|GLAUCOMA SURGERY UPDATE
|Year : 2015 | Volume
| Issue : 1 | Page : 18-24
Leonard K Seibold, Jeffrey R SooHoo, Malik Y Kahook
Department of Ophthalmology, University of Colorado Eye Center, Aurora, CO 80045, USA
|Date of Web Publication||1-Jan-2015|
Leonard K Seibold
University of Colorado Eye Center, 1675 Aurora Court, Mail Stop F 731, P.O. Box 6510, Aurora, CO 80045
Source of Support: None, Conflict of Interest: None
| Abstract|| |
In recent years, many new procedures and implants have been introduced as safer alternatives for the surgical treatment of glaucoma. The majority of these advances are implant-based with a goal of increased aqueous drainage to achieve lower intraocular pressure (IOP). In contrast, endoscopic cyclophotocoagulation (ECP) lowers IOP through aqueous suppression. Although ciliary body ablation is a well-established method of aqueous suppression, the novel endoscopic approach presents a significant evolution of this treatment with marked improvement in safety. The endoscope couples a light source, video imaging, and diode laser to achieve direct visualization of the ciliary processes during controlled laser application. The result is an efficient and safe procedure that can achieve a meaningful reduction in IOP and eliminate or reduce glaucoma medication use. From its initial use in refractory glaucoma, the indications for ECP have expanded broadly to include many forms of glaucoma across the spectrum of disease severity. The minimally-invasive nature of ECP allows for easy pairing with phacoemulsification in patients with coexisting cataract. In addition, the procedure avoids implant or device-related complications associated with newer surgical treatments. In this review, we illustrate the differences between ECP and traditional cyclophotocoagulation, then describe the instrumentation, patient selection, and technique for ECP. Finally, we summarize the available clinical evidence regarding the efficacy and safety of this procedure.
Keywords: Cyclophotocoagulation, Diode Laser, Endoscope, Glaucoma, Minimally- or Micro-invasive Glaucoma Surgery
|How to cite this article:|
Seibold LK, SooHoo JR, Kahook MY. Endoscopic cyclophotocoagulation. Middle East Afr J Ophthalmol 2015;22:18-24
| Introduction|| |
The treatment of glaucoma continues to focus on the reduction of intraocular pressure (IOP) as the only modifiable risk factor for the disease. Surgical methods of IOP reduction have traditionally aimed at increasing aqueous outflow through a guarded filtration surgery or implantation of a glaucoma drainage device (GDD). In more recent years, minimally-invasive techniques and devices have emerged for the surgical treatment of glaucoma under the moniker of minimally- or micro-invasive glaucoma surgery (MIGS).  These procedures are largely device oriented and seek to augment physiologic outflow pathways as opposed to the creation of subconjunctival filtering blebs as seen with trabeculectomy and GDD implantation. These MIGS procedures offer the benefits of shorter operative times, rapid vision recovery, lower risk profiles, and the ability to combine easily with cataract surgery. Furthermore by sparing the conjunctiva, more invasive filtration surgery remains a viable option if indicated in the future. However, despite their less invasive methods, most MIGS procedures still lower IOP solely through increased aqueous outflow.
Endoscopic cyclophotocoagulation (ECP) is a versatile MIGS procedure that uniquely lowers IOP through the reduction of aqueous humor production. While transscleral ciliary body ablation is a long-established treatment for refractory glaucoma, ECP accomplishes this task in a more controlled and predictable fashion to achieve significant IOP reduction while maintaining a high safety profile.  The key feature of ECP is direct visualization of the ciliary processes as the target tissue for ablation.  The surgeon is able to titrate the extent of ciliary body ablation to maximize IOP lowering while minimizing collateral damage and adverse events. As with other MIGS procedures, ECP is accomplished from an ab interno approach and can be easily performed at the time of cataract surgery or as a stand-alone treatment. However in contrast to many MIGS procedures, the extent of ECP treatment can be titrated allowing it to be utilized in advanced or refractory glaucomas as well. In this review, we will discuss the technology, instrumentation and procedure for ECP as well as summarize the preclinical and clinical data for this procedure.
| History of Cyclodestructive Procedures|| |
The treatment of glaucoma through the ablation or destruction of the ciliary body can be traced back to the 1930s.  Several different methods have been employed including diathermy, cryotherapy, ultrasound, and even surgical excision. Although the modalities have varied over the years, the goal of treatment is the reduction of aqueous humor formation through the destruction of ciliary body epithelium. In cyclocryotherapy, a cryoprobe was applied to sclera in order to freeze the underlying ciliary body.  In the 1970s, the Nd: YAG and diode laser platforms emerged as a means to achieve transscleral cyclophotocoagulation (CPC) using a contact probe. , The energy from the 810 nm diode laser passes through the conjunctiva and sclera and is readily absorbed by pigmented ciliary body tissues to generate adequate thermal energy for coagulation. These early attempts all targeted the ciliary epithelium inside the eye from an external approach. While this allowed for a nonincisional treatment, the lack of direct visualization of the target tissue led to imprecise applications resulting in undertreatment with lack of effect or overtreatment with collateral tissue damage. Vision and globe threatening complications such as chronic uveitis, hypotony, and phthisis occurred at unacceptably high rates. These inherent characteristics of traditional cyclodestructive procedures have led most surgeons to reserve this treatment modality for end-stage and refractory glaucoma or eyes with limited vision potential.
| Instrumentation for Endoscopic Cyclophotocoagulation|| |
In 1992, Martin Uram developed the technology necessary for ECP using an intraocular endoscope paired with a diode laser to achieve CPC from an ab interno approach.  The instrumentation consists of the laser endoscope itself and the console to which it is attached. The laser endoscopy console (Endo Optiks, Little Silver, NJ, USA) [Figure 1] combines a 175 W xenon light source for illumination, 810 nm diode laser for photocoagulation, helium-neon laser aiming beam, and video imaging for intraocular visualization. The endoscopy probe [Figure 2] contains all three fiber groupings and is available in 19, 20, or 23 gauge sizes with a field of view ranging from 70° to 140° and depth of focus spanning 1-30 mm. The probe tips are either straight or curved and fit easily through a 2.0 mm clear corneal incision. An additional advantage to the 23-gauge probe is its compatibility with all 23-gauge vitrectomy trocar systems. The probes can be sterilized and reusable up to 25 times or more.
|Figure 1: The laser endoscopy setup consisting of the laser console with attached monitor for visualization. The endoscopy probe is connected to the console by three separate cables: One each for diode laser, video imaging, and xenon light source|
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|Figure 2: The endoscopy probe used for endoscopic cyclophotocoagulation. Probe tips may be curved or straight|
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| Histopathology of Cyclophotocoagulation|| |
Although CPC and ECP both achieve aqueous suppression through ablation of the ciliary processes, there is a clear distinction between the two treatments when evaluating the extent of tissue destruction. McKelvie and Walland performed histologic analysis of enucleated eyes that had been treated with transscleral CPC in vivo.  All cases showed destruction of the pigmented and nonpigmented epithelium. Furthermore, they observed pigment clumping, coagulative necrosis, ciliary muscle destruction, and vascular damage. The surrounding sclera, iris, and pars plana were also damaged in some of the eyes. Similarly, Schlote et al. found obliteration of the vascular supply after CPC treatment in rabbit eyes. 
In human autopsy eyes, Pantcheva et al. compared the tissue effects of ECP to CPC.  Eyes treated with CPC demonstrated destruction of the pigmented and nonpigmented epithelium, pigment clumping, coagulative necrosis and destruction of the deeper ciliary stroma [Figure 3]a. By contrast, ECP-treated eyes showed destruction of the nonpigmented epithelium with little effect outside of the ciliary processes [Figure 3]b. Scanning electron microscopy displayed shrinkage and effacement of the processes without gross architectural destruction or collateral damage.
Alvarado compared the histologic changes of ECP and CPC in enucleated human eyes that were previously treated.  The CPC-treated eyes displayed obliteration of the ciliary muscle with scar tissue formation and lack of vasculature. In ECP eyes, the ciliary epithelium remained continuous and uniform with intact cell membranes, while the stroma showed loss of smaller blood vessels but intact larger vessels.
|Figure 3: (a) Light microscopy of ciliary processes after trans-scleral cyclophotocoagulation treatment showing separation of the pigmented and nonpigmented ciliary epithelium (wavy arrow), pigment clumping (arrowheads), coagulative necrosis of the underlying ciliary stroma (asterisk), and gross destruction of the tissue architecture (straight arrows). (b) Light microscopy of ciliary processes treated with endoscopic cyclophotocoagulation showing destruction of the nonpigmented epithelium and clumping of the pigmented epithilium (arrowheads) without gross architectural destruction or collateral damage|
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| Indications and Patient Selection|| |
Although well-defined indications for ECP are lacking, the procedure can be utilized over a broad range of glaucomatous disease; but patient selection is important for achieving good outcomes with this treatment. Although initially performed in refractory glaucoma cases, ECP may be utilized in mild, moderate, or severe stages of many types of glaucoma. The procedure is ideally performed in pseudophakic or aphakic eyes as a stand-alone procedure, or in combination with cataract extraction. Good candidates for combined phacoemulsification-ECP are patients with a visually significant cataract and coexisting glaucoma that is either uncontrolled with medications or medically controlled with difficulty affording, administering or tolerating their medications. Uncontrolled pseudophakic patients at high risk for failure or complications after traditional filtration surgery are often good candidates for ECP as a stand-alone procedure before attempting more invasive treatments. ECP may be combined with other MIGS procedures such as Trabectome (Neomedix, Tustin, CA, USA) or the iStent (Glaukos, Laguna Hills, CA, USA) to achieve IOP reduction through both decreased aqueous production and increased aqueous outflow. Additionally, ECP can be indicated in patients who remain uncontrolled after previous filtration procedures including trabeculectomy and GDD implantation. Patients with pseudoexfoliation glaucoma are typically poor candidates due to buildup of fibrillar material on the ciliary processes that minimizes laser uptake.  Caution should also be used when considering ECP in patients with a history of inflammatory eye disease due to the risk of significant postoperative inflammation and cystoid macular edema (CME) or hypotony. Finally, ECP in phakic patients is possible but can be technically difficult and lead to zonular damage or cataract progression.
| Procedure|| |
Prior to the start of the procedure, the three component cables of the ECP probe should be securely connected to the laser console. The camera image should be focused with the desired orientation and illumination adjusted outside the eye prior to the initiation of surgery. The laser should be set to continuous duration with an initial power of 0.25 W and an aiming beam setting of 20-30. A variety of anesthesia may be used successfully for ECP including intracameral, sub-Tenon's, or retrobulbar routes of administration. If intracameral anesthesia is utilized, increased intravenous sedation may be needed to maximize patient comfort during the laser application.
Depending on surgeon preference, a temporal or superiorly placed clear corneal incision is performed near the limbus, approximately 2.0 mm in width. The ciliary sulcus is deepened with cohesive viscoelastic to improve visualization of the ciliary processes. The probe is then inserted through the corneal wound and positioned in the sulcus at or near the pupillary border [Figure 4]. The surgeon then directs his/her gaze towards the monitor to gain orientation in the sulcus and identify the target tissue. During treatment, approximately 6-7 ciliary processes should be in view at all times as this places the probe at an optimal distance for absorption of laser energy. Once the aiming beam is placed over a ciliary process, the foot pedal is depressed to deliver laser energy in a continuous fashion. Treatment is titrated according to the visualized tissue response. The process should whiten and shrink to a variable degree after appropriate treatment [Figure 5]. If the probe is closer to the processes, a shorter duration and/or lower power will be needed to reach the desired effect. Rupture or popping of the processes should be avoided as an indication of over treatment. The probe can then be advanced along the adjacent processes while applying laser energy. The entire visible area of each ciliary process should be treated including anterior and posterior edges as well as crypts in between processes.
|Figure 4: During endoscopic cyclophotocoagulation, the sulcus is deepened with cohesive viscoelastic and the probe enters through a clear corneal incision. The probe tip is positioned just beneath the pupillary border, and laser energy is applied to the ciliary processes|
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|Figure 5: Surgeon views during endoscopic cyclophotocoagulation. Appropriately treated ciliary processes on the left display shrinkage and whitening in comparison to untreated processes on the right. Note approximately 6-7 processes are in view during treatment suggesting appropriate distance between the probe and target tissue|
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Treatment should be carried to the extent of visualization in one direction, and then the probe is rotated 180° with rotation of the image on the monitor, and treatment is continued as far as possible in the other direction. With a curved probe, a single incision allows treatment of approximately 270° of ciliary processes. If more treatment is desired, a second incision may be placed 180° away from the initial wound to gain access to the subincisional processes and complete a 360° treatment for additional IOP lowering.
After completion of the laser treatment, a thorough removal of viscoelastic must be completed using either manual or automated irrigation and aspiration to prevent postoperative IOP spikes. Intracameral carbachol (Miostat, Alcon Laboratories, Fort Worth, Texas, USA) may be instilled at the end of the case for postoperative IOP control, although this may increase or prolong inflammation.  Oral acetazolamide may also be given in the postoperative period to mitigate IOP spikes if no contraindication is present. The corneal wounds should be closed in a watertight fashion with hydration and 10-0 nylon sutures if necessary.
In aphakic or pseudophakic patients, a pars plana approach (ECP plus) may also be utilized to achieve a more thorough treatment of the ciliary processes when aggressive IOP lowering is desired. A standard 2 or 3 port pars plana vitrectomy must be performed initially, followed by insertion of the probe through one of the sclerotomies. Once the processes are visualized, treatment is carried out in the same fashion as the anterior approach. The anterior 1-2 mm of pars plana may also be treated in severe, refractory cases but may increase the risk for hypotony postoperatively.
Postoperative care should include topical and/or subconjunctival antibiotics and corticosteroids to prevent infection and control the inflammatory response. Steroid therapy should be tapered as inflammation resolves as a steroid-induced IOP increase may occur. Patients should be maintained on IOP lowering medications as needed to control postoperative IOP spikes until the final IOP lowering effect is realized, typically after cessation of steroid therapy.
| Clinical Outcomes|| |
Endoscopic cyclophotocoagulation alone
Several studies have demonstrated the efficacy and safety of ECP in the treatment of many types and severities of glaucoma. The earliest report was by Uram in 1992, where he treated 10 eyes with uncontrolled neovascular glaucoma (NVG).  Using a pars plana approach, between 90° and 180° of ciliary processes were treated with a significant decrease in mean IOP from 43.6 to 15.3 mm Hg at 8.8 months follow-up. In another retrospective analysis, Chen et al. performed ECP on 68 eyes with refractory glaucoma from a range of etiologies.  All eyes had failed prior filtration surgery and some had failed CPC as well. A total of 180-360° of processes were treated through either a limbal (56 eyes) or pars plana incision (12 eyes). After 1-year of follow-up, mean IOP decreased 34% from 27.7 mm Hg preoperatively to 17.0 mm Hg postoperatively, while medication use was also reduced by an average of one medication. Success was defined as IOP < 21 mm Hg and was achieved in 94% of eyes at 1-year and 82% at 2 years. Complications included fibrin exudation (24%), hyphema (12%), CME (10%), and choroidal detachment (4%) although no cases of hypotony or phthisis were reported.
Lima et al. prospectively studied outcomes in 68 eyes after either ECP or the Ahmed glaucoma implant.  Enrolled eyes were pseudophakic with uncontrolled IOP >35 mm Hg and had undergone one or more previous trabeculectomies. Success was defined as an IOP >6 mm Hg and <21 mm Hg with or without medication use. At 2 years follow-up, mean IOP fell from 41.2 mm Hg to 14.7 mm Hg in the Ahmed group and from 41.6 mm Hg to 14.1 mm Hg in the ECP group. The success rate was similar between the Ahmed and ECP group (70.6% and 73.5%, respectively) although more complications occurred after Ahmed glaucoma valve implantation. Complications seen more frequently in the Ahmed group included choroidal detachment, decreased visual acuity, early hypotony, and shallow anterior chamber while hyphema was the only complication seen more commonly after ECP.
When used after tube shunt surgery, ECP has also been shown to be safe and effective. Francis et al. described outcomes of a prospective case series of 25 eyes with uncontrolled IOP after Baerveldt tube shunt surgery.  At 1-year of follow-up after 360° ECP treatment, mean IOP was reduced from 24.0 to 15.4 mm Hg and medication use was reduced from a mean of 3.2 medications per patient to 1.5. Success was defined as IOP reduction of 3 mm Hg or greater, discontinuation of non tolerated glaucoma medications, and IOP < 21 mm Hg. At 1-year, success was achieved in 88% of patients and remained steady at 2 years without any serious complications.
Combined phacoemulsification/endoscopic cyclophotocoagulation
More recently, ECP has been utilized as a MIGS adjunct in the treatment of patients with coexisting cataract and glaucoma. Similar to other MIGS procedures such as the iStent or Trabectome, ECP can be easily performed through a standard clear corneal incision used for cataract removal with little additional operating time and risk. One obvious advantage of ECP over other MIGS procedures is the lack of implants or disposable hand pieces required for each case.
A number of clinical studies demonstrating the efficacy and safety of combined phacoemulsification and ECP (phaco/ECP) is growing with encouraging results. Shortly after he described the initial use of ECP in NVG, Uram achieved good control with combined phaco/ECP in 10 eyes with uncontrolled open angle glaucoma and cataract.  After a mean follow-up of 19.2 months, mean IOP decreased from 31.4 mm Hg preoperatively to 13.5 mm Hg postoperatively with a significant drop in medication use for all patients. Transient vitreous hemorrhage occurred in one patient, but there was no occurrence of CME or other significant complication. Kahook et al. compared outcomes of combined phaco/ECP from a 1-site versus 2-site approach with the second incision allowing a more complete 360° treatment.  This retrospective analysis was nonrandomized with a total of 15 patients in the 1-site group and 25 patients in the 2-site group. After 6 months of follow-up, the 2-site group maintained a lower IOP than the 1-site group (13.0 vs. 16.0 mm Hg) and required less medication as well (0.52 vs. 1.93 medications). Their findings help illustrate the potential to titrate IOP reduction based on the extent of the ciliary body treated. Another retrospective analysis by Clement et al. looked at outcomes of 63 glaucomatous eyes from 59 patients undergoing combined phaco/ECP.  At 1-year, IOP was reduced from 21.1 mm Hg on 2.7 medications preoperatively to 16.1 mm Hg on 1.5 medications while visual acuity was significantly improved. Success was achieved in 55.5% of eyes, defined as an IOP reduction of >20% and IOP of 6-21 mm Hg. They also noted a greater IOP reduction with higher baseline IOP and older age. The most common complications were fibrinous uveitis (11.1%) and acute or chronic IOP elevation (3.2% and 7.9%, respectively), while CME occurred at a rate of 3.2%. Lindfield et al. performed a similar retrospective study on 58 glaucomatous eyes undergoing phaco/ECP.  They found a greater mean IOP reduction at 2 years from 21.5 mm Hg to 14.4 mm Hg but medication usage was unchanged throughout (mean of 1.97 preoperatively and 2.07 at 2 years postoperatively). At 24 months, 76% maintained an IOP of <21 mm Hg and 20% IOP reduction from baseline. The only ECP related complication reported was anterior uveitis in 5% with no reports of CME, hypotony, or fibrinous reaction.
In a prospective randomized trial, Gayton et al. compared outcomes of combined phaco/ECP to combined phaco/trabeculectomy.  After 2 years, success defined as IOP <19 mm Hg was achieved without medication in 30% of the ECP group and 40% of the trabeculectomy group. The same IOP goal was achieved with medication use in 65% of the ECP group and 54% of the trabeculectomy group. Additional surgery was required in 14% of the ECP group and 10% of the trabeculectomy group. IOP reduction was similar between the two groups at 8.6 mm Hg for trabeculectomy and 8.8 mm Hg for ECP.
The above data support the efficacy and safety of ECP combined with phacoemulsification as a treatment for coexisting cataract and glaucoma of various subtypes. It should be noted that most of the available data is retrospective in nature and lacks a control group to better isolate the IOP lowering effect of ECP from that associated with phacoemulsification alone. Prospective, randomized trials are still needed to better characterize the IOP lowering effect and safety of this popular surgical approach, in addition to identifying patient factors that may predict success or failure.
The use of ECP has also been found moderately beneficial in pediatric glaucomas. Carter et al. reported the outcomes of 36 eyes of 20 pediatric glaucoma patients treated with a single-incision ECP.  Baseline IOP was reduced from 35.1 mm Hg to 23.6 mm Hg (30% decrease) after an average of 1.4 laser procedures. Success, defined as IOP <21 mm Hg, was achieved in 34% after the initial procedure. After re-treatment in 25% of eyes, success rose to a cumulative 43% at last follow-up. Complications occurring only in aphakic patients included two cases of retinal detachment, one case of hypotony, and vision loss from hand motion to no light perception in another case. A later report by Al-Haddad found limited success with the use of ECP in refractory pediatric glaucoma with corneal opacities.  The endoscope was found to be useful in lowering IOP by ECP in addition to providing visualization for tube shunt placement where direct visualization was not possible.
| Alternative Endoscope Uses|| |
Aside from its use for CPC, the endoscope has a number of unique alternative uses in ophthalmic surgery. The endoscope enables visualization of several areas of the anterior and posterior chamber that are not possible with the traditional operating microscope alone. Anteriorly, the endoscope can be used to visualize the anterior chamber angle in a variety of clinical settings. Goniosynechiolysis or iStent placement may be performed under endoscopic guidance, precluding the need for head repositioning or intraoperative gonioscopy.  Goniotomy may be performed in congenital glaucoma using a 2- or 3-port approach with the endoscope used for visualization. , In the 3-port approach, the endoscope is used for visualization through one incision while the micro-vitreo retinal blade is passed through a separate incision for incision of the trabecular meshwork. In the 2-port technique, a specially designed goniotomy blade attachment (Endooptiks, Inc.) is attached to the end of the endoscope to make an incision through trabecular meshwork. If a cyclodialysis cleft is suspected, the endoscope can allow identification of its location and size in addition to providing a means of treatment for smaller clefts through direct laser application. Caronia et al. reported the successful treatment of a 2.5 clock hour cleft using this technique with normalization of IOP postoperatively. 
Due to its location behind the iris root, the ciliary sulcus is essentially impossible to view intraoperatively without the use of the endoscope. Sulcus visualization with the endoscope is useful in a number of clinical scenarios. First, in the setting of a complicated cataract removal or secondary intraocular lens (IOL) placement, the integrity of zonular and capsular support may be assessed to determine the most appropriate location for IOL placement. After IOL insertion, the position of the IOL haptics can be verified by direct visualization and adjusted as necessary. In eyes with uveitis-glaucoma-hyphema syndrome, there is typically inappropriate contact of an IOL haptic with uveal tissue such as iris or ciliary body resulting in chronic inflammation, bleeding, and/or IOP elevation. Using an endoscope, the location of the offending implant can be readily identified to direct appropriate treatment through removal or repositioning [Figure 6]. In eyes with chronic hypotony from hyposecretion, the endoscope provides visualization of the ciliary body to assess for potential causes including atrophy, detachment, or tractional membranes. In the case of cyclitic membranes, one report found endoscopic evaluation and surgical removal of fibrous membranes was successful in normalizing IOP in 7 of 9 patients with hypotony. 
|Figure 6: Endoscopic view of the ciliary sulcus in a patient with uveitis-glaucoma-hyphema syndrome. The intraocular lens haptic (straight arrows) is lying outside the capsular bag in the sulcus space. The iris displays transillumination defects (asterisks) adjacent to the haptic from chronic contact and chaffing|
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In glaucoma surgery, the endoscope can assist in achieving accurate placement of a tube shunt within the narrow ciliary sulcus or through pars plana. Subsequent obstruction of a posteriorly placed tube shunt can be identified with the endoscope as well. Finally, retinal surgeons may utilize the endoscope to aid in visualization during vitrectomy, particularly in cases with cornea or lens opacity. Retinal pathology located far anteriorly, such as proliferative vitreoretinopathy, may be better identified with the endoscope as well. Furthermore, the coaxial laser capabilities allow the surgeon to perform retinal photocoagulation to these hard to reach areas.
| Conclusions|| |
Among the recent advances in glaucoma surgery, ECP is becoming widely utilized as a straightforward and safe, yet effective manner of reducing IOP in the treatment of glaucoma. In contrast to other MIGS procedures, ECP lowers IOP via aqueous suppression and does not require device implantation or conjunctival disruption. ECP may be easily combined with phacoemulsification in patients with coexisting cataract and glaucoma to lower IOP or reduce medication burden. Combination with procedures that enhance outflow of aqueous humor, such as the iStent, is possible and currently being investigated for long-term outcomes. ECP has been successfully used in most types of glaucoma and may be useful at any stage of disease making it a versatile surgical treatment for glaucoma. The endoscope itself is a valuable intraoperative tool that may be utilized by other subspecialists in the diagnosis and treatment of ocular pathology in situations where standard microscopic view is difficult or impossible. Future prospective and controlled studies are needed to better define the safety and efficacy of ECP and its role as a MIGS procedure.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]