The only proven treatment for reducing the risk of glaucoma progression is reducing intraocular pressure. When IOP cannot be managed by medications, surgery is considered. Trabeculectomy has been shown to successfully lower IOP, but it also has shortcomings.
"The biggest issues with trabeculectomy are the potentially severe complications that can occur early and late postoperatively," says Ike K. Ahmed, MD. "These complications are primarily due to overfiltration, leaks and infection. When complications do occur, they can lead to severe vision loss that can be a life-long issue for patients."
Because of these complications, there has been a search for surgical treatment alternatives. "Some alternatives appear to be promising. However, to achieve targets that are very low, we still appear to need to go to trabeculectomy," says Dr. Ahmed, who is in practice in
The Evolution of Trabeculectomy
George L. Spaeth, MD, believes the trabeculectomy should still be the gold standard of glaucoma treatment, but it is not the same trabeculectomy that was performed in the 1950s. "Trabeculectomy as it is presently done is not a trabeculectomy. Trabeculectomy started as a procedure in which a section of the trabecular meshwork was excised in hopes that aqueous would exit through the cut edges of Schlemm's canal," explains Dr. Spaeth, the Louis J. Esposito Research Professor and director of the Glaucoma Service at
In today's trabeculectomy, the trabecular meshwork is no longer cut out. "Surgeons specifically and carefully do not cut out the trabecular meshwork. They cut out the tissue anterior to the trabecular meshwork, so it is no longer a trabeculectomy. During the past 20 years, the way the scleral flap is closed has also evolved, because full-thickness and guarded filtering procedures are associated with two major problems: too much aqueous coming through and too little aqueous coming through," he adds.
Too much aqueous exiting through the flap can cause low pressures, which can lead to hemorrhages and shallowing of the front of the eye, as well as predispose patients to cataracts. In contrast, too little aqueous exiting the eye does not provide enough pressure lowering. "That can happen late when the conjunctiva heals down onto the epi-sclera," Dr. Spaeth notes.
To address some of these issues, surgeons began using mitomycin over the filtration area. Dr. Spaeth says that while it helped fluid exit the eye better and provided less scarring in the area where it was applied, it actually predisposed to scarring where it was not applied. "Mitomycin, when applied only to one localized area, caused excess thinning of the conjunctiva in that area and predisposed to inflammation and scarring of the tissues adjacent to where it was applied," he explains. "The consequence was troublesome blebs that were predisposed to getting infected. I was opposed to the use of mitomycin because it caused so many serious problems. But then, doctors in
Instead of the filtering bleb being localized right over the scleral flap, the aqueous spread out over the top of the eye."
While that hasn't completely eliminated the scarring problem, it is significantly less than it was even 10 years ago.
Cutting the sutures or using releasable sutures has also been proposed to regulate outflow. Dr. Spaeth notes that many of the newer procedures are guarded filtration procedures that are very similar to a modern trabeculectomy.
Alternative Procedures
Dr. Ahmed says trabeculectomy is usually reserved for end-stage or advanced glaucoma cases. "That's not necessarily true with these newer procedures because of how ultra low-risk they are. They can be used earlier; however, they are definitely not ready to replace trabeculectomy. They are low risk, but they lack the efficacy of trabeculectomy.
It's not so much a matter of retiring the trabeculectomy as it is perhaps time for an earlier intervention in glaucoma, perhaps something that could be used with cataract surgery to lower pressure further than cataract surgery alone," he says.
Ex-PRESS Shunts
Dr. Ahmed says that the Ex-PRESS shunt offers more control and possibly a bit more reproducibility compared to trabeculectomy. "It's not a huge difference from trabeculectomy," he says.
Steven R. Sarkisian Jr., MD, who is in practice in
"These are patients who typically need to have a very low pressure, who have advanced glaucoma, and who are noncompliant with drops or intolerant to eye drops," he says. "In my hands, the Ex-PRESS mini glaucoma shunt is the preferred procedure over trabeculectomy because I feel that it has fewer postoperative complications. It is a move toward small-incision surgery for the treatment of glaucoma. However, trabeculectomy is required in a few limited cases."
A recent study found that the Ex-PRESS device under a scleral flap had similar IOP-lowering efficacy to trabeculectomy with a lower rate of early hypotony.1 In this retrospective comparative series of 100 eyes, 50 eyes in 49 patients treated with the Ex-PRESS miniature glaucoma implant under a scleral flap were compared with 50 matched control eyes in 47 patients treated with trabeculectomy. Success was defined as having an IOP between 5 mmHg and 21 mmHg, with or without glaucoma medications and without additional glaucoma surgery or removal of the implant. Eyes with IOPs below 5 mmHg during the first postoperative week were considered to have early postoperative hypotony. While patients implanted with the Ex-PRESS had higher IOPs early in the postoperative period, the reduction was similar in both groups after three months, and early postoperative hypotony and choroidal effusion were significantly more frequent after trabeculectomy compared with the Ex-PRESS implant under a scleral flap.
Dr. Sarkisian notes that both trabeculectomy and the Ex-PRESS shunt procedure result in a bleb, which is not ideal. "Patients are at long-term risk of infection. There is still no perfect procedure to treat glaucoma; however, the Ex-PRESS is a move in the right direction. With trabeculectomy, typically, there is a 1,000- to 2,000-µm hole in the eye.
This requires the placement of more sutures in the flap to reliably regulate flow. With the Ex-PRESS, the implant itself, because of the small 50-µm lumen, offers resistance to flow as well. Although you still need a scleral flap with the Ex-PRESS, the number of sutures required is fewer, and there is no need for an iridectomy. Furthermore, you do not need to rush to close the flap because the anterior chamber typically stays deep after you insert the Ex-PRESS and before you sew down the flap," he explains.
In a recently published retrospective, consecutive case series, 345 eyes had either the Ex-PRESS with or without cataract surgery.2 At three years after surgery, success was 94.8 percent and 95.6 percent in the Ex-PRESS and combined groups, respectively.
Canal Procedures
Three commonly performed canal procedures are the trabectome, canaloplasty and trabeculotomy ab externo. A recent review compared these three procedures.3
Trabeculotomy ab interno performed with the trabectome has been shown to lower IOP by almost 40 percent by 12 months with minimal complications. The trabectome alone and in combination with cataract surgery appears to lower IOP well. Canaloplasty alone has been found to lower IOP by 38 percent. When combined with cataract surgery, IOP was lowered 44 percent at 24 months. Trabeculotomy ab externo also lowers IOP well, especially in older adults, and phacotrabeculotomy lowers IOP to 21 mmHg or less in 84 percent of patients with supplemental use of medications and in 36 percent of patients without medications at three years.
A separate study found that trabectome offers a minimally invasive method of controlling IOP in open-angle glaucomas.4 In a retrospective case series of 1,127 trabectome surgical procedures, 738 underwent trabectome only and 366 underwent trabectome-phacoemulsification surgeries. In patients who underwent trabectome-only procedures, mean preoperative IOP of 25.7 ±7.7 mmHg was reduced by 40 percent to 16.6 ±4 mmHg at 24 months. There were no cases of prolonged hypotony, choroidal effusion, choroidal hemorrhage or infections. Medications decreased from 2.93 to 1.2 by 24 months. For patients who underwent trabectome-phacoemulsification procedures, baseline IOP of 20.0 ±6.2 mmHg decreased by 18 percent to 15.9 ±3.3 mmHg at 12 months, and medications decreased from 2.63 ±1.12 to 1.50 ±1.36.
"With canaloplasty, there is no bleb," Dr. Sarkisian says. "The data do look promising. In fact, canaloplasty looks like it can provide lower pressures than endoscopic cyclophotocoagulation or trabectome."
Another option is the iStent trabecular micro-bypass stent by Glaukos, although this is not yet approved by the Food and Drug Administration. A recent German study found that, in patients with cataracts and glaucoma, this stent significantly decreased IOP and drug burden.5 This prospective, 24-month, uncontrolled, non-randomized, multicenter study included 47 patients who underwent clear cornea phacoemulsification cataract extraction with ab interno gonioscopically guided implantation of the study stent. At baseline, patients' mean IOP was 21.5 ±3.7 mmHg, and patients were taking a mean of 1.5 ±0.7 ocular hypotensive medications. Six months after stent implantation, mean IOP was 15.8 ±3 mmHg, which is a mean IOP reduction of 5.7 ±3.8 mmHg (25.4 percent).
Additionally, patients' mean number of medications after six months was 0.5 ±0.8, which is a mean decrease of 1.0 ±0.8 medications (66.7 percent). Seventy percent of patients were able to discontinue all glaucoma medications. No complications or serious adverse events were reported.
ECP
Endoscopic cyclophotocoagulation is a relatively new method of cyclodestruction that can be used to manage refractory glaucomas.
A recent study conducted in India found that ECP significantly decreased IOP, significantly improved best-corrected visual acuity and decreased the number of antiglaucoma medications.6 This study included 50 eyes of 50 patients with refractory glaucoma whose IOPs could not be controlled with maximal medical therapy. These eyes underwent ECP by the anterior or pars plana route. Success was defined as an IOP of 22 mmHg or less either with or without medications. Patients were followed for three to 21 months (average of 12.27 months). IOP decreased significantly from 32.58 ±9.16 mmHg to 13.96 ±7.71 mmHg at last follow up. Additionally, patients' best-corrected visual acuity significantly improved, and the average number of antiglaucoma medications decreased from 2.51 ±097 to 1.09 ±1.16. In this study, ECP had a success rate of 82.2 percent.
"I perform ECP in combination with cataract surgery on patients who have early, moderate cases of glaucoma who don't necessarily require a pressure in the very low teens. It's a nice adjunct to cataract surgery, especially if a patient is on several medications and cataract surgery alone is probably not going to lower the pressure sufficiently well. I also find it to be very helpful in advanced glaucoma when a patient has already had a filtering procedure or a tube shunt and needs a lower pressure," Dr. Sarkisian says.
He explained that an excellent phaco/ECP patient is someone who needs to have a pressure somewhere in the mid to high teens, who is already on two or three glaucoma drops, and whose pressure is maybe in the high teens or low 20s. "Often, I can get these patients to their target pressure, and I can get them off one of their eye drops as well.
That combined procedure is a helpful paradigm because its focus is directly on the ciliary body, unlike transscleral cyclophotocoagulation, which typically causes a lot of collateral damage. Because it goes through the conjunctiva and sclera and destroys nerve tissue, it tends to cause problems, such as inflammation and hypotony; however, with ECP, I have not seen evidence of postoperative hypotony," he adds.
Dr. Sarkisian and his colleagues recently presented a study on ECP at the annual ASCRS meeting that found that ECP combined with cataract surgery is a reasonably safe and effective procedure and that it reduces patient dependency on medications while avoiding some of the complications of glaucoma filtration surgery. (Traynor MP, et al.
Combined cataract surgery and endoscopic cyclophotocoagulation in patients with glaucoma without prior incisional glaucoma surgery. Poster at the annual ASCRS meeting,
Additionally, hypotony-related complications including maculopathy, choroidal effusions and optic disc edema were not demonstrated in any of the study eyes. The study included 183 eyes of 137 patients. Of these 183 eyes, 178 were treated 360 degrees, three were treated 270 degrees, and two were treated 180 degrees. IOP was reduced from a preoperative average of 18.8 mmHg to 15.7 mmHg at 12 months. IOP-lowering medications were reduced from a preoperative average of 1.85 to 1.33 at 12 months. Of the 183 eyes included in the study, 158 (86.3 percent) reached an IOP lower than 21 mmHg and lower than their preoperative IOP. One hundred fifteen (62.8 percent) maintained an IOP lower than 21 mmHg and lower than their preoperative IOP over a mean follow-up of 8.1 months.
According to Dr. Sarkisian, several surgeries provide similar IOPs: phaco combined with ECP, phaco combined with trabectome, and early data suggest phaco combined with the iStent. However, none of them will offer pressures low enough for patients who fit the trabeculectomy profile. "They are very helpful tools in our surgical armamentarium, and the advantage of these procedures is that you still have the freedom and the ability to do filtering surgery at a later date if it's required," he says.
Further Studies Needed
Although the future role of trabeculectomy in glaucoma treatment may be uncertain, it is definitely not time to completely retire the procedure. "We need to see efficacy results at longer time points for these newer procedures. Typically, a patient who requires surgery needs a very low pressure. With these new devices and procedures, there will need to be a change in outlook of what surgery means. It may become something we use earlier in the treatment paradigm. However, for very advanced patients —for those needing pressures of 8 or 9 mmHg—I don't see trabeculectomy being retired at this point," Dr. Ahmed concludes.
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2. Kanner EM, Netland PA, Sarkisian SR Jr, Du H. Ex-PRESS miniature glaucoma device implanted under a scleral flap alone or combined with phacoemulsification cataract surgery. J Glaucoma 2009;in press.
3. Godfrey DG, Fellman RL,
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5. Spiegel D, Garcia-Feijoo J, Garcia-Sanchez J, Lamielle H. Coexistent primary open-angle glaucoma and cataract: Preliminary analysis of treatment by cataract surgery and the iStent trabeulcar micro-bypass stent. Adv Ther 2008;25(5):453-464.
6. Murthy GJ, Murthy PR, Murthy KR, Kulkarni VV, Murthy KR. Indian J Ophthalmol 2009;57(2):127-132.
