Anterior chamber paracentesis is the removal of fluid from the anterior chamber, the area just anterior to the iris and lens, and immediately posterior to the cornea. Although not often formally taught nor performed in the Emergency Department, an anterior chamber paracentesis is a fairly quick, simple, and safe procedure with important diagnostic and therapeutic roles.1–20 The long-term prognosis is directly related to the duration of symptoms for disease states that present with increased intraocular pressure, such as acute closure glaucoma and central retinal artery occlusion. In a sense, “Time is Eye.” The Emergency Physician should become familiar with this technique. Its use can potentially prevent irreversible vision loss, especially when medical management is not sufficient in lowering intraocular pressure.
The eye is a fluid-filled, closed system with a one-way valve. Aqueous humor is produced by the ciliary body and flows from the posterior chamber to the anterior chamber. Once in the anterior chamber, the aqueous humor then travels through a fine trabecular meshwork at the anterior chamber angle (the one-way valve) and leaves via the canal of Schlemm.
Intraocular pressure normally measures between 10 and 22 mmHg. This represents the balance between the production and outflow of aqueous humor.3 Tonometry is used to measure intraocular pressure (Chapter 156). An increase in aqueous humor production, resistance to the outflow of aqueous humor, or additional fluid (e.g., pus or blood) in the vitreous body can severely increase intraocular pressure, potentially causing permanent visual loss due to ischemia. In addition to medical therapies, removing fluid via an anterior chamber paracentesis will reduce intraocular pressure to help prevent further ischemia.
Central retinal artery occlusion (CRAO), usually from an atherosclerotic embolic event, is another potential cause of visual loss that may benefit from an anterior chamber paracentesis in combination with digital ocular massage (Chapter 157) and medical management.4 Decreasing intraocular pressure increases retinal perfusion in an attempt to propagate the embolus distally and minimize the amount of visual loss. Traumatic retrobulbar hemorrhages and other extraocular causes of elevated intraocular pressure do not benefit from an anterior chamber paracentesis.
An anterior chamber paracentesis will immediately reduce intraocular pressure but is not a treatment that resolves the underlying cause of the elevated intraocular pressure. Medical management is usually initiated first to lower intraocular pressure before attempting an anterior chamber paracentesis. An anterior chamber paracentesis is indicated whenever elevated intraocular pressure threatens visual loss and medical management is not successful in lowering intraocular pressure. Reducing the intraocular pressure acutely with an anterior chamber paracentesis in disease states such as acute angle closure glaucoma, uveitis, hyphema, central retinal artery occlusion, and suppurative endophthalmitis will help prevent further irreversible vision loss, especially if used in conjunction with other medical modalities.5–7
There are numerous nonemergent indications for an Ophthalmologist to perform an anterior chamber paracentesis. Diagnostically, an anterior chamber paracentesis ...