Medical and surgical progress against glaucoma in recent years has been nothing short of spectacular, statistics indicate. Reflecting these advances, the risk of blindness from glaucoma has dropped by half in the last generation.
The good news continues with the recent advent of MIGS — minimally invasive glaucoma surgery. MIGS refers to a whole class of surgical procedures that have significantly added to ophthalmologists’ tools to fight the disease. MIGS procedures are safer, with less risk and faster recovery than traditional glaucoma surgeries.
The MIGS challenge
In most cases, glaucoma is associated with high pressure in the eye. This high pressure is caused by a buildup of the natural aqueous fluid that fills the healthy eye. The fluid normally drains through what is known as the trabecular meshwork, which is a filter-like ring at the base of the iris, and from there enters the eye’s drainage canal. When the drain is not functioning properly, eye pressure builds up and eventually damages the optic nerve, which carries visual information from the eye to the brain. This progressive damage leads to vision loss.
The objective of MIGS is the same as traditional, more invasive glaucoma surgery: to lower the pressure by creating better drainage for the aqueous fluid.
Over the past few years, a number of new MIGS procedures have gained FDA approval and are being used more and more frequently by cataract and glaucoma specialists. In fact, notes Dr. Wan, MIGS procedures have now become one of the hottest topics at meetings such as the recent annual meeting of the American Society of Cataract and Refractive Surgery, attended by Dr. Wan. Already, these procedures have significantly altered how he manages many glaucoma patients.
MIGS combined with cataract surgery
MIGS procedures are often performed in conjunction with cataract surgery in patients who may have both cataracts and glaucoma, which is a common combination. In fact, some MIGS procedures are FDA-approved to be done only combined with cataract surgery. Interestingly, doctors have noted that simply removing the cataract often helps improve glaucoma control. In fact, Dr. Wan finds that the majority of glaucoma patients get some lowering of eye pressure just from cataract surgery alone. But depending on the individual patient’s needs, that reduction may be insufficient.
“When we combine a MIGS procedure with cataract surgery, we up the odds of getting a significant pressure drop,” says Dr. Wan. “And the amount of drop is generally better than what we would get from cataract surgery alone."
The beauty of MIGS procedures is that they can be done in conjunction with cataract surgery quite naturally, without additional incisions or anesthesia and the risk that brings. Two eye problems can be taken care of at the same time with one trip to the operating room.
A variety of procedures
The challenge of MIGS is the sheer number of devices and procedures now becoming available. Some of the most promising include:
The iStent is the first and so far, still the gold standard MIGS procedure, which Dr. Wan has been using successfully for the last few years. The iStent is a 1 mm device that is placed into the trabecular meshwork during cataract surgery. It is the smallest implantable device approved by the FDA. Taking only a few minutes to secure, it lowers pressure by bypassing the diseased meshwork to allow fluid to reach the eye’s natural drainage canal.
The Kahook Blade Goniotomy is a variation of an older surgical procedure in which the trabecular meshwork is opened and removed, allowing fluid to drain directly into the drainage canal.
Canaloplasty is a procedure in which a special micro-catheter is threaded into the drainage canal and used to open and widen the canal, easing fluid drainage.
There are additional new devices, including the CyPass MicroStent and the XEN Gel Stent which have recently entered the market for MIGS. Although these have been approved for use by the FDA, patients who are candidates for these devices are still waiting for insurance coverage to catch up with the scientific acceptance. These and other devices on the horizon make this an exciting and optimistic time for glaucoma patients.
Sorting out the options
Even with MIGS, glaucoma remains a challenging disease. Dr. Wan says these new procedures are not 100 percent successful. “It’s kind of like a plumbing problem with a clogged drain,” says Dr. Wan. “You might not always know where in the pipes the clog is. But at least now with MIGS, we have ways of bypassing different points where the blockage is likely to be.”
The number of new MIGS devices and procedures now available presents something of a challenge in itself, says Dr. Wan. While they all seem to work, it may take some time to determine which device or procedure may be best for each individual patient.
Dr. Wan points out that eyedrops, the mainstay of glaucoma treatment for generations, are effective, but have their limitations. They’re expensive and can be inconvenient and irritating to use. Many patients find it difficult to stick to their drop regimen consistently, leading to fluctuating pressures and risking progression of their glaucoma. Considering these drawbacks, he sees a logical role for MIGS.
“If we can offer a safe, reproducible, effective procedure that can get patients off eyedrops and stabilize the pressures better, it gives us a new option for glaucoma, and may well end up being cheaper in the long run.”