Second and third generation Molteno implants incorporate a biological valve and studies show considerable improvement in postoperative outcome over the older style Ahmed and Molteno implants.
Baervedlt shunts (non-valved) have been shown to have lower rates of surgical failure than Ahmed shunts (valved),[REF][REF] this have may be related to the high rate of valve failure, or to the larger plate surface of the Baerveldt shunt.