Testing Low Vision Patients

Contrast sensitivity testing is very useful for low vision evaluation. VectorVision offers a range of products for testing patients with poor vision. The best test to use depends on the level of the patient’s vision and the objective of the evaluation. The standard CSV-1000E test face can be used with patients who have visual acuity of 20/70 or better. If the patient can correctly identify only a few gratings at the 8 foot test distance, the patient should be moved to 4 feet and retested. If the patient is still unable to identify more than a few contrast gratings, then it is best to switch to one of the tests described below. For these tests, the recommended test distance is 1 meter.

CSV- l000LV

The CSV-l000LV is designed for evaluating patients who have worse than 20/70 acuity. At a test distance of 1 Meter, the letter size is equivalent to 20/630 ETDRS LogMAR acuity. This test presents letters at 8 contrast levels.


CSV-1000 1.5 Cycles per Degree

VectorVision has developed a special test face with large sine-wave gratings to aid in the evaluation of low vision patients. The test face provides a test for 1.5 cycles/degree at a test distance of eight feet. Eight pairs of two contrast circles are presented to the patient, with one circle in each pair containing a grating and the other circle is blank. The patient is asked to identify which circle contains the sine-wave gratings. The circles are presented side-by-side, as opposed to top and bottom (as with the standard CSV-1000E test face). The test is very useful for establishing the base level of contrast sensitivity for a patient and tracking changes over time related to disease progression or treatment.


The ELCT (Evans Letter Contrast Test) was designed specifically for use to evaluate low vision patients. It presents large-format (20/630 sloan acuity) letters in groups of three. Each group of three letters has the same contrast level. Sixteen different contrast levels are presented, including the high contrast acuity. The ELCT is useful for establishing an accurate measure of visual capability for low vision patients and for tracking changes in vision over time. To learn more about ELCT, please visit the ELCT page.