ABSTRACT

Accordingly, cutting of the proximal parts of the trabecular meshwork does not affect outflow resistance.12 There is also considerable evidence that the endothelial lining of Schlemm’s canal does not significantly contribute to aqueous humor outflow resistance. The size and number of pores in the inner wall endothelium appear to be high (between 1000 and 2000 pores/mm2) and more than adequate to allow unhindered flow of aqueous humor.19,20 Indeed, by using scanning electron microscopy and hydrodynamic calculations, Bill and Svedbergh concluded that inner wall pores would generate, at most, 10% of the observed aqueous humor outflow resistance,20 a result that has been confirmed in independent studies.21,22 A recent report challenged this point of view by showing that the

characteristics of inner wall pores depend on fixation conditions.The density of inner wall pores increases with the volume of fixative perfused through the outflow pathway and decreases with post-mortem time.23