A-lines are obtained from an OCT scan of the eye, some of which pass through the iris and the lens and some of which pass through the lens but not the iris. An interface is detected from the A-lines； at least some of this interface is assumed to correspond to either the anterior or posterior of the iris. For each A-line, a first metric is derived from pixels near the detected first interface, such that the first metric reflects an OCT signal intensity associated with the interface, and a second metric is derived from pixels further from the interface, such that the second metric reflects OCT signal attenuation below the detected interface. An attenuation parameter is calculated for each A-line, based on the first and second metrics, and the iris's edge is detected by determining whether each A-line passes through the iris, based on the attenuation parameter.
