Preparation of autologous serum and platelet-rich plasma eye drops
peripheral venous blood
STERILE, CLOT
For the preparation of AS eye drops, 24 mL of peripheral venous blood was allowed to clot for 2 h at room temperature (20–25 °C) to separate the serum completely from the solid constituents. After centrifugation at 3500 g for 15 min, the serum was carefully isolated under sterile conditions in a laminar flow hood. Next, the serum was diluted to 20% (vol/vol) concentration with 0.1% (wt/vol) sodium hyaluronate preservative-free eye drops (Tearin Free; DHP Korea Co., Ltd, Seoul, Korea). Aliquots of diluted serum were stored in sterile 5 mL bottles with ultraviolet-light protection.For the preparation of PRP eye drops, 22 mL of venous blood was withdrawn in a tube with 3 mL of 3.2% sodium citrate, and the tube was shaken slowly to prevent clotting. The blood was injected into a PRS Bio Kit (Prodizen, Seoul, Korea) through the blood inlet. The PRS Bio Kit and counter-balance kit (Prodizen, Seoul, Korea) were inserted into the centrifuge and centrifuged at 3000 g for 3 min. After centrifugation, the blood was divided into three layers (plasma, buffy coat, and red blood cells). The buffy coat was extracted using a 1-cc syringe, and plasma was extracted using a 5-cc syringe. Using a PRP connector, the buffy coat was mixed with the plasma to prepare PRP. PRP was diluted to 20% (vol/vol) concentration with 0.1% (wt/vol) sodium hyaluronate preservative-free eye drops (Tearin Free; DHP Korea Co., Ltd, Seoul, Korea).Patients were instructed to store opened and unopened bottles of AS and PRP eye drops at 4 °C in a refrigerator and − 20 °C in a freezer, respectively.