Endoscopic Cyclophotocoagulation

IIC Aqueous Humor Reduction Procedure


36 Endoscopic Cyclophotocoagulation


Ramya N. Swamy, Vikas Chopra, and Brian A. Francis


The Procedure


The objective of most glaucoma surgery is to improve aqueous outflow. Treatments to reduce aqueous inflow by treating the ciliary body have existed since the 1950s.1 Cyclodestruction can be achieved through various means including cryotherapy and laser, but cyclophotocoagulation has been the most commonly employed process. Transscleral cyclophotocoagulation (TCP) was introduced in the 1970s as a way to treat intractable end-stage glaucoma.2 However, because TCP application is nontargeted and can have significant collateral tissue damage, a more tissue-specific application to decrease aqueous production was needed. The diode laser employed in the transscleral method was modified by Martin Uram3 for use through an endoscopic system to perform endoscopic cyclophotocoagulation (ECP), which allowed visualization and tissue-targeted application of laser energy.4,5


Rationale Behind the Procedure


The ciliary processes consist of pigmented ciliary epithelium (PCE) and nonpigmented ciliary epithelium (NPCE), which in concert produce the aqueous humor. Histopathologically, Pantcheva et al6 found that eyes that have been treated with ECP demonstrate less histopathological damage compared with eyes that had undergone TCP. Other histopathological studies have demonstrated that ECP-treated eyes showed loss of melanin granules in the treated areas when compared with relative preservation of the ciliary stroma and blood vessels in the untreated areas.7 An animal study by Lin8 in rabbits using fluorescein angiography demonstrated disrupted blood flow to the ciliary processes immediately following treatment with TCP and ECP. However, 1 month later, the ECP-treated ciliary processes showed some degree of reperfusion, demonstrating that the effects were somewhat reversible and might enable retreatment and fewer side effects such as hypotony. This is likely due to the fact that ECP enables guided delivery of laser energy because it permits direct visualization of the treatment. This has expanded the use of ECP from recalcitrant glaucoma to eyes with better visual potential.


In addition, ECP is the only minimally invasive glaucoma surgery (MIGS) procedure that targets aqueous production and thus offers an alternative mechanism of action to lower the intraocular pressure (IOP). Therefore, it can be performed after other angle-based surgeries have failed, and it can be combined easily with other glaucoma surgeries or phacoemulsification utilizing the same clear-corneal incision. Because ECP does not involve disruption of the conjunctiva or sclera, it spares those tissues for future trabeculectomy ab externo or aqueous tube shunt implantation. This makes ECP one of the few procedures that can be performed at any stage of glaucoma ranging from mild to refractory.


Patient Selection


Since ECP was first introduced, the patient population that might benefit from this procedure has expanded to include a range from mild glaucoma to end-stage glaucoma, as well as in combination with other procedures. The following patient populations can be treated with this procedure9:


• Patients with both cataracts and ocular hypertension who can benefit from cataract surgery combined with ECP, with the goal of reducing the number of glaucoma medications, thus reducing costs and eliminating compliance issues


• Patients with mild-to-moderate open-angle glaucoma (primary open angle, pigmentary, pseudoexfoliation) who are undergoing concomitant cataract surgery or as a stand-alone ECP procedure


• Patients at potentially increased risk of complications from filtering surgery (postvitrectomy, aphakia, history of suprachoroidal hemorrhage)


• Patients who require surgical treatment to lower the IOP but do not want to undergo more invasive procedures. In these patients, ECP may also be combined with angle-based MIGS procedures such as trabecular bypass stent (iStent) or trabeculotomy ab interno (Trabectome) along with cataract extraction if needed.


• Patients who have had complications from filtering surgery (trabeculectomy) in the contralateral eye


• Patients who have previously undergone filtering surgery or aqueous drainage implantation but continue to have an elevated IOP


• Patients on anticoagulant therapy for systemic diseases at increased risk of intraocular bleeding with filtering surgery or aqueous shunt implantation


• Patients with anatomic narrow angles with plateau iris configuration


• Patients with corneal opacification with limited view of the anterior and posterior chambers


• Patients with angle-closure glaucoma who are not candidates for angle-based surgeries (trabecular bypass)


• Pediatric patients with congenital glaucoma who have failed traditional surgeries such as goniotomy and trabeculotomy


Surgical Technique


The only endoscopic system that is currently approved for use in the United States by the Food and Drug Administration is the E2 system by Beaver Visitec (originally EndoOptiks, Waltham, MA). This machine involves a single probe that combines an 810-nm diode laser, a helium-neon aiming beam, a 175 W xenon light source, and a camera for video imaging (Fig. 36.1). These elements are combined in a 20-gauge probe, which offers a 110- degree field of view and depth of focus of 1 to 30 mm. The endoprobes are available in the straight or curved configurations.


The typical settings that are used on the machine include the following:


• Aiming beam set at 20 to 40


• Power of 0.25 to 0.40 W


• Continuous ablation time, which can be controlled by the surgeon via the foot pedal


• The intensity of the light source is adjusted based on surgeon preference to lightly illuminate the ciliary processes while still being able to appreciate their whitening and shrinkage, which are the end points of treatment.


While performing the procedure, the surgeon sits temporally or superiorly for the best approach. To perform ECP using the anterior-segment approach, a 2- to 2.4-mm clear corneal incision is typically created, or the main incision from the concurrent cataract extraction can be utilized. A cohesive viscoelastic is used to deepen the anterior chamber as well as to inflate the sulcus space to create room between the iris and the lens. The endoprobe is then positioned outside the incision and the camera probe is rotated to align the view and to bring the image into focus. The endoprobe is then inserted into the anterior chamber and guided toward the sulcus space while being visualized through the operating microscope. The surgeon then directs her/his view toward the monitor. The endoprobe is advanced until six to eight ciliary processes are visualized on the monitor with the proper illumination setting (Fig. 36.2). The aiming beam is then placed on a single process, and laser energy is applied via the foot pedal until whitening and shrinkage of the ciliary process is seen. The epithelium in between each process should also be treated. Care must be taken to ensure that the ciliary process is treated and not the adjacent iris tissue (Fig. 36.3). In contrast to performing the TCP, the surgeon should use the visible whitening and shrinkage of the ciliary processes as the end point of treatment and avoid any inadvertent “pops” or explosion of the ciliary processes. At the end of the procedure, all the viscoelastic must be thoroughly removed using either automated or manual irrigation and aspiration methods to prevent postoperative IOP spikes.


When ECP is performed through a posterior pars plana approach, the technique is modified. This approach can only be performed in aphakic and pseudophakic eyes. The surgeon sits superiorly and a conjunctival peritomy is made nasally and temporally. Sclerostomies are then made 3 to 3.5 mm posterior to the limbus using a 20-gauge myringovitreoretinal (MVR) blade or keratome. An anterior chamber maintainer supplies infusion during the procedure. Endoscope-guided vitrectomy is then typically performed prior to the ECP using the same sclerotomies. After the completion of the vitrectomy, the ECP probe is placed through one of the sclerotomies and advanced until the ciliary processes are visualized. This approach typically facilitates visualization of all of the ciliary processes as well as the pars plana, which enables greater and more effective treatment. Treatment, therefore, needs to be titrated to ensure the patient does not develop hypotony.


Additional Considerations and Surgical Tips


• The amount of energy delivered to an individual ciliary process is determined by the proximity of the probe to the tissue target as well as the duration of treatment and the power level.


• The ciliary sulcus must be widely expanded with a viscoelastic that pushes the iris anteriorly to the cornea and the lens posteriorly. A poorly inflated sulcus will result in inadequate treatment and trauma to the iris (Fig. 36.4).


• While treating the ciliary processes, it is recommended to let the laser “soak in” after the initial whitening and shrinkage of the process to achieve a greater reduction in the IOP. However, be careful not to overtreat, which results in the process exploding with a “pop” and causing greater postoperative inflammation.


• In unicameral or fully vitrectomized eyes with aphakia, an anterior chamber maintainer is typically needed to keep the eye pressurized during the procedure (Fig. 36.5).







• When treating greater than 270 degrees, a second incision placed 90 to 180 degrees away from the first incision is helpful for accessing all the ciliary processes. In situations where phacoemulsification cataract surgery is combined with ECP, the second incision could be a previously placed paracentesis that can then be enlarged to accommodate the endoscope.


• The endoscope tip should be wiped cleaned each time it is withdrawn from the eye, and additional viscoelastic should be added to the anterior chamber and sulcus space to improve the view and access to the ciliary processes.


• Scleral depression may facilitate a more complete treatment during an anterior approach by providing greater access to the ciliary processes and the areas in between that contain ciliary epithelium.


• Anesthetic placement using a retrobulbar, peribulbar, or sub-Tenon’s approach is typically needed to provide adequate anesthesia for the procedure and to keep the patient from feeling discomfort.


• If intracameral anesthetic is used, it should be flushed directly into the ciliary sulcus space. This may be inadequate for anything greater than a light treatment.


Complications


Endoscopic cyclophotocoagulation has been shown to have a good safety profile, especially in comparison with transscleral cyclophotocoagulation or cryoablation.


A retrospective study by Chen et al10 in patients with refractory glaucoma who underwent ECP found that the most common complications with the procedure were fibrin exudates (24%), hyphema (12%), cystoid macular edema (10%), and vision loss of more than two Snellen lines (6%). Most of these complications were amenable to treatment in the postoperative period, especially with aggressive postoperative steroids as well as anti-inflammatory treatment. In addition, it is important to identify patients at higher risk of inflammation (diabetics, patients with angle-closure glaucoma or uveitis) and treat them more aggressively with anti-inflammatory medications in the postoperative period to minimize these complications.


Other potential complications include risk of damage to the iris either through mechanical trauma or inappropriate application of laser energy to the iris.11 This can usually be avoided by adequate inflation of the ciliary sulcus. Choroidal effusions have also been noted.12 These may be a result of intraoperative hypotony, especially in aphakic or unicameral patients. Using an anterior chamber maintainer can help minimize this complication. Another potential cause is uveal inflammation following the procedure, which should be treated with aggressive but short-term anti-inflammatory medications. In phakic patients, there is always a risk of violating the lens capsule. It is recommended that only the most experienced surgeons perform ECP on phakic patients, and only on those patients with a deep anterior chamber that allows good inflation of the sulcus space. Because the ECP probe cannot be visualized via the microscopy during the treatment, there is the possibility of the probe causing damage to the iris or corneal endothelium without the surgeon being aware of it. A case report in the literature presents a patient whose iris adhesion to the treatment probe resulted in aniridia.13


A theoretical complication is sympathetic ophthalmia because there is a breakdown of the blood–aqueous barrier while performing the procedure. However, there have been no reported cases of this occurring in the ECP literature, although cases have been reported with TCP. In a retrospective case series, a total of six patients were noted to present with sympathetic ophthalmia, an incidence rate of 0.001% following transscleral cyclophotocoagulation. However, all of these eyes had previously undergone at least one other surgical procedure, and two eyes had also experienced prior trauma.14 Hypotony and phthisis bulbi are also potential complications of ECP that the surgeon needs to aware of, especially in patients who are undergoing more aggressive treatment using the posterior-segment approach. Studies of TCP patients have shown that there is a dose–response relationship with the degree of energy applied and hypotony.15 In high-risk patients undergoing ECP, care must be taken to ensure that one to three clock positions of ciliary processes are left untreated so that some aqueous production remains. The case of a patient with underlying rheumatologic disorder who undergoes TCP and subsequently develops necrotizing scleritis has been reported,16 and the risk of similar complications likely exists in similar patient populations.


Postoperative Management


Depending on the level of treatment and the patient’s ocular status, ECP can induce variable but significant degrees of inflammation. Aggressive management of this inflammation plays a key role in postoperative care to achieve success while minimizing inflammation-related complications. Typically, patients receive intracameral steroids and optionally systemic steroids at the time of the procedure. Frequent use of topical steroids administered every hour may be necessary for the first few days after the procedure. On occasion, patients may also benefit from a short course of oral steroids.


Management of steroid use, however, needs to be tailored to the degree of inflammation that is noted postoperatively. This is important because many of the patients who have glaucoma can be steroid responders, and use of steroids can mask the IOP-lowering effects of ECP. Therefore, once inflammation is under control, steroids should be tapered. This can be done with the concurrent use of nonsteroidal anti-inflammatory drugs to prevent rebound inflammation.


Safety, Efficacy, and Clinical Results


There are reports in the literature of ECP being successfully utilized across various patient populations, either as a stand-alone procedure or as an adjunct to phacoemulsification or filtering surgeries in mild, moderate, and refractory glaucomas. When ECP was first introduced, it was used primarily for refractive cases or end-stage cases. In the initial study utilizing ECP, Uram3 demonstrated its efficacy in 10 patients with neovascular glaucoma.


Advanced Glaucoma Treatment

Chen et al10 performed a retrospective study of ECP in 68 eyes with refractory glaucoma (defined as elevated IOP despite maximally tolerated medical therapy, and a history of failed filtering procedure or previous TCP). They reported a 90% success rate (as defined by IOP < 21 mm Hg) at 1-year follow-up. These eyes underwent 180 to 360 degrees of endoscopic cyclophotocoagulation, with the majority through a limbal incision but a few through a pars plana approach. The ECP-treated eyes demonstrated a reduction in mean IOP from 27.7 mm Hg to 17.0 mm Hg over a 12-month follow-up period. In addition, there was a statistically significant reduction in the number of glaucoma medications (an average of one less glaucoma mediation). More importantly, none of the treated eyes suffered major complications such as hypotony or phthisis.


An early randomized study by Gayton et al11 compared the effectiveness of cataract surgery combined with trabeculectomy versus cataract surgery combined with ECP as the primary surgical treatment for glaucoma. Fifty-eight eyes were randomized to the two groups and were followed over a 2-year period. IOP control was defined as < 19 mm Hg. The two groups achieved comparable success in IOP reduction without the need for additional medications (40% of eyes treated with combined cataract surgery and trabeculectomy versus 30% of eyes treated with combined cataract surgery and ECP). Additionally, rates of treatment failure between the two groups were also comparable, with three eyes in the trabeculectomy group and four eyes in the ECP group needing additional surgical intervention at the end of the study period.


A prospective study by Lima et al12 compared Ahmed drainage implantation versus ECP in eyes with prior failed trabeculectomy with antimetabolite. The two groups achieved equivalent IOP lowering, with the IOP in the Ahmed group lowered from a preoperative average of 41.3 mm Hg to 14.7 mm Hg postoperative, and in the ECP group from a preoperative average of 41.6 mm Hg to 14.1 mm Hg postoperative. However, compared with the ECP group, the Ahmed group had a higher rate of postoperative complications (choroidal detachment, shallow anterior chamber, hyphema).


The ECP procedure has also been studied in patients with refractory glaucoma following previously implanted aqueous drainage implant. Francis et al17 conducted a prospective study in 25 eyes with uncontrolled IOP despite maximally tolerated medical therapy and a previously implanted, functional Baerveldt 350-mm2 aqueous shunt. All eyes underwent 360-degree ECP treatment and were followed for up to 2 years. At 1-year follow-up, the mean IOP decreased by 30.8% from the preoperative 24.0 mm Hg to 15.7 mm Hg postoperative. There was a significant reduction in the number of topical medications needed to control IOP from 3.2 preoperative to 1.5 postoperative. Again, similar to the other studies mentioned thus far, no major complications were noted. Transscleral diode laser has been successfully utilized to treat refractory glaucoma and pseudoexfoliation glaucoma, even as primary therapy,18 and ECP likely will be just as successful with likely fewer side effects and complications.


ECP Plus

The ECP-plus procedure entails a pars plana approach with treatment of the pars plana (Fig. 36.6). Its use in ultra-refractory glaucoma was reported in 20165 by Tan et al19 in a retrospective, noncomparative, interventional case series. The patient population included 53 eyes of 53 consecutive patients who had failed multiple glaucoma surgeries, including trabeculectomy and aqueous tube shunt. The mean preoperative IOP dropped from 27.9 to 10.2 at 6 months and 10.7 at 12 months. The cumulative treatment success was 81% at 6 months and 78% at 12 months. The number of medications fell from 3.4 ± 1.2 pretreatment to 0.8 ± 1.0 at 1 to 6 months and 0.7 ± 1.2 at 12 months postoperatively. Early complications included hypotony, fibrinous uveitis, and cystoid macular edema. Late complications occurred in 16% of subjects and included hypotony, choroidal detachment, cystoid macular edema (CME) without hypotony, and failed corneal graft.19


Endoscopic Cycloplasty and Lens Extraction for Plateau Iris Syndrome

The treatment of severe plateau iris syndrome with lens extraction and endoscopic cycloplasty (ECPL) (Fig. 36.7) was described in a prospective case series by Francis et al20 of 12 eyes of six patients with plateau iris refractory to laser iridotomy and iridoplasty, miotic and other glaucoma medical treatment, with appositional angle closure in at least three quadrants. The surgery consisted of lens extraction and ECPL, and an endoscopic diode laser treatment of the ciliary processes in the superior, nasal, and inferior quadrants. Ultrasound biomicroscopy (UBM) measurement parameters included anterior chamber depth (ACD), angle opening distance (AOD 500), trabecular ciliary process distance (TCPD), iris ciliary process distance (ICPD), iris depth (ID), iridocorneal angle (ICA), and sulcus angle (SA). Four novel measurements included ciliary process thickness (CPT), ciliary process width (CPW), ciliary process area (CPA), and iris ciliary process contact length (ICPCL). The ACD, AOD 500, and ICA all increased significantly (p < 0.001). ICPD, CPT, CPW, CPA, and ICPL all decreased significantly (p < 0.01). Parameters remaining unchanged were the TCPD, ID, and SA. The untreated quadrants showed measurements similar to the preoperative measurements, supporting the assertion that the effect seems to be mostly from the laser treatment rather than from the lens extraction alone. Similar results have also been demonstrated by Ahmed et al.21


Oct 29, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Endoscopic Cyclophotocoagulation
Premium Wordpress Themes by UFO Themes