The Trigeminal nerve supplies sensory innervation to the cornea.  The

Trigeminal nerves are accompanied by parasympathetic and sympathetic nerves from the pterygopalatine or sphenopalatine ganglion.  This is a discussion of a newly found connection. This is an interesting abstract I recently found that helps explain why SPG Blocks are effective for eye pain:
Am J Rhinol Allergy. 2011 Jan-Feb;25(1):50-3. doi: 10.2500/ajra.2011.25.3550.
A previously undescribed branch of the pterygopalatine ganglion.
Oomen KP1, Ebbeling M, de Ru JA, Hordijk GJ, Bleys RL.

Endonasal and infrazygomatic pterygopalatine ganglion (PPG) block for facial pain provides pain relief in a broader area than expected on anatomic grounds. The aim of this study was to search for neural structures in the pterygopalatine fossa (PPF) that could explain unexpected pain relief after PPG blockage.

The neural PPF content was explored through human cadaver study and nerve-specific staining. Five human PPF specimens were dissected as whole-mount preparations with the aid of an operation microscope and stained for acetylcholinesterase. One of these specimens was partially sectioned and analyzed through nitric oxide synthase (NOS) immunohistochemistry.

A previously unknown nerve was identified. The nerve runs between the PPG and the ophthalmic nerve and was identified in all five specimens. NOS-containing nerve fibers were present but did not occupy the complete nerve area.

Because it is likely that the nerve contains sensory fibers, our findings may provide an anatomic basis for unexplained pain relief in the ophthalmic area after PPG blockage.