Contrast sensitivity can be measured in various ways that, depending on the clinical situation, may or may not reflect similar information. Under pathologic conditions, there will be differences in static grating plates versus temporally alternating oscilloscope sine waves versus Snellen acuity letters of decreased contrast. Choosing an appropriate methodology for the information needed is recommended. Orientation of gratings may give different results depending on the location of brain lesions. The “normal” side may be abnormal in amblyopia and hemianopia, a reflection of the binocularity of vision. Increased intracranial pressure with pseudotumor causes a contrast sensitivity abnormality that reverses to normal within days of shunting. Refraction is important for Snellen (letter) and contrast sensitivity but less so in grating, and it influences contrast sensitivity significantly. Recognition contrast sensitivity targets (letters) degrade faster with eccentric viewing than gratings, a finding important in low-vision aid therapy.