MIGS – New treatments for glaucoma
MIGS stands for minimally invasive glaucoma surgery. This acronym refers to a range of implants, devices, and techniques all designed to reduce intraocular pressure, the primary aggravating factor in glaucoma. Glaucoma is caused by the accumulation of a fluid called aqueous humor within the eye. This increases intraocular pressure, damaging the optic nerve and leading to a loss of visual field and eventually vision. MIGS procedures improve the drainage of this fluid from the eye or decrease its secretion, thereby lowering intraocular pressure.
What is a MIGS?
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"Minimally invasive" means that the technique uses tiny incisions and/or microscopic equipment, which have been designed to reduce surgical risks compared to procedures such as trabeculectomy.
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In fact, the term MIGS encompasses all new surgical techniques designed to treat glaucoma.
A closer look at the diode laser
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Diode lasers are at the crossroads between MIGS and older glaucoma treatments. Improvements in lasers have led to better predictability.
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The micropulsed diode laser is less powerful but better tolerated than the conventional diode laser.
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Diode lasers can reduce aqueous humor secretion by retracting the ciliary bodies.
Why so many innovations in glaucoma treatments?
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Glaucoma remains one of the neglected areas of ophthalmology. Many patients become blind despite appropriate treatment and repeated surgeries.
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Therefore, the idea of offering intermediate treatments between drops and surgery took root among ophthalmologists.
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Objective: to offer earlier a treatment that is safer and as effective as surgery in order to preserve vision.
What are the main MIGS?
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These new products have been developed in recent years, but some have already been withdrawn because they were ineffective or dangerous.
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It is important to understand that MIGS are not a miracle cure for glaucoma, but rather additional therapeutic solutions for specific cases.
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The first 3 MIGS presented are the main ones used on the market:
iStent
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The iStent is a tube less than 1 millimeter in diameter that is inserted into the trabecular meshwork, the natural drainage channel for aqueous humor.
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It is made of titanium and is non-ferromagnetic. It aims to bypass blockages in the trabecular meshwork, thereby improving fluid drainage from the eye and reducing eye pressure.
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It is common practice to implant two iStent devices in the eye to improve intraocular pressure (IOP) levels. In France, the iStent is only reimbursed following cataract surgery.
Microshunt Preserflo
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Formerly known as InFocus, the Preserflo bypass system is a small tube that is inserted into the eye to create a new drainage pathway for aqueous humor.
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It acts like a trabeculectomy: excess fluid flows towards the filtration bubble located under the conjunctiva (transparent membrane of the eye), under the upper eyelid.
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This improves fluid drainage from the eye and reduces eye strain. The tube is made of inert plastic, already used for cardiac stents.
The XENgel or Xen implant
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The XENgel implant is a thin tube that is inserted into the eye to create a new drainage pathway for fluid.
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Just like PreserFlo, it acts as a bypass: excess aqueous humor is drained into the filtration bubble formed by the conjunctiva (the membrane of the eye), under the upper eyelid.
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It is composed of porcine gelatin.
Ab-interno canaloplasty with iTrack
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Canaloplasty is a type of glaucoma surgery that aims to clean and widen the trabecular meshwork, the drainage channel for aqueous humor.
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"Ab-interno" simply describes the direction in which the main drainage channel is accessed during the operation (through the inside of the eye, in front of the pupil, rather than from the side).
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The iTrack is a thin catheter that is inserted into the drainage channel. A gel is injected into the catheter, which dilates the drainage channel.
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The procedure removes blockages in the trabecular meshwork, improving the flow of aqueous humor. To our knowledge, this procedure is not used by any French team.
Endocyclophotocoagulation (ECP)
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Endo-cyclophotocoagulation is based on the principle of a laser probe that directly targets the ciliary body. It is in fact a diode laser delivered internally.
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The laser reduces the activity of the ciliary body, which means that less aqueous humor will be produced, which will mechanically reduce eye pressure.
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The effect is temporary as the ciliary body eventually recovers, but if effective, the treatment can be repeated.
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The machine is expensive and available in few hospitals. Furthermore, its indications are rare.
Hydra
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The Hydrus is a drain the size of an eyelash that is placed in the trabecular meshwork (Schlemm's canal). It acts like a mesh to expand and keep the drainage canal open. It is made of nickel and aluminum.
Trabectome
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The trabectome uses an electrical impulse to remove a portion of the obstructed trabecular meshwork. This increases the flow of fluid through the eye's natural drainage pathway.
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Widely used in India, moderately in the USA and very little in Europe, the device is present in a few hospitals.
CyPass
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The Cy-Pass microtube is a tube inserted into the eye that creates a deeper aqueous humor diversion than other drains. The aqueous humor is drained beneath the sclera, not beneath the conjunctiva, thus avoiding the risk of scarring of the filtration bleb.
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The Cy-Pass was withdrawn from the market in August 2018 because monitoring and safety studies revealed an increased risk of corneal endothelial cell loss (leading to Fuchs' dystrophy). The device is no longer in use, but it remains in place in monitored patients with good tolerance.
Suis-je éligible à une opération type MIGS ?
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In most cases, MIGS is suitable for patients with mild to moderate glaucoma that is too severe for eye drops alone but not severe enough to qualify for trabeculectomy. MIGS placement is commonly combined with cataract surgery.
What are the alternatives?
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Eye drops, consultation and operating room lasers, as well as filtering surgeries (trabeculectomy and sclerectomy) are the standard treatments for glaucoma.
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It is unlikely that a MIGS will be offered to you as a first-line treatment other than the iStent during cataract surgery.
Operations
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Although “Minimally invasive”, glaucoma surgical techniques using MIGS are performed in the operating room, on an outpatient basis, under local anesthesia.
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It usually takes one to two weeks to recover from the operation. You will likely need to use antibiotic and anti-inflammatory eye drops for several weeks or months after the operation to aid healing.
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You will also need to attend regular follow-up appointments, scheduled by your surgeon, to ensure the treatment is still effective in reducing your eye pressure. Depending on the technique used, the number of follow-up appointments may be fewer or the same as for a trabeculectomy.
Conclusion
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MIGS is a rapidly developing area of glaucoma treatment. New devices are regularly introduced to the market, while others are modified or even withdrawn.
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Although the potential of MIGS is generating a lot of excitement, long-term follow-up and safety studies are still needed to determine if MIGS is better than operations performed for decades such as trabeculectomy or non-penetrating deep sclerectomy.
Frequently Asked Questions
Will my eyesight be improved by the operation?
No! Vision lost due to glaucoma cannot be restored, and glaucoma cannot be cured. All glaucoma treatments aim to prevent further damage to the optic nerve and vision loss.
Will I be able to stop using the hypotensive eye drops after the operation?
In some patients, MIGS reduces pressure enough to eliminate the need for glaucoma eye drops, but this effect may only last a few years. Always follow your ophthalmologist's advice regarding eye drops.