Which structure is primarily assessed for electrical activity during the EOG test?

The structure primarily assessed for electrical activity during the Electrooculography (EOG) test is the retinal pigment epithelium. The EOG test measures the electrical potential difference between the cornea and the retinal pigment epithelium as the eye moves. This potential change is primarily attributable to the ionic movements across the retinal pigment epithelium, which maintains the trans-retinal potential necessary for phototransduction.

In the EOG procedure, electrodes are placed on the skin near the eyes to detect these electrical potentials generated by the differences in ion concentration across the retinal pigmented layer. As the eyes move, the electrical potential changes correspond to alterations between the corneal and retinal pigment epithelial surfaces, giving insight into the health and functionality of the retina and the underlying structures. Thus, the retinal pigment epithelium is crucial in the assessment of these electrical activities during the EOG test.