The Ocular Response Analyzer utilizes a rapid air impulse, and an advanced electro-optical system to record two applanation pressure measurements; one while the cornea is moving inward, and the other as the cornea returns. Due to its biomechanical properties, the cornea resists the dynamic air puff causing delays in the inward and outward applanation events, resulting in two different pressure values.
The average of these two pressure values provides a repeatable, Goldmann-correlated IOP measurement (IOPG). The difference between these two pressure values is Corneal Hysteresis (CH); a new measurement of corneal tissue properties that is a result of viscous damping in the corneal tissue. The ability to measure this effect is the key to understanding the biomechanical properties of the cornea.
The CH measurement also provides a basis for two additional new parameters: Corneal-Compensated Intraocular Pressure (IOPCC) and Corneal Resistance Factor (CRF). IOPCC is an Intraocular Pressure measurement that is less affected by corneal properties than other methods of tonometry, such as Goldmann (GAT). CRF appears to be an indicator of the overall “resistance” of the cornea.