| 摘要 |
PROBLEM TO BE SOLVED: To measure a center of a cornea and to accurately measure a periphery of the cornea. SOLUTION: When one of fixation optotypes out of an optical axis is lit, a visual line of an eye to be examined is inclined. A radius of curvature of the center is calculated based on a circular arc Ra of 1/4 of an upper part reflected at the center of the cornea of a reflected image of the cornea. An intersection of the line and the arc Ra is obtained, and an ellipse is specified by a least square method. A radius of curvature of the periphery is obtained by using a circular arc Ra' of 1/2 of a lower part reflected at the periphery. Intersections of lateral and longitudinal scanning line groups of an imaging means and the arc Ra' are obtained, an ellipse is calculated by the least square method, and the radius of curvature and an astigmatism are similarly calculated from their ellipses. When a reflected image of a cornea for another fixation optotype is obtained by changing the line by a similar method, its image is captured and a similar calculation is conducted, the radii of curvature of the center and the periphery from the center of the cornea can be measured. |
