Lactoferrin as a biomarker of ocular diseases and contact lens discomfort

Lactoferrin (Lf) is frequently described as a diagnostic marker for different ocular diseases, such as dry eye (DE), Sjo & BULL;gren's syndrome, and diabetic retinopathy. We therefore performed a meta-analysis on the average Lf concentration in healthy subjects and those affected by ocular diseases. The results suggest that Lf level is a good candidate as a DE syndrome diagnostic biomarker, even though there is still a need for further development of standardized protocols of tear collection, processing, and storage. One of the risk factors for DE is contact lens (CL) wear and DE prevalence is known to be higher in CL wearers than non-wearers. To investigate Lf as a biomarker for CL discomfort, we developed a diagnostic method based on terbium fluorescence to detect Lf directly into human tears. Lf concentration was found to be unchanged after a period of CL wear and after a period of CL suspension. Instead, the results reveal a significant change in Lf affinity for terbium upon CL wear. It is known that an alteration of the protein conformational state or of its substrate-binding site leads to protein inactivation and triggers an inflammatory response. Indeed, high levels of protein denaturation have been found to be correlated with adverse effects, such as papillary conjunctivitis and CL discomfort.