2 The condition, current treatments and procedure
2.1 Glaucoma is usually a chronic condition associated with elevated intraocular pressure. The commonest type of glaucoma in the UK is primary open-angle glaucoma, also known as chronic open-angle glaucoma. It leads to progressive damage to the optic nerve. Early stages are usually asymptomatic but as the condition progresses it causes visual impairment and, if untreated, blindness.
2.2 Treatment is usually eye drops containing drugs that either reduce the production of aqueous humor or increase its drainage. Surgical procedures such as trabeculectomy, drainage tubes, deep sclerectomy, viscocanalostomy or laser trabeculoplasty may also be used.
2.3 Ab interno supraciliary microstent insertion for primary open-angle glaucoma aims to increase outflow using the suprachoroidal space, without manipulating the conjunctiva and sclera or creating a filtering bleb. The procedure can be done at the same time as phacoemulsification cataract surgery, or by itself. This guidance only covers the use of ab interno supraciliary microstent insertion for primary open-angle glaucoma when it is done with phacoemulsification.
2.4 Using local anaesthesia, a small incision is made in the cornea. For the phacoemulsification, a small probe that emits ultrasound waves is inserted into the eye to break the lens into pieces. The pieces are removed and a small plastic lens is inserted. For the supraciliary microstent insertion, the anterior chamber of the eye is deepened using viscoelastic. Intraoperative gonioscopy is used to visualise angle structures. A tiny stent is put into the supraciliary space, between the ciliary body and the sclera. The microstent creates a permanent drainage channel, using the uveoscleral pathway. It directs aqueous outflow from the anterior chamber, through and around the microstent, to the suprachoroidal space.