Flow Rate Measurement Of In Situ Perfusion Through The Aqueous Humor Outflow Network

A system was developed to measure the instantaneous perfusate flow rate through the aqueous humor outflow network of a human eye, while under constant pressure. The system monitors real-time weight changes of a perfusate reservoir associated with perfusate flow through the aqueous humor outflow network. The recorded weight changes of the reservoir are used as an indicator of flow rates. Methods to determine time and flow rate resolution and to control for evaporation were also developed. The system is capable of measuring flow on a uL/min scale; determined by the following model, which also includes a range of uncertainty (implies flow rate resolution) and time resolution. Q = (ΔW/Δt – E) / ρ ± 0.0003 / (Δt * ρ) Where: Q - flow rate (mL/min), ΔW/Δtt - is the weight change over time as recorded by the balance (g/min); Δt is the time resolution, E - rate of evaporation (g/min); empirically found and assumed to be constant, ρ - density of the perfusate (g/mL); a density value of 1g/mL is used, 0.0003 - nonlinearity of balance (g), The system was set up using a porcine eye specimen; the cornea was punctured to determine the systems ability to monitor the increase in flow rate. A second test was conducted, in which an undisclosed compound was perfused through the porcine AH outflow network. The system was able to monitor the flow rate changes due to the corneal puncture and added compound.