Outflow Facility in Isolated Porcine Eyes after Creation of an Intrascleral Canal by Injection of Stabilized Hyaluronic Acid

To investigate outflow facility in isolated porcine eyes after creation of an intrascleral canal by injection of stabilized, nonanimal, hyaluronic acid gel (NASHA; Q-Med AB, Uppsala, Sweden). Outflow facility of 60 porcine eyes was measured after creation of an intrascleral canal into the anterior chamber by injection of NASHA gel using six different combinations of needle size (21, 23, and 27 gauge) and canal length (4.6 mm). Ten eyes were tested in each of the six subgroups and an additional 10 were control eyes. After cannulation of the anterior chamber and adjustment of the inflow rate to achieve a stable pressure of 10 mm Hg, an intrascleral channel was created by injection of NASHA gel. The inflow rate was then increased to achieve a stable pressure of 20 mm Hg and then again adjusted to maintain a stable pressure of 30 mm Hg. A significant increase in outflow facility was found between the control group and the NASHA gel-injected group (60 eyes) for both the 10- to 20-mm Hg and the 20- to 30-mm Hg pressure change (P < 0.001). Increase in outflow facility was independent of the canal lengths and the needle sizes used for both the 10- to 20-mm Hg (P = 0.82) and 20- to 30-mm Hg (P = 0.99) pressure change. A single ab externo intrascleral canal created by injection of NASHA gel increases the outflow facility in isolated porcine eyes. This is a potentially promising new technique for lowering intraocular pressure. It remains to be seen whether these positive results can be reproduced for significant periods in humans.