Diadenosine Polyphosphates and Mucin Associated With Ocular Surface Disorders

Dry eye disease, ocular graft-versus-host disease (GVHD), and superior limbic keratoconjunctivitis (SLK) are all ocular surface disorders which mostly involve the outer surface of the eye. Many of the ocular surface disorders may result from or be aggravated by the mechanical stress from eyelid blinking. Specifically, SLK is an inflammatory ocular surface disorder characterizing by redundant superior bulbar conjunctiva. Since redundant superior bulbar conjunctiva can cause a significant mechanical force during eyelid blinking, we found that conjunctival resection with Tenon's capsule excision is helpful in relieving the symptoms of SLK patients. Therapeutic contact lens, protecting the ocular surface from the microtrauma between eyelid and ocular surface, is also an effective treatment for severe dry eye disease, ocular GVHD, and SLK. Although shearing force/mechanical stress has been studied in many different tissues and disease entities, the impact of shearing force over ocular surface is still unclear. While the importance of mechanical stress in ocular surface disorder has been reported, the specific molecule involving the pathogenesis is still unknown. Diadenosine polyphosphates are a family of dinucleotides. They can enhance tear secretion and increase corneal wound healing rate from previous reports. Shear-stress stimuli was also noted to be able to induce diadenosine polyphosphates releasing from human corneal epithelium. In addition, mucin, one of the three components of tear film, has been greatly emphasized in the pathogenesis of dry eye disease. There are also some reports about the shearing force compensating the mucin contents in the inflammatory lung/bowel diseases. If diadenosine polyphosphates or mucin indeed play a role in mechanical stress-related ocular surface disorders, it will be a promising therapeutic targeting in the future.