Minimally invasive glaucoma surgery

Micro-invasive glaucoma surgery (MIGS) is the latest advance in surgical treatment for glaucoma, which aims to reduce intraocular pressure by either increasing outflow of aqueous humor or reducing its production. MIGS comprises a group of surgical procedures which share common features. MIGS procedures involve a minimally invasive approach, often with small cuts or micro-incisions through the cornea that causes the least amount of trauma to surrounding scleral and conjunctival tissues. The techniques minimize tissue scarring, allowing for the possibility of traditional glaucoma procedures such as trabeculectomy or glaucoma valve implantation (also known as glaucoma drainage device) to be performed in the future if needed. Micro-invasive glaucoma surgery (MIGS) is the latest advance in surgical treatment for glaucoma, which aims to reduce intraocular pressure by either increasing outflow of aqueous humor or reducing its production. MIGS comprises a group of surgical procedures which share common features. MIGS procedures involve a minimally invasive approach, often with small cuts or micro-incisions through the cornea that causes the least amount of trauma to surrounding scleral and conjunctival tissues. The techniques minimize tissue scarring, allowing for the possibility of traditional glaucoma procedures such as trabeculectomy or glaucoma valve implantation (also known as glaucoma drainage device) to be performed in the future if needed. Traditional glaucoma surgery generally involves an external (ab externo) approach through the conjunctiva and sclera; however, MIGS procedures reach their surgical target from an internal (ab interno) route, typically through a self-sealing corneal incision. By performing the procedure from an internal approach, MIGS procedures often reduce discomfort and lead to more rapid recovery periods. While MIGS procedures offer fewer side effects, the procedures tend to result in less intraocular pressure (IOP) lowering than with trabeculectomy or glaucoma tube shunt implantation. Glaucoma is a group of eye disorders in which there is a chronic and progressive damage of the optic nerve. Increased intraocular pressure (IOP) is the main and only modifiable risk factor, attributed to the progression of the disease. During the last 25 years, glaucoma management has been based in the use of pharmaceutical therapies and incisional surgery. MIGS procedures can provide the patient sustained IOP reduction while minimizing the risk and complications associated with glaucoma interventions and decrease the dependence of glaucoma medications. MIGS procedures offer an excellent safety profile, with minimal incidence of complications, especially when compared with other forms of glaucoma surgery. MIGS objective, like all glaucoma surgeries, is to achieve lowering of IOP by either increasing aqueous humour outflow, the fluid that is produced by the eye and fills the space between the cornea and the lens, or decreasing the production of aqueous humour. MIGS can be divided in procedures that lower IOP by using micro-stents and minimally invasive procedures. The iStent Trabecular Micro-Bypass Stent, or simply iStent, is the smallest implantable medical device, designed to lower intraocular pressure by facilitating trabecular outflow of aqueous fluid. The trabecular outflow is one of the major outflow pathways for aqueous humor in the eye and has been the target of both pharmaceutical and surgical therapeutic approaches in glaucoma. The 1-millimeter long iStent is a titanium device inserted via an internal approach through the trabecular meshwork into Schlemm’s Canal, bypassing the trabecular meshwork and facilitating flow of aqueous from the eye. Studies have shown that the iStent is an effective procedure, typically lowering intraocular pressure to the mid-teens. The iStent is the first MIGS device to get FDA approval for implantation in combination with cataract surgery. The device has also been shown to offer better IOP control than cataract surgery alone up to one year of follow-up in a large randomized controlled FDA study, although the effectiveness was significantly reduced by 2 years. Safety of the iStent was comparable to cataract surgery alone which is much better than conventional trabeculectomy. Common complications include failure to implant the device, touching the iris with the device, and touching the undersurface of the cornea (endothelium) with the device. Multiple studies have since confirmed the MIGS-type efficacy and safety profile of the iStent. To address the reduced effectiveness at 2 years, some studies have been performed with multiple iStents.