ahmed valve
Pronunciation: ah-med valve
Glaucoma drainage device with flow restrictor to regulate aqueous humor outflow.
Full Definition
The Ahmed valve is a type of glaucoma drainage device (tube shunt) that incorporates a flow restrictor mechanism to prevent excessive aqueous humor drainage in the immediate postoperative period. Unlike other tube shunts, the Ahmed valve has a built-in valve mechanism that theoretically reduces the risk of early postoperative hypotony. The device consists of a silicone tube connected to a plate that is implanted under the conjunctiva. It is typically used in cases where conventional filtration surgery has failed or is likely to fail, such as in neovascular glaucoma or previous surgical failures.
Usage
Usage note: Capitalize 'Ahmed' as it's a proprietary name. Specify model number when available.
In Context
- "An Ahmed valve was implanted in the superotemporal quadrant for refractory glaucoma." — Operative report
- "The Ahmed valve showed good flow regulation without early hypotony complications." — Follow-up note