Early Intra Ocular- Pressure Control Using Aqueous Suppressive Agents After Ahmed Glaucoma Valve Implantation

The AGV implant is designed to open when the IOP is between 8 mmHg and 10 mmHg, and thus maintains an IOP of 8 mmHg or higher. In the early period after glaucoma drainage device (GDD) surgery the intraocular pressure (IOP) classically goes through 2 phases. The hypotensive phase occurs immediately after surgery, lasts around 1 week. This is followed by the hypertensive period where the IOP tends to rise steadily above 21mmhg.

The hypertensive response seems to occur more commonly after Ahmed GDD surgery than nonvalved implants, It was reported to occur in 40% to 80% of cases. Although the hypertensive phase can last as long as 6 months it is usually during the first 1 to 4 weeks, when there is intense congestion of the bleb wall, that IOP is highest.

Previous study showed that when aqueous comes into contact with conjunctiva and Tenon's capsule,an inflammatory reaction occurs.Factors such as prostaglandins, eicosanoids, tissue growth factor beta (TGF β)has been shown to occur in glaucomatous aqueous. These mediators induce an inflammatory reaction, and if excessive, will result in fibrosis and poor functioning of the bleb. High pressure within the bleb also results in the secretion of TGF β by the bleb lining. It may result in inflammation of the bleb wall and subsequent fibrosis and poor bleb function. The investigators supposed that with early use of aqueous suppressant medication after AGV implantation, the concentration of inflammatory mediators decreased in subconjunctival space and may lead to better IOP control after shunt surgery.