Measuring contrast sensitivity of the human eye with modified Siemens stars.

Purpose: The purpose of this study is to evaluate a new testing procedure to measure contrast sensitivity of the human eye using modified Siemens stars as test patterns. This test is called the Star-Ring Test.

Methods: The modified Siemens stars consist of alternating light and dark stripes in a radial arrangement having a sinusoidal luminance pattern. This pattern is displayed on a PC monitor. The pattern includes a black ring that is intended to mark the resolution threshold. Subjects are asked to use a button to change either the contrast of the pattern or the size of the ring until stripes can be resolved only outside of the ring. The area inside the ring appears uniformly gray at this point. The usefulness of the Star-Ring Test was investigated in three experiments: (1) influence of rotation of the test pattern and number of presentations per trial; (2) validity and reliability compared with the Vistech chart; and (3) practicability for subjects with abnormal contrast vision.

Results: The contrast sensitivity functions for stationary and rotating patterns were nearly identical, whereas rotating patterns provide a lower scatter of values. Five presentations per trial were adequate to estimate accurate values. Compared with the Vistech chart, contrast sensitivities estimated by the Star-Ring Test are slightly lower. The repeatability coefficient (RC) of contrast adjustment ranged from 0.22 to 0.38 log units, whereas the Vistech chart yields RC values from 0.34 to 0.67 log units. The ring adjustment mode showed a RC of 0.13 log units. The mean duration of the measurement with naïve subjects involving contrast adjustment was 67 s and involving ring adjustment 81 s.

Conclusions: The Star-Ring Test is a rapid and reliable test of contrast sensitivity.