Contrast sensitivity testing is becoming more widely used clinically to evaluate and manage treatment of patients in cases where standard acuity is inadequate. Standard visual acuity, using high contrast black on white letters, is not sensitive enough to detect subtle changes in vision related to clinical evaluation for eye disease and quality of vision.  The purpose of this presentation is to provide background information about contrast sensitivity testing and to explain how the test is used clinically to better treat eye care patients. The presentation will include the scientific basis for contrast sensitivity testing and information on how to clinically administer the test and plot the results. Specific clinical application of contrast sensitivity testing for cataract evaluation, glaucoma detection and treatment, and refractive surgery evaluation will be presented. Case reports for specific patients will be presented showing pre and post treatment contrast sensitivity results.