Figure 2. Bridge heights in Insall and Dunn chambers during use.

Bridge heights are measured in µm at 4 locations across the Insall chamber narrow and wide bridges and the Dunn chamber using a #1.5, 0.16–0.18 mm cover slip. Chambers were filled with fluorescein and images were taken in a z-stack using 1 µm intervals to calculate the distance between the bridge and cover slip. The bridge height was consistent at all sites in the Insall chamber with less than 1 µm variation demonstrating that thin cover slips can be used without affecting the geometry of the chamber and hence the diffusion profile.