Deep Sclerectomy Surgery for Glaucoma
Konrad S. Palacios
José I. B. Sanchis
Konrad W. S. Wenyon
INTRODUCTION
Nonpenetrating glaucoma surgery, such as deep sclerectomy, has become more popular among surgeons in Europe,1 primarily because of its safety. Deep sclerectomy was described by Epstein and Krasnov in the late 1950s and subsequently revised by Fyodorov and others. Deep sclerectomy involves creating two partial-thickness scleral flaps with the second, deeper flat at 90% depth. During the procedure, the inner flap is removed, creating an intrascleral lake. The procedure is termed “nonpenetrating” because the inner wall of Schlemm canal, trabecular meshwork, and Descemet membrane remains intact. Filtration across the outer flap is allowed to create a conjunctival bleb. A dual mechanism of action is proposed with both enhanced uveoscleral outflow through the area of uvea exposed during the inner dissection and the formation of the conjunctival bleb. Other names for deep sclerectomy include nonpenetrating trabeculectomy and external trabeculectomy.
STUDIES
• In 1984, Zimmerman reported a retrospective study showing comparable results between the trabeculectomy (without antimetabolites) and nonpenetrating trabeculectomy in terms of intraocular pressure (IOP) control, but with lower postoperative complications such as shallow anterior chamber, uveitis, hyphema, and loss of vitreous; in their study, trabeculectomy (n = 86) controlled the IOP of 70% of patients (with or without medications), whereas nonpenetrating trabeculectomy (n = 71) similarly controlled the IOP in 84% of patients with a mean follow-up of 1.7 years.2
• In a prospective study in which patients (n = 39) were randomized to receive deep sclerectomy in one eye and trabeculectomy in the other, El Sayyad et al. reported success rates (i.e., IOP < 21 mm Hg) of 92.3% and 94.9% at 1 year (p = 0.9) for deep sclerectomy and trabeculectomy, respectively; serious complications were more prevalent with
trabeculectomy.3 In El Sayyad’s study, both groups were treated with postoperative 5-fluorouracil (5-FU) subconjunctival injections at the discretion of the investigators.
trabeculectomy.3 In El Sayyad’s study, both groups were treated with postoperative 5-fluorouracil (5-FU) subconjunctival injections at the discretion of the investigators.
• The results of deep sclerectomy are improved when combined with an implant. The implant is designed to maintain the suprachoroidal space (i.e., intrascleral bleb) avoiding the closure of the sclerectomy. The implants can be absorbable or nonabsorbable.
In a case series of 105 eyes with an average follow-up of 64 months, Shaarawy et al., using absorbable implants of collagen, reported a success rate of 91% (IOP < 21 mm Hg with or without medications) at 96 months; half of the eyes underwent laser goniopuncture with a mean time to goniopuncture at 21 months, and 23% received postoperative 5-FU injections.4 They reported no incidence of flat anterior chamber or endophthalmitis.4
Using the nonabsorbable T-Flux implant (IOL TECH Laboratories, France), Jungkim et al.5 reported a case series of 35 eyes with 12-month follow-up demonstrating a lowering of IOP from 33 mm Hg to a approximately 15 mm Hg with an average of 0.1 antiglaucoma medications. Ates et al.6 reported similar results in a small case series of 25 eyes.
The advantages of other methods using cheaper materials, like viscoelastic, show some long-term validity.7 It has been over 50 years since trabeculectomy was popularized; we are familiar with its advantages, disadvantages, and success rate but trabeculectomy comes with a price, and this is its complications. Most of the complications are related to excessive filtration, especially in the early postoperative period, such as flat anterior chamber, hypotony, choroidal detachment, and cataract formation. With trabeculectomy, complications occur in 10% to 18% of patients. The well-guarded dissection in deep sclerectomy reduces the complications related to overfiltrations.8
• An important point exists when analyzing the results of nonpenetrating surgery. Deep sclerectomy is highly dependent on the technical skills of the surgeon, which can show large differences when results from different authors are compared. Deep sclerectomy has a long learning curve during which the surgical time is longer and the initial outcomes might not be very satisfactory.
Dahan and Drusedau reported the results including patients from the learning curve, during which time perforations into the anterior chamber were 1 in 3, necessitating converting to a standard trabeculectomy. They also mention that as the manual technique improves, the perforation rate drops to 1 in 20.9
In our personal experience, the first 20 cases were converted to penetrating trabeculectomies for different reasons. Deep sclerectomy is not a simple surgery; on the contrary, time is needed to learn it properly, but once it is mastered, it is elegant, secure, and comfortable for the patients in most of the cases.
One of the surgeons with more expirience in Europe is André Mermoud and his group. They presented the results of 52 patients with Deep sclerectomy folow up for 10 years with a initial IOP around 26 mm Hg; 89% of them had an IOP < 21 with or without medication, 61% of them need goniopuncture during the follow-up.10
REFERENCES
1. Baudouin C, Rouland JF, Le Pen C. Change in medical and surgical treatments of glaucoma between 1997 and 2000 in France. Eur J Ophthalmol. 2003;13(suppl 4): S53-S60.
2. Zimmerman TJ, Kooner KS, Ford VJ, et al. Trabeculectomy vs nonpenetrating trabeculectomy: a retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg. 1984;15:734-740.
3. El Sayyad F, Helal M, El-Kholify H, et al. Nonpenetrating deep sclerectomy versus trabeculectomy in bilateral primary open angle glaucoma. Ophthalmology. 2000;107:1671-1674.
4. Shaarawy T, Mansouri K, Schnyder C, et al. Long-term results of deep sclerectomy with collagen implant. J Cataract Refract Surg. 2004;30:1225-1231.
5. Jungkim S, Gibran SK, Khan K, et al. External trabeculectomy with T-Flux implant. Eur J Ophthalmol. 2006;16:416-421.
6. Ates H, Uretmen O, Andaç K, et al. Deep sclerectomy with nonabsorbable implant (T-Flux): preliminary results. Can J Ophthalmol. 2003;38:482-488.
7. Ravinet E, Bovey E, Mermoud A. T-flux implant versus Healon GV in deep sclerectomy. J Glaucoma. 2004;13:46-50.
8. Drolsum L. Conversion from trabeculectomy to deep sclerectomy. Prospective Study of the first 44 cases. J Cataract Refract Surg. 2003;29:1378-1384.
9. Dahan E, Drusedau M. Non penetrating filtration surgery for glaucoma: control by surgery only. J Cataract Refract Surg. 2000;26:696-701.
10. Bissig A, Rivier D, Zaninetti M, Shaarawy T, Mermoud A, Roy S. Ten years follow-up after deep sclerectomy with collagen implant. J Glaucoma. 2008; 17: 680-686.
SURGICAL TECHNIQUE
• The surgery can be done with any type of local anesthesia; the authors prefer sub-Tenon and peribulbar anesthesia. If the procedure is to be combined with phacoemulsification, it will also benefit from intracameral anesthesia.
For sub-Tenon anesthesia, we use a mixture of Lidocaine 5% plus Bupivacaine 0.75%, 1.5 mL of each for a total volume of 3 mL. We use around 1.5 mL of this and keep the rest in case we need complementary anesthesia.
We also use drops of topical anesthesia and begin with a buttonhole in the conjunctiva/Tenon (Fig. 23-1A) in the inferotemporal quadrant introducing an 18-gauge Angiocath (Fig. 23-1B); usually after the infusion of the anesthetic, we have a chemosis (Fig. 23-1C) that helps with the initial conjunctival dissection.
• Nonpenetrating surgery should be performed in the superior quadrant of the globe; the reason is that filtration surgery has been associated with infections when it is done at the inferior quadrant.
To have a better exposure of the superior surgical field a traction suture can be used to rotate the globe inferiorly. A 5-0 black silk for the superior rectus or a corneal traction suture of 7-0 or 8-0 (Fig. 23-2A) black silk or vicryl can be used. The authors prefer the corneal traction suture (Fig. 23-2B).
• The conjunctival flap can be initiated at the limbus (Fig. 23-3A) or the fornix (Fig. 23-3B and C); authors prefer a limbus base with an L-shaped incision that is a modification of the Dahan incision (inverse L) (Fig. 23-3D). This is made using a Westcott scissors and a nontoothed utility forceps. It is important to extend the dissection in the subconjunctival space at either the nasal or the temporal side to the main incision. The sclera can be cleaned of any adhesions with the use of a scarifier.
Bleeding vessels should be lightly cauterized (Fig. 23-4A), or another option is to use the scarifier (Fig. 23-4B); the technique is the same as that of trabeculectomy.
• The superficial scleral flap measures 5 × 5 mm, and the measurements can be done with a caliper (Fig. 23-5A and B) or with a marker. For example, the Huco Vision has two different makers. One is the (Dahan) double-ended T-Flux trapezoidal marker that measures 5 × 5 × 2 mm at one end and a smaller 3.3 × 3 × 1 mm at the other end (Fig. 23-5C and D). Another is the (Mermoud) nonpenetrating glaucoma surgery double-ended marker that is 4 × 5 mm at one end and 4 × 4 mm at the other end. Authors prefer the trapezoidal
maker, but there are no differences if the flap is square (Fig. 23-5E and F) or trapezoidal (Fig. 23-5G and H).
maker, but there are no differences if the flap is square (Fig. 23-5E and F) or trapezoidal (Fig. 23-5G and H).
It is important to dissect the flap far anteriorly into the cornea, enough to ensure that we will be able to create a wide trabeculodescemetic window. The flap thickness should be between one-half and one-third of the sclera.
• The second or deep scleral flap (Fig. 23-6A) is the critical part, and it should have a total depth of 90% to 99% of scleral thickness; one tip is to start the dissection far back away from the limbus and progressively deepen in order to get the desired depth (Fig. 23-6B). As we get closer to the clear cornea, more care has to be taken. The reason is that the trabeculodescemetic membrane is very thin and can break easily just by a little excess of pressure; the dissection can be made more safely with a spatula (Fig. 23-6C). A diamond knife is too sharp and makes it very easy to perforate the trabeculodescemetic membrane. There is a diamond knife designed for dissecting this membrane, which is the Dahan Diamond Schlemm canal opener knife. Personally, authors prefer a 45-degree-angled steel knife.
• During the dissection when we start observing the change in color between the sclera and the clear cornea, it is better to do small cuts at the sides of the flap (Fig. 23-7A). We need to get far anterior into the clear cornea before we amputate the deep scleral flap (Fig. 23-7B). If the surgeon is working alone, a tip is to use an additional stitch to fix the superior scleral flap and to get a better view of the surgical field (Fig. 23-7C).
• The trabeculodescemetic membrane (Fig. 23-8A and B) is the key point of the surgery, and therefore, special care must be taken to prepare for it. The first and most important step is to get the right depth. The second step is to peel the Schlemm canal (Fig. 23-8C), and sometimes when we have done a very deep dissection, it will be already removed. After this, we can dilate the temporal and nasal sides of Schlemm canal, and this maneuver can be done with a spatula (Fig. 23-8D). Authors prefer the Mermoud predescemetic spatula (Huco Vision SA) or a scraper; the one shown in the figure is the Dahan trabecular meshwork scraper (Fig. 23-8E). When the canal is properly dilated, the aqueous humor will flow abundantly.
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