Minimally Invasive Glaucoma Surgery (MIGS)
What is Minimally Invasive Glaucoma Surgery?
Minimally Invasive Glaucoma Surgery (MIGS) is a new and evolving area of glaucoma surgical treatment. It aims to lower intraocular pressure with a procedure or device that is minimally invasive and has little or no effect on the surface layers of the eye.
All MIGS procedures have the following characteristics:
- This procedure is performed within the eye targeting the junction between iris and cornea (Iridocorneal angle)
- Usually in combination with cataract surgery
- Minimal tissue handling or destruction
- Relatively quick procedure
- Very good safety profile
- Multiple treatments are possible
MIGS is best suited to eyes with mild to moderate glaucoma or ocular hypertension with an open angle. MIGS can also be helpful for REDUCING the need for topical glaucoma medication.
Types of MIGS:
In glaucoma, the natural drainage pathway inside the eye (where fluid normally drains out of the eye) becomes clogged or blocked. This results in a rise in eye pressure which can in turn damage the optic nerve. Most MIGS operations are designed to fashion alternative or augmented pathways for extra fluid to leave the eye (more fluid out equals to lower eye pressure).
There are a number of MIGS procedures available in Australia and you should speak with your ophthalmologist to see if one is suitable for you.
iStent Inject: The iStent Inject is a tiny device (less than 1 mm in length), which is made of surgical-grade titanium. Typically, two stents are inserted sideways through a small incision in the cornea into the primary fluid canal (Schlemm’s canal), usually at the time of cataract surgery.
The iStent Inject should be considered in all patients with mild to moderate open-angle glaucoma treated with eye drops, who are undergoing cataract surgery. Potential benefits to these patients include:
- A reduction in IOP
- Reduce need for glaucoma medication.
The latter may be particularly beneficial in patients who are experiencing side effects from their glaucoma medication or have difficulty adhering to regular medication use. The post-operative recovery is rapid and usually no longer than cataract surgery alone, hence patients are able to return to normal activities more quickly. The iStent Inject cannot be seen or felt, and it has an excellent safety profile with no major complications have been reported in the literature relating to the iStent itself. However, the effect of the iStent Inject can reduce over time and glaucoma eye drops may need to be resumed.
A patient with this device can be scanned safely and immediately after implantation in an MRI machine meeting the following conditions:
- Static magnetic field: 3-Tesla or less
- Maximum spatial magnetic field of 4,000 gauss/cm (40 T/m) (extrapolated)
- Maximum MR system reported, whole body averaged specific absorption rate (SAR) of 4 W/kg (First Level Controlled Operating Mode)
- Hydrus: This device is curved and flexible. It is approximately the size of an eyelash and is made of a metallic alloy of nickel and titanium. The Hydrus is inserted in the iridocorneal angle via a small incision in the cornea. The tiny Hydrus stent is designed to be inserted into the primary fluid canal (Schlemm’s canal) of the eye and open the channel to allow blocked fluid to flow more freely, thus reducing high eye pressure.
Similar to the iStent, it is suitable for patients with mild to moderate open-angle glaucoma treated with eye drops who require cataract surgery. Again, post-operative recovery is rapid and patients may experience a modest reduction in eye pressure and/or need for glaucoma medication. The Hydrus is not invisible. Similar to the iStent, it is safe to have an MRI scan in most machines following the Hydrus procedure.
CyPass: The CyPass is a small flexible tube, only 6 mm in length, made of a special plastic material. It is inserted into the eye and cannot be seen or felt. The CyPass is completely MRI safe. It bypasses the blocked drainage channel and allows fluid to drain into an alternative natural fluid drainage channel inside the eye.
The CyPass has been shown to effectively lower eye pressure and need for glaucoma medication when performed with cataract surgery in patients with glaucoma in a large clinical trial. It may provide greater eye pressure reduction and a higher chance of being medication-free. It is suitable for patients with open-angle glaucoma and is typically performed at the time of cataract surgery. The CyPass can also be performed by itself where eye pressure is not controlled with medications or following other MIGS procedures or traditional glaucoma surgery.
