Combined canaloplasty and phaco offer advantages

Some key points of a phacoviscocanalostomy include creation and removal of a visco deep flap, removed by cutting a groove


Removal of the deep flap is completed with scissors


Healon GV (Abbott Medical Optics, Santa Ana, Calif.) is injected into the cut ends of Schlemm canal to keep the ostia open


The inner lining of Schlemm's canal is removed to increase out flow through the Trabeculo-Descemet's window
Source: Manijeh S. Wishart, M.D.

Consecutive nonpenetrating glaucoma surgery and cataract removal with lens replacement is likely to offer challenges to new surgeons
Surgeons who combined circumferential viscodilation and tensioning of Schlemm’s canal with clear corneal phacoemulsification and posterior chamber IOL implantation found it offered safe and effective pressure-reducing results.
The procedure in adult patients with open angle glaucoma (OAG) aimed to evaluate the safety and efficacy of circumferential viscodilation and tensioning of the inner wall of Schlemm’s canal, a nonpenetrating surgical procedure known as canaloplasty that has emerged in recent years as a treatment for OAG.
An international multi-center prospective study of 54 adults with OAG who underwent canaloplasty combined with cataract surgery found good results, including a drop in the mean baseline IOP from 24.4 mm Hg+/–6.1 (SD) and a mean of 1.5+/–1.0 medications per eye to a one-month mean post-op IOP of 13.6+/–3.8 mm Hg. At one year post-op the mean pressure was 13.7+/–4.4 mm Hg, and medication use had dropped to a mean of 0.2+/–0.4 per patient, according to the study published in the March 2008 issue of the Journal of Cataract and Refractive Surgery.
“The key take-home point is that surgeons—based on one-year follow up—can anticipate successful reduction in IOP and no bleb formation,” said Brad Shingleton, M.D., assistant clinical professor of ophthalmology, Harvard Medical School, Boston, and an author of the study. “We have retained and enhanced Schlemm’s canal function with this procedure.”
The safety results also impressed the authors. Surgical complications were found in five eyes (9.3%) and included hyphema, Descemet’s tear, and iris prolapse. In addition, transient IOP elevation of more than 30 mm Hg was observed in four eyes (7.3%) one day post-op.
High-resolution ultrasound biomicroscopic (UBM) images were obtained pre-op and post-op using an 85 MHz center frequency system (iUltraSound, iScience Interventional, Menlo Park, Calif.) to characterize the anterior angle morphology. The surgical approach followed temporal clear corneal phacoemulsification and posterior chamber IOL implantation with the glaucoma procedure.
The glaucoma portion began with dissection of the sclera to access Schlemm’s canal, followed by traditional viscocanalostomy and deep sclerectomy to access the canal. A microcatheter (iScience Interventional) was used to dilate Schlemm’s canal and install a trabecular tensioning 10-0 polypropylene suture. The surgeons formed a Descemet’s window at the surgical site, followed by excision of the deep flap and watertight closure of the superficial tissues to prevent bleb formation.
Dr. Shingleton said the results are important because a significant mean pressure reduction was achieved without the use of infection-prone blebs.
“What is very special about this procedure is that we are not creating a bleb,” said Dr. Shingleton. “Any surgical procedure that we can do without bleb formation is a major step forward for us. So for that reason alone we are very encouraged and optimistic.”
The combined canaloplasty is not for every OAG patient. The procedure did not produce the extremely low pressures produced by antimetabolite-enhanced filters. It is a better fit for OAG patient with advanced disease, high pressures, and the need for multiple medications, Dr. Shingleton said.
Roger L. Stamper, M.D., professor and Director of Glaucoma Services, University of California, San Francisco, performs canaloplasty surgeries on infants but was critical about the significance of the research.
“Each surgeon was allowed to decide whether the particular patient involved should get combined surgery, cataract only, or something else,” Dr. Stamper said. “Thus, we really don’t know which patients under what conditions got other kinds of surgery. Therefore, we can only look at this as a safety study.”
The authors restricted participation to patients with pre-op IOP of at least 21 mm Hg and open angles.
The recent research on combined canaloplasty and phacoemulsification cataract surgery found a significantly greater IOP reduction than was found in a July 2007 study in the Journal of Cataract and Refractive Surgery on cases of canaloplasty alone. The authors of the combined study said that the combined procedure appeared to take advantage of and sustain the well-established post-op reduction in IOP from cataract surgery.
The research leaves unanswered the question of whether the combined procedure is more efficacious than cataract surgery alone, Dr. Stamper said. Other common effective combined operations include cataract and trabeculectomy, cataract and ExPRESS miniature glaucoma shunt (Optonol Ltd., Israel), cataract and Trabectome (Neomedix, Tustin, Calif.), and cataract along with endocyclophotocoagulation.
“We can always use a ‘better’ operation, but this study does not really give us a clue as to whether the cataract plus canaloplasty is in any way better, although the safety profile seems OK,” Dr. Stamper said.
A potential disadvantage of the combined canaloplasty and cataract procedure, Dr. Stamper said, is that it is a complicated and somewhat lengthy surgery that surpasses the surgical time (and possibly the skill demands) of all other combined procedures.
Thomas K. Mundorf, M.D., Charlotte, N.C., agrees that there appears to be a learning curve to the procedure, but he said that shouldn’t dissuade surgeons from attempting it if it continues to garner positive research findings.
“With healing/scarring of the ocular tissues being a frequent etiology for failure of filtering procedures, canaloplasty may offer an avenue somewhat isolated from these risk factors,” said Dr. Mundorf.
Among the surgeons Dr. Mundorf has spoken to who have performed the combined procedure, as well as canaloplasty alone, their opinions and continued use of it are largely shaped by their early experiences with success or complications both during and following the procedures.

Editors’ note: Dr. Shingleton has financial interests with iScience Interventional (Menlo Park, Calif.). Dr. Stamper previously had financial interests with iScience and now has financial interests with Optonol (Israel) and Transcend (Atlanta). Dr. Mundorf has no financial interests related to his comments.

Contact information

Mundorf: 704-334-3222, tommundorf@aol.com
Shingleton: 617-314-2614, bjshingleton@eyeboston.com
Stamper: 415-476-3717, stamperr@vision.ucsf.edu