View of iStent on a Sovereign. The iStent is barely visible to the naked eye, and is positioned below the front upper hoof of the horse on the coin. This coin measures 21mm in diameter, and the iStent is less than 1mm in length. This stent is made of titanium and is inserted into the drainage angle to help lower eye pressure. It is a less invasive type of surgery compared to trabeculectomy, with a lower risk of serious complications. Eye pressure reductions with this technique are less than with trabeculectomy however; iStent is a technique suited for those with less advanced disease.