Comparison of Glaucoma Drainage Implants: M4 vs FP7 and S2

Shuchi B. Patel, MD


July 23, 2013

Clinical Experience With a Novel Glaucoma Drainage Implant

Kim J, Allingham RR, Hall J, Klitzman B, Stinnett S, Asrani S
J Glaucoma. 2013 May 17. [Epub ahead of print]

Study Summary

The recent release of the M4 Ahmed glaucoma valve (AGV) drainage implant has prompted interest in determining whether it provides an improved safety and efficacy profile. The M4 is essentially the Ahmed S2 model (AGV S2; New World Medical Inc., Rancho Cucamonga, California) with the modification of having a polyethylene shell in the hopes that it will help eliminate some of the limitations of existing valves.

Kim and colleagues from Duke University, Durham, North Carolina, performed a retrospective study to evaluate the safety and efficacy of the M4 compared with the S2 and FP7 models in patients with glaucoma. The medical records of patients who underwent implantation of the AGV FP7, S2, and M4 were reviewed, and a total of 154 eyes from 149 patients were analyzed. All procedures were performed at Duke University by 1 of 7 surgeons. The primary outcome measure was cumulative probability of success, defined as an intraocular pressure (IOP) between 5 mm Hg and 18 mm Hg and > 20% reduction of IOP without loss of light perception, need for additional IOP-lowering surgical procedures, or removal of AGV.

The FP7, S2, and M4 groups had 66, 38, and 40 eyes, respectively, with a follow-up time of at least 16 months. The preoperative IOP differences between the M4 and FP7 groups and the M4 and S2 groups were statistically significant (P = .04 and .01, respectively). The mean IOP reductions (P = .31) and cumulative probabilities of success at 1 year and 18 months (P = .99) for the 3 groups are shown in the Table.

Table. Mean IOP Reductions and Cumulative Probability of Success

Group Mean Pre-IOP (mm Hg) Mean IOP at 1 Year* (mm Hg) Probability of Success
1 year 18 months
FP7 31.0 ± 10.6 13.9 ± 5.5 70% 61%
S2 33.5 ± 12.1 15.8 ± 8.1 66% 53%
M4 27.0 ± 12.0 15.0 ± 4.0 80% 52%
*P = .31
P = .99

The predominant cause of failure in all 3 groups was inadequate control of IOP as a result of an IOP > 18 mm Hg, < 20% reduction of IOP, or additional IOP-lowering surgery being necessary. At 1 year, there was no statistical difference in the number of medications among groups (P = .41), visual acuity (P = .77), or complications.


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