“…Adobe Photoshop, 23,34,37 Engauge Digitizer, 32 GIMP, 27 JHU’s FieldDigitize, 7,10,24 MathWorks MATLAB, 14 NIH’s ImageJ, 18,31 Scion Image, 34,36 UCL’s Retinal Area Analysis Tool, 28 UTHSCSA ImageTool 29,33 ), or handheld devices to convey position information to computer software. 5,20,21,23,26 To our knowledge, however, none of these previous studies have explored the variability of calculated retinal areas or the error rates of digitizers. Here, the term “error” refers to an omission or erroneous classification of one isopter: mislabeling an isopter target size, mislabeling an isopter as seeing or non-seeing, or missing an isopter during digitization.…”