Reliability of the Vistech Contrast Test System in a life-span adult sample

To assess the reliability of the Vistech Contrast Test System (VCTS), contrast sensitivity functions (CSF's) were estimated using all forms of the VCTS in 92 subjects aged 20 to 73 years, who were refracted for the test distance. Over a 3-month period, nine estimates at each spatial frequency and an equivalent number of acuity measures were obtained. The contrast sensitivity of older adults was lower than that of the younger adults, particularly at higher spatial frequencies. Practice effects which varied as a function of spatial frequency were also observed. Reliabilities for single-form estimates of contrast sensitivity (CS) were frequency-dependent, and ranged from 0.41 to 0.65. Three-form average estimates of CS yielded reliabilities ranging from 0.62 to 0.77. Consistent with the assertion that low VCTS reliabilities are due, in part, to measurement error, the reliabilities for acuity were uniformly higher than for the VCTS. Results are discussed in relation to clinical use of the VCTS across the life-span.