Initial Experience With the New Ahmed Glaucoma Valve Model M4: Short-term Results

Abstract

The AGV M4 effectively reduced IOP in the first postoperative month, but IOP steadily increased thereafter. Consequently, failure rates were high after 1 year of follow-up.

Clinical Experience with the M4 Ahmed Glaucoma Drainage Implant

“…We believe this definition does not reflect our intention of describing the transient spike in IOP in the initial period after implantation (1-4 months). When comparing the average IOP in Cvintal et al’s 11 study at 1 week, 1 month, and 3 months, the 1-month IOP appears to be an average of the 2 endpoints, which indirectly supports the notion that the M4 valve does not create a hypertensive spike at the 1-month visit. However, as in Cvintal et al’s 11 study, the IOP at our study peaked at around 6-8 months and then slowly stabilized.…”

“…When comparing the average IOP in Cvintal et al’s 11 study at 1 week, 1 month, and 3 months, the 1-month IOP appears to be an average of the 2 endpoints, which indirectly supports the notion that the M4 valve does not create a hypertensive spike at the 1-month visit. However, as in Cvintal et al’s 11 study, the IOP at our study peaked at around 6-8 months and then slowly stabilized. The hypertensive spike difference between the three studies appears to be more based on the definition of the phenomenon, rather than differing results.…”

“…At 1-year follow-up, our patients, on average, were able to achieve an IOP of 15.8, which is consistent with the literature range of IOP obtained with other Ahmed valves (FP7: 13.8-17.7, S2: 15.8-17.7, M4: 15.0-20.3). 10 11 14 - 17 About 5.2% of patients developed chronic hypotony and 10.3% of patients required further surgical intervention for IOP lowering, most commonly CPC/ECP. The device appears to have an average complication rate in the Ahmed class requiring revision or device removal (hypotony: 3-13%, removal/revision: 0-15.4%).…”

“…This was consistent with our study. Cvintal et al’s 11 study defined a hypertensive phase as rise in IOP over 6 months from the IOP measured at 1 week, and reported a hypertensive spike in 63% of the cases. We believe this definition does not reflect our intention of describing the transient spike in IOP in the initial period after implantation (1-4 months).…”

“…For the Kaplan-Meier analysis, surgical failure was defined as a final IOP less than 5 mm Hg or greater than 21 mm Hg, and/or a <20% reduction in IOP from baseline, following Cvintal et al 11 Time to event was defined as the follow-up period. If a patient dropped out or the follow-up period ended before surgical failure occurred, his/her time-to-failure data were considered right-censored.…”