PURPOSE: To gain insight into the association between optical and neural components of contrast sensitivity (CS), operationalized as spatial CS (optical and neural) or temporal CS (solely neural), and reading speed in a clinical sample of healthy adults of various ages. Furthermore, precision and agreement of the two methods were assessed.
METHODS: The Mars test and the temporal CS implementation of the C-Quant device were used to measure spatial CS and temporal CS, respectively. Tests were performed with 71 normally sighted adults: mean age 55 (range 18-86) years. Pearson's correlation analyses were performed between spatial CS or temporal CS, and reading speed and partial correlations controlled for age are presented. Precision of the measurement was defined by the coefficient of repeatability and repeated measures standard deviations. Differences between spatial CS and temporal CS values were determined with 95% limits of agreement.
RESULTS: A correlation was found between reading speed and both spatial CS (r = 0.470; P < .001) and temporal CS (r = 0.258; P = .04); partial correlations controlled for age were r = 0.175 (P = .17) and r = 0.152 (P = .24), respectively. Coefficient of repeatability was 0.13 log units and 0.24 log units for spatial CS and temporal CS test, respectively. A proportional difference of 0.1 log units was found between spatial CS and temporal CS measurements.
CONCLUSIONS: A significant correlation was found between both spatial CS and temporal CS and reading speed indicating that, besides optical components, neural aspects may be important in defining reading speed. The stronger correlation between spatial CS and reading speed is suggested to reflect a deterioration of both optical and neural factors with increasing age. The coefficients of repeatability for spatial CS and temporal CS found in the present study are in agreement with previous research, and the difference found between the two methods might be attributed to the psychometric differences between the methods.