DISTANCE OPTIMIZING APPARATUS FOR A PLACIDO-BASED EYE OBSERVATION SYSTEM

摘要

An apparatus assists a user of a placido-based eye observation system (10) to place the placido at an optimum distance from an observed eye. A light source is configured as a point source. The light source and a CCD camera (34) are attached to the placido at opposed locations that are spaced from the viewing axis, but symmetric with respect to it. Light is emitted by the source towards the eye (24), and reflected by the apex of the cornea of the eye on the main axis. The reflected source light appears in the field of view of the CCD camera (28) as a bright point image. The location of the point image within the field of view informs how far away the eye is from the placido. The placido is moved until the point image is positioned within the field of view at a reference position. In a manual embodiment a screen shows what is in the field of view, and an operator looks at the screen, and uses a joystick (18) to control movement of the placido. In an automated embodiment a computer analyzes the field of view, determines the position of the point image, and drives a closed loop system to maintain the distance at the optimum value.