Sensory-secretory neuroimmune circuits of the ocular surface

The ocular surface is a sensory-rich mucosal barrier in which trigeminal input, autonomic output, tear composition, epithelial stress, glandular secretion, goblet-cell function and local immunity are closely coupled. This review uses the sensory-secretory mucosal immune unit as a tissue-level map across four measurable output domains: secretory function, neural state, immune activity and barrier integrity. The term is not proposed as a new anatomical compartment or as a renamed lacrimal functional unit or eye-associated lymphoid tissue. Direct ocular evidence is distinguished from ocular-adjacent observations and cross-barrier analogies, particularly for cytokine-neuron, microbiome-neuron and mucosal-drainage pathways. Dry eye disease, allergic conjunctivitis and neurotrophic keratopathy are compared as overlapping but distinct patterns of circuit failure, with dry eye disease framed as sensory-autonomic dysfunction, allergic conjunctivitis as type 2 neuroimmune amplification and neurotrophic keratopathy as sensory denervation with impaired epithelial repair. The review also considers lacrimal drainage, nasal mucosal continuity and regional eye-draining lymph nodes as conditional antigen-handling routes. Emphasis is placed on paired secretory, neural, immune and barrier readouts that may help define the dominant failing process and guide intervention studies.