Minimally Invasive Glaucoma Surgery
Defining Minimally Invasive Glaucoma Surgery
The acronym MIGS stands for Minimally Invasive Glaucoma Surgery, a collection of contemporary surgical procedures designed to manage eye pressure with less trauma than traditional operations. This approach represents an evolution in modern glaucoma care, offering a safer option for many patients requiring surgical intervention.
The “Minimally Invasive” part refers to the use of micro-incisions, often self-sealing and made through the cornea. These tiny cuts allow surgeons to use microscopic instruments and devices, such as stents, to access the eye’s drainage system without the larger external incisions required in older procedures. This internal (ab interno) approach is a key feature that distinguishes MIGS from conventional surgery.
“Glaucoma” is a group of eye diseases that cause progressive damage to the optic nerve, the structure responsible for transmitting visual information to the brain. This damage is most frequently associated with elevated pressure inside the eye, which is the primary modifiable risk factor for the condition. Untreated glaucoma can lead to irreversible vision loss, starting with peripheral sight and potentially progressing to total blindness.
The third element, “Surgery,” encompasses techniques and devices used to alter the eye’s fluid dynamics and lower internal pressure. These procedures are typically quick, often lasting about ten minutes, and are performed using local anesthesia. The goal is to achieve sustained pressure reduction while minimizing the risks associated with more extensive incisional surgeries.
Treating Intraocular Pressure
The fundamental problem in most common forms of glaucoma is a dysfunction in the eye’s drainage system, leading to elevated Intraocular Pressure (IOP). The eye constantly produces aqueous humor, a clear fluid. In a healthy eye, fluid production balances drainage, maintaining stable pressure.
In glaucoma, the natural drainage channel, the trabecular meshwork, becomes blocked, preventing aqueous humor from exiting efficiently. This blockage causes fluid to back up, leading to a rise in IOP that damages the optic nerve. The primary objective of MIGS is to reduce this pressure and prevent further vision loss.
MIGS technologies reduce pressure by improving aqueous humor outflow, often by enhancing or bypassing blocked drainage pathways. Tiny devices like the iStent or Hydrus microstent are implanted to create an alternate route through the trabecular meshwork, allowing fluid to flow more freely into Schlemm’s canal, the main collector channel.
Other procedures, such as goniotomy or trabeculotomy, physically remove a section of the meshwork to open the eye’s natural drain. Some devices, like the XEN Gel Stent, create a new outflow channel to redirect fluid into the subconjunctival space, just under the outer membrane of the eyeball.
A different mechanism, utilized by Endocyclophotocoagulation (ECP), involves decreasing aqueous humor production by treating the ciliary body cells with a precise laser beam. Regardless of the specific mechanism, each MIGS technique restores a healthier balance between fluid production and drainage to control IOP.
Distinguishing Features of the Approach
MIGS offers a favorable safety profile compared to older, traditional incisional surgeries like trabeculectomy or tube shunts. While conventional procedures are effective at lowering pressure, they require larger incisions and carry a higher risk of serious complications, such as hypotony (dangerously low eye pressure) or infection. The micro-incisions and tissue-sparing nature of MIGS minimize structural disruption.
Patients appreciate the significantly faster recovery time associated with the minimally invasive approach. Due to reduced trauma, most patients experience less post-operative discomfort and can return to daily activities within a few days to a week, a substantial difference from the multi-week recovery often needed after traditional surgery.
MIGS procedures are frequently combined with cataract surgery, a common scenario for older adults. Since the same small corneal incision can often be used for both, the surgeon can efficiently treat both conditions in one operation. This combined approach offers convenience by reducing the number of surgeries and recovery periods.
The minimally invasive nature preserves the option for more aggressive traditional surgery later, if needed. Because MIGS procedures do not disturb the conjunctiva, they do not compromise the success rate of a future trabeculectomy or shunt implantation. This staged approach provides a gentler starting point, reserving higher-risk traditional surgeries for advanced disease.
Who is a Candidate for MIGS
MIGS is generally intended for patients with mild to moderate open-angle glaucoma. The effectiveness of the procedures offers a substantial pressure reduction for these stages, providing a balance of safety and efficacy that is often preferred over the higher risks of major surgery. For patients with advanced or severe glaucoma, the more dramatic pressure-lowering effect of traditional incisional surgery remains the most appropriate treatment option.
A common scenario for MIGS is combining it with cataract surgery (phacoemulsification). Performing the MIGS procedure concurrently is an efficient way to manage both conditions with a single procedure and recovery period, especially since cataract removal itself can sometimes help lower IOP.
Patients who have not achieved target eye pressure with drops or laser therapy, or those who struggle with medication adherence and side effects, are strong candidates. MIGS can often reduce or eliminate the need for daily glaucoma drops, improving quality of life and treatment compliance.
The decision to proceed with MIGS is determined by a comprehensive assessment of disease severity, overall eye health, and the desired target pressure. While MIGS expands treatment options, it is not a cure for glaucoma and cannot reverse existing optic nerve damage. Therefore, the suitability of the procedure is determined by a specialist to ensure the chosen intervention provides the necessary pressure control to halt further vision loss.