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Cataract Surgery | Oct 2011

The Future of Glaucoma Treatment

The goal is to control IOP without burdening the patient.

For the past several years, prescription of pharmacologic agents has been the dominant approach to the treatment of glaucoma. Other options are available; however, the potential for complications with glaucoma surgery and significant advances in the efficacy of antiglaucomatous eye drops have kept these alternatives in the background. Today, surgical options are emerging that may change the landscape of glaucoma treatment; these include drainage devices and techniques that have lower risk profiles than trabeculectomy and present the opportunity to lower intraocular pressure (IOP) and reduce medication use in glaucoma patients.

PROMISING OPTIONS

Endocyclophotocoagulation (ECP). Included among these new procedures are new less-invasive approaches to cyclodestruction. These tissue ablation procedures do not require a fistula or create a bleb and therefore have quicker recovery times than trabeculectomy. ECP is the controlled ablation of ciliary processes under direct endoscopic visualization to suppress aqueous production. ECP can be conducted alone or in conjunction with cataract surgery. (Editor’s Note: For more information on phaco-ECP, see Combined ECP and Cataract Surgery, page 64.) In one study, 79% of eyes that underwent a combined procedure achieved a long-term decrease in IOP 3 years after surgery versus 38% of eyes that underwent phacoemulsification only. Additionally, 68% of phaco-ECP patients decreased their medication use, versus 11% of phaco-only patients.1 There was no difference in the risk profiles of the groups.

Nonpenetrating canaloplasty. This procedure creates a pathway for aqueous in Schlemm canal using an ophthalmic viscosurgical device (OVD) and a microcannula. One difference between viscocanalostomy and canaloplasty is that the latter opens the entire length of the canal, not just one section. Robert Stegmann, MD, has reported excellent IOP lowering with use of canaloplasty.2 According to his research, 92% of patients (n=34) achieved an IOP of 12 mm Hg postoperatively, down from an average before surgery of 44.5 mm Hg. Additionally, complications are far less frequent and severe after nonpenetrating canaloplasty than with other traditional glaucoma surgeries.

Glaucoma shunts. Shunting procedures using an ab externo approach include the Ex-Press Glaucoma Filtration Device (Alcon Laboratories, Inc., Fort Worth, Texas) and the Solx Gold Shunt (Solx, Inc., Waltham, Massachusetts). The Ex-Press Glaucoma Filtration Device is an adaptation of trabeculectomy; it shortens operating room time, eliminates the need for iridotomy, standardizes the outflow hole to 50 μm, and provides faster visual recuperation. The Solx Gold Shunt is inserted into the superciliary space to allow aqueous to exit from the anterior chamber and into the suprachoroidal space. The eye’s natural pressure differential between the anterior chamber and the suprachoroidal space allow continued outflow of aqueous.

MIGS. Microinvasive glaucoma surgery (MIGS) spares the conjunctiva and does not destroy the surrounding tissues. Instead, MIGS procedures focus on restoring the trabecular meshwork and the physiologic outflow systems for aqueous in the anterior chamber. Several techniques are still in development. The CyPass Micro-Stent (Transcend Medical, Inc., Menlo Park, California) is implanted into the superciliary space via a small guide wire. The Hydrus Intracanalicular Implant (Ivantis, Inc., Irvine, California) is implanted into Schlemm canal to act as scaffolding to allow aqueous to flow. Neither device has published efficacy results, but both appear promising.

The first MIGS device to be marketed in Europe is the iStent Micro-Bypass Stent (Glaukos, Laguna Hills, California). The iStent is inserted into Schlemm canal through a 1-mm clear corneal incision or through the phaco incision when the implantation procedure is com-Z bined with cataract surgery. This stent restores the natural outflow channels, and the safety profile is comparable to that of cataract surgery alone. In a terminal washout study comparing cataract surgery alone to cataract surgery with an iStent, the iStent group achieved a mean target pressure of 16.6 mm Hg, equivalent to an approximately 3 mm Hg greater reduction in IOP versus cataract surgery alone.3 Additional studies show that this treatment is potentially titratable, allowing physicians to reach lower target IOPs with the implantation of additional iStents.4

CONCLUSION

Glaucoma has historically been a difficult disease to manage. Topical medication only postpones surgery and often causes changes in the conjunctival and scleral tissues after long-term use. Trabeculectomy effectively lowers IOP, but it also can cause complications immediately following surgery or in the long term. Today’s surgeons are also burdened with decisions about cost, forced to decide if the latest technology is worth the price.

The new technologies described above present excellent opportunities in the treatment of glaucoma to provide good IOP control and maintain a low risk profile. As surgeons, we now have the ability to control IOP without burdening patients with medications, and it is up to us to make treatment decisions based on what is best for the patient.

Matteo Piovella, MD, is Director of the Centro di Microchirurgia Ambulatoriale, Monza, Italy. Dr. Piovella states that he is a consultant to Abbott Medical Optics, Inc. and BVI Beaver Visitec International. He may be reached at tel: +39 039 389 498; email: piovella@piovella.com.

  1. 1.Berke SJ.Phacoemulsification combined with endoscopic cyclophotocoagulation in the management of cataract and medically controlled glaucoma:a large,long term study.Paper presented at:American Glaucoma Society 16th Annual Meeting;March 4,2006;Charleston,South Carolina.
  2. Grieshaber MC,Pienaar A,Oliver J,Stegmann R.Canaloplasty for primary open-angle glaucoma:long term outcome. Br J Ophthalmology.2010;94(11):1478-1482.
  3. Fea AM.Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary openangle glaucoma. J Cataract Refract Surg.2010;36:407-412.
  4. Ahmed,Ike K.Multiple iStent Schlemm’s Canal Implants with Phaco.Paper presented at:American Glaucoma Society Annual Meeting;San Diego;March 5-9,2009.

TAKE-HOME MESSAGE

• About 68% of patients experienced a decrease in glaucoma medication use after phaco-ECP.
• Complications after nonpenetrating canaloplasty are less frequent than after traditional glaucoma procedures.
• MIGS procedures spare the conjunctiva and do not destroy the surrounding tissue.

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