 The stimulation of a variety of cell types may lead to the release of microparticles (MPs)  These submicron vesicles bud off from the plasma membrane of the parent cell  They can disseminate a variety of bioactive effects which reflect the cell of origin  They are pro inflammatory and play an important role in mediating inflammation, haemostasis, thrombosis, angiogenesis and vascular reactivity

 Elevated levels of MPs occur in inflammatory and autoimmune diseases, atherosclerosis, malignancy and infection  Their levels may reflect disease activity and they can act as useful biomarkers  There is no uniform definition of MPs  Identification in previous studies has been based on their characteristic composition and size  This can help differentiate them from other subcellular structures including apoptotic bodies and exosomes

 MPs are described as small membrane bound vesicles ranging in size from 0.1–1μm  They are released from the precursor cells by exocytic budding of the plasma membrane  This process produces a phospholipid rich surface from the plasma membrane lipid bilayer  The membrane (including surface proteins and receptors), cytoplasmic, antigenic and nuclear constituents of the MP released reflect the origin cell  Their composition is also influenced by the type of stimulus leading to their production

 We aimed to investigate if MPs were present in the tears of patients with ocular surface inflammation  Identification was based on their previously described characteristic features › Vesicular shape › 0.1-1μm in size › Outer phospholipid membrane  Scanning electron microscopy (SEM) and nile red stain (a lipophilic stain) were used to identify these  Tear samples were collected from 5 inflamed eyes and 4 non-inflamed eyes

 The diagnosis in the eyes with ocular surface inflammation was › 3 corneal ulcers, 2 conjunctivitis  Particles characteristic of MPs were identified in all the samples from eyes with ocular surface inflammation  These particles were not present in samples from the control eyes

Multiple particles with the characteristic appearance of microparticles (arrow) in tear sample Low power SEM. Box indicates area shown in high power in next slide

Multiple particles with the characteristic appearance of microparticles (arrow) in tear sample High power SEM

Characteristic particles staining with nile red Colour fluorescent picture

 We have demonstrated the presence of particles characteristic of MPs in the tears of 5 eyes with ocular surface inflammation  These were not present in the 4 control eyes  MPs are increasingly recognised to play an important role in mediating various disease processes  Further investigation is merited to further define the role of MPs in mediating ocular surface disease