Suprachoroidal Approach to Glaucoma Surgery
Ramesh S. Ayyala, MD, FRCS, FRCOphth; Farhan A. Irshad, MD, FACS; and Iqbal “Ike” K. Ahmed, MD
Surgical approaches to the suprachoroidal space range from traditional procedures aimed at draining fluid from the suprachoroidal space (blood or transudate) to implantation of newer devices that drain aqueous humor into the space as a means of controlling elevated intraocular pressure (IOP). The novel devices that access the suprachoroidal space, either from an ab externo or an ab interno approach, are still in early development, and evidence-based medicine is lacking. We will cover the more traditional aspects of the suprachoroidal space as it relates to glaucoma in this chapter and only touch on the basics of the novel devices toward the end of this chapter.
BASIC ANATOMY
The suprachoroidal space is a potential space between the choroid and the sclera. It is limited anteriorly by the attachment of the longitudinal ciliary muscle to the scleral spur and posteriorly by the scleral aperture of the optic nerve. This space is not continuous and is segmented by the outward passage of the vortex veins, by the perforating short posterior ciliary arteries, and the loose attachment of the choroid to the sclera.
BASIC PHYSIOLOGY
Transmural pressures in the choroidal circulation are affected by the same hydrostatic and oncotic pressures found throughout the peripheral vasculature. In the setting of increased blood pressure or low IOPs, this transmural pressure rises, leading to the passage of transudative serum from choroidal vessels into the suprachoroidal space. Transudative fluid and the large molecule proteins it is associated with create its own oncotic pressure, drawing further fluid into the suprachoroidal space.
SURGICAL PROBLEMS ENCOUNTERED IN THE SPACE
The following are problems that may be encountered during surgery:
- Collection of fluid in this space (either protein-rich fluid as in choroidal effusion or blood-mixed fluid as in choroidal hemorrhage) is usually located posterior to the ora serrata. This usually occurs in the immediate postoperative period with hypotony after glaucoma filtration surgery. Collection of fluid pushes the choroid/retina complex inward in a segmental fashion because of the outward passage of the vortex veins. Thus, indirect ophthalmoscopy or ultrasound scan will reveal the effusion as a dark brown, translucent, dome-shaped elevation involving 1 to 4 quadrants on indirect ophthalmoscopy. Significant effusion can result in kissing choroids and compromise vision.
- Detachment of the longitudinal ciliary muscle to the scleral spur (cyclodialysis) can result in direct communication between the anterior chamber and the suprachoroidal space (cleft), which results in increased flow of aqueous humor into the suprachoroidal space and hypotony. The cleft can be visualized directly on gonioscopy as a dark area of detachment at the root of the iris with the white undersurface of the sclera visible or by using high-frequency ultrasound.
- Redirection of the aqueous humor into the suprachoroidal space via artificial communication channels (ie, shunts and stents) can reduce and control the IOP.
Figure 67-1. Choroidal effusion.
Choroidal Effusion
Choroidal effusion (Figure 67-1) is a collection of protein-rich fluid in the suprachoroidal space in response to hypotony following glaucoma filtration surgery. This is more likely to occur in patients with altered choroidal vascular dynamics and patients with obesity.
Hypotony could be the result of overfiltration or a leaky bleb. Ciliary body detachment can occur following anterior migration of the ciliary body, resulting in decreased aqueous secretion, worsening of hypotony, and shallowing of the anterior chamber.
Patients can present with painless loss of vision or shadows in the peripheral visual fields. Conservative treatment includes topical steroids alongside cycloplegic agents along with a course of low-dose oral steroids (20 to 30 mg prednisolone on a tapering regimen over 2 to 3 weeks).
SLIT-LAMP PROCEDURES
Leaky blebs should be addressed by suturing the bleb at the slit lamp. A flat anterior chamber should be addressed immediately with an injection of a highly cohesive viscoelastic substance, such as Healon GV (Johnson & Johnson Vision). This can be done at the slit lamp under topical anesthesia. The resultant anterior chamber deepening and increase in IOP achieved with this procedure may also be helpful in treating choroidal effusions, effectively squeezing the effusion from the suprachoroidal space.
A highly cohesive viscoelastic injection (0.1 cc; Healon GV or Healon 5) into the anterior chamber can also be tried to decrease choroidal effusions by a squeegee-type of mechanism.
Figure 67-2. Kissing choroidal effusions.
Indications for surgical intervention include shallow to flat anterior chamber, decrease in vision with kissing choroidals (Figure 67-2), or effusions persisting longer than 6 to 8 weeks. Flat anterior chambers are among the most common reasons for choroidal effusion drainage. When conservative management (often with frequent topical corticosteroids and cycloplegia) fails to resolve persistent choroidals, choroidal effusion drainage is indicated. Furthermore, prophylactic posterior sclerotomies are often indicated in high-risk individuals prone to develop choroidal effusions following glaucoma or other ocular surgeries.
ANESTHESIA
Choroidal drainage can be performed under topical anesthesia supplemented by subconjunctival injection of preservative-free lidocaine 1% mixed with preservative-free epinephrine 1:1000 (7.5 cc of lidocaine with 2.5 cc of epinephrine). Injection of this combination achieves several things, including regional anesthesia, control of bleeding, and dissection of the subconjunctival space with minimal trauma.
TECHNIQUE
The procedure is performed in the operating room using the operating microscope. Following the placement of the lid speculum, the anterior segment is examined under the microscope. The anterior chamber depth, shape, location, and presence of the bleb are noted. The absence of red reflex under the scope indicates the presence of significant choroidal effusion.
Because the bleb is usually present in the superior limbal area in glaucoma patients, the preferred location for the surgery is the inferior temporal or nasal quadrants. Either via a paracentesis or using a 30-gauge needle (our preferred technique), 0.1 to 0.2 cc of viscoelastic substance is injected into the anterior chamber. This will deepen the anterior chamber and increase the IOP to facilitate the surgery. It is important to maintain the IOP higher than 20 mm Hg throughout the surgery, both to facilitate complete escape of the choroidal fluid through the sclerotomy and to prevent the occurrence of hemorrhage during the procedure. This is achieved by using an anterior chamber maintainer. (Alternatively, one can use a 23-gauge butterfly needle that is connected to a bottle held as high as possible.)
A 7-0 Vicryl (Ethicon, Inc) traction suture is placed to the 6 o’clock limbus, and the eye is rotated superiorly. Limbal peritomy is performed in the inferior temporal quadrant followed by the sub-Tenon’s injection of a lidocaine-epinephrine mixture. Posterior dissection is performed in the same plane using Westcott scissors. Hemostasis is achieved by using underwater cautery. Approximately 4 mm posterior to the limbus, a 4-mm radial scleral incision is performed using a 15-degree blade. The dissection is carried gently deeper until the suprachoroidal space is entered. Careful dissection can be ensured by having the assistant hold the lips of the incision apart using 0.12 forceps. Injury to the choroid should be avoided. As soon as the suprachoroidal space is entered, straw-colored fluid is seen to exit the incision. The lips of the incision are parted to facilitate further escape of the fluid. As the choroidal effusion escapes, the IOP decreases, unless the pressure is maintained using the chamber maintainer as described previously. This procedure is repeated until all of the fluid escapes. Similar incision can be performed in the inferior nasal quadrant should the patient have significant effusion in that quadrant. As the effusion decreases, the pupillary reflex turns red. This can be confirmed with indirect ophthalmoscopy. The sclerotomy incision is left open to weep. The conjunctiva is secured back to the limbus using either a 10-0 nylon or Vicryl suture. We prefer to inject 0.1 to 0.3 cc of viscoelastic into the anterior chamber at the end of the procedure to maintain the IOP around 20 mm Hg. The bleb should also be examined to make sure that a leaky bleb does not exist.
Postoperative care consists of frequent application of a topical steroid along with cycloplegics for at least 1 month. Less than 5% of the choroidal effusions recur. Recurrence may be significant enough to require repeat drainage. If this were to happen, we prefer to close the scleral flap of the trabeculectomy operation with additional transconjunctival sutures to decrease the aqueous outflow at the end of the choroidal effusion drainage.
If combined with another surgical procedure, posterior sclerotomy should always be performed first as it decreases the amount of plasma proteins, inflammatory exudates, and fluid accumulation in the suprachoroidal space during surgery. As a result, even with lowering of IOP during surgery, there is less accumulation of fluid driven by osmotic pressure. It should also be noted that the technique for posterior sclerotomy is the same whether the procedure is performed for choroidal effusion drainage or for a suprachoroidal hemorrhage.
POSTOPERATIVE COMPLICATIONS
Complications include cataract formation, recurrence of choroidal effusions, and rarely retinal detachment and endophthalmitis. Usually, choroidal detachments are known to resolve completely within 6 weeks of a posterior sclerotomy. WuDunn and colleagues noted a success rate of 77% per drainage procedure. Cataracts are known to be a frequent complication after drainage of choroidal effusions and may be related to either reduced aqueous humor circulation around the lens or to lens-corneal touch. One study by WuDunn and colleagues noted a 77% cataract development rate in phakic eyes after choroidal effusion drainage.1 Other complications associated with drainage of choroidal detachments include hyphema, vitreous hemorrhage, retinal tear or detachment, and recurrent suprachoroidal hemorrhage. As with any other ocular surgery, endophthalmitis remains a concern, but rates are comparable to other ophthalmic procedures.
SPECIAL SITUATIONS
High-risk groups include nanophthalmic and hyperopic eyes as well as individuals who have previously developed effusions. As a result, scleral windows are often performed prophylactically in nanophthalmic eyes during other ocular surgeries to avoid potential complications. Patients with uveal effusion syndrome have both thick sclera and elevated episcleral venous pressure that often necessitates prophylactic sclerotomy. In addition, patients with raised episcleral venous pressure are prone to develop both intraoperative and postoperative choroidal effusions. This includes patients with Sturge-Weber syndrome, carotid cavernous fistulas, choroidal hemangioma, and dural sinus shunts.2,3
Aside from scleral windows, key preventative steps include small incision size, precise attention to adequate and full-time pressurization of the eye, and avoidance of any anterior chamber shallowing using bimanual techniques during anterior segment procedures.
SUPRACHOROIDAL HEMORRHAGE
Suprachoroidal hemorrhage usually occurs during or in the immediate postoperative period following glaucoma filtration surgery. It occurs as a result of an initial effusion or separation of the choroid from the sclera with associated rupture of the choroidal blood vessels leading to collection of blood in the suprachoroidal space. As opposed to choroidal effusion, which is painless, suprachoroidal hemorrhage is associated with severe pain.4,5
Intraoperative Suprachoroidal Hemorrhage
If the patient complains of severe pain in the middle of surgery, one should suspect suprachoroidal hemorrhage. The anterior chamber tends to become shallow with the increase in the IOP along with the appearance of a rapidly increasing dark shadow in the fundus with alteration of the red reflex. As soon as the diagnosis is suspected, one should stop further intraocular manipulation and close the wound. The diagnosis can be confirmed by indirect ophthalmoscopy and ultrasound. Once the diagnosis is confirmed, the quadrant with the maximum hemorrhage should be identified. A sclerotomy may be performed as described previously in that quadrant to drain out the blood. Drainage of even small quantities of blood will help decrease the pain and resolve the hemorrhage faster.
Suprachoroidal Hemorrhage in the Postoperative Period
Patients with a past history of multiple intraocular surgeries, aphakia with poorly controlled glaucoma, and older patients on blood thinners with uncontrolled hypertension are at higher risk of developing hemorrhage. Patients often present with sudden onset of ocular pain following a Valsalva maneuver. Examination will reveal decreased vision, elevated IOP, and shallow to flat chamber. Fundus exam will demonstrate dark shadows in the periphery. Ultrasound examination will demonstrate the presence of blood with high internal reflectivity. Because the blood clots soon after the bleeding, it is not possible to drain it until the blood clot begins to break down. Initial treatment is directed toward achieving symptomatic relief and consists of topical and systemic glaucoma medications to control elevated IOP, topical and systemic steroids to decrease inflammation, cycloplegic agents to deepen the chamber, and pain medications to control the pain. The indications for surgery include continued pain, kissing choroidal detachments, persistent shallow to flat chamber, and decrease in vision. Drainage of a suprachoroidal hemorrhage is similar to the drainage of effusions, typically performed after clot liquefaction (10 to 14 days).
CYCLODIALYSIS CLEFT REPAIR
Indications
Cyclodialysis clefts are the result of trauma. The cleft is created by the disinsertion of the longitudinal ciliary muscle from the scleral spur. This could be secondary to blunt trauma, such as fist or ball injury, or could be an unwanted complication of a surgical procedure such as the 25-gauge vitrectomy. It usually presents with very low IOPs and decreased vision. Diagnosis is confirmed by careful gonioscopy and high-frequency ultrasound. These clefts can usually be observed for resolution over 6 to 8 weeks. Various measures, including cycloplegia, injection of viscoelastics, argon laser treatment, and cryotherapy, can be used to treat a cyclodialysis cleft. If these measure fail, however, incisional surgery should be attempted in order to prevent complications associated with intractable hypotony, including hypotony maculopathy. It should be noted that cyclodialysis cleft creation has been used in the past for treatment of primary open-angle glaucoma, although results have often been unpredictable.
Surgical Technique
Various surgical techniques exist for repair of cyclodialysis clefts. Three common methods will be discussed here, including direct cyclopexy, cross-chamber cyclopexy, and iris base fixation techniques. For each technique, it is important to begin with the injection of viscoelastic material in the anterior chamber. This allows for the globe to become more rigid and also allows for better direct visualization of the cleft. Once visualized, the extent of the cleft should be marked using cautery or a marking pen for later reference. Next, it is necessary to create a limbus-based conjunctival peritomy adjacent to the cleft.
Direct Cyclopexy Technique
Originally described by Naumann, the direct cyclopexy technique has the benefit of direct visualization of the disinsertion of the ciliary body and scleral spur and thus allows the most anatomically precise closure of the cleft. However, this technique is also the most complex, and as such, comprehensive understanding of angle anatomy is required.6
After sufficient viscoelastic material is injected into the anterior chamber, a rectangular scleral flap at 60% scleral depth is created 4 mm radial to the limbus. The flap should extend at least 2 mm beyond the edge of the cyclodialysis cleft. Once the flap is dissected, a full-thickness incision through the bed of the dissection should be made about 1.5 mm posterior to the limbus. This incision should allow entry into the cleft and release of aqueous. Using 10-0 nylon sutures on a tapered vascular blood vessel needle, the ciliary body should be sutured directly to the sclera. Each suture should first pass through the anterior lip of the wound, then through the ciliary muscle, and finally out through the posterior lip of the scleral wound.
The sutures should only be tied after all have been placed in the appropriate areas. Cryotherapy can then be applied to the base of the scleral wound to enhance the adhesion of the sclera to the ciliary body. Next, the scleral flap is closed using 10-0 nylon, and finally, the conjunctiva is closed.
Cross-Chamber Cyclopexy Technique
The cross-chamber cyclopexy technique, developed by Metrikin et al,7 requires an aphakic or pseudophakic eye and is derived from the principles of suturing posterior chamber intraocular lenses. It is also less technically challenging than the previously described technique. In this procedure, a 1- to 2-mm corneal keratotomy is made exactly 180 degrees opposite the location of the cyclodialysis cleft. This can be accomplished with a super-sharp blade. Once again, viscoelastic material should be injected to help maintain a formed anterior chamber. Next, a 27-gauge needle is inserted ab externo through the sclera located 1.5 mm posterior to the limbus at one end of the cleft. This needle is then passed through the ciliary sulcus between the iris and posterior chamber intraocular lens. A 10-0 double-armed polypropylene suture on a straight needle is then threaded into the opening of this needle by inserting it through the previously made keratotomy site. The 27-gauge needle is subsequently pulled out of the eye along with the straight needle of the polypropylene suture. Next, this needle is reinserted into the sclera located 3 mm adjacent to the original entry site. The second arm of the polypropylene suture is then passed into the barrel of the needle before it is extracted from the eye again.
The 2 ends of the suture are then pulled tight, thus firmly bringing the ciliary body up against the wall of the sclera and closing the cyclodialysis cleft. The suture is tied, and the knot is buried. This procedure is then repeated along the length of the entire cleft as often as necessary. Once again, cryotherapy is applied to the base of the sclera to promote and maintain further adhesion. After closure of the conjunctiva and corneal keratotomy, any remaining viscoelastic material should be removed from the anterior chamber.
Iris Base Fixation Technique
The iris base fixation procedure was developed by Mills et al8 and is considered to be easier than the previously described techniques for cyclodialysis repair. Because it tends to create peripheral anterior synechiae, it is usually more appropriate for closure of smaller and shorter clefts.
Once again, a 1- to 2-mm keratotomy is made through the peripheral cornea; however, this incision is made 1-mm anterior to the limbus, adjacent to the location of the cleft. Next, a 60% thickness rectangular scleral flap is fashioned overlying the area of the cleft. One arm of a 10-0 nylon suture on a curved needle is then passed through the keratotomy, catching peripheral iris before exiting through the scleral bed, 1 mm posterior to the limbus. This procedure is then repeated with the other arm of the suture at a distance of 1 mm from the first bite. This suture is pulled tight, which often causes the pupil to peak as the peripheral iris is brought into contact with the scleral wall. Additional mattress sutures are placed along the peripheral iris to cover the entire length of the cleft. The scleral flap is closed using 10-0 nylon suture. The conjunctival peritomy is then closed. Any remaining viscoelastic material should be removed from the anterior chamber.
Figure 67-3. Schematic of the gold shunt. (Reprinted with permission from Solx, Inc.)
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