Red blood cell membrane integrity in primary open angle glaucoma: ex vivo and in vitro studies

Purpose There is increasing evidence that abnormal perfusion of the optic n erve head is an important factor involved in the pathophysiology of glaucom a. Transport and distribution of oxygen to the tissues takes place through the erythrocyte membrane. Red blood cell (RBC) acetylcholinesterase (AChE) is a marker of RBC membrane integrity. The aim of this study was to find ou t whether RBC membrane integrity is preserved in primary open angle glaucom a (POAG), and whether it is modified by the use of topical timolol maleate and pilocarpine. Method RBC AChE activity was determined ex vivo by Kaplan's spectrophotomet ric method in 19 POAG patients undergoing topical treatment for glaucoma wi th timolol, pilocarpine or a combination of the two drugs, and compared wit h that in 20 controls. To assess the effect of antiglaucomatous therapy in our findings, we carried out an in vitro study in 26 non-glaucomatous patie nts in which we measured RBC AChE activity after incubation of blood with e ither timolol maleate, pilocarpine or a combination of the two drugs, using the same spectrophotometric method. Results There was a significant increase in RBC AChE enzyme activity in POA G patients compared with the control group (p < 0.002). However, timolol an d pilocarpine, individually or in combination, have the opposite effect, si gnificantly decreasing RBC AChE activity (p < 0.05). Conclusion This change in RBC AChE enzyme activity could suggest alteration s in RBC membrane integrity in primary open angle glaucoma. Whether or not this finding has implications regarding the microcirculation at the optic n erve head needs to be investigated further.