Canaloplasty modified to treat patients with disrupted Schlemm’s canal

Issue: December 25, 2016

Patients with primary open-angle glaucoma who have a disrupted Schlemm’s canal wall due to prior glaucoma surgery may benefit from a modified non-filtering canaloplasty technique.

“The premise condition of successful standard canaloplasty is the circumferential dilation of Schlemm’s canal and the placement of the suture,” Ningli Wang, MD, PhD, president of the Chinese Ophthalmological Society, said. “However, this is not practical for primary open-angle glaucoma patients with disrupted Schlemm’s canal, who have higher failure and incidence of complications when they receive repeated glaucoma filtering surgeries.”

Wang is a co-corresponding author of a 26-patient study in the Journal of Glaucoma that compared standard canaloplasty in patients without a history of glaucoma surgery and modified canaloplasty in patients with failed glaucoma and disrupted Schlemm’s canal.

The study assigned 17 patients to standard canaloplasty and nine patients to the modified technique. At 12 months, there was not a significant difference in IOP and the mean number of medications: 17.8 mm Hg vs. 16.7 mm Hg, respectively, and 0.9 medications vs. 0.3 medications, respectively.

The rate of successful circumferential catheterization was also not significant between standard and modified canaloplasty: 88.2% vs. 77.8%.

Steps

To perform the modified technique, the surgeon first approached the Schlemm’s canal lumen, where a scleral flap was created next to the previous surgical flap. Then, away from the prior surgical site, catheterization of Schlemm’s canal occurred, guided by an illuminated microcatheter.

Relay suture with guidance of an illuminated trocar. A 10-0 polypropylene suture was placed within the remaining length of the canal (a). The illuminated trocar was guided to be inserted beneath the scleral flap containing the disrupted canal (b). The needle with placed 10-0 suture was attached to the trocar (c). The 10-0 suture was withdrawn, and the two ends of the suture loop were approximated (d).

Source: Wang N

“When the microcatheter reached the distal limit of the Schlemm’s canal lumen, a radial scleral cut was made and the distal tip was exposed at the cut,” Wang told Ocular Surgery News. Next, a 10-0 polypropylene suture was tied and tracked in the Schlemm’s canal, followed by the injection of sodium hyaluronate 1.4%.

“A relay suture guided by an illuminated trocar was then manipulated to bridge the tissue containing the disrupted Schlemm’s canal,” Wang said. “The trocar was inserted beneath the deep scleral flap and pierced out at the other side of the prior surgical flap.”

Afterward, a needle was attached to the trocar and withdrawn to the site of the initial insertion. Lastly, the two ends of the suture were tightened.

Wang said the positioning of Schlemm’s canal might be more difficult with the modified technique because of tissue scarring and collapse of the Schlemm’s canal lumen originating from the bypass of the aqueous humor after glaucoma filtering surgery.

Hyphema

The most common study complication was hyphema, but it was not significantly different in the two groups: 29.4% for standard canaloplasty and 33.3% for the modified technique. All patients in both groups resolved spontaneously within 10 days.

Although the study was restricted to a limited number of cases, “our results indicate that compared to traditional surgical options, modified canaloplasty is practical and has at least an equivalent success rate and fewer complications,” Wang said.

The investigators continue to follow up with patients receiving standard and modified canaloplasty. “Preliminary results show that the more previous surgeries, the worse the control of the IOP postoperatively,” Wang said. “However, surgery failure is not relevant to the time between operations. It is the length of the disrupted Schlemm’s canal that is pertinent to the success of the modified surgery.”

In the future, the authors will evaluate the success rate of the placement of the tensional suture for both procedures and analyze the risk factors applicable to surgery failure.

“We are also detecting the fluorescein imaging to assist in assessing distal aqueous outflow, which is more important to the patient receiving modified canaloplasty because of the limited drainage region,” Wang said. – by Bob Kronemyer

Reference:
Xin C, et al. J Glaucoma. 2016;doi:10.1097/IJG.0000000000000420.

For more information:
Ningli Wang, MD, PhD, can be reached at Department of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; email: wningli@vip.163.com.

Disclosure: Wang reports no relevant financial disclosures.