Subretinal injection rate of tissue plasminogen activator (tPA) solution and air using a 38-gauge cannula in a retina mimicking model

Abstract By investigating the correlation between the injection rate and pressure of subretinal tissue plasminogen activator (tPA) and air using a standard VCS system with a 38-gauge cannula, we aimed to establish guidelines for stable injections. We fabricated a retina mimicking model (RMM) with 1% agarose solution and an aluminum plate, and substituted submacular hemorrhage (SMH) and tPA with blood-mimicking fluid (BMF) and balanced salt solution (BSS), respectively. The diameter of the pre-bleb mimicking SMH in RMM was 2.10 ± 0.32 cm, increasing to 3.11 ± 0.36 cm and 2.93 ± 0.26 cm after bleb propagation with BSS and air, respectively. BSS injection rates were 3.17 ± 0.47 µl/sec, 4.74 ± 0.80 µl/sec and 7.54 ± 0.75 µl/sec at 8, 12, and 16 psi, respectively. Air injection rates were 78.18 ± 2.97 and 123.63 ± 12.46 µl/sec at 3 and 4 psi, respectively. Injection at 2 psi required initiation at 4 psi, resulting in a rate of 52.75 ± 9.87 µl/sec. By experimenting with different pressures in the RMM, we found 12 psi to be the minimum for proper BSS injection and 3 psi for air. These findings provide crucial parameters for safer surgery to prevent irreversible damage.