Seasonal variation of tear fluid extracellular vesicles and it’s correlations with ocular biometry
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This study has two purposes: First, to investigate the associations between extracellular vesicles (EV) levels, ocular biometry and/or refractive error, secondary, to assess if there are any changes in EV levels with regards to season and/or ocular growth. EVs are known to play a part both in healthy and diseased eyes, as they play a role in corneal wound healing process, RPE drusen formation and primary open angle glaucoma progression. There has been discussion about a possibility of EV’s regulating eye growth and thus myopization. The empirical part of this cross-sectional study was conducted from August 2018 to March 2020. To create a baseline, ocular biometry measurements and tear samples were collected 36 participants in winter 2018. Eight of these participants volunteered for the follow-up study. Extracellular vesicles were isolated with experimental method combining ultracentrifugation and size exclusion chromatography. Isolated particles were run on nanoparticle tracking analysis. Tear fluid nanoparticles in the size range of EVs were observed and counted. However, to confirm that these in fact are EV’s, electronic microscopy would be needed for the identification of tetraspanin CD63, an EV marker protein. We noticed that eye growth was considerable slower from April to September compared with December to April. Our results suggest that this growth pattern was similar to how particle size and count changed. Over summertime axial growth slowed down as the EV particle size and count increased and vice versa for wintertime. This indicate that EV particle size may carry information related to eye growth, however this initial project is just one of many first small steps for future work.