A 66 y.o. male sp an Ahmed glaucoma valve one year earlier comes in with R eye redness
Two images are shown: the patch where his glaucoma valve drains and the anterior chamber.
The anterior chamber is completely flat. acuity is 20/50 .
just for reference this is a normal depth of the anterior chamber
Our patient had hypotony of the eye with collapse of the anterior chamber. This is a known complication of the Ahmed valve. A valve is placed for glaucoma when medication and trabeculectomy fail to decrease eye pressure.
To review:
The aqueous humor is made in the ciliary body, travels out through the pupil into the anterior chamber and is mostly drained through the trabecular meshwork lining Schlemm’s canal. A small amount drains directly into the sclera. This is essentially what an Ahmed valve does. Aqueous humor travels into the anterior chamber and is drained into the sclera by means of the reservoir in the valve. The drainage of aqueous humor can be blocked by inflammation or the iris itself in angle closure glaucoma
Glaucoma is the second leading cause of blindness in the world( cataracts are number one) and is essentially a chronic optic neuropathy caused by increased intraocular pressure. The highest prevalence of open angle glaucoma is found in African countries and the Afro- Caribbean population. Lowering the pressure can be achieved by medical treatment, laser, or surgery which includes trabeculectomy or the use of a drainage implant
Our patient had an assessment of the valve done with a Seidel test to see if it was leaking increased aqueous humor through the conjunctiva. It was not leaking. He was not on medications known to cause hypotonia: nitrates, carbonic anhydrase inhibitors, clonidine or beta blockers. Inflammation with decreased ciliary body production of fluid was felt to be the cause of low eye pressure. His glaucoma meds were briefly stopped and in follow up in clinic the pressure in the eye rose. His vision remained intact.
https://www.youtube.com/watch?v=-FNO1WoVoZQ
https://eyeguru.org/videos/glaucoma/aqueous-humor-pathway
Villarrubia H, Bell N. Hypotony https://doi.org/10.1093/oso/9780195382365.003.0023
Riva I, Roberti G, Oddone F, et al. Ahmed glaucoma valve implant: surgical technique and complications. Clin Ophthalmol 2017;11:357-367.
Goel M, Picciani G, Lee R et al. Aqueous humor dynamics: a review Open Ophthalmol J. 2010;4:52-59.