Use of microbubble ultrasound contrast agent to demonstrate the iris valve effect in human eye bank eyes

PURPOSE: To demonstrate that the interface between the normal iris and the lens surface functions as a flap valve. METHOD: Microbubble ultrasound contrast agent was injected into the anterior and posterior chambers of human eye bank eyes and the distribution of contrast imaged with high-frequency ultrasound. RESULTS: Contrast agent did not enter the posterior chamber when injected into the anterior chamber, but contrast agent injected into the posterior chamber easily flowed into the anterior chamber. CONCLUSIONS: The iris–lens interface normally functions as a flap valve, preventing retrograde flow from the anterior to the posterior chamber. A temporary increase in anterior chamber pressure thus results in iris concavity in pigmentary dispersion syndrome.