Nonpenetrating filtering procedures: viscocanalostomy and collagen wick.

Unroofing of Schlemm's canal without entering the anterior chamber has been performed previously to lower intraocular pressure. Initial results were good, but long-term results were discouraging, and the techniques were abandoned. Recently, two variations have surfaced. Visco canalostomy is a technique devised by Robert Stegmann of South Africa. The glaucoma drainage device (Collagen Wick) was initially introduced by Koslov in Russia. These techniques are described in this article.