Figure 1: The proposed mechanism of light exacerbation of headaches through the convergence of the retinal input and nociceptive trigeminal afferents on the same thalamic projection neurons in the posterior group of the thalamus (Po).
The retinal afferents originate from RGCs or from ipRGCs and modulate the activity of neurons receiving nociceptive information through the spinal trigeminal nucleus from the meningeal covering of the brain (the dura mater). Noseda et al.1 provide convincing anatomical and physiological evidence for these interactions. Blind migraine sufferers (where only ipRGCs, but no RGC are present) still experienced light aggravation during headaches. In those patients in which all vision had been lost, light did not exacerbate migraines.
