Background No general standards exist for the optimal dilution factor of autologous-serum-eye-drops (ASED) to treat dry eye syndrome (DES).^{1 2} While dilution reduces patient burden, simplifies logistics and potentially decreases anti-proliferative effects from TGF-β, better epithelial healing with non-diluted ASED in Sjögren Syndrome, but not in non-Sjögren DES have been reported.².

Purpose The ratio of serum to tear concentration for a range of metabolites in ASED after prolonged storage time was determined to define dilution that maintains metabolite concentrations equal or above those in tears.

Material and methods After autologous whole blood donation, unit dose ASED were prepared and stored at −20°C for 9 months. Concentration changes of 14 sphingolipids (SLs), 14 lysophosphatidylcholines (LPCs) and 76 phosphatidylcholines (PCs) were determined in ASED on day 0 and day 273 by LC-MS/MS using the Absolute/DQ-p180-Kit (Biocrates Life Sciences) and compared to those in tears of the same person.

Results The concentrations of all SLs in ASED increased by 30%–80% within 9 months. Compared to tears, the concentrations were 10-fold (day 0) to 14-fold (day 273) higher. The concentrations of all LPCs decreased by 50%–75%, with 20 and five times higher levels on day 0 and day 273 in ASED compared to tears. Most PCs showed a less than two-fold increase, while PC ae C30:1/C38:1/C38:2 increased by five–six-fold. In sum, all PC-concentrations were about 16–19-fold higher in ASED (day 0–day 273) than in tears.

Conclusion We observed an increase in SLs probably through the release of sphingosine-1-phosphate from platelets during blood clotting. The decrease in LPCs may be linked to a shift from LPCs to PCs through the presence of LPC-acyltransferases. After 9 months at −20°C, the LPC levels still exceeded those in tears by five-fold. These data support a dilution up to five-fold as suggested by others (reviewed in ²). Because certain patient populations may benefit from less diluted ASED, an individual approach seems indicated until more clinical information stratified by cause and severity of DES is available.

References and/or acknowledgements 1. Drew VJ, et al. Front Med (Lausanne)2018;5:33.

2. The Royal College of Ophthalmologists guidelines on serum eye drops for the treatment of severe ocular surface disease2017.

No conflict of interest.