Bleb morphology and post-op outcomes with the EX-PRESS device

This discussion includes a review of the recently published study, â€œAssessment of bleb morphologic features and postoperative out- comes after EX-PRESS drainage device implantation versus trabeculectomy.â€1 This was a retrospective, consecutive, case control series that included 70 patients (35 patients in the EX-PRESS device [Alcon, Fort Worth, Texas] group and 35 patients in the trabeculectomy group). Total follow up was at least 2 years; mean was about 28 months. The EX-PRESS device is â€œnonvalved and is placed under a partial thickness scleral flap. Similar to trabeculectomy, aqueous humor is allowed to drain and collect into a bleb formed in the sub-Tenonâ€™s space.â€1 As stated in the publication, the use of the device has steadily increased since it was first introduced, mainly because of perceived improvement in aqueous filtration and the possibility of avoiding an iridectomy.

Implantation

All patients received the EX-PRESS P-50 micron device. During implantation, the plate rests flat against the sclera when it is positioned slightly posterior to the blue line. Each patient received fornix-based conjunctival incisions; 27-gauge needles were used for all cases to allow for a water-tight fit around the device post-implantation. It takes a little bit of effort to get the device inserted through the needle entry tunnel, so there is a slight learning curve. However, if the surgeon makes a side slit externally with a 27-gauge needle, implantation seems to be a lot easier. In all cases, we made trapezoidal flaps with a 3-mm base. Viscoelastic may be attached to the 27- gauge needle so the surgeon can deepen the chamber upon entry if needed. In our study,Â complete success was defined as IOP â‰¥5 mm Hg and â‰¤18 mm Hg and at least a 30% decrease in IOP. A significant decrease in IOP was needed to call the procedure a complete success. Qualified success was the same definition but with the use of IOP-lowering medication post-op.

Pearl: Despite the flow regulating 50- micron internal lumen on the P-50 device, hypotony is still possible and the scleral flap should be securely sutured with 10-0 nylon as would be done with standard trabeculectomy.

Study results

The Moorfields Bleb Grading System (MBGS) includes three different categories to be exam- ined: bleb area, bleb height, and bleb vascularity. The study found that bleb vascularity for the EX-PRESS device group was less than in the trab group up to 18 months of follow up. At final follow up, the vascularity was similar between the two groups. Additionally, the blebs were more diffuse in the EX-PRESS device group from 3 months to 18 months, after which findings were similar between groups. Bleb height was lower in the EX-PRESS device group up to 3 months of follow up and higher in the EX-PRESS device group from 6 months to 18 months of follow up, but this difference disappeared at the last follow up.

IOP control

There was a statistically significant difference in IOP control at 1 week, 1 year, and at last follow up. The pressure for the EX-PRESS device patients was slightly higher at baseline, but this was not statistically significant. At about 6 months, there was a slight deviation of the pressure between groups, with the EX-PRESS device patients having slightly higher mean pressure at last follow up and 1Â year. However, the percent of IOP lowering (45% and 48%) was similar in both groups.

Complete success was achieved in 77% of patients in the EX-PRESS device group and 74% of patients in the trabeculectomy group. There was an additional 5.71% and 8.57% for the EX-PRESS device and trabeculectomy groups, respectively, for qualified success. The P values were not different between the two groups.

: Specifics of the EX-PRESS P-50 device

Complications

Overall, the complication rates were similar. However, the study found less hypotony in the EX-PRESS device group, 2/35 versus 5/35 in the trabeculectomy group. Incidence of hyphema was also less in the EX-PRESS device group, likely because there is less tissue manipulation. In the EX-PRESS device group, only one patient had micro-hyphema compared with four patients in the trabeculectomy group.

Post-op vision

Additionally, we assessed best corrected visual acuity post-op in patients. The EX-PRESS de- vice group returned to baseline visual acuity after 1 week versus the trabeculectomy pa- tients who took about 1 month to return to baseline visual acuity. The study also examined the number of post-op visits in the first 3 months after both procedures. Our results found that patients in the EX-PRESS device group were seen by their ophthalmologist on average six times during the first 3 months, whereas the trabeculectomy patients came back an average of eight times. This was statistically significant and seems to validate anecdotal information about quicker recovery times with the EX-PRESS device.

There were no real differences between the number of medications used pre-op or post-op between the two groups.

Conclusions

Results show complete and qualified successes were similar between groups. The percentage of IOP lowering was similar between groups. MBGS initially favored the EX-PRESS device, but then became equivalent the further out from surgery the patient was. However, we did find quicker visual recovery and fewer post-op visits after the EX-PRESS device.

The EX-PRESS device in practice

With these results in mind, how can the surgeon best use the EX-PRESS device in practice? The EX-PRESS Glaucoma Filtration Device is intended to reduce intraocular pressure in glaucoma patients where medical and conventional surgical treatments have failed. If a patient is deemed high risk for hypotony, theÂ EX-PRESS device should be considered as an alternative to traditional trabeculectomy due to the flow regulation that the device pro- vides. If there is a need for quicker visual recovery, as is the case with the monocular patient, I would recommend the EX-PRESS device because the visual recovery is possibly faster than traditional trabeculectomy. In these patients, that 3-week difference is crucial and in my mind justifies the added cost of surgery incurred with use of the EX-PRESS device. I do favor the EX-PRESS device over trabeculectomy in patients who are anticoagu- lated due to the lower risk of bleeding with the EX-PRESS device.

I also recommend use of the EX-PRESS device for patients undergoing combined cataract extraction and filtration surgery to lessen tissue manipulation and cause less in- flammation post-op. The EX-PRESS device, in my mind, is a single improvement to one step of the gold standard procedure of trabeculectomy. We will still require many more advances such asÂ wound modulators that enhance success without increasing late complications, as well as sutureless wound closure methods that avoid early bleb leaks. Our approach to filtration surgery continues to evolve and will allow for better outcomes and increased patient satis- faction.

Reference

1. Good TJ, Kahook MY. Assessment of bleb morphologic features and postoperative outcomes after EX-PRESS drainage device implantation versus trabeculectomy. Am J Ophthalmol. 2011 Mar;151(3):507-13.e1. Epub 2011 Jan 13.