Glaucoma valve

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A glaucoma valve is a medical shunt used in the treatment of glaucoma to reduce the eye's intraocular pressure (IOP).

1 Mechanism
2 Types
3 Indications
4 Surgical technique
5 Complications
6 References
7 See also
8 External links

[edit] Mechanism

The device works by bypassing the trabecular meshwork and redirecting the outflow of aqueous humor through a small tube into an outlet chamber or bleb. The IOP generally decreases from around 33 to 10 mmHg by removing aqueous on average 2.75 microliters/min.^[1]

[edit] Types

In comparison to the the newer valved implant, like the Ahmed glaucoma valve implant, there are also several different the non-valved glaucoma drainage implants, like Molteno implant or the Baerveldt tube shunt.

[edit] Indications

The glaucoma valve impalnt is indicated for glaucoma patients not responding to maximal medical therapy, with previous failed guarded filtering surgery (trabeculectomy).

[edit] Surgical technique

The flow tube is inserted into the anterior chamber of the eye and the plate is implanted underneath the conjunctiva to allow flow of aqueous fluid out of the eye. Molteno and other non-valved implants require ligating the tube till the surgical wound is mildly fibrosed and water-tight. This induced potentially dangerous spikes in the intraocular pressure (IOP). Ahmed glaucoma valve on the other hand does not have such a limitation and avoids spikes in IOP.

[edit] Complications

The ongoing scarring over the conjunctival dissipation segment of the shunt may become too thick for the aqueous humor to filter through. This may require preventive measures using anti-fibrotic medication like 5-fluorouracil (5-FU) or mitomycin-C (during the procedure), or creating a necessity for additional surgery.