Neurokinin a is a main constituent of sensory neurons innervating the anterior segment of the eye.
Schmid E, Leierer J, Doblinger A, Laslop A, Fischer-Colbrie R, Humpel C, Theodorsson E, Teuchner B, Lalehabbasi D, Dragosits E, et al. Invest Ophthalmol Vis Sci. 2005 Jan; 46(1):268-74.