Anterior chamber paracentesis is the removal of fluid from the anterior chamber. The anterior chamber is the area just anterior to the iris and lens and immediately posterior to the cornea. Although not often formally taught or performed in the Emergency Department, an anterior chamber paracentesis is a quick, simple, and safe procedure with important diagnostic and therapeutic roles.1-28 The long-term prognosis is directly related to the duration of symptoms for disease states that present with increased intraocular pressure (IOP) 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 IOP.
ANATOMY AND PATHOPHYSIOLOGY
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. The aqueous humor from the anterior chamber travels through a fine trabecular meshwork at the anterior chamber angle (i.e., the one-way valve) and leaves via the canal of Schlemm.
IOP normally measures between 10 and 21 mmHg. This represents the balance between the production and outflow of aqueous humor.3 Tonometry is used to measure IOP (Chapter 188). An increase in aqueous humor production, resistance to the outflow of aqueous humor, or additional fluid (e.g., pus or blood) in the eye can severely increase IOP and potentially cause permanent visual loss due to ischemia. Removing fluid via an anterior chamber paracentesis, in addition to medical therapies, will reduce IOP 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 189) and medical management.4,21 Decreasing IOP increases retinal perfusion in attempts to propagate the embolus distally and minimize the amount of visual loss. Traumatic retrobulbar hemorrhages and other nonintraocular causes of elevated IOP do not benefit from an anterior chamber paracentesis.
An anterior chamber paracentesis will immediately reduce IOP but is not a treatment that resolves the underlying cause of the elevated IOP. Medical management is usually initiated first to lower IOP before attempting an anterior chamber paracentesis. An anterior chamber paracentesis is indicated whenever elevated IOP threatens visual loss and medical management is not successful in lowering IOP. Reducing the IOP acutely with an anterior chamber paracentesis in disease states such as acute angle-closure glaucoma, uveitis, hyphema, central retinal artery occlusion, and suppurative endophthalmitis may help prevent further irreversible vision loss if used in conjunction with other medical modalities.5-7,23
There are numerous nonemergent indications for an Ophthalmologist to perform an anterior chamber paracentesis. Diagnostically, ...