Evaluation Of Blood Vessel Leakage By Angiography After Experimental Model Of Glaucoma Filtration Surgery

Abstract

 

Purpose:

 

The role of blood vessels in the conjunctiva during healing is not clear and the anti-fibrotic effect of an anti-VEGF drug may be due to a direct effect on tenon’s fibroblasts, inhibition of neovascularization or blood vessel leakage caused by VEGF. The aims of this study were (i) to develop a high-resolution angiography methodology to quantitatively measure the leakiness of conjunctival blood vessels during wound healing, and (ii) to examine the effect of mitomycin C and bevacizumab on blood vessel leakage.

 

Methods:

 

A rabbit scarring model of GFS was used with 5 arms (n=5) as follows: (A) bevacizumab injection (1.25 mg); (B) water sponge; (C) MMC (0.2 mg for 2 min); (D) IgG tissue tablet (1.25mg); (E) bevacizumab tissue tablet (1.25 mg). Fluorescein angiography with HRAII using an adaptive lens (f=25 mm) was developed to examine bleb blood vessel leakage at the filling phase at days 3, 10, 17, 24, 30 postoperatively. The images were analysed by Matlab software for increases in the averaged signal in designated areas (10x10 pixels) around the inserted tube and 1 mm away from the tube. The coefficient factor (k) of the averaged signal to the linear trend line was used as an indicator of leakage; with a higher coefficient factor indicating increased leakage.

 

Results:

 

Visual observation of blood vessels of the slow release bevacizumab tissue tablet group showed less leakage compared to the water sponge group at day 3 (Fig.1). Quantitative measurement showed that around the tube at day 3, the group treated water sponge had significantly higher leakage (k=10) comparing to groups treated with bevacizumab or IgG (K≈4). The MMC treated group also showed high leakage (k≈9). Low leakage was observed in all groups at day 10, 17, 24 and 30, suggesting the absence of significant neovascularization. All groups showed higher leakage around the tube compared to away from the tube suggesting ongoing vascular leakage and inflammation.

 

Conclusions:

 

HRAII can be used to evaluate the leakiness of conjunctival blood vessels. Mitomycin C and water sponge are resulted with high leakage in conjunctival blood vessels during the early phase of wound healing following GFS. Neovascularization at the resolution of the HRAII does not appear to play a major part in conjunctival wound healing.  

 

Keywords: wound healing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • vascular endothelial growth factor