Blood Pressure, Ocular Blood Flow, And Glaucoma

Despite an association between increased ocular perfusion pressure (OPP) and glaucoma, increasing blood pressure in an effort to modulate OPP appears to offer no value for treating glaucoma, according to a study published in a 2010 issue of the American Journal of Ophthalmology.  Caprioli and Coleman from the Jules Stein Eye Institute at the University of California, Los Angeles, conducted the study, which reviewed current literature and presented the findings of the Blood Flow in Glaucoma Discussion Group. 

"There is currently no evidence that manipulation of blood pressure or blood flow improves outcomes in glaucoma," the authors wrote.  "Although low OPP is now an established risk factor in glaucoma, is is not clear whether it is truly independent of the sum of 2 separate risk factor-high [intraocular pressure] and low blood pressure."

While in theory, controlling OPP via blood pressure may seem appealing, modulating OPP in practice is complicated by a range of factors, including the potential for inaccuracy in OPP measurements, the authors noted.  OPP measured during a routine examination may vary significantly from a patients physiologic OPP and therefore may not accurately correlate with the perfusion of the optic nerve head. 

The authors added that there is currently little evidence to identify which vascular beds are important in the development and prevention of glaucoma, and therapies not targeted to those beds could cause an unwarranted increase in overall pressure and an attendant increase in morbidity and mortality.  "There is the possibility that improving optic nerve perfusion by diverting blood from elsewhere (such as retinal capillary beds) may have unforeseen adverse effects, " they wrote. 

While future drugs developed to target specific pathways or receptors may offer hope for treatment of glaucoma via OPP modulation current evidence does not support such treatment.  "Glaucoma is a heterogeneous group of related diseases," the authors noted.  "There may be subgroups of patients in whom vascular factors are important, (but) those patients subgroups have not been well identified."