Initial Experience With the New Ahmed Glaucoma Valve Model M4

Short-term Results

Victor Cvintal, MD; Marlene R. Moster, MD; Andrew P. Shyu, BS; Katie McDermott, BS; Feyzahan Ekici, MD; Michael J. Pro, MD; Michael Waisbourd, MD


J Glaucoma. 2016;25(5):e475-e480. 

In This Article


Seventy-five eyes of 73 patients were included in the study with a mean age (±SD) of 72.3±11.9 years. The patient demographics and clinical characteristics are summarized in Table 1. Females represented 63% of the group, whereas whites were 56%. More than half (59%) of the total sample had primary open-angle glaucoma, whereas 10 (13%) had chronic angle-closure glaucoma and 9 (12%) had uveitic glaucoma. The mean number of previous glaucoma surgeries (±SD) was 0.8±1.1. Thirty-four eyes (45%) had no prior glaucoma surgery, and 27 (36%) had 1 glaucoma surgery. Twenty-eight eyes (37%) had a prior trabeculectomy, and 9 (12%) had a prior tube shunt. At the 3-, 6-, and 12-month follow-ups, 52, 51, and 21 eyes were seen, respectively. Seventy-three eyes were seen at last follow-up. The mean follow-up time (±SD) was 209±98 days.

Operative Data

Forty-four eyes (59%) had the Ahmed M4 placed superotemporally, whereas 15 (20%) had it placed inferotemporally. The majority of the eyes (86%) had the tube placed in the anterior chamber. Sixty-two (84%) had a processed half cornea (VisionGraft) and 11 (15%) had a processed double-thickness pericardium (Tutoplast) as a patch graft to cover the tube.

IOP Control

Figure 1 shows the course of mean IOP during the study. Using the mixed model for statistical analysis in Table 2, the mean preoperative IOP was 31.2 mm Hg (95% CI, 29.6–32.7). A statistically significant lower IOP was observed in all follow-up visits compared with the preoperative baseline (P<0.01). In addition, the 3-, 6-, and 12-month IOP measurements significantly increased from the 1-month IOP (P<0.01). During the first 6 months, 15/24 (63%) eyes were reported to have a HP.

Figure 1.

The course of mean intraocular pressure (IOP) from preoperative to follow-up after Ahmed glaucoma M4 implantation. Error bars indicate 1 SD.

Visual Acuity

The VA at baseline was 0.8 (95% CI, 0.6–1.0). There were no significant changes (P=0.79) at 12 months with a VA of 0.9 (95% CI, 0.7–1.1). There were no cases of loss of light perception or diplopia. At 6 and 12 months, 18 eyes had a vision improvement of ≥2 Snellen lines from baseline, whereas 13 eyes had a vision loss of ≥2 Snellen lines.

Number of Glaucoma Medications

The change in average number of glaucoma medications (±SD) is presented in Table 2. There was a significant decrease in mean number of glaucoma medications at all follow-up visits compared with baseline (P<0.01). A significant increase in medication was also seen from 1 to 3 months (P<0.01), and 3 to 6 months (P<0.01). However, there was no significant difference in the average number of medications between 6 and 12 months (P=0.31). At last follow-up, 35 (47%) eyes had no adjunctive medication, 13 (17%) were on 1 medication, 10 (13%) were on 2 medications, 15 (19%) were on 3 medications, and 2 (3%) were on 4 or more medications, respectively.

Surgical Failure

Thirty-four (47%) eyes were considered a surgical failure at last follow-up visit, with 23/34 (68%) surgical failures due to high IOP. Nine (26%) eyes failed due to a <20% reduction of IOP from baseline to last follow-up visit, and 2 (6%) failed due to a reoperation for glaucoma. In addition, 16 eyes (22%) were considered qualified success and 23 (32%) were considered complete success. The mean number of glaucoma medications for eyes that failed was 1.3±1.3, whereas eyes classified as qualified success had an average of 2.5±0.8 (P<0.01). The Kaplan-Meier survival analysis shows a cumulative probability of failure of 32% at 6 months and 72% at 1 year (Fig. 2). The estimated median time to failure was 8.5 months.

Figure 2.

Kaplan-Meier cumulative probability curve of failure using the study's criteria in patients who underwent Ahmed glaucoma M4 implantation.


Thirty-three (44%) of the total eyes had at least 1 complication (Table 3). The majority of eyes with complications (42%) only had 1 complication, whereas 11 (33%) eyes had 2 complications, and 6 (18%) had 3 complications. Most of the early complications were hyphema (16%), with 11 of the eyes presenting the complication 1 day following surgery. In addition, choroidal effusion and flat or shallow anterior chambers were seen in 7% of the eyes. One case of aqueous misdirection was successfully treated with Nd:YAG hyaloidotomy 1 day after AGV implantation. Corneal edema was the only complication seen in both early and late stages. Two eyes needed surgery (Descemet's Stripping Endothelial Keratoplasty and an additional tube) to resolve chronic corneal edema, with 1 having preexisting bullous keratopathy. There were 9 late complications, with corneal edema (n=3) and tube obstruction (n=3) being the most prevalent reasons. Because of early or late postoperative complications, 13 (18%) patients had complications that required reoperation unrelated to glaucoma.

Reoperations for Glaucoma

There were 12 reoperations for glaucoma after the AGV M4 implant, resulting in 16% of the total eyes. All reoperations for glaucoma occurred after 3 months, as the main reason for reoperation for glaucoma was high IOP (68%). Five had a new tube implanted, 3 had endoscopic cyclophotocoagulation, 2 had transcleral cyclophotocoagulation with a diode laser, and 1 had the tube removed. Out of the total superotemporal implants, 6/44 (14%) needed reoperations, whereas 4/15 (27%) of the inferotemporal implants required reoperations (P=0.53).