Minimally Invasive Glaucoma Surgery (MIGS) represents a significant advancement in treating glaucoma, a condition that damages the optic nerve. These procedures use microscopic equipment and tiny, self-sealing incisions, typically made through the cornea. The primary objective of MIGS is to safely lower the pressure inside the eye (intraocular pressure or IOP), which is directly linked to optic nerve damage. Unlike conventional surgeries, MIGS procedures are designed to minimize tissue disruption and surgical trauma.
The “minimally invasive” aspect refers to the smaller surgical footprint compared to procedures like trabeculectomy, which require larger incisions and more extensive anatomical alteration. MIGS uses an ab interno approach, meaning the surgeon accesses the target area from inside the eye. This preserves the outer layers of the eye, such as the conjunctiva and sclera, which reduces the risk of complications. Preserving this tissue also maintains the option for more traditional surgeries later if the glaucoma progresses.
Understanding Glaucoma and Intraocular Pressure
Glaucoma is a group of eye conditions that progressively injure the optic nerve, the bundle of nerve fibers that transmits visual information to the brain. This damage leads to blind spots and, if left untreated, can result in irreversible vision loss. The most important modifiable risk factor for this damage is elevated intraocular pressure (IOP).
The pressure within the eye is maintained by a balance between the production and drainage of aqueous humor, a clear, watery fluid. This fluid is secreted by the ciliary body and flows into the anterior chamber (the space between the iris and the cornea). The fluid normally drains primarily through the trabecular meshwork, a spongy tissue structure. In open-angle glaucoma, the most common form, the drainage angle is open, but the trabecular meshwork becomes less efficient. This resistance causes the fluid to accumulate, raising the IOP and stressing the optic nerve fibers.
Mechanism of Fluid Flow Restoration
MIGS procedures physically improve the eye’s natural fluid drainage system to lower intraocular pressure. Devices and techniques are categorized based on the specific part of the outflow pathway they target.
Trabecular Bypass Procedures
One major category focuses on the trabecular meshwork and Schlemm’s canal, which is the eye’s main drainage channel. Trabecular bypass procedures involve implanting microscopic stents (e.g., iStent or Hydrus) through the trabecular meshwork into Schlemm’s canal. These devices create a permanent bypass, allowing aqueous humor to flow directly from the anterior chamber into the canal, bypassing the resistance of the meshwork. Other canal-based procedures, such as the Kahook Dual Blade goniotomy or the Trabectome, remove or incise a section of the trabecular meshwork tissue to open the pathway.
Subconjunctival Procedures
A second mechanism involves procedures that access the subconjunctival space, a different route for fluid drainage. Devices like the XEN Gel Stent bypass conventional pathways entirely, shunting aqueous humor from the eye to the space beneath the conjunctiva, where it is absorbed. Many MIGS procedures are performed in conjunction with cataract surgery, as the corneal incision created for cataract removal provides convenient access, combining two treatments into a single surgical event.
Patient Candidacy and Recovery Expectations
MIGS is recommended for patients with mild to moderate open-angle glaucoma, aiming for moderate pressure reduction and reduced reliance on daily eye drops. Ideal candidates are often those already scheduled for cataract surgery, as combining the procedures is efficient and safe. The favorable safety profile, including a low risk of complications like dangerously low eye pressure, makes MIGS a favored option for earlier intervention compared to traditional surgery.
The recovery experience is a significant advantage of MIGS. Due to the small incisions and minimal tissue disruption, post-operative care is less complex, and recovery time is significantly shorter than for traditional glaucoma surgeries. While traditional procedures can require two to three months of recovery, most MIGS patients resume normal activities within one to two weeks. The entire recovery process is typically completed in two to four weeks, contributing to high patient satisfaction and a quicker return to daily life.