(A, B) Left and right image of a stereo pair of an optic disc, the original captured image was cropped and separated. The left and right stereo images can be fused by holding the page at about 30 cm (12 in.) from the eye and gazing into infinity. (C) Planimetry by three glaucoma specialists superimposed, to show how the reference standard in (D) is created. It shows the cup and rim of each expert in bright red, green, and blue (rim), respectively, pale red, green, and blue (cup). Thus, where all three experts indicated cup, white is shown, and where all three experts indicated rim, gray is shown. (D) Reference standard developed from the planimetries shown in (C).