Role of phacotrabeculectomy shifting but not disappearing

May 1, 2014

Based on unknown preoperative anatomic considerations, efficacy, and safety data, phacotrabeculectomy may be a better option than phacoemulsification alone or combined with a microincision glaucoma surgical procedure in eyes with advanced glaucoma needing cataract surgery and low IOP.

 

Take Home

Based on unknown preoperative anatomic considerations, efficacy, and safety data, phacotrabeculectomy may be a better option than phacoemulsification alone or combined with a microincision glaucoma surgical procedure in eyes with advanced glaucoma needing cataract surgery and low IOP.

 

Dr. Fellman

By Cheryl Guttman Krader; Reviewed by Ronald L. Fellman, MD

Dallas-The advent of microincision glaucoma surgical (MIGS) procedures that are performed in conjunction with cataract surgery does not herald the demise of phacotrabeculectomy. Rather, it is the beginning of a better era in which surgeons can match their glaucoma procedure to the patient’s needs, according to Ronald L. Fellman, MD.

“Phacotrabeculectomy is still alive and still has a role, thanks mainly to the many benefits of small incision cataract surgery that revolutionized the combined procedure,” said Dr. Fellman, an attending surgeon and clinician at Glaucoma Associates of Texas, Dallas, and clinical associate professor emeritus, Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas. “It is true that there is less filtering surgery being done today, but that is because we are better able to use it selectively in patients needing a filter.

“Remember, there is a fundamental difference between a filtering procedure and MIGS,”

Dr. Fellman continued.

Dr. Fellman explained that trabeculectomy creates a new drain shunting aqueous under the conjunctiva, abandoning the eye’s natural drainage system. In contrast, MIGS procedures are mostly Schlemm’s canal-based and aim to increase flow into the natural collector channels.

Their success likely depends on having an intact collector channel system to accept the flow, close proximity of the device or incision to a collector, and favorable canal wound healing (Fig 1), Dr. Fellman said. He added that his group is now studying how the outcome of ab interno trabeculectomy (Trabectome, NeoMedix) correlates with flow observed through the channels in the OR.

However, information from histopathology studies show that at least in eyes with advanced glaucoma, there is atrophy of the collector channels. Although surgeons can get a sense intraoperatively of collector channel patency (the episcleral venous fluid wave, [Fig 2]), there is no currently available method for making the assessment preoperatively in order to try to predict the efficacy of a MIGS procedure.

 

Cataract surgery alone vs. a combined procedure

Cataract surgery alone can result in long-term intraocular pressure (IOP) reduction, however, the long-term IOP-lowering effect of cataract surgery is probably more limited in eyes with established glaucoma that have a diseased outflow system, Dr. Fellman said.

To illustrate his points, he cited results from the Ocular Hypertension Treatment Trial where 63 control eyes underwent cataract surgery and had an average IOP reduction of 4 mm Hg followed by a slight rise during ongoing follow-up.

“However, none of those patients were on medications or had visual field loss or optic nerve damage,” he said. “In contrast, in a study by Seabaugh et al. of medically controlled patients with primary open angle glaucoma (POAG), IOP decreased by a mean of just 1.8 mm Hg and 38% of patients required additional medication for IOP control.”

In addition, data from a study by Shingleton et al. showed that in a cohort of eyes with POAG that underwent cataract surgery, 16% of eyes had a postop day 1 spike in IOP >30 mm Hg.

“Consider whether the patient’s disc can withstand such an IOP spike,” said Dr. Fellman, adding that emerging evidence indicates that some MIGS procedures can significantly blunt the spike.

Data from studies of phacotrabeculectomy support it as a more appropriate option than phaco alone in patients with more advanced glaucoma. In a study by Jin et al., mean IOP decreased from 23 mm Hg preop to 12.7 mm Hg on postop day 1. At the end of follow-up, mean IOP was 14.9 mm Hg and mean daily glaucoma medication use was reduced from 1.67 to 0.23.

 

Another study by Shingleton et al. of patients with pseudoexfoliation glaucoma showed IOP increased on postop day 1 in some eyes that had cataract surgery alone, whereas there was a mean decrease of 5.5 mm Hg in a group undergoing phacotrabeculectomy. At 10 years, the IOP was still reduced by an average of about 6.5 mm Hg in eyes having combined surgery, but by less than 3 mm Hg in eyes that had cataract surgery alone.

“We also know from the Collaborative Initial Glaucoma Treatment Study that patients who have more advanced visual field damage and receive initial filtration surgery have less subsequent visual field loss than those who receive medications,” Dr. Fellman said.

Take-home pearls

Dr. Fellman concluded that until techniques emerge for preoperative assessment of the capacity of the collector channels, surgeons should consider phacotrabeculectomy for any eye with advanced glaucoma needing cataract surgery and a low IOP. When performing the filtering procedure, flow should be titrated in the operating room to blunt the IOP spike on postop day 1. In addition, he recommended incorporating Tenon’s into the wound closure, noting that in his experience, this technique confers better long-term bleb morphology.

 

Ronald L. Fellman, MD

E: rfellman@glaucomaassociates.com

Dr. Fellman is a consultant to EndoOptiks and receives grant support from Glaukos, SOLX, Transcend, and Carl Zeiss Meditec.