CPT® Code 92120

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Tonography, as defined by CPT® Code 92120, is a diagnostic procedure that measures the changes in intraocular pressure (IOP) resulting from sustained pressure applied to the eyeball using a tonometer. This procedure is essential for assessing aqueous outflow and plays a critical role in the detection of glaucoma, a condition characterized by increased IOP that can lead to optic nerve damage and vision loss. The tonography process involves the use of an indentation tonometer, such as the Schiotz tonometer, which is designed to record the amount of indentation made on the cornea by a known weight. During the procedure, the patient is positioned supine, and local anesthetic drops are applied to the cornea to minimize discomfort. The tonometer's footplate is then placed on the cornea, and a plunger is used to apply varying weights to measure the force required to indent the cornea. This force is translated into a measurement of IOP, typically expressed in millimeters of mercury (mm Hg), using a graph or conversion chart. Additionally, the perilimbal suction method can be employed, which intentionally increases IOP by obstructing the circulation and flow of aqueous humor, further aiding in the evaluation of the eye's pressure dynamics. Overall, tonography is a valuable tool in ophthalmology for monitoring and diagnosing conditions related to intraocular pressure.