Minimally invasive glaucoma surgeries

Glaucoma is an optic neuropathy leading to permanent blindness when poorly treated. The main risk factor is increased intraocular pressure. This is linked to a pathology of the aqueous humor drainage filter, the trabecular meshwork, whose access is blocked in the case of angle-closure glaucoma or pathological and fibrosed in the case of open-angle glaucoma, the most common. The only treatment for glaucoma is based on pressure reduction, which can be achieved through medications, laser, or surgery. The standard surgery is trabeculectomy, which involves removing the trabecular meshwork and the sclera to allow the aqueous humor to drain into a virtual external space between the sclera and the conjunctiva. This surgery has proven its effectiveness but still presents a relatively high number of intraoperative or postoperative risks. To reduce these risks, so-called minimally invasive surgeries have been developed over the last fifteen years. Trabeculectomy-type evacuation surgeries are now performed by inserting microtubes either internally or externally. In both cases, this surgery reduces the surgical risk, particularly hemorrhagic risk, and is faster and more standardized. However, the presence of aqueous humor outside the scleral wall in a space called the filtration bleb exposes the patient to a number of complications, the main one being failure with pressure rise due to progressive fibrosis of the evacuation site. Despite all surgical and pharmacological efforts, the recurrence of ocular hypertension after surgery unfortunately remains a poorly resolved problem. However, an alternative to evacuation surgery has been developed in parallel: trabecular surgery, which consists of opening the trabecular meshwork and access to Schlemm's canal to restore filtration by the natural emunctories. It is therefore a very low-traumatic surgery almost exclusively combined with cataract surgery because access to the canal is facilitated and the main studies have demonstrated the superiority of minimally invasive trabecular surgery compared to spontaneous pressure lowering after cataract surgery. Techniques may include the placement of micro-shunts such as stents, of variable size, or a simple opening, particularly by Excimer laser. These are already well-validated technologies that have largely changed the surgical landscape of glaucoma and improved its overall prognosis by reducing the risk of complications. All of these surgeries are grouped under the umbrella term minimally invasive glaucoma surgeries or MIGS.