Overview of Minimally Invasive Glaucoma Surgery
Glaucoma is a long-term eye condition that gets worse over time. It impacts the optic nerve and can cause changes in vision and problems with the eyes. It is the second leading cause of irreversible blindness worldwide. Glaucoma’s main factor that can be controlled is the pressure inside the eye, known as intraocular pressure, which is also the main way to treat this condition.
There are different treatments for glaucoma depending on its severity. For mild to moderate cases, medications can be used to manage it, as well as laser procedures to help reduce the eye pressure. However, more severe cases or ones where the eye pressure is not able to be controlled may require surgical treatment. Two types of surgeries used include ‘trabeculectomy’ (a surgery to create a new opening in the eye for fluid to escape) and implantation of a glaucoma drainage device to help lower eye pressure.
Recently, scientists have been exploring new ways to treat glaucoma with less invasive surgeries. These are referred to as microinvasive or minimally invasive glaucoma surgeries (MIGS). They aim to quickly and effectively reduce eye pressure while also causing less damage to the eye tissue and allowing for speedier recovery.
There are many ways MIGS can help, including bypassing a part of the eye called the trabecular meshwork, improving the outflow of fluid from the eye, and reducing the eye’s fluid production, among others.
MIGS has changed how glaucoma is managed due to less damage to eye tissues, faster recovery after surgery, and greater satisfaction among patients. MIGS also comes with a wider range of choices for doctors with positive results. It can also be combined with cataract surgery to reduce the overall surgery time.
MIGS has many benefits such as:
* Reduced risk of complications like internal bleeding and fluid accumulation in the eye
* Minimal changes to the eye’s structure, offering improvements with little disruption
* Performed using a clear corneal incision, directly visualizing the target
* Excellent alternative to traditional surgeries to lower eye pressure
* Quick recovery time for patients
There are four main types of MIGS based on how they lower eye pressure:
1. Increasing fluid outflow from the eye through various stents or tissue removal procedures.
2. Increasing fluid outflow from the eye through the suprachoroidal space.
3. Changing fluid flow to go through the subconjunctival space.
4. Reducing fluid outflow via ciliary process ablation.
Each procedure has its own unique characteristics and advantages in managing and treating glaucoma. Given the variety of MIGS options available, the best choice will depend on the specifics of the patient’s condition and the doctor’s judgment on what would be most beneficial.
Anatomy and Physiology of Minimally Invasive Glaucoma Surgery
Minimally invasive glaucoma surgery, also known as MIGS, is a procedure that helps lower eye pressure (also referred to as IOP – intraocular pressure) by changing the way the clear liquid in your eye (aqueous humor) flows. MIGS can play around with a part of the eye known as the trabecular meshwork. The flow of this eye fluid, which typically faces resistance, can be improved by using a small device called a stent. This stent helps the fluid move smoothly from the front part of the eye (anterior chamber) into a circular channel (Schlemm’s canal), effectively reducing the eye pressure.
Another method to improve fluid flow and reduce resistance in the trabecular meshwork involves surgical procedures called goniotomy or trabeculectomy. In these procedures, tissue is modified by making cuts or removing parts, enabling better drainage of the fluid via Schlemm’s canal. An alternative to this involves enlarging the Schlemm canal using a gel-like substance (viscoelastic), this enhances the normal flow of this eye fluid.
MIGS can also improve flow in another part of the eye called the uveoscleral outflow. A super tiny stent can be inserted into a layer of the eye (suprachoroidal space). If this isn’t possible, then the eye fluid can be diverted into the area beneath the thin protective layer of the eye (subconjunctival space) with a tiny inside-to-outside (ab interno) incision.
Lastly, another method involves lessening the production of this eye fluid through what’s known as ciliary processes. This is done through a procedure called endocyclophotocoagulation, wherein a laser is inserted through a clear part of the eye’s surface (corneal incision). The device responsible for the fluid production (ciliary body) is treated using this laser to reduce the overproduction of eye fluid.
Why do People Need Minimally Invasive Glaucoma Surgery
Minimally invasive eye surgery might be an option if you’re dealing with glaucoma, which is a condition that damages your eye’s optic nerve. This procedure might be appropriate for a few different situations:
1. If you have a mild to moderate case of glaucoma.
2. If you have specific types of glaucoma, like primary open-angle glaucoma (a common type where the fluid in the front of your eye doesn’t drain properly), pigmentary glaucoma (a rarer form where pigment from your iris blocks fluid drainage), or pseudoexfoliation glaucoma (a condition characterized by accumulation of small, white protein fibers in the eye).
3. If the pressure inside your eye stays high even after maximum medical treatments and a type of laser treatment called trabeculoplasty.
4. If you’re having trouble sticking to your prescribed treatments.
5. If you’re having bad reactions to the medication you’re taking for glaucoma.
When a Person Should Avoid Minimally Invasive Glaucoma Surgery
There are situations where a person cannot undergo MIGS, a minimum invasive type of eye surgery used to reduce built up pressure inside the eye. Conditions that may prevent this surgery include:
– If a person has ‘active neovascular glaucoma,’ – a severe type of eye disease where new, abnormal blood vessels grow on the iris (the colored part of the eye), this operation may not be suitable.
– If someone has ‘primary or secondary angle-closure glaucoma,’ – eye conditions that occur when the natural drainage channels in the eye become blocked, causing pressure to build up, they are unsuitable for this surgery.
– If someone has ‘corneal opacity,’ which means the clear front surface of the eye is not clear and looks cloudy or scaly, they would not be eligible for MIGS.
– If they have ‘angle dysgenesis,’ – a congenital defect where the structures responsible for fluid drainage in the eye don’t develop properly, performing MIGS can be risky.
– If the pressure in the veins lining the eyes is abnormally high, this can occur due to conditions like ‘Sturge Weber syndrome,’ ‘thyroid eye disease,’ or ‘retrobulbar tumors,’ – a tumor behind the eyeball, MIGS may not be the appropriate treatment.
Equipment used for Minimally Invasive Glaucoma Surgery
To carry out your treatment, your doctor will need to use several pieces of medical equipment. These are:
– iStent: A small tube that helps to drain fluid from your eye to lower pressure, mainly used for glaucoma patients.
– iStent Inject: A newer version of the iStent and serves the same function.
– Hydrus Implant: A small device that’s put into the eye to help with fluid flow.
– Gonioscope: A special lens used to examine the front part of your eye, including the drainage angle.
– Trabectome: A medical device that removes some eye tissue to help fluid drain out.
– Kahook Dual Blade: A knife that is used by doctors for removing eye tissue, improving fluid drainage and lowering eye pressure.
– Excimer Laser: A form of laser used in eye surgeries.
– Viscoelastic: A type of solution used in eye surgeries to maintain the shape of the eye during procedures.
– iTrack 360 Microcatheter: A small tube that’s used for minor, less invasive eye surgeries.
– Xen Implant: This is a tiny tube that goes into your eye to help lower pressure in the eye.
– CyPass Implant: This is another form of implant that aids in lowering pressure in the eye.
– Cyclodiode: A procedure where a laser is used to lower pressure in the eye when other treatments don’t work. This procedure is commonly used in severe glaucoma cases.
Who is needed to perform Minimally Invasive Glaucoma Surgery?
Eye doctors, especially those who know a lot about glaucoma (a eye condition that can damage your optic nerve), may suggest special, tiny eye surgeries called MIGS (Minimally Invasive Glaucoma Surgeries) for their patients. These surgeries are less risky and you may recover faster. In the process, there’s a whole team who helps to look out for your health. This includes the operating room staff, eye-specific nurses, staff who help to get the right medicines in the surgery (pharmacists), anesthesiologists (experts who help you sleep through the surgery), and eye care professionals called optometrists. This team works together to make sure you get the best possible results from your surgery.
How is Minimally Invasive Glaucoma Surgery performed
The Trabecular Meshwork Bypass is a procedure used to help with a condition called glaucoma, which causes damage to the optic nerve due to increased pressure in the eye. It works by creating a new pathway for the fluid (known as aqueous humor) in the eye to drain more efficiently, thereby reducing the pressure inside the eye. The operation achieves this by inserting tiny stents, or tubes, that bypass a part of the eye called the trabecular meshwork. This process is called Minimally Invasive Glaucoma Surgery (MIGS).
This procedure is usually recommended for people with types of glaucoma like Primary Open-Angle Glaucoma (POAG), PseudoExfoliative Glaucoma (PXFG), Pigmentary Glaucoma, or when the pressure inside the eye is too high. The Trabecular Meshwork Bypass is not suitable for everyone, especially if they have conditions like Primary Angle-Closure Glaucoma (PACG), Neovascular Glaucoma (NVG), any abnormal development of the front part of the eye, cloudiness of the cornea, or certain conditions like Sturge Weber syndrome that increase the pressure in the veins of the eye. The procedure can sometimes cause complications such as bleeding in the eye, misplaced or obstructed stents, or transient increase in eye pressure.
There are different types of stents used for this procedure, such as the iStent, iStent Inject, and Hydrus Stent. Each stent has a different size and design but works in similar ways. The iStent, which was the first one to be approved in 2012, is a very tiny tube made of a non-magnetic material. It is implanted inside the eye to create a new channel for draining the eye fluid. Studies have shown that this stent can reduce eye pressure by approximately 25% in about 70% of patients. In 2018, a new version of the iStent, called the iStent Inject, was introduced. This second-generation trabecular meshwork bypass stent is smaller and leads to a higher decrease in eye pressure compared to the original iStent. It can reduce eye pressure by up to 39% in some patients.
The Hydrus stent is a bit different. It’s longer and has a unique shape, with three small openings. Made up of a material that can remember its shape, this stent is also implanted in the eye to allow the fluid to drain more easily. According to studies, this stent can reduce eye pressure by more than 20% in around 80% of patients, and 73% of patients didn’t need to use additional glaucoma medications.
Other than stents, there are also trabeculotomy procedures that achieve similar outcomes. For example, the Kahook Dual Blade (KDB) Goniotomy uses a special double-blade that makes small incisions in the trabecular meshwork to remove the obstructive tissue. This process decreases the need for future surgeries as it lessens the potential for tissue scarring. Other tissue removal options include using the Trabectome, a special tool that uses heat to remove the trabecular meshwork, and Laser Trabeculostomy, which uses laser beams to remove the necessary tissue.
These methods can be incredibly effective in managing glaucoma and reducing intraocular pressure, thus preventing further damage to the optic nerve and preserving your vision.
Possible Complications of Minimally Invasive Glaucoma Surgery
In medical terms, there are several possible complications after certain eye surgeries. These might include:
Hyphema, which is bleeding inside the front part of your eye.
Hypotony, a condition where the pressure in your eye is lower than normal which might make the eye feel soft.
Various issues with the stent, a tiny tube placed in the body to support a blood vessel. Problems can include displacement (moving from its original spot), malposition (badly placed or aligned), obstruction (something blocking it), migration (moving far from its original spot), and fragmentation (breaking into pieces).
Conjunctival gaping, which is a wound or gap in the clear tissue covering the white part of your eye.
Peripheral anterior synechiae, a condition where the eye’s iris sticks to the lens or the cornea (the clear front part of the eye).
A temporary rise in eye pressure, known as Intraocular Pressure (IOP).
Post-operative inflammation, which is swelling and redness after surgery.
Retinal detachment, a serious condition where the retina (the layer at the back of your eye that senses light) pulls away from its normal position.
Choroidal detachment, which involves the layer below the retina moving away from its normal position.
Cystoid macular edema, a painless disorder which affects the central retina, or macula, leading to distorted vision.
Displacement or partial dislocation of the IOL (Intraocular lens), a lens implanted in the eye during cataract surgery.
Posterior capsular opacification, also called a secondary cataract, a condition that causes blurry vision.
