Urokinase-type plasminogen activator to prevent haze after photorefractive keratectomy, and pregnancy as a risk factor for haze in rabbits.

Abstract

To observe the effect of urokinase-type plasminogen activator (uPA) on the development of subepithelial haze after photorefractive keratectomy (PRK) and to assess pregnancy as a risk factor for haze. In 30 rabbits, both eyes of 27 were subjected to PRK and both eyes of 3 served as the nonsurgical control. In the first part of the experiment, for 7 days after PRK, three rabbits (one was pregnant) received aprotinin in one eye and no aprotinin in the contralateral eye. uPA activity was measured by a spectrophotometric method from tear samples in these eyes. In the second part, for 5 days after PRK, 24 rabbits (8 were pregnant) were treated with uPA in one eye and no uPA in the contralateral eye. Haze grading was performed according to the system of Hanna. In the first experiment, the aprotinin-treated eyes and the aprotinin-untreated eye of the pregnant rabbit showed development of haze. In the second, there were clear corneas in 24 of 24 uPA-treated eyes and in 15 of 24 uPA-untreated eyes. Post-PRK haze formed in 9 of 24 uPA-untreated eyes (7 of the 9 haze observations in pregnant rabbits). Within the uPA-untreated group, haze formed in corneas of 7 of 8 pregnant versus 2 of 16 nonpregnant rabbits. There was a strong association between the uPA treatment and clear corneas (P = 0.003) and between pregnancy and haze (P = 0.002). The present results suggest that pregnancy is a risk factor for post-PRK haze in untreated rabbit eyes and that uPA is effective in preventing the occurrence of haze.