FACTORS AFFECTING THE PORES OF THE INNER WALL ENDOTHELIUM OF SCHLEMM CANAL

Purpose. A linear relationship between the density of pores in the inn er wall of Schlemm's canal and aqueous outflow facility has been repor ted previously in a study in which investigators examined only eyes fi xed at constant pressure, so that fixative flow rates differed from ey e to eye. Because pores may form as a function of flow race, the purpo se in the current study was to verify the previous findings, using con stant flow perfusions. Methods. Outflow facility was measured in enucl eated human eyes. Eyes were fixed under either constant flow or consta nt pressure conditions, microdissected to expose the inner wall of Sch lemm's canal, and prepared for scanning electron microscopy. The densi ty and diameter of pores in the inner wall were measured. Results. Sta tistical analysis showed no correlation between outflow facility and e ither the density or the diameter of pores. Pore density decreased sig nificantly during the hours after death. Examining only eyes for which experimentation was started within 20 hours of death, we found that p ore density increased significantly with the volume of fixative that h ad been perfused through the outflow pathway. Conclusions. The correla tion found by Allingham et al between outflow facility and pore densit y in the inner wall endothelium was not confirmed. However, the relati onship between pore density and volume of fixative perfused is consist ent with and may be responsible for the finding in the previous study. Because fixation conditions can influence the apparent pore density i n the inner wall endothelium significantly, the conclusion reached pre viously, that pores contribute only 10% of the aqueous outflow resista nce, may require reevaluation.