external limiting membrane external limiting membrane the external limiting membrane (or outer limiting membrane) is one of the ten distinct layers of the retina of the eye. it has a network-like structure and is situated at the bases of the rods and cones. external limiting membranedetailsidentifierslatinmembrana limitans externata98a15.2.04.011fma58683anatomical terminology additional images rods and cones section of retina. (membrana limitans externa labeled at right, third from the bottom.) plan of retinal neurons. (membrana limitans externa labeled at left, second from the bottom.)