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Canaloplasty shows promise as glaucoma therapy
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LAS VEGAS — Canaloplasty appears to be effective in improving circumferential outflow in patients with primary open-angle glaucoma, according to a surgeon speaking here during the AAO meeting.
OSN Glaucoma Section Member Richard A. Lewis, MD, used the iTrack Microcatheter (iScience) to improve outflow through Schlemm’s canal. Canaloplasty is a nonpenetrating, blebless surgical technique in which a suture is passed through Schlemm’s canal with the help of a microcatheter and tied with a small amount of tension to reopen the canal, Dr. Lewis explained.
Richard A. Lewis |
Dr. Lewis said after Schlemm’s canal is identified and entered with the minicatheter, the surgeon uses a viscoelastic to dilate the entire 360° of the canal. The catheter is then navigated through the canal, which is facilitated by a lighted, flashing beacon mounted on the end of the device.
Once canalization is complete, a suture is threaded through the canal and tied off, Dr. Lewis said.
In a multicenter, prospective study in 92 patients, canaloplasty reduced IOP from a mean of 23.3 mm Hg at baseline to a mean 14 mm Hg at 1 year postop, he said.
“I think this procedure provides an interesting and unique opportunity to work in a space that glaucoma surgeons have not worked in, not only to provide surgical control of glaucoma, but also to provide medical treatment as well, in a long-term example,” Dr. Lewis said.
Follow-up of more patients at 1 year is pending, he said.
Following are additional glaucoma highlights from the AAO meeting. Most of these originally appeared as daily coverage on OSNSuperSite.com. Look for more in-depth articles on these subjects in upcoming issues of OSN.
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Image: Moskowitz A, OSN |
Suprachoroidal space is good target for aqueous in glaucoma
To improve aqueous outflow in glaucoma, the suprachoroidal space provides many advantages over the subconjunctival space as a target site for aqueous diversion, according to Robert D. Fechtner, MD, FACS.
Dr. Fechtner said the subconjunctival space is a “dreadful” target for aqueous diversion, despite the popularity of trabeculectomy, because it results in poor cosmesis, a lifetime risk of endophthalmitis and an unpredictable wound-healing response. He proposed using the suprachoroidal space instead, as it is a normal route for aqueous outflow and heals more predictably.
Dr. Fechtner described results using the Solx Gold Micro-Shunt, which is designed to divert aqueous to the suprachoroidal space. In a nonrandomized study of 76 eyes with a mean preop IOP of 27.5 mm Hg, treatment with the Gold Micro-Shunt resulted in a 37% mean reduction in IOP at 24 months’ follow-up, Dr. Fechtner said. No severe hypotony or suprachoroidal hemorrhages were seen in the study, he said.
Trabeculectomy remains most popular surgical option
Despite the development of other surgical approaches for lowering IOP, trabeculectomy remains the most popular choice among ophthalmologists because of several key advantages, said Claude F. Burgoyne, MD, who delivered a presentation on behalf of John C. Morrison, MD.
One advantage of trabeculectomy is its efficacy, Dr. Burgoyne said. When performed with adjunctive antifibrotic agents such as mitomycin-C (MMC), trabeculectomy can achieve IOPs lower than surgery without adjunctive agents for several types of glaucoma, including open-angle glaucoma, pseudophakic glaucoma and some secondary glaucomas, he said.
A second advantage is its flexibility; trabeculectomy can be modified to improve pressure control and to increase safety. Surgical modifications include titrating the amount of antimetabolite used based on the perceived need, preventing MMC exposure to tissues and choosing between a limbus-based and fornix-based conjunctival flap. For high-risk eyes, safety can be improved by creating larger or thicker flaps to reduce the extent of pressure reductions, he said.
The degree of postoperative IOP reduction can be adjusted using laser suture lysis or releasable sutures, Dr. Burgoyne said
Finally, trabeculectomy is a repeatable procedure, and failed surgeries can be revised. Scarred blebs can be needled at the slit lamp and revised with antimetabolites, he said.
Sleep apnea may be a risk factor for glaucoma
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Image: Moskowitz A, OSN |
Sleep apnea may be a significant risk factor for developing glaucoma, according to Parag A. Gokhale, MD.
Dr. Gokhale discussed the results of a meta-analysis evaluating the association between sleep apnea and glaucoma. Sleep apnea is defined as a complete cessation of airflow lasting 10 seconds or more during sleep. Several studies support the association between glaucoma and the sleep disorder, he said.
A Swedish study including 114 subjects suspected of sleep apnea found that 69 patients had sleep apnea, and, of those, five had glaucoma. In a second study, the same researchers examined 30 patients with primary open-angle glaucoma (POAG) and found that six patients also had sleep apnea, Dr. Gokhale said.
Dr. Gokhale also described an American study that reviewed sleep histories of patients with either normal-tension glaucoma or suspected normal-tension glaucoma. They compared the findings to a control group of healthy subjects.
The researchers found that seven of 23 glaucoma patients and three of 14 glaucoma suspect patients had sleep apnea, but none of 30 control patients had the condition.
A Chinese study further supports the association, Dr. Gokhale said. This study found that both abnormal visual fields and suspicious optic discs were more common in patients with severe obstructive sleep apnea than in age-matched controls. Similarly, another study found that 34 patients with sleep apnea had thinner retinal nerve fiber layers than age-matched controls.
On the other hand, two recent larger-scale studies found no association between sleep apnea and glaucoma. But despite this conflicting evidence, Dr. Gokhale said he believes sleep apnea is a risk factor for glaucoma.
“In my glaucoma patients, I do take a brief sleep history and refer these patients for sleep studies if the symptoms are positive,” he said. He urged the audience to do the same.
Dr. Gokhale noted that the most likely etiology to explain the association is ischemic damage to the optic nerve, possibly related to abnormal blood flow autoregulation, hypoxia, hypertension or arteriosclerotic disease.
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Image: Moskowitz A, OSN |
Focus NTG treatment on targeted IOP reduction
Medications and surgery can each be useful in managing patients with normal tension glaucoma, (NTG), but regardless of the approach chosen, treatment should focus on lowering IOP to a targeted level, said Roger A. Hitchings, FRCOphth.
Mr. Hitchings said a number of prospective, randomized studies have underscored the importance of achieving a targeted IOP reduction to prevent glaucomatous progression in NTG. However, recommendations vary, ranging from about 12% to the 30% reduction recommended by the Normal Tension Glaucoma Study, he said.
“If you achieve that target, you can benefit,” he said. Referring to a study performed at Moorfields Eye Hospital in London, he said, “Those eyes with more than a 25% reduction as opposed to those eyes with less than a 25% reduction in pressure, ... [had] a statistically significant difference in the time to progression.”
Regarding choice of medication for NTG patients, he said carbonic anhydrase inhibitors can be effective, but they do not work at night. Drugs that act to increase aqueous outflow also are not effective, “because outflow is usually normal in these individuals,” Mr. Hitchings said.
Prostaglandin derivatives have been shown to generate an average 20% IOP reduction when used as initial therapy for NTG, although these drugs reduce IOP by an average of 30% when used in POAG.
“In any event, you want to have a one eye trial, with the other eye as a control” to determine whether an added drug will be of benefit, he said.
Laser therapies are also of little benefit because aqueous outflow is assumed to be normal in NTG patients, Mr. Hitchings noted. Laser trabeculoplasty would be effective only if a NTG patient had an outflow obstruction, he said.
Regarding surgery, randomized, controlled trials comparing trabeculectomy and nonpenetrating procedures have shown that trabeculectomy provides significantly more pressure-lowering effect. More patients treated with trabeculectomy achieve IOPs of 15 mm Hg or lower, he said.
Consider evaluating for vascular dysfunction in NTG patients
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Image: Moskowitz A, OSN |
When evaluating NTG suspects, physicians should consider checking for a history of vasospasm or vascular disorders, Ivan Goldberg, MBBS, FRANZCO, recommended. Such vascular disorders have been linked to other conditions, and patients with such conditions are prone to other ocular disorders, including increased risk of retinal hemorrhage, he said.
“All glaucoma patients have damage that is pressure-dependent or pressure-independent. So anything we say under the banner of normal pressure glaucoma, we must also remember that this applies to patients with so-called high pressure or classic primary open-angle glaucoma,” Dr. Goldberg said.
“I think it’s helpful to think of vasospasm as vasoconstriction that is inappropriate to the metabolic needs of the tissue at that time, either because it has occurred unnecessarily or it has occurred in a prolonged fashion, when the need for vasoconstriction has passed,” he said.
Dr. Goldberg noted that some have proposed the term “vascular dysregulation” to reflect the complexity of glaucoma. Patients with such vascular disorders are more prone to retinal hemorrhage, have altered choroidal circulation control and have increased retinal markers and signs of permeability, as well as altered retinal blood vessel stiffness, he said.
Further complicating understanding the role of vasospasm in glaucoma is that there are numerous degrees and forms of it.
“Individuals can have different degrees of vasospasm, and different triggers of vasospasm,” Dr. Goldberg said. “Patients with vasospasm have a more severe untreated course, but seem to respond better to pressure control. Patients with ischemic patterns of disease, on the other hand, seem to progress more slowly and seem to be less influenced by pressure reduction.”
Symptoms of vasospasm include a history of cold hands or feet and migraine. Useful questions that the ophthalmologist can use to evaluate for vasospasm in the glaucoma patient include whether their hands or feet feel cold, whether the patient tends to feel cold more often than others and whether they wear socks to bed.
Men with longer axial lengths may be at risk for NTG
Longer-than-normal axial length may be a risk factor associated with the development of NTG, according to a poster presentation by Elsuo Chihara, MD, and colleagues.
The researchers measured the axial lengths of 153 eyes in patients with NTG and 235 eyes in patients with POAG. They compared the findings to the axial lengths for 300 control eyes.
They found that eyes in the NTG and POAG groups had similar refractive errors but differed in axial lengths. The mean axial length of eyes with NTG fell between the mean axial lengths of eyes with POAG and eyes in the control group.
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Both men and women in the POAG group had mean axial lengths that were significantly greater than those for the NTG and control groups, the authors noted.
Diode laser may be effective for neovascular glaucoma
Endoscopic cyclophotocoagulation with a diode laser may be effective for treating neovascular glaucoma, according to a small study presented in a poster.
Rodolfo M. Banda-Gonzales, MD, and Vincent R. Vann, MD, PhD, reviewed the results of endoscopic cyclophotocoagulation performed using a diode laser in 18 eyes of 18 patients. IOP averaged 44.19 mm Hg preoperatively and decreased to 22.96 mm Hg at final follow-up, according to the study authors.
However, the authors warned that there is a risk for hypotony, which occurred in four eyes (22%) in the study.
Trabeculectomy with MMC effective in uveitic glaucoma
Trabeculectomy with adjunctive MMC can effectively manage patients with complex refractory uveitic glaucoma, according to a poster presentation.
Alastair Lockwood, MBBS, and colleagues evaluated the efficacy of the surgery in a prospective study including 26 eyes in 23 consecutive patients.
At a mean follow-up of 650 days, IOP had decreased from 26.7 mm Hg to an average of 11.5 mm Hg, with 92% of eyes reaching “complete success,” defined as an IOP of 21 mm Hg or less without medication, according to the study.
Only one eye (3.8%) lost more than two lines of vision, which was caused by delayed hypotony maculopathy, the authors noted.