Quantification of corneal neovascularization. A graphics editing software (Photoshop CS2; Adobe Systems Inc.; Berkeley, CA) and a mathematical program (MATLAB; MathWorks Inc.; Natick, MA) were used to analyze slit lamp digital corneal photographs. These metrics were computed as follows: neovascular area, which measures the area of the corneal vessels themselves; vessel caliber, which determines an approximate mean diameter of the corneal vessels; and invasion area, which measures the fraction of corneal area in which neovascular incursion is seen.