Tears secreted collect in the fornix conjunctiva of the upper lid, and pass over the eye surface to the lacrimal puncta, small holes found at the inner corner of the eyelids.

Each acinus consists of a grape-like mass of lacrimal gland cells with their apices pointed to a central lumen.

This communicating branch carries postganglionic parasympathetic axons from the pterygopalatine ganglion.

The parasympathetic innervation to the lacrimal gland is a complex pathway which traverses through numerous structures in the head.

They project axons which exit the brainstem as part of the facial nerve (CN VII).

It emerges to the middle cranial fossa and travels anteromedially to enter the foramen lacerum.

The postganglionic neurons then send axons which travel with the zygomatic nerve to enter the inferior orbital fissure.

Treatment varies according to aetiology and includes avoidance of exacerbating factors, tear stimulation and supplementation, increasing tear retention, eyelid cleansing, and treatment of eye inflammation.