A synechia happens when the iris adheres to either the cornea or lens. Synechiae can be caused by ocular trauma, iritis or iridocyclitis and may lead to certain types of glaucoma. Anterior synechia causes closed angle glaucoma, which means that the iris prevents proper drainage of the aqueous. This raises the intraocular pressure. Posterior synechia also cause glaucoma, but with a different mechanism. In posterior synechia, the iris adheres to the lens, blocking the flow of aqueous humor from the posterior chamber to the anterior chamber. This blocked drainage also raises the intraocular pressure. Eyedrops to dilate your eyes, can prevent the formation of synechia. Eyedrops to lower your intraocular pressures may also be necessary.