What is MIGS Glaucoma Surgery?
Microinvasive Glaucoma Surgery (MIGS) is a minimally invasive alternative glaucoma surgery using easy-to-use devices, with small incisions, high safety, minimal disturbance to the normal eye structure, and effective in lowering intraocular pressure.
The risk of complications during and after surgery is low, and recovery is faster than conventional glaucoma surgery. This method can be performed even if conventional glaucoma surgery has failed.
Who is suitable for MIGS glaucoma surgery?
- Patients with early to moderate stage glaucoma
- Open-angle glaucoma
- Unable to control intraocular pressure despite using all glaucoma medications
- Have factors that prevent eye drop use, such as allergy to glaucoma eye drops
Who is not suitable for MIGS surgery?
- Closed-angle glaucoma
- Shallow anterior chamber
- Unable to use eye drops completely after surgery
- Unable to follow up after surgery
- History of allergy to Mitomycin C (MMC), which is used in some types of MIGS surgery
What is iStent infinite?
iStent infinite or iStent infinite Trabecular Micro-Bypass System (Glaukos Corp., Aliso Viejo, CA, USA) is a type of MIGS consisting of 3 stents contained in a ready-to-use system that drains aqueous humor from the eye through the conventional outflow pathway. It is made of titanium, measuring 360 microns in length and 360 microns in base width. The surface of the iStent infinite is coated with heparin, a natural anticoagulant, to prevent blood clotting upon contact with the device, reducing the risk of thrombus formation inside and increasing safety during use.
Although the iStent infinite is small, it can drain aqueous humor at a rate equal to the average production inside the eye, approximately 2.5 microliters per minute. The tip of the device is arrow-shaped with 4 side holes that help drain aqueous humor in all directions from the anterior chamber to Schlemm’s canal and eventually out of the eye. The base of the device is a wide circular plate (iStent inject W), and the central rod is embedded in the trabecular meshwork.
iStent infinite is implanted inside the eye at the angle. When all 3 stents are implanted, they occupy only 3% of the total angle, leaving 97% of the tissue undisturbed. The leftmost and rightmost devices are approximately 120 degrees apart.
This surgery can be performed alongside cataract surgery or as a stand-alone procedure. Studies on the appropriate number of devices (1, 2, and 3) using indicators such as intraocular pressure and the number of glaucoma medications reduced after surgery found that increasing the number of iStents used improves treatment efficacy. Comparing the use of 2 versus 3 devices,
it was found that using 3 iStents is significantly more effective than using 2. Additionally, it can be an option for patients with advanced glaucoma.
The image shows the position and spacing of each iStent infinite implanted at the angle. The tip of the iStent infinite is arrow-shaped (located in Schlemm’s canal), the middle is a rod with a hollow tube (embedded in the trabecular meshwork), and the base is a circular plate with a central hole (inside the eye) serving as the drainage pathway for aqueous humor out of the eye at the angle.
Dr. Natamon Srisamran
Glaucoma Specialist Ophthalmologist
Eye and Laser Center, Phyathai 1 Hospital
