The Graham Field Ishihara charts are the most widely recognized tests for color vision deficiency. Each book contains a series of pseudo-isochromatic plates, which feature a circle of dots appearing randomized in color and size. Within the pattern are dots which form a number or shape clearly visible to those with normal color vision, but invisible or difficult to see for those with a defect. The 1254 (14 plate) and 1257 (10 plate) models are ideal for quick screenings in schools or general practice. The 1255 (24 plate) and 1256 (38 plate) versions provide a more thorough diagnostic evaluation, allowing practitioners to determine the specific type and severity of the color deficiency.