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A Csutak, DM Silver, J Tózsér, Z Hassan, A Berta; Urokinase-type Plasminogen Activator to Prevent Haze After Photorefractive Keratectomy and Pregnancy as a Risk Factor for Haze in Rabbits . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4233.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: 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. Methods: Both eyes of 24 rabbits underwent PRK surgery (6D spherical correction, 68 micron ablation depth): 8 of the rabbits were pregnant. Animals were handled and treated in adherence to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. One eye of each of 24 rabbits was treated with 1 drop of antibiotic containing 50 IU/ml uPA, hourly on the first day after PRK and five times a day for the next 4 days. The 24 contralateral eyes were treated with the same antibiotic eyedrop regimen after PRK, but without uPA. From the fifth post-operative day, both eyes were treated equally with antibiotic drops. Tear samples were collected before and after PRK and plasminogen activator activity (PAA) in the tear samples was measured by a spectrophotometric method using human plasminogen and chromogenic peptide substrate S-2251. Haze grading was performed using the system of Hanna. The Yates' correction for the chi-squared test was used to test for associations between prognostic outcomes. Results: None of the uPA-treated eyes developed haze, while 38% of the contralateral untreated eyes developed haze. Clear corneas were found in 24 out of 24 uPA-treated eyes (8 of the 24 were in pregnant rabbits) and in 15 out of 24 untreated eyes (1 of the 15 was in a pregnant rabbit). Post-PRK haze (grade 1) formed in 9 out of 24 untreated eyes (7 of the 9 haze observations were in pregnant rabbits). Within the untreated group, haze formed in corneas of 7 out of 8 pregnant versus 2 out of 16 non-pregnant rabbits. There is a strong association between the uPA treatment and clear corneas (p=0.003) as well as pregnancy and haze (p=0.002). Surface epithelial roughness but no haze was observed in 1 uPA-treated eye and in 1 untreated eye (neither rabbit was pregnant). Relative PAA followed patterns seen in previous studies. Conclusion: 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 incidence of haze.
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