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Rate of Descemet’s membrane detachment after canaloplasty may be higher than expected
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The first non-company-sponsored study to detect Descemet’s membrane detachment after canaloplasty to treat open-angle glaucoma found a 7.4% incidence rate.
The retrospective chart review included all patients who underwent canaloplasty at one institution between January 2007 and July 2011. Overall, 12 of 162 eyes developed Descemet’s membrane detachment (DMD).
Ramesh S. Ayyala
“The true incidence of DMD following canaloplasty has not been published prior to our study,” co-author Ramesh S. Ayyala, MD, FRCS, FRCOphth, director of Glaucoma Service at Tulane University Medical Center, said. “Unlike any other glaucoma surgery, canaloplasty can actually create DMD because of the injection of viscoelastic into Schlemm’s canal.”
Ayyala, who performed all the surgeries, thought that the detachment incidence rate would be lower.
“Previously published smaller studies have recorded a rate between 1% and 3%,” he said, attributing his study’s higher incidence to the fact that it evaluated corneas more carefully and counted small detachments. “Small DMDs are very easy to ignore, and they can disappear without one’s knowledge. In fact, most patients resolve their DMDs spontaneously.”
As surgeons increasingly embrace canaloplasty, Ayyala said it is important that they are aware of not only the likelihood of Descemet’s membrane detachment, but also of the probable anatomic location and how to manage the complication.
“Fortunately, the majority of DMDs are small and resolve on their own,” Ayyala told Ocular Surgery News.
Excessive viscoelastic
Most Descemet’s membrane detachments are located in the inferior quadrants.
“This could be secondary to excessive Healon GV (sodium hyaluronate 1.4%, Abbott Medical Optics) injection that accumulates in this location or may indicate a congenital weakness in the canal wall itself, considering the fact that inferior quadrants are the last to close, embryologically speaking,” Ayyala said.
The study, which appeared in the Journal of Glaucoma, found that visual acuity, IOP and number of glaucoma medications were not affected in any of the 12 eyes with Descemet’s membrane detachment, all of which were followed for at least 12 months. However, Ayyala has observed that if detachment is present in the first eye operated on, there is a greater chance that detachment will develop in the fellow eye after canaloplasty.
To reduce the likelihood of a Descemet’s membrane detachment, the surgeon should closely monitor new nurses, who may inject excessive amounts of viscoelastic.
“When we first started performing canaloplasty 7 years ago, the Healon GV was injected without any standard control,” Ayyala said.
Approximately 1 year later, iScience Interventional, maker of the ophthalmic microcatheter iTrack 250A, which in January sold its canaloplasty business to Ellex Medical Lasers Limited, standardized the amount of viscoelastic injected by recommending quarter turns of the syringe pump.
“The syringe is turned by the nurse as the surgeon instructs aloud to inject,” Ayyala said. “Usually, each turn of the syringe is accompanied by a loud click.”
The syringe releases roughly 2 µL of viscoelastic per click, and the maximum that can be injected is about 1 µL to 2 µL per clock hour.
“The recommendation is to inject one click every 2 to 3 clock hours, while the catheter is moving,” Ayyala said.
Detachment management
In the study, the majority of the detachments measured less than 3 mm and remained away from the visual axis.
“These smaller DMDs can be observed, and they tend to resolve within 1 to 3 months,” Ayyala said.
Larger detachments and those that have blood mixed with Healon may be drained, either with a 30-gauge needle or by slit incision with a 15° sharp blade, at the slit lamp.
“Even though most of these larger DMDs are recognized at the time of the surgery, I prefer to perform the drainage at 1 week, as the DMD is less likely to reoccur or expand,” Ayyala said.
Ayyala’s go-to surgery for open-angle glaucoma is now canaloplasty, and he estimated he has performed some 300 procedures since 2007. Surprisingly, he has encountered only one case of Descemet’s membrane detachment that encroached the visual axis and progressed to corneal decompensation. The 86-year-old male patient ultimately required penetrating keratoplasty. – by Bob Kronemyer
Reference:
Jaramillo A, et al. J Glaucoma. 2014;doi:10.1097/IJG.0b013e318279ca7f.For more information:
Ramesh S. Ayyala, MD, FRCS, FRCOphth, can be reached at Glaucoma Service, Department of Ophthalmology, Tulane University Medical Center, 1430 Tulane Ave., SL-69, New Orleans, LA 70112; 504-988-2261; email: rayyala@tulane.edu.Disclosure: Ayyala has no relevant financial disclosures.
Perspective
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Douglas J. Rhee, MD
Dr. Ayyala and colleagues have demonstrated that Descemet’s detachment occurs in approximately 7% of patients undergoing canaloplasty but that more than 90% of these resolve spontaneously. If resolution does not appear to be proceeding, it is prudent to consider drainage, especially if the visual axis is involved. If a larger series presents itself, it would be helpful to identify risk factors as to which eyes are more likely to have a visually significant complication from the Descemet’s detachment. Although a significant untoward side effect, Descemet’s detachment from canaloplasty seems to be self-limited and predominantly without immediately evident visual significance. Similar to other nonpenetrating glaucoma filtration surgery (ie, not full thickness, such as trabeculectomy), canaloplasty has a good safety profile.
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