Systemic research update of minimally invasive glaucoma surgery

Glaucoma is the leading cause of irreversible blindness worldwide.Conventional glaucoma surgeries have disadvantages like injuring the tissue of conjunctiva and sclera.Recently, there have been many new treatments called minimally invasive glaucoma surgery (MIGS) sprung up, which aims to lower intraocular pressure and reduce the use of glaucoma medications with less ocular injury.The resistance of aqueous outflow comes from both proximal and distal anatomically.The proximal resistance comes from trabecular meshwork and the inner wall of Schlemm canal (SC), while the distal resistance is decided by the outer wall of SC, aqueous vein, collector canals, episcleral veins and intrascleral venous plexus.Therefore, we could classify the MIGS by anatomical site and the mechanism to control intraocular pressure into different types.First, the MIGS acts on trabecular meshwork, which could be separated into removing proximal resistance including increasing trabecular meshwork bypass, expanding SC, cutting through trabecular meshwork and removing both proximal and distal resistance including Xen Gel Stent and PRESERFLO Microshunt.Second, MIGS procedures reduce intraocular pressure by increasing suprachoroidal drainage or by disrupting the ciliary body to reduce aqueous humor production.The MIGS expanding suprachoroidal drainage is independent of intraocular pressure level, like Cypass Micro-Stent, iStent Supra and iSTAR MINIject.The MIGS destroying ciliary body to reduce humor production include ultrasound cycloplasty, micropulse cyclophotocoagulation, and endocyclophotocoagulation.Despite MIGS can control intraocular pressure effectively in a less invasive way, close follow-ups are still necessary to see its long-term effectiveness and safety.However, the emerging implants are quite confusing to many ophthalmologists.It is especially true for Chinese surgeons as most MIGS are still under clinical trial and have not entered Chinese market.Therefore, this article summarizes the current mainstream MIGS and discussed the design and surgical outcomes of these surgeries.

Glaucoma; Minimally invasive glaucoma surgery; Intraocular pressure