Corneo-scleral topography system

A method for making an ophthalmic topography measurement of a target surface including the cornea, the limbus and at least a portion of the adjacent scleral region, comprising:

• conditioning at least a portion of the target surface such that it diffusely reflects an image projected thereon;
• projecting a selected image onto a substantial portion of the target surface;
• obtaining an image of the diffusely reflected image;
• extracting selected features of the image;
• and
• using the extracted features to determine a corneo-scleral surface topography,
• wherein the step of extracting selected features of the image comprises
• finding the center of the image, referred to as a starting node;
• extracting a plurality of horizontal line features from the image to form a horizontal line array;
• extracting a plurality of vertical line features from the image to form a vertical line array;
• finding an intersection point in the horizontal and vertical line arrays;
• finding a plurality of neighboring intersection points in the horizontal and vertical line arrays, wherein each intersection point is a node;
• continuing finding a plurality of neighboring intersection points in the horizontal and vertical line arrays until a satisfactory number of intersection points (nodes) have been found to determine the topography of the corneo-scleral surface, further comprising
• determining a region of interest (ROI) in the center of the image;
• computing a sum of all pixels in a row, saving the sum as computed for all rows, and saving the sum in a row sum array;
• computing a sum of all pixels in a column, saving the sum as computed for all columns, and saving the sum in a column sum array;
• determining a peak value in the row sum array corresponding to a Y coordinate of a center of a reticle image;
• and
• determining a peak value in the column sum array corresponding to a X coordinate of a center of a reticle image on the image.