Minimally Invasive Glaucoma Surgery

What is MIGS?

The recent most increased interest in glaucoma surgery has been in Minimally Invasive Glaucoma Surgery (MIGS) with formidable results in mild to moderate glaucoma. These are designed to improve the safety of surgical intervention for glaucoma. Although initially coined minimally invasive, the term micro seems more appropriate because it truly differentiates these microscopic ophthalmic procedures from other minimally invasive surgical procedures (i.e., general surgery). Most MIGS procedures enhance physiologic outflow and are aimed at a different patient population than traditional filtration surgery. As opposed to competing with traditional filtering surgery, MIGS seems to be more of an alternative to medical therapy in an effort to address adherence challenges, adverse events, and quality-of-life (QOL) issues with topical medications.

I-stent

The iStent Trabecular Micro-Bypass Stent (Glaukos, Laguna Hills, CA) received FDA approval in 2012. The device is a heparin-coated, non-ferromagnetic titanium stent with a snorkel shape to facilitate implantation. The device is placed using a single-use, sterile inserter through a 1.5mm corneal incision. The iStent itself is the smallest FDA approved device, measuring at 0.3mm in height and 1mm in length. The iStent is a safe minimally invasive glaucoma surgery (MIGS) procedure that can reduce the need for daily use of glaucoma eye drops. A small (1mm) titanium drainage stent is inserted into the eye’s natural drainage channel to lower intraocular pressure. Most clinical trials concluded that iStent implantation with phacoemulsification resulted in a significantly lower, long-term decrease in IOP and number of medications used compared to phacoemulsification alone. No major complications have been reported.

XEN Glaucoma Implant

The XEN Glaucoma Implant (AqueSys Implant) was created by AqueSys Inc acquired by Allergan. The implant itself is made out of a soft, collagen-derived, gelatin that is known to be non-inflammatory. The Xen Gel Stent aims to reduce intraocular pressure by inserting a small drainage tube into the eye. The stent allows fluid to drain from the anterior chamber into a reservoir (bleb) under the conjunctiva. The goal of implantation is to create an aqueous humor outflow path from the anterior chamber to the subconjunctival space. The implant is injected through a small corneal incision with the use of an inserter similar to those used for IOLs. Similar to other implants, it can be performed in conjunction with cataract surgery.
All shunts perform approximately the same function of lowering the eye pressure. It’s important to note that no treatment is guaranteed to completely eliminate the need for eye drops, but the strong results seen in the use of either the Istent or XEN Gel Stent give the right patients a very strong choice for eliminating the need for them.
Your Glaucoma specialist will discuss the best one for you.

How will the shunt affect the appearance of the eye?

I-stent

The I-stent does not appear on the outside of the eye and does not create a bleb outside as it relies on the existing venous outflow system of the eye to help drain the aqueous fluid out.
Initially after surgery, the eye will be red and swollen to a variable degree. The recovery is rapid and redness should be short lived.

XEN Gel Implant:

Successful MIGS surgery takes much less time than many other types of Glaucoma surgery, typically lasting 30 minutes at the most. At Moorfields Eye Hospital Dubai/Abu Dhabi, MIGS implantation is usually performed under local anaesthesia, although general anaesthesia is also possible under certain circumstances.
Typically a drug called Mitomycin C (anti-scarring medication) is also used at the time of surgery if indicated to suppress healing.

The Surgery Itself

Successful MIGS surgery takes much less time than many other types of Glaucoma surgery, typically lasting 30 minutes at the most. At Moorfields Eye Hospital Dubai/Abu Dhabi, MIGS implantation is usually performed under local anaesthesia, although general anaesthesia is also possible under certain circumstances.
Typically a drug called Mitomycin C (anti-scarring medication) is also used at the time of surgery if indicated to suppress healing.

Complications at the time of surgery

Complications occurring at the time of MIGS surgery are extremely rare with an excellent safety profile. Complications when they do occur, tend to occur during the first 2 weeks after the surgery (see Success rates and complications).

After Surgery – Postoperative Care

The day of surgery and the next day

You will usually be discharged home from hospital later the same day after surgery. It is usually necessary for the operated eye to be examined again one day after surgery.
The eye is normally patched the first night after surgery and the patch removed the following day. If the un-operated eye does not see well, then the operated eye will not be patched. Instead, a clear shield will be placed on the operated eye so that you will still be able to see to get around after surgery.

What should I expect to feel during the postoperative period?

It is normal for the vision to be blurred and the eye to be uncomfortable after surgery. The period of blurring is variable. The blurring is usually worst for the first 1 to 2 weeks after surgery, and improving slowly afterwards. It takes about 1 month for the eye to feel completely normal though vision would stabilise much earlier.

Eye Drops

Eye drops and tablets to lower the eye pressure are not normally required for the operated eye during the first night after surgery, unless the surgeon recommends that you continue to use them. It is important to continue any eye drops for the un-operated eye unless advised otherwise.
The following day, the postoperative eye drops are usually started after removal of the eye patch and cleaning of the eye. The postoperative eye drops will usually consist of an antibiotic and anti-inflammatory steroid eye drops to use for the first month after surgery. You will be advised if any changes in these are required at each clinic visit.
To start with the steroid eye drop will be used intensively (every 2 hours or about 8 times daily) during the day and the antibiotic 4 times daily.

Postoperative visits to clinic

As the intraocular pressure may be too high or too low in the first week after shunt surgery, the patient is usually examined in clinic two weekly for approximately the first month, with visits reducing in frequency after that. If indeed the pressure is too high or too low, rest assured that your specialist will manage this appropriately.

Activity and Instructions of care after MIGS

Following surgery you are able to read and watch television as normal as these activities will not harm your eye. It is however important to avoid strenuous activity during the first few weeks after surgery. The following table is a general guide to do’s and don’ts.
IF ANYTHING DO NOT RUB/BUMP/PRESS THE EYE. IN DUSTY ENVIRONMENTS PLEASE WEAR EYE SHIELD OR YOUR OWN GLASSES. DO NOT STOP YOUR EYE DROPS UNLESS THE DOCTOR ADVISES. DO NOT USE ANY OTHER PRODUCTS IN THE EYE.
If in doubt please ask your doctor or nurse in clinic.

When can I go back to work?

The duration of time off work will depend on a number of factors such as the nature of your employment, the state of the vision in the other eye and the pressure in the operated eye.
Typically someone working in an office environment would require 1 week off if the postoperative course is smooth. Someone whose occupation involves heavy manual work or work in a dusty environment may require 2 weeks or upto 1 month (e.g. builders, working in dessert).

When is the eye back to normal?

It takes 1 month for the eye to feel completely normal in most cases, and sometimes longer in more complicated cases. At that point, the patient will usually have a refraction (spectacle) test as often the spectacle prescription will be slightly different than before surgery.

Success Rates and Complications

Success rates

Most glaucoma surgical studies examine success rates over a 5 year period. The I-stent and XEN gel implant are showing good results with 80-90% qualified success in most studies. Although a sizable proportion of patients achieve good pressure control without the need for continued glaucoma medication, many patients still require some medication to assist the shunt in controlling the pressure especially if they are on more than one drop. In such circumstances, the medication required is usually less than that required before the surgery.

Complications

As with any surgery, there is a potential for complication or problems to arise. Complications can occur during the surgery, shortly after the surgery or many months after surgery.
Severe complications are rare and may happen either if the eye pressure drops very low, or very quickly during the early postoperative period, or if the eye becomes infected.
Bleeding
The most serious problem that can occur is bleeding inside the eye. This can lead to loss of vision and even blindness but occurs in less than 1 in 1000 patients. There are measures taken to prevent this but this is not a predictable complication.
Infection
An infection inside the eye can be very serious and also cause loss of vision or blindness. This also happens in less than 1 in 1000 patients. Measures are taken and aseptic techniques used to prevent this complication.
Eye Pressure
After the operation the eye pressure may be too high or too low. This may require additional treatment in the outpatient clinic or sometimes further surgery is required.
Inflammation
This can occur inside the eye and is usually treated with eyedrops.
If the operation is not performed in a timely manner then there is potential for further irreversible visual loss due to high pressure/fluctuating pressure in the eye leading to blindness.
However the informed decision rests with the patient and your Glaucoma specialist will be available and very happy to discuss your concerns and expectations before proceeding with surgery.