A Review of Emerging Tear Proteomics Research on the Ocular Surface in Ocular Allergy

SIMPLE SUMMARY: Ocular allergy is a localised form of allergy occurring on the surface of the eye and surrounding tissues. Typical signs and symptoms of ocular allergy include itching, redness, swelling of the eyelids and inflammation. Emerging studies on ocular allergy have shown that tears collected from ocular allergy sufferers show significantly different protein contents than in healthy populations. Differences in protein contents in tear samples have been hypothesised to be caused by a number of allergy-mediated factors, including long-term inflammation and eye-rubbing. Excessive eye-rubbing due to allergy-associated itch has also been shown to have significant effects on the physical shape of the eye, thereby potentially causing progressive vision problems in ocular allergy sufferers. This review aims to summarise and explore recent findings in ocular allergy protein research. This is to help determine which ocular surface proteins differ between ocular allergy sufferers and healthy controls, and the role each protein may play in the underlying chemistry of ocular allergy. Additionally, potential benefits of expanding the current pool of research into ocular surface proteins in ocular allergy sufferers in terms of diagnosis and treatment of the condition is discussed. ABSTRACT: Ocular allergy is an immunoglobulin E-mediated Type I hypersensitivity reaction localised to the ocular surface and surrounding tissues. Primary signs and symptoms of ocular allergy include itching, redness, irritation and inflammation. Eye-rubbing caused by itching has been shown to alter ocular surface protein concentrations in conditions linked to ocular allergy such as keratoconus. In keratoconus, the cornea begins to thin and sag over time, leading to progressive vision loss and blindness in severe conditions. Due to the high incidence of ocular allergy sufferers rubbing their eyes in response to symptoms of itching, the protein landscape of the ocular surface may be significantly altered. Differential protein expression caused by long-term inflammation and eye-rubbing may lead to subsequent changes in ocular surface structure and function over time. This review aims to summarise and explore the findings of current ocular allergy proteome research conducted using techniques such as gel electrophoresis, mass spectrometry and lab-on-a-chip proteomics. Proteins of interest for this review include differentially expressed immunoglobulins, mucins, functional proteins, enzymes and proteins with previously uncharacterised roles in ocular allergy. Additionally, potential applications of this research are addressed in terms of diagnostics, drug development and future research prospects.