Abstract
Abstract: :
Purpose: To assess the relationship among visual acuity, contrast sensitivity and cortical function based on fMRI, including volume and level of activation (Z–score). Methods: Monocular logMAR visual acuity and CSF were measured utilizing forced choice procedures. CSF data were collapsed into a single index by the use of weighted mean contrast sensitivity (WMCS), defined as the mean of the products of each spatial frequency multiplied by its corresponding contrast sensitivity. FMRIs were obtained with a 1.5T GE Signa scanner and visual stimuli included 1.0 and 2.0 c/deg vertical, sinusoidal gratings. Subjects included eight normal adults. Results: fMRI volume and level of activation exhibited overall low correlations with visual acuity. Statistically significant correlations were obtained between WMCS and fMRI volume (R= .765, P= .027) and fMRI level of activation (R= .645, P= .007) with right eye stimulation with the 1.0 c/deg grating. In general, significant relationships between WMCS and fMRI parameters were maintained when subject age was held constant and when data from 5 amblyopic subjects expanded the range of values and increased the number of subjects for analysis. Conclusions: FMRI volume and level of activation (Z–score) were more closely associated with CSF, as defined by WMCS, than visual acuity. The results support the hypothesis that the CSF may reflect the underlying visual cortical cells responsible for fMRI volume and level of activation.
Keywords: visual acuity • contrast sensitivity • imaging/image analysis: clinical