Ординатура / Офтальмология / Английские материалы / Atlas of Glaucoma, Second Edition_Choplin, Lundy_2007

Figure 18.5 Creation of fornix-based conjunctival flap.

After the application of anesthetic, a fornix-based flap is created in the superior temporal or nasal quadrant.

of aqueous with no loss of anterior chamber depth or iris prolapse, and as such are effectively inconsequential and may even contribute to enhanced IOL lowering. Macroperforations are grossly evident violations of the TDW and result in anterior

chamber instability. This often necessitates conversion to standard trabeculectomy, although some surgeons have managed to tamponade the perforation with a collagen implant (Aquaflow device).

POSTOPERATIVE MANAGEMENT

Immediate

The post-operative management of NPGS is similar to that following a standard trabeculectomy. Patients are placed on topical antibiotics and steroids. Subconjunctival antimetabolite injections are used in a parallel manner with respect to indication, technique, timing and dosing. The major distinction in the post-operative care in NPGS from standard trabeculectomy is the contraindication of ocular massage by either the surgeon or the patient – this may rupture the TDW. Some surgeons also administer pilocarpine post-operatively to prevent iris apposition to the TDW.

Figure 18.7 Application of mitomycin C. Traditionally, the use of mitomycin C (MMC) and other antimetabolites was avoided in NPGS. However, more surgeons are using antibmetabolite therapy as an adjunctive therapy with NPGS. Most surgeons will apply MMC at the completion of the superficial flap. Note that the MMC-soaked sponge is being held under the superficial flap while the edge of the conjunctival flap is being elevated to preclude wound leaks.

Long term

In DS, the collagen implant typically dissolves by 9 months, after which time the scleral lake will maintain itself (Figure 18.18), providing the important conduit of aqueous flow. Late increases in IOP are related to increased resistance at the TDW (healing of microperforations), intrascleral lake fibrosis, or episcleral fibrosis (Table 18.3). If IOP increases above target postoperatively, laser goniopuncture (Figures 18.19, 18.20) should be attempted first, and is required in 10–63% of cases (Table 18.4). Although this effectively converts NPGS to a penetrating procedure, performed in the

Figure 18.8 Outline of the deep flap. The next step is the creation of the deeper flap at 90% scleral thickness, which represents the most technically challenging step of NPGS, and should be performed under high magnification. The dimensions of the deeper flap are slightly smaller than those of the superficial flap. In DS it is a 4 mm 4 mm square flap, whereas it is a smaller parabola in VC. Here the outline of the deeper flap has been scored with the ‘Safety Trifact’ diamond blade.

safety of the postoperative period after bleb formation, it dramatically reduces the concern for hypotony-related problems. Intrascleral or episcleral fibrosis should be considered and managed as in trabeculectomy, with antimetabolite and needling.

Rarely, an acute rise in IOP after NPGS can occur due to iris adherence or incarceration at the TDW in the early postoperative period or following goniopuncture – particularly if the openings are too large or placed too posteriorly. Iris incarceration can be managed with Nd:YAG synechiolysis and/or argon laser peripheral iridoplasty. Failing laser treatment, the iris can be swept away with

Outer wall of SC being lifted

Inner wall of SC

Scleral spur

Figure 18.10 Continuing the deep flap dissection. At the correct depth, advancing the flap anteriorly, the scleral fibers in the dissection bed change from a random arrangement, to an organized arrangement circumferential to the limbus; this represents the glistening white scleral spur which is just posterior to SC. Continuing the dissection forward at this level will unroof SC beyond which is a natural plane between Descemet’s membrane and the overlying stroma requiring little, or no force to advance.

Figure 18.11 Finishing the deep flap dissection. The dissection must continue at least 1 mm into clear cornea to create an adequate TDM. Vertical relaxing incisions are required at the lateral edges of the flap to carry the flap into the cornea. Great care must be taken not to rupture DM which is susceptible to trauma at this step – this is facilitated using a ‘Safety Trifacet’ diamond blade. The TDW may be bulging forward if the IOP is very elevated, increasing the risk of inadvertent rupture; therefore, it would be prudent to perform a paracentesis in this circumstance.

Figure 18.16 VC – Closure of the superficial flap. The superficial flap is then reflected back into place and sewn tightly. Finally, high-viscosity viscoelastic is injected underneath the flap to maintain the scleral lake. High-viscosity viscoelastics have been shown to prevent fibrinogen migration, thus minimizing scar formation, which could obliterate the scleral lake over time.

a 27-gauge needle inserted into the anterior chamber at the limbus.

Review of literature

Early NPGS studies, primarily evaluating VC or DS without an implant, suggested lesser efficacy in lowering IOP as compared to MMC trabeculectomy. However, refinements to technique such as spacemaintaining devices, antimetabolite use, and postoperative modulation with Nd:YAG goniopuncture, have resulted in comparable if not superior IOP lowering while maintaining an excellent safety profile, particularly in DS with collagen implant. The IOP-lowering efficacy of VC is probably not as great as in DS with an implant. In the review of current

Figure 18.17 Conjunctival closure. The conjunctival flap is closed in the usual fashion for both procedures. The authors prefer a 10-0 Vicryl suture on a vascular needle, passed in horizontal mattress fashion across the extent of the incision.

literature, it is worth noting that some studies have considered postoperative laser goniopuncture a failure, citing that this effectively converts NPGS into a penetrating procedure. Proponents of NPGS have countered that the need for post-operative modulation of flow with goniopuncture is no different from the need to perform argon suture lysis which, although effectively converting a guarded procedure to full thickness, is not associated with the same risks as full-thickness procedures. Currently, longterm data on NPGS are evolving which suggest that altered bleb morphology achieved with NPGS (shallow and diffuse in DS, and non-existent in VC) reduces the risk for late leakage, blebitis and endophthalmitis. A review of major studies evaluating NPGS is presented in Tables 18.5 and 18.6.

Table 18.5 Outcomes of Non Penetrating Glaucoma Surgery and Trabeculectomy

289 surgery penetrating-Non

Table 18.5 (Continued)

glaucoma of Atlas 290

DS: deep sclerectomy, DSCI: deep sclerectomy with collagen implant, VC: viscocanalostomy, Trab: trabeculectomy, Phaco: phacoemulsification, DSASI: deep sclerectomy with autologous scleral implant, DSSK: Deep sclerectomy with SKGEL implant, DSTF: Deep scleretomy with T-Flux implant, POp: Postoperative, IOp: Intraoperative, 5FU: 5-fluorouracil, GP: goniopuncture, NR: not reported, NA: not applicable.

1 A 1-0 chromic suture was used as a collagen implant.

surgery penetrating-Non