Incisional Glaucoma Surgery is traditionally recommended when attempts with medical or laser treatment have failed. If medical or laser treatment hasn’t been able to stop the progression of glaucoma and/or vision loss from glaucoma, your doctor may recommend surgical management. The goal of glaucoma surgery is not to improve vision but rather to lower intraocular pressure and reduce the risk of glaucomatous progression. All glaucoma procedures achieve this goal in one of three ways:
- Improve the existing drainage system (MIGS)
- Create a new drainage system (XEN Gel stent, Trabeculectomy, Tube shunts)
- Decrease aqueous production with cyclo ablative procedures (Laser: CPC, micropulse, ECP)
- MIGS or Minimally Invasive Glaucoma Surgery typically enhances the flow through the eye’s normal drainage system (drainage angle). This is done either by placing a stent (iStent inject or Hydrus microstent) or opening up the drainage canal by removing the tissue that is blocking it and enhancing outflow (Goniotomy, Gonioscopy Assisted Transluminal Trabeculotomy, Trabectome, Canaloplasty). Some of these MIGS are done in conjunction with cataract surgery, others can be done as standalone procedures. Your doctor will decide which MIGS procedure would be best suited for your glaucoma depending on the type and severity of the disease.
- XEN Gel Stent
- XEN Gel Stent is a type of MIGS procedure that is less invasive than traditional glaucoma filtering surgery but achieves a similar outcome of lowering intraocular pressure by diverting the flow of fluid and creating a new path for the fluid to drain out of the eye. The stent is a small 6 mm long collagen tube with an internal diameter of 45 microns that redirects the fluid inside the eye (aqueous humor) into the subconjunctival space creating a filtering “bleb” or reservoir. From here, the fluid is then absorbed by the body. The intraocular pressure is now reduced because fluid can easily flow out through the stent into the new reservoir under the conjunctiva (the superficial layer that covers the white of the eye).
- Xen Gel Stent is commonly performed with the use of anti-scarring medication such as Mitomycin (MMC) in an effort to improve the chance of success. (see Trabeculectomy below for additional information)
- A trabeculectomy is a classic glaucoma filtering procedure that lowers intraocular pressure by creating a new drainage pathway out of the eye. Unlike the XEN gel stent and glaucoma drainage devices, a trabeculectomy does not involve placing any stents or implants in the eye. Instead, a sort of “one-way valve” is created in the white wall of the eye (sclera) by making a partial thickness scleral flap and removing a small amount of tissue (trabecular meshwork). This then allows the fluid from inside the eye to flow freely into the subconjunctival space creating a filtering “bleb” and lowering the eye pressure.
- There is always a certain amount of healing/scarring response to any incisional surgery. In the case of Trabeculectomy, the scleral flap needs to remain open so the fluid can flow freely and the surgery can be a success. Therefore, an anti-scarring medicine called Mitomycin (MMC) is applied at the time of surgery in an effort to reduce this scarring response and improve the chances of a successful outcome. However, even with the use of Mitomycin, some patients can still form an exuberant healing response.
- Glaucoma Drainage Implant (aka “Tube shunt”)
- Glaucoma drainage implants (GDI’s) are prosthetic devices used to lower the pressure inside the eye and prevent further vision loss from glaucoma. Some are valved (Ahmed glaucoma valve) and others are non-valved implants (Baerveldt, Molteno) and this affects when the implants become fully functional. Regardless of the type of implant, all glaucoma drainage devices consist of a tube and plate design. The implant plate is placed on the white wall of the eye (sclera) between the extraocular muscles in the upper and outer quadrants. The silicone tube, which is connected to the plate, is then inserted into the front of the eye between the cornea and the iris usually. This allows the fluid inside the eye to drain through the tube, out over the plate where a bleb or reservoir is created, lowering the intraocular pressure. The fluid inside the reservoir is then slowly absorbed back into the surrounding tissues and body.
- In an effort to reduce the irritation and possible exposure of the tube shunt, a patch graft is regularly placed over the tube to protect it.
- The glaucoma drainage implant is not readily visible since it is covered by the upper eyelid.
- Cyclo-ablative Procedures (Laser – Performed in Ambulatory Surgery Center/OR)
- In cyclo ablative procedures, the secretory epithelium of the ciliary body is damaged with laser, which leads to reduced fluid production inside the eye and lower intraocular pressure (IOP). With Diode CPC and Micropulse CPC, this laser energy is applied from the outside by placing the probe over the white wall of the eye and targeting the ciliary body underneath it. These types of laser are not invasive and do not require making incisions to enter the eye, while others like ECP do. All of the cyclo ablative procedures are outpatient and performed in an ambulatory surgery center because they require anesthesia for pain control.
- Transscleral Diode Cyclophotocoagulation (Diode CPC)
- This type of laser is typically reserved for refractory cases of glaucoma that have failed prior surgical procedures or in patients who have a guarded visual prognosis and those who may not be good candidates for incisional surgery. The laser is performed by placing a probe over the white wall of the eye and delivering targeted laser energy to the ciliary body tissue directly underneath it to cause atrophy. This results in less fluid being formed inside the eye and thus a lower eye pressure. The laser can take up to 6 weeks to take full effect so it may take some time before the pressure comes down. In some patients, this laser is combined with an injection of a pain killer (chlorpromazine) behind the eyeball to relieve pain in patients with blind, painful eyes secondary to elevated intraocular pressure. The procedure takes about 5-10 minutes and will require the use of drops afterward to reduce the inflammation in the eye.
- Micropulse Cyclophotocoagulation (Micropulse CPC)
- Micropulse CPC is similar to diode CPC in that the laser is applied by placing the probe on the white wall of the eye targeting the ciliary body. The main difference is the Micropulse laser delivers a series of repetitive short pulses of energy alternating with rest periods in between pulses. This is thought to allow for a “cooling period” between bursts, potentially minimizing collateral tissue damage and inflammation in the eye. This feature allows the Micropulse CPC laser not only to be used in patients with severe refractory glaucoma but also in those with mild/moderate glaucoma or patients who may not be good candidates for incisional surgery. The procedure takes about 10 minutes and is done at an outpatient surgical facility with the aid of local anesthesia to minimize discomfort.
- Endocyclophotocoagulation (ECP)
- Endocyclophotocoagulation is often performed with cataract surgery in an effort to lower IOP or reduce dependence on glaucoma drops postoperatively. After the cataract is removed, the laser probe is placed through the same incision used for the cataract surgery and allows for direct visualization of ciliary body processes. The laser is then applied in a continuous fashion for 180-360 deg until a blanching effect is seen and the ciliary processes begin to shrink. The procedure takes about 10 -15 minutes to perform.