adjunctive medication for control. In another study by the same group in which trabeculectomy was performed in one eye and deep sclerectomy with collagen implant in the other, the results were comparable although pressures were slightly lower for the eyes having trabeculectomy: 12.9 mmHg at 2 years compared to 13.9 mmHg for the DSCI eyes with equal overall success rates; however, the DSCI eyes had 50% less hyphema and serous choroidal detachments in the early postoperative period.58 One almost 4-year study in patients with exfoliative glaucoma showed roughly half controlled at 19 mmHg or below without medications and only one-third of patients with primary open-angle glaucoma controlled by the same criteria; the authors conclude that deep sclerectomy with implant works better in eyes with pseudoexfoliation than in eyes with primary open-angle glaucoma.59 Over 2 years, deep sclerectomy without implants, mitomycin-C, or goniopuncture works almost as well as trabeculectomy without mitomycin-C, but the trend of IOP suggests some loss of efficacy over time,60

although results of DSCI may be maintained even up to 8 years of follow-up.61,62

Postoperative Nd:YAG laser goniopuncture is required to con-

trol pressure in anywhere from 3% to 80% with the average settling around 50% with long-term follow-up61–64; intraoperative mito-

mycin-C application seems to reduce the need for this maneuver.64 In one study, IOP fell from a pre-laser average level of 32 mmHg to an immediate post-laser level of 17 mmHg with maintenance of this level for at least 6 months.65 Complications of Nd:YAG gonio­ puncture have been limited to iris incarceration into the site with subsequent elevation of IOP.67

Filtering blebs have been small or not observed; inflammation is reduced compared to trabeculectomy perhaps because no iridectomy is performed.66

Despite the fact that this operation, theoretically at least, does not depend on filtration under the conjunctiva for success, the suc-

cess rate appears enhanced with the use of intraoperative application of mitomycin-C to the operative site.67,68 However, in one

randomized clinical trial in west African patients, the authors were unable to show any difference up to 18 months between those having deep sclerectomy with mitomycin-C and those not receiving mitomycin.69 In this same study, while the results at 1 year were mildly encouraging with about 70 % having IOPs under 18 mmHg, the results at 18 months were quite disappointing in both groups with success hovering only around 35%.

As with trabeculectomy, the operation seems to work better in eyes not previously treated with topical medications for glaucoma.70 The procedure also seems to work in highly myopic eyes despite the thin sclera.71 Success in eyes with uveitic glaucoma has also been reported.72

Deep sclerectomy with collagen implant can be successfully combined with phacoemulsification cataract surgery.73 In one retrospective study of consecutive cases, there was no difference in pressure control or major complications between combined phacoemulsification with trabeculectomy and phacoemulsification with deep sclerectomy except a significantly higher risk of bleb leaks in the phacoemulsification with trabeculectomy group.74

Complications include perforation of the trabecular meshwork with need to convert to trabeculectomy,45,75 scleral ectasia,76 iris incarceration,51,77,78 hemorrhagic Descemet’s detachment,79 hypotony,80,81 and vitreous hemorrhage.82 Bleeding into the anterior chamber from the site of deep sclerectomy during gonioscopic examination can occur quite late in the postoperative period (Box 38-3).82 Having to convert to trabeculectomy because of

Box 38-3  Complications of deep sclerectomy

Conversion to trabeculectomy because of penetration through trabecular meshwork

Scleral ectasia

Iris incarceration, prolapse or peripheral anterior synechiae Descemet’s detachment

Hypotony

Hyphema

Serous choroidal detachment Vitreous hemorrhage

Late anterior chamber bleeding during gonioscopy

perforation into the anterior chamber through Descemet’s membrane or trabecular meshwork produces, as expected, ultimately a lower IOP than uncomplicated deep sclerectomy but increases the early postoperative complication rate and prolongs the time to recovery of best vision.83

The operation is technically difficult and can be highly variable in the exact morphology of what is accomplished, even in the hands of experienced and capable surgeons.84 Placing a trabeculotome in Schlemm’s canal before dissecting the internal scleral block seems to improve the accuracy.85 Some have suggested that

the internal scleral block can be more easily removed by erbium, excimer or CO2 lasers.86–88

In summary, deep sclerectomy with or without an implant offers acceptable pressure levels, often with the need for adjunctive topical antiglaucoma medications, with a low rate of hypotony and bleb-related complications. Generally, this operation has been more accepted in Europe but, perhaps, because of its technical demands and its somewhat inferior pressure lowering, Americans by and large have stood on the sidelines waiting for more and longer term prospective, randomized trials.89

Shunts into schlemm’s canal

Another approach that seems to have potential as an effective operation in open-angle glaucoma is to bypass the obstructed trabecular meshwork by implanting a stent ab interno into Schlemm’s canal, shunting aqueous from the anterior chamber directly into Schlemm’s canal. The first such shunt was proposed by Rhea Brown. A slightly different version made from silicone tubing bent at a right angle was proposed by Spiegel and co-workers.90 Early clinical trials suggest that this technique is feasible and both reduces IOP and the need for glaucoma medications.91 Using a variation of this technique in cultured human anterior segments, Bahler and co-workers showed that one shunt produced the largest IOP reduction and increase in facility of outflow but that each additional shunt in a different quadrant up to a total of four did, indeed, show increments of pressure reduction and outflow facility increase.92 Theoretical calculations by Zhou and Smedley suggest that a single shunt should be able to lower IOP into physiologic ranges.93 A large-scale clinical trial of one such microshunt (iStent®, Glaukos Corp, Laguna Hills, CA) is under way. No longterm data are available at the time of this writing.

An alternative approach to bypassing the trabecular meshwork is to ablate it. Goniotomy has been used for over 70 years in congenital glaucoma. However, it does not work in adult open-angle glaucoma possibly because the goniotomy knife causes damage to the outer wall of Schlemm’s canal with resultant scarring and blockage of aqueous drainage beyond Schlemm’s canal. Francis and colleagues set out to design an instrument that would ablate the trabecular meshwork without damaging the outer wall of Schlemm’s canal.94 The resulting instrument has a smooth but tiny tip that fits into Schlemm’s canal by inserting it through the trabecular meshwork under gonioscopic control. A wire delivers a radiofrequency current that destroys the intervening trabecular meshwork between the wire and the tip-plate which protects the outer wall of Schlemm’s canal from damage (Fig. 38-4). The concept was proven in eye-bank eyes as well as in rabbits.

A clinical trial in 37 adult eyes with open-angle glaucoma covering 3–13 months follow-up was recently reported.95 Mean preoperative IOPs were about 28 mmHg with mean postoperative pressures ranging from about 18 mmHg on the first postoperative day to 17.5 mmHg at 6 months and 16.3 mmHg at 12 months. Numbers of medications decreased from 1.2 preoperatively to 0.4 at 6 months postoperatively.Vision returned to preoperative levels within 3 weeks in all but one patient who had trauma resulting in a hyphema. Blood reflux into the anterior chamber occurred in most patients but cleared by about 1 week. One patient had late hyphema following blunt trauma. No other complications occurred. The authors conclude that the operation may be useful as an alternative to goniotomy in infantile glaucoma and useful in adult open-angle glaucoma, somewhere between laser trabeculoplasty and filtering surgery. Larger trials with longer follow-up are awaited.

The idea of shunting fluid from the anterior chamber into the suprachoroidal space is not new. The operation was cyclodialysis, in which a cut down was made through sclera onto the suprachoroidal space after which a special spatula was inserted anteriorly along the scleral wall into the anterior chamber to disrupt the ciliary body insertion into the sclera.This allowed aqueous direct access to the suprachoroidal space where the colloidal pressure is higher and

the tissue pressure is lower.96 Cyclodialysis was used as early as the 1930s by Otto Barkan among others.97,98 Cyclodialysis was used

extensively in the 1950s and early 1960s especially in aphakic glau-

coma and could be combined with intracapsular cataract extraction.99,100 Cyclodialysis seems to be effective at lowering the IOPs

to normal in experimental rats made glaucomatous.101 Although still used by some in combination with modern cataract extraction techniques, it has been largely abandoned, in part because of the variability of pressure control, in part because of the complications of anterior chamber bleeding, stripping of Descemet’s membrane,

and hypotony, and in part because of the advent of the safer and more predictable trabeculectomy and tube-shunt procedures.102,103

Adding a seton or stent to maintain patency of the cylclodialysis cleft was first described in the 1960s.104 Nesterov used a scleral strip in the cleft in an attempt to keep it open longer.105 This procedure seemed to increase outflow facility by about 25%.106 In monkey eyes, this procedure resulted in a four-fold increase in uveoscleral outflow facility.107 The late Michael Yablonski revived this idea and reported a series of cases successfully treated with a combination trabeculectomy and cyclodialysis augmented by two silicone tubes into the suprachoroidal space.108 More recently, a similar procedure was described using a single silicone tube with successful results.109 The Solx Company (Boston, MA) has begun making a thin gold wafer with microchannels that fits between the anterior chamber and the suprachoroidal space and drains fluid through the microchannels; some of the channels are not open and can be opened later by a titanium-saphire laser (which also can be used for trabeculoplasty).110 Initial presentations show IOPs settling at about 17 mmHg at 6 months (Fig. 38-5).As of this writing, there

Fig. 38-4  Trabecular meshwork ablation instrument (Trabectome®). Gold tip fits into Schlemm’s canal. Radiofrequency current ablates trabecular meshwork. Gold plate of tip protects outer wall of Schlemm’s canal from damage.

(Courtesy of NeoMedix, Tustin, CA.)

Fig. 38-5  Gold microshunt from anterior chamber to suprachoroidal space. (Courtesy of Solx Corp, Boston, Mass.)

are no published reports of clinical trials but the concept certainly shows promise; the idea of being able to modulate the flow in the postoperative period is very attractive.

Summary

Several new approaches to glaucoma surgery have been described in the last few years.The ideas are novel and have theoretical attraction

although many are based on old concepts. Several have had good initial results. However, few have had a long follow-up, rigorous trials, and randomized, prospective studies to establish their place in the armamentarium. One would hope that one of these will become a standard of treatment like the trabeculectomy in its time.

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