninjured corneas were 3.35 +/- 0.91 X 10(-4) cm min-1, 0.56 +/- 0.15 hour-1, 0.60 +/- 0.17, 0.40 +/- 0.02 mm and 290 +/- 35 micron2, respectively (mean +/- SD). The values of Kac, CT and CS increased markedly after freezing and decreased gradually with passage of time. The Kac and CT recovered to normal level by the 6th and 4th week after freezing, respectively. The positive significant correlation was found between the values of Kac and CT (r = 0.84, P less than 0.001), and between those of kac and CT (r = 0.58, P less than 0.001). On the contrary, no significant correlation was found between Kac and CS. The CS did not recover completely and remained about 32% larger than the values of the normal eyes even 30 weeks after freezing. Transmission and scanning electron microscopy of the endothelium revealed that the junctional complexes were reformed soon after the endothelial cells had made contact with each other, and the complexes became almost normal about 4 weeks after freezing. Normalization of the junctional complexes appeared to coincide with recovery of the Kac and CT.