Do myopes process defocus any differently than emmetropes? Does being frequently exposed to low levels of optical blur lead to long-term cortical changes? By 2050 myopia’s prevalence is expected to reach 52% of the global population.
Moreover, long-term anatomical changes in the myopic eye appeared to be related to the neural processing of defocus. Lastly, myopia has been linked to long-lasting changes in cortical dynamics and structure in visual areas. We thus hypothesized that adults suffering from low and moderate myopia process optical blur differently than emmetropic adults. The aim was to examine the interaction between myopia and optical blur at the cortical level, characterizing its temporal and spatial dynamics. Emmetropes (n=10) and low to mild myopes (n=11) were tested in the condition of -2 diopters of lens-induced blur. Subjects passively viewed flickering dartboards and responded to an illusory contour recognition task while high-density EEG was recorded. Myopes did not show a behavioral advantage at the illusory contour detection task in blur, when compared to emmetropes. The processing of flickering dartboards did, however, differ between groups in terms of topography of neural activity between 50 to 110 ms after stimulus onset (F (1,19) = 4.99, p =.04, η2 =.20). In turn, illusory contour detection elicited significantly different topographies of brain activity between groups within the 235 to 362ms period (F (1, 19) = 4.73, p =.04, η2 =.19). To our knowledge, this is the first study of myopia pairing high density EEG and a behavioral task. Its results tie in findings of structural changes in the myopic brain with evidence of the role of blur in myopias physiopathology. As such, it opens the way for an integrative model of myopia, from progression to
long-term consequences.