Glaucoma Drainage Devices

Drainage Devices for Glaucoma

Glaucoma Drainage Devices Historical Perspective

For over a century it has been known that fluid build-up in the eye can result in loss of vision.  It should come as no surprise, then, that the idea of shunting aqueous fluid from the anterior chamber into the space between the sclera and conjunctiva (subconjunctival space) has been around almost that long.  One of the problems encountered with early attempts to create these fistulas was the body’s natural tendency to close them by creating scar tissue.

One solution to this problem was to place an object (called a “seton”) in the fistula in order to force it to remain open.  Fluid could then flow around the object keeping the fistula open.  The first documented attempt to use a seton to shunt fluid out of the eye was reported in 1907 by Rollet[1]. He implanted a horse-hair thread extending from the anterior chamber into the subconjunctival space.  Other exotic materials such as silk,[2] gold,[3] platinum,[4] and even glass[5] have since been tried without success.

It turns out that it’s not enough to simply place a rod or thread in the fistula.  In order to maintain fluid flow a tube must be used.  Even with a tube, however, the normal healing response will scar down the subconjunctival space into which the fluid is flowing.  Something else had to be added: a physical plate that would prevent the conjunctiva from scarring down to the sclera.

Modern Versions of Glaucoma Drainage Devices

The modern versions of these tube plus plate implants (now termed glaucoma drainage devices) have been around almost as long as trabeculectomy.  Trabeculectomy was first described by Drs. Koryllos in 1967[6] and Cairns in 1968[7]. This was followed only one year later by Dr. Molteno’s published description of a glaucoma drainage device in 1969.[8]

[Surgical Demonstration: MOLTENO3 G-series Glaucoma Implant in Primary Glaucoma [Internet]. YouTube. 2016 [cited 2016 Oct 16]. Available from: https://youtu.be/8yAqC7aim1s]

Also known as aqueous shunts or drainage implants, these plate-shaped devices must be sutured onto the surface of the eye beneath the conjunctiva.  The hollow tube which connects to the plate is either inserted through the cornea or sclera at the time of initial surgery or at a later date.  Once the tube has been properly inserted these implants function by draining fluid from the inside of the eye into a reservoir around the plate and underneath the conjunctiva.

The fluid that collects around the implant forms a bleb, similar to what is seen after trabeculectomy.  Unlike the bleb seen after trabeculectomy, however, the bleb that forms after placement of a glaucoma drainage device is further back along the wall of the eye and well-hidden underneath the eyelid.  How does this fluid get out of the bleb?  It is believed that it diffuses through the bleb wall into capillaries.  From there it flows back into the blood system.

Common Indications

Placement of a glaucoma drainage device is the preferred surgery in congenital glaucoma that fails to respond to goniotomy or trabeculotomy, glaucoma that has resulted from injuries to the eye, and neovascular glaucoma.  They are also used to treat glaucoma patients who have no lens in the eye (this is called ”aphakia”) and those who have undergone corneal transplant surgery.  Its most common indication, however, is in patients who have failed other glaucoma surgeries such as trabeculectomy and canaloplasty.

References

1) Rollet M. Le drainage au irin de la chambre anterieure contre l’hypertonie et al douleur. Rev Gen Ophthalmol. 1906;25:481.

2) Zorab A. The reduction of tension in chronic glaucoma. Ophthalmoscope. 1912;10:258.

3) Stefansson J. An operation for glaucoma. Am J Ophthalmol. 1925;8:681-92.

4) Muldoon WE, Ripple PH, Wilder HC. Platinum implant in glaucoma surgery. Arch Ophthalmol. 1951;45:666.

5) Bock RH. Subconjunctival drainage of the anterior chamber by a glass seton. Am J Ophthalmol. 1950;33:

6) Koryllos K. The excision of the corneoscleral meshwork (trabeculectomy) as an antiglaucomatous operation. Delt Ell Ophthalol. 1967:35147–155.

7) Cairns JE. Trabeculectomy. Preliminary report of a new method. Am J Ophthalmol. 1968;66(4):673-679.

8) Molteno AC. New implant for drainage in glaucoma. Clinical tril. Br J Ophthalmol. 1969;53(9):606-615

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