Aqueous humor (AH) is a dynamic intraocular fluid that supports the vitality of 
tissues that regulate intraocular pressure. We recently discovered that 
extracellular nanovesicles called exosomes are a major constituent of AH. 
Exosomes function in extracellular communication and contain proteins and small 
RNA. Our goal was to characterize the physical properties of AH exosomes and 
their exosomal RNA (esRNA) content. We isolated exosomes from human AH collected 
during cataract surgery from five patients using serial ultracentrifugation. We 
measured the size and concentration of AH exosomes in solution using 
nanoparticle tracking analysis. We found a single population of vesicles having 
a mean size of 121 ± 11 nm in the unprocessed AH. Data show that centrifugation 
does not significantly affect the mean particle size (121 ± 11 nm versus 
124 ± 21 nm), but does impact the final number of exosomes in solution (87% loss 
from the unprocessed AH; n = 5). We extracted esRNA from the pooled human AH 
samples using miRCURY RNA isolation kit from Exiqon. The quality of extracted 
esRNA was evaluated using Agilent Bioanalyzer 2100 and was used to generate a 
sequencing library for small RNA sequencing with Illumina MiSeq sequencer. More 
than 10 different miRNAs were identified; abundant species included miR-486-5p, 
miR-204, and miR-184. We found that the majority of extracellular vesicles in 
the AH were in the exosome size range, suggesting that miRNAs housed within 
exosomes may function in communication between AH inflow and outflow tissues.