To See or Not to See: A Systematic Review of the Importance of Human Ocular Surface Cytokine Biosignatures in Ocular Allergy

Abstract

Cytokines are key cell signalling proteins in a number of immune and homeostatic pathways of the human body. In particular, they mediate intracellular mechanisms of allergy on the ocular surface by triggering cellular responses that result in typical physiological ocular allergy symptoms, such as itchiness, watery eyes, irritation, and swelling. Given the recent research focus in optometry on the aetiology of corneal ectasia subtypes like keratoconus, there is an increasing need for the development of new clinical diagnostic methods. An increasing trend is evident among recent publications in cytokine studies, whereby the concentrations of cytokines in healthy and disease states are compared to derive a specific cytokine profile for that disease referred to as ‘biosignatures’. Biosignatures have diagnostic applications in ocular allergy as a cheap, non-invasive alternative to current techniques like IgE antibody testing and skin prick tests. Cytokine detection from tear samples collected via microcapillary flow can be analysed either by enzyme-linked immunosorbent assays (ELISA), multiplex magnetic bead assays, or immunoblot assays. Characterising patient hypersensitivities through diagnostic tests is the first step to managing exposure to triggers. Investigating cytokine biosignatures in ocular allergy and their links to physiology are imperative and will be the focus of this systematic review article.

Survey of cytokines on ocular surfaces of atopic dogs by multiplex analysis using two sampling methods – a pilot study

“…Acute (seasonal allergic conjunctivitis) and iatrogenic (giant papillary conjunctivitis) forms of conjunctivitis demonstrated a lack of cytokine changes in the tears, while chronic diseases including vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) produced T helper (Th)1, Th2 cytokines and chemokines. [20][21][22] As observed in atopic dogs in this pilot study, IL-8 concentrations were found to be increased in the conjunctival epithelium of VKC and AKC in humans. IL-8 concentrations were correlated with disease severity as well as with the numbers of neutrophils and eosinophils.…”

Total IgE in tears accurately reflects the severity and predicts the prognosis of seasonal allergic conjunctivitis

“…The diagnosis of ocular allergies is primarily clinical, although laboratory tests can be useful in supporting the diagnosis 6 . At present, laboratory tests for AC mainly include cytological examination, skin prick tests, and total IgE antibody detection 15–17 . The detection of eosinophils is a complex procedure with a low detection rate of approximately 60% in conjunctival scrapings from patients with mild allergic conditions 18 .…”

Changes in Anterior and Posterior Corneal Elevation in Patients With Allergic Conjunctivitis

“…Allergic conjunctivitis (AC) is a common ocular surface disease that affects more than 20% of the population (1). It is well established in the literature that AC is closely related to the occurrence of keratoconus (KC) (2)(3)(4).…”