Cortical Activity at Baseline and During Light Stimulation in Patients With Strabismus and Amblyopia

This research measures and compares the cortical activity at baseline and during light stimulation (LS) in patients with strabismus and amblyopia (SA) and healthy controls (HCs), to understand the differences in its functionality and propose LS as a potential brain stimulator. This observational, longitudinal, prospective study enrolled 17 SA patients and 17 HCs from Querétaro, México. Electroencephalography (EEG) and digital brain mapping (DBM) were used to identify changes in frequency, voltage, and brain coherence. A total of 68 DBM was analyzed for this purpose. Our results indicate that at baseline, patients with strabismus and amblyopia present: i) lower frequency of alpha-wave activity (<inline-formula> <tex-math notation="LaTeX">$p=0.029$ </tex-math></inline-formula>) with an abnormal distribution within hemispheres, ii) theta-wave with a predominance in the frontal lobes, which relates these visual conditions to neurodevelopmental disorders, iii) higher values of low voltage (<inline-formula> <tex-math notation="LaTeX">$p < 0.001$ </tex-math></inline-formula>) and lower values of and high voltage (<inline-formula> <tex-math notation="LaTeX">$p=0.001$ </tex-math></inline-formula>) iv) interhemispheric asynchronicity with a predominance in the left hemisphere. On the other hand, the administration of LS modulates the brain activity of SA patients by i) modifying high and low voltages (<inline-formula> <tex-math notation="LaTeX">$p < 0.001$ </tex-math></inline-formula> and 0.022 respectively), which define the anteroposterior gradient ii) eliminating theta-waves, iii) distributing alpha-wave activity towards the occipital lobes iv) bringing synchronicity between hemispheres. For the HC group, LS alters the distribution of alpha waves within hemispheres, and the state of interhemispheric synchronicity. There were no statistically significant changes in the frequency of the alpha-wave or the anteroposterior gradient. To summarize, LS provokes a state of malleability in the brain of SA patients, by increasing the cortical connectivity, enhancing neural activation and bringing to balance the interhemispheric communication, which converts it into a potential brain stimulator that should be considered as a complementary therapy in the treatment of these patients.