Assessment of Bleb Morphologic Features and Postoperative Outcomes After Ex-PRESS Drainage Device Implantation Versus Trabeculectomy


To investigate bleb morphologic features and postoperative outcomes after Ex-PRESS drainage device (Alcon Laboratories) implantation versus trabeculectomy.


Retrospective, consecutive case-control series.


Information was collected from the charts of 35 consecutive Ex-PRESS procedures and 35 consecutive trabeculectomy procedures with at least 2 years of follow-up. Intraocular pressure (IOP), bleb morphologic features, reduction of dependence on medication, visual recovery, number of postoperative visits, and postoperative complication rates were compared between groups.


Average follow-up was 28 months (standard deviation, 3.23 months). Mean IOP measurements were similar after 6 months, then became slightly higher in the Ex-PRESS group at 1 year and at the final follow-up ( P = .004 and P = .008, respectively). Final percent IOP lowering was similar between groups ( P = .209). Unqualified success was achieved in 77.14% of Ex-PRESS and 74.29% of trabeculectomy procedures at last follow-up ( P = 1.00). An additional 5.71% and 8.57% reached qualified success for Ex-PRESS and trabeculectomy surgeries, respectively ( P = .99). Evaluation by the Moorfields Bleb Grading System revealed less vascularity and height but more diffuse area associated with the Ex-PRESS blebs, although these differences were absent at study completion. There were fewer cases of early postoperative hypotony and hyphema and quicker visual recovery in the Ex-PRESS group. The Ex-PRESS group required fewer postoperative visits compared with the trabeculectomy group ( P < .000).


Success of Ex-PRESS surgery, as defined in our study, was similar to trabeculectomy. Final IOP measurements were slightly lower after trabeculectomy compared with Ex-PRESS. Differences in some postoperative outcomes faded with follow-up. There remains a need for long-term prospective studies comparing these 2 procedures.

Surgical intervention often is needed in glaucoma patients who experience visual field deterioration or progression of optic neuropathy despite maximum pharmacologic intervention, laser therapy, or both. The most commonly performed invasive surgical procedure in this setting is trabeculectomy, which involves the creation of a partial thickness scleral flap and fistula into the anterior chamber, leading to formation of a sub-Tenon bleb. The Ex-PRESS drainage device (Alcon Laboratories, Fort Worth, Texas, USA), which is nonvalved and is made of medical grade 316L stainless steel, has been introduced as an alternative to trabeculectomy filtration surgery. The device is placed under a partial thickness scleral flap, and, similar to trabeculectomy, aqueous humor is allowed to collect and drain into a bleb formed in the sub-Tenon space. The use of the Ex-PRESS drainage device has increased steadily since its introduction because of perceived improvements in the reproducibility of aqueous filtration when compared with trabeculectomy while avoiding the need for a surgical iridectomy.

Anecdotal and published data also have suggested that patients may recover vision more quickly while experiencing fewer postoperative complications after Ex-PRESS implantation when compared with traditional trabeculectomy. Many of these reports, however, were short-term analyses or lacked a control group. A report by de Jong investigating the success of Ex-PRESS compared with trabeculectomy was carried out in a prospective fashion and included 80 eyes of 78 patients. That study did not include information such as time until restoration of vision to baseline values, number of postoperative visits after each procedure, or an analysis of bleb morphologic features during follow-up. The current study focuses on comparative analyses of several postoperative outcome metrics including intraocular pressure (IOP), bleb morphologic features, reduction of dependence on medications, vision, number of postoperative visits in the first 3 months, as well as postoperative complication rates after either Ex-PRESS drainage device implantation or traditional trabeculectomy with at least 2 years of follow-up.


This was a retrospective, consecutive case-control series. Thirty-five consecutive Ex-PRESS shunt procedures using the P-50 model were compared with 35 consecutive trabeculectomy surgeries. All patient data were obtained from the clinic of a single glaucoma specialist (M.Y.K.) who performed all of the procedures. The main outcome measures were: mean IOP, bleb morphologic features based on the Moorfields Bleb Grading System, and postoperative complications. Photographs needed to complete bleb morphologic features analysis routinely are obtained in our glaucoma service as part of a prospective study of all surgical patients who have undergone glaucoma filtration surgery. Because Moorfields Bleb Grading System photographs are obtained with eyes infraducted, the implanted Ex-PRESS devices could not be visible during the grading process. Thus, the evaluation of all photographs was performed in masked fashion. Approval was obtained to use these photographs for the purposes of this report. Secondary outcomes in this study included postoperative medication use, logarithm of the minimal angle of resolution visual acuity, and mean number of postoperative visits over the first 3 months. Unqualified success was defined as an IOP of 5 mm Hg or more and 18 mm Hg or less and at least a 30% decrease in IOP without the use of IOP-lowering medications. The definition of qualified success was the same as unqualified success, but with use of IOP-lowering medications. Treatment failure was defined as the need for additional IOP-lowering surgery because of elevation of IOP, advancing visual field defects, changes in optic nerve head morphologic features, or a combination thereof. Fisher exact tests were used to assess differences between the groups in terms of bleb morphologic features, complication rates, success rates—both qualified and unqualified, failure rates, and demographics. Student t tests were used to assess differences in IOP at each visit and the number of postoperative visits between the 2 study groups.


The 2 groups were similar in terms of age ( P = .88), sex ( P = .81), and preoperative medication use ( P = 1.00). The underlying types of glaucoma, lens status (phakic, aphakic, or pseudophakic), and race characteristics were similar between the 2 groups, as detailed in the Table . The decision to perform Ex-PRESS surgery versus trabeculectomy surgery was based on patient informed consent. Each patient was given the option of undergoing Ex-PRESS implantation versus traditional trabeculectomy and was informed that there were no clear data distinguishing the performance of one over the other. Available literature was given to each patient before his or her decision.


Detailed Demographic Characteristics for the Ex-PRESS (Alcon Laboratories, Fort Worth, Texas, USA) and Trabeculectomy Groups

Ex-PRESS Trabeculectomy P Value
Age 68.9 69.3 .88
Sex (male/female) 19/16 17/18 .81
POAG 21 22 1.00
CACG 5 5 1.00
PXF 5 5 1.00
PDG 4 3 .99
Black 10 8 .78
White 18 15 .63
Hispanic 5 10 .24
Asian 2 1 .99
Other 0 1 .99
Preoperative medications 2.29 (± 0.75) 2.25 (± 0.77) 1.00
Phakic/aphakic/pseudophakic 12/1/22 10/0/25 .80/.99/.61

CACG = chronic angle-closure glaucoma; PDG = pigment dispersion glaucoma; POAG = primary open-angle glaucoma; PXF = pseudoexfoliation glaucoma.

Data from 70 total patients were evaluated for this report. Average follow-up for all patients was 28 months (standard deviation, 3.23 months) and was similar between groups ( P = .855). All patients received 0.4 mg/mL mitomycin C soaked in 2 corneal shields cut in half for 2 minutes over the scleral bed at time of surgery. Ex-PRESS group blebs seemed to be consistently less vascular in all 3 vascularity categories of bleb grading. The most pronounced differences in vascularity were found to be in the peripheral aspect of the bleb and the peripheral, non–bleb-related conjunctiva, denoted as 3b and 3c in the Moorfields Bleb Grading System. All differences in bleb vascularity disappeared at last follow-up. Bleb height was found to be lower in the Ex-PRESS group in the early postoperative period of up to 3 months of follow-up. From 6 to 18 months of follow-up, the Ex-PRESS group had greater bleb height, but this difference also disappeared by the final follow-up. Ex-PRESS group blebs were more diffuse than the trabeculectomy group from 3 to 18 months of follow-up, but these differences also disappeared at the last follow-up. Detailed Moorfields Bleb Grading System characteristics are included in Figure 1 .


Bar graph showing Moorfields Bleb Grading System data for the Ex-PRESS (Alcon Laboratories, Fort Worth, Texas, USA) and trabeculectomy patients for the duration of postoperative follow-up. The black asterisks above the bars represent P values that are statistically significant and different between the Ex-PRESS group and the trabeculectomy group. Scoring was carried out according to standard Moorfields Bleb Grading System protocol ( ) using reference photographs of the various aspects of the bleb ( ). All photographs were evaluated in masked fashion without indication of type of procedure or timeline when photographs were obtained for each patient. Six criteria are assessed that pertain to the 3 main aspects of the bleb: (1) area, (2) height, and (3) vascularity. (1) Bleb area is assessed based on maximal bleb area and central demarcation area. A score of 1 to 5 is given based on extension, from 0% to 100% extension. Graph 1a compares the central demarcation area with the total conjunctival area, and graph 2a compares the peripheral margins with the total conjunctival area. The chart above shows that the Ex-PRESS group had higher scores for both graph 1a and graph 2a from 3 months to 18 months of follow-up, with similar scoring at the final follow-up. (2) Bleb height, labeled as criteria 2, represents the highest point of the bleb and is graded from 1 to 4 against reference photographs, with 1 being the least height and 4 being the greatest height. Our data found the Ex-PRESS group to have lesser bleb height in the early postoperative period until 6 months of follow-up and then greater bleb height from 6 months to 18 months of follow-up. Both groups were similar in bleb height at final follow-up. (3) Bleb vascularity has 3 criteria, each of which is scored from 1 to 5, with 1 corresponding to avascular and 5 corresponding to severe vessel inflammation. Graph 3a represents the vascularity at the central demarcation area of the bleb, graph 3b represents the vascularity at the peripheral part of the bleb, and graph 3c represents the vascularity at the peripheral, nonbleb conjunctiva. Our data show that the Ex-PRESS group overall had less vascularity, with the most pronounced difference in bleb vascularity at the peripheral part of the bleb.

IOP was similar between the 2 groups at baseline and in the early postoperative period, with the 1-week follow-up being the exception where the Ex-PRESS group ( P = .019) had slightly higher IOP. The IOP for the Ex-PRESS group was higher than the trabeculectomy group at 1 year and at the last follow-up ( P = .004 and P = .008, respectively). Overall the reductions in IOP at last follow-up were similar at 11.9 mm Hg (45%) and 12.1 mm Hg (48.45%) for the Ex-PRESS and trabeculectomy groups, respectively (P = 0.209). Figure 2 shows the IOP trends between the 2 groups over the course of the study.


Graph showing average intraocular pressure (IOP) and P values for the Ex-PRESS (Alcon Laboratories, Fort Worth, Texas, USA) and trabeculectomy patients at each follow-up. The diamonds represent the Ex-PRESS group and squares represent the trabeculectomy group. Both groups have upward trending IOPs after 6 months of follow-up, but the Ex-PRESS group IOP trend is more significant, as indicated by the P value comparison of the 2 groups.

Overall, complications rates were lower but were not significantly different in the Ex-PRESS group, with fewer cases of early postoperative hypotony (2/35) and hyphema (1/35) with Ex-PRESS compared with trabeculectomy (5/35 [ P = .428] and 4/35 [ P = .356], respectively). All cases of hypotony had resolved by the 3-month follow-up visit and all cases of hyphema resolved without need for surgical intervention. Groups were similar with regard to vision at baseline ( P = .451) and last follow-up ( P = 1.00). Ex-PRESS patients returned to near baseline levels of logarithm of the minimal angle of resolution vision by the 1-week postoperative visit. Trabeculectomy patients returned to near baseline vision by 1 month. Figure 3 provides detailed vision data for both groups. The Ex-PRESS group required fewer postoperative visits (6.05; standard deviation [SD], 0.54) compared with trabeculectomy (8.23; SD, 0.92; P < .000) during the first 3 months of follow-up. The mean number of preoperative medications used in the Ex-PRESS group was 2.29 (SD, 0.75), and that in the trabeculectomy group was 2.25 (SD, 0.77; P = .826). The mean number of medications used at last follow-up was 0.15 (SD, 0.35) and 0.20 (SD, 0.41) for the Ex-PRESS and trabeculectomy groups, respectively ( P = .585). More patients in the Ex-PRESS group underwent laser suture lysis (18/35) compared with those who underwent trabeculectomy (7/35; P = .012). Those who underwent laser suture lysis in the Ex-PRESS group had the procedure done at an earlier stage after surgery (11.49 ± 3.51 days) compared with those who had laser suture lysis in the trabeculectomy group (15.80 ± 4.22 days; P < .000). An equal number of patients (2/35) underwent bleb needle revision in both groups. Bleb needle revision with adjunctive mitomycin C was performed at 6 months and 13 months after surgery in the 2 patients from the Ex-PRESS group and at 5 months and 10 months after surgery in the 2 patients from the trabeculectomy group. Only a single bleb needling procedure was performed in each of these patients, and the treating physician deemed all procedures successful. The number of patients undergoing bleb revision was insufficient to make any meaningful comparisons for the purposes of this study.

Jan 16, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Assessment of Bleb Morphologic Features and Postoperative Outcomes After Ex-PRESS Drainage Device Implantation Versus Trabeculectomy

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