1. A method of detecting a living human eye comprising the steps of: presenting a first image on a computer screen, wherein the computer screen is oriented to face a user; positioning at least one camera proximate the computer screen, wherein the at least one camera is oriented to face the user so that light emitted by the computer screen as the first image is reflected by the user and captured by the at least one camera; obtaining a second image through the at least one camera; and determining whether at least a portion of the second image includes a representation of the first image on the computer screen reflected by a curved surface consistent with a human eye.