DRY EYE SYNDROMES

Tear film biomarkers offer the potential to significantly improve the diagnosis and management of dry eye syndromes, Franz Grus MD, PhD told a session of the 6th EuCornea Congress in Barcelona, Spain.
“We all know that there is a poor correlation between clinical parameters and disease severity in dry eye syndromes. More advanced and objective indicators of abnormalities would be very useful in the management of these diseases,” said Prof Grus, Head of Experimental Ophthalmology at the University Medical Center Mainz, Germany. 
Presenting during a focus session on dry eye diagnosis and management, Prof Grus discussed so-called biomarkers, which are measurable indicators of a particular biological state or condition.
“Our goal is to identify and validate the potential protein biomarkers present in the tear film for the spectrum of dry eye diseases using a targeted proteomics strategy. This would allow us to take a very small tear film sample, identify a cluster of proteins and employ this to signal the presence of dry eye. We could then distinguish between different dry eye subgroups based on their expression levels,” said Prof Grus.
Protein and peptide expressions reflect the current state of disease or health, a ‘snapshot’ of body functions at any given time. Obtaining and analysing these molecules might be of great help in both diagnosis and prognosis of these varied and often complex conditions.
“Dry eye disease also currently suffers from a lack of objective criteria for clinical trials of new treatment options, and biomarkers might alleviate this need,” he added.
Protein microarrays are used to detect upregulation of proteins such as calgranulin, an inflammatory marker expressed by neutrophils that is elevated in all dry eye subgroups. 

TISSUE COATING
Microarrays can also detect downregulation of a biomarker like proline-rich protein 4 (PRR4), which mediates protective functions on the ocular surface, such as modulation of microflora. PRR4, which is abundant in tears but decreased in dry eye subgroups, is also thought to be of protective importance in the tear film. 
“We have even noticed changes in biomarker profiles after patients switch from conserved to unconserved intraocular pressure-lowering drugs. Besides looking for the proteins themselves, we also try to discover post-translational modifications, which may largely determine the ultimate cell regulatory function of these proteins, as well as their resistance against degradation,” said Prof Grus.
The use of biomarkers is a promising approach for diagnosis and better understanding of the disease pathomechanisms within the dry eye spectrum, as well as personalised medicine based on the biomarkers present in each patient, he emphasised. 
Franz Grus: grus@eye-research.org