Corneal topographer with central and peripheral measurement capability
AssigneeVismed
InventorDale A. Rorabaugh
Life of this patent
Estimating the term…
Abstract
A videokeratograph has a placido disc with rings concentric about a central axis, a center positioned on the central axis, and an observation opening at the center. A plurality of fixation points are positioned in the placido disc spaced from the center opening and distributed circumferentially around the central axis, whereby rings on the placido disc spaced from the center are reflected from the central zone of the cornea. A video camera positioned on the center axis behind the placido disc observes an image of the placido disc reflected from the cornea. A processor coupled to the video camera determines the shape of the central zone of the cornea.
Claims24
A method of determining a shape of the cornea of an eye, comprising the steps of:
- moving at least one of an eye and a placido disc to position the eye on a central axis of the placido disc, wherein a center opening is formed in the placido disc on the central axis;
- illuminating the eye with the placido disc;
- fixating the eye along a first viewing axis that passes from the eye toward a first fixation point positioned on the placido disc at a location spaced from the center opening;
- observing an image of the placido disc reflected from the eye, whereby the central zone of the cornea of the eye reflects an image of a portion of the placido disc spaced from the center opening;
- and
- determining from the observed image the shape of at least the central zone of the cornea.
A corneal topographer, comprising:
- a target having a center positioned on a central axis and at least one fixation point positioned on the target at a location spaced from the center such that a central zone of a cornea of an eye positioned at an observation station and located on the central axis and fixated on said at least one fixation point will reflect an image of a portion of the target spaced from the center;
- a detector positioned to detect an image of said target reflected from the cornea of an eye positioned at the observation station;
- and
- a processor configured to determine a shape of at least the central zone of the cornea based on the detected image.
A corneal topographer, comprising:
- means for projecting a test image onto a cornea of an eye when the eye is located at an observation station and is oriented along a central axis;
- means for fixating the eye along at least one fixation axis which passes from the eye to a fixation point that is spaced from the central axis;
- means for detecting a portion of the test image reflected from the cornea of the eye while the eye is fixated along the at least one fixation axis;
- and
- means for determining a shape of at least a central region of the cornea of the eye based on the detected reflected test image.
Dependencies are inferred from the claim text.