Following a head injury a man lost his tears from his both eyes. Absence of lacrimation is due to injury to:

The greater petrosal nerve exits the geniculate ganglion and ultimately innervates the lacrimal gland. The injury to the greater superficial petrosal nerve may cause reduction or absence of tear production. Unilateral loss of lacrimation suggests injury at or proximal to the geniculate ganglion. Ref: BDC, 4th edition, IIIrd volume, Page 23, 63.