sentences:  Bleb forming procedures include ab externo trabeculectomy and deep sclerectomy.Ab externo trabeculectomy (AET) involves cutting from outside the eye inward to reach Schlemm's canal, the trabecular meshwork, and the anterior chamber.Also known as non-penetrating trabeculectomy (NPT), it is an ab externo (from the outside), major ocular procedure in which Schlemm's canal is surgically exposed by making a large and very deep scleral flap.