Valve Membrane Adhesion as a Cause of Ahmed Glaucoma Valve Failure

Histopathologic Findings in Early Encapsulated Blebs of Young Patients Treated With the Ahmed Glaucoma Valve

“…The bleb itself was under high pressure and let out a gush of aqueous humor once opened or punctated with softening of the eye immediately thereafter. Therefore, we could not confirm the observation of Feldman et al, 6 who reported on valve membrane adhesion in 2 adult patients as cause of AGV failure or a fibrovascular tissue ingrowth into the valve mechanism itself as reported by Hill et al 7 Trigler et al 8 found fibrovascular ingrowth in the valve chamber to be responsible for AGV failure in 6 very young patients (age range from 1 to 122 mo). Three of these children had undergone earlier surgical manipulation on an encapsulated bleb before AGV removal.…”

“…Usually, removal of these fibrous capsules leads to an enduring drop of IOP, but in some patients these cysts reappear and require repeated surgical procedures. [5][6][7][8] The Ahmed glaucoma valve (AGV) consists of a flexible silicone base plate with a sheet-like silicone valve, equipped with a silicone tube of 0.64-mm outer diameter, connecting the anterior chamber with the subtenon space. During insertion, the AGV is fixed to the sclera and covered by tenon and conjunctiva, forming a filtering bleb far away from the limbal region.…”

Tube Fenestrations in Baerveldt Glaucoma Implant Surgery: 1-year Results Compared with Standard Implant Surgery

“…33,34 Other reported difficulties with valved implants include variable valve function, 35 variable valve resistance, 36 and late valve failure. 37,38 Finally, as increased plate surface area seems to improve IOP control up to a certain size, 39,40 valved implants may not achieve the same IOP as nonvalved implants with larger surface areas.…”

Intraluminal Pressure Response in Baerveldt Tube Shunts

“…However, both early and late valve failure have been described with these models. [1][2][3] In most nonvalved models, an open silicone tube drains aqueous to an episcleral plate. With this design, long-term pressure control is dependent on fibrovascular encapsulation of the episcleral plate to provide enough resistance to flow to prevent hypotony.…”