An ophthalmic microsurgical system is described for treatment of eye diseases, such as glaucoma, using minimally invasive surgical techniques. The microsurgical system includes a thin walled outer sheath microcannula 1 slidably disposed about an inner member 4, which extends slightly beyond the distal end of the microcannula 1. The inner member 4 may be straight or curved and may optionally include a surgical instrument and/or a sensor or signaling beacon. The microsurgical system is used in a surgical procedure for opening Schlemms Canal to provide drainage of aqueous fluid in order to relieve excess intraocular pressure that results from glaucoma and other diseases of the eye.