The Effect of Optical Blurring on theVisual Cortex Response Studied by Functional Magnetic Resonance Imaging

Background and Aim: Optical blur due to refractive errors causes reducing retinal image quality and induces changes in how visual system responds. The purpose of this study is to evaluate the effect of myopic optical blur on visual cortex response by functional magnetic resonance imaging (fMRI). Materials and Methods: Five healthy volunteers with various degrees of myopia and age range 18-25 years (two females and three males) participated in this study. The results of functional magnetic resonance imaging of 18 emmetropic people (without refractive error) participated in a recent fMRI study with the same scanning conditions were applied as the control data. The functional scans were obtained by a Phillips scanner using a sine-wave grating visual task with spatiotemporal frequency of 2cpd/8Hz. The percentage of BOLD (Blood-Oxygen-Level-Dependent) signal change and number of activated voxels in different scan series were compared with each other after image processing. Results: Non-linear reduction of visual cortex response due to increasing optical blur was observed in this study. The number of activated voxels and the percentage of BOLD signal change were both reduced in different amounts of myopia.Conclusion: Considering the effect of optical blur on visual cortex responses in different amounts of myopia, it is better to provide the optimum optical correction during cognitive neuroscience fMRI research and FMRI study of neurologic diseases using patterned visual stimuli.