Dynamics Of Autoregulatory Response Of Ocular Hemodynamics To Postural Changes In Glaucoma Patients And Healthy Controls

Abstract

 

Purpose:

 

An altered autoregulation of the optic nerve head perfusion has been discussed as a possible pathogenic factor in glaucoma. A previous study performed by our group showed a defective adaptation of ocular perfusion to posture changes in glaucoma patients. The aim of the present study was to describe the dynamics of this adaptation and to compare glaucoma patients and healthy volunteers.

 

Methods:

 

Peak systolic velocity (PSV) and end–diastolic velocity (EDV) of the ocular blood flow in the short posterior ciliary artery supplying the optic nerve head were measured every single minute for a period of 15 minutes after a postural change from supine to a sitting postion (color Doppler imaging – CDI; Siemens Elegra, 7.5 MHz). Systolic and diastolic blood pressure levels were recorded parallel to the CDI measurements.

 

Results:

 

Table 1 summarizes the results of the CDI measurements. After an initial drop blood flow velocities in the control persons recovered continuously within 9 to 15 minutes. In the glaucoma population the initial drop was not that pronounced but no recovery can be observed. In contrast, blood flow velocities further decreased during the observation period. An unpaired t–test was used to compare blood–flow velocities in supine to sitting position. Significant differences are marked with an asterisk. No significant difference in systolic and diastolic blood pressure levels following postural change were found in both groups at the time of the CDI measurements.

 

Conclusions:

 

The data show defective autoregulatory control in glaucoma patients. In addition the present study demonstrates the adaptation of ocular perfusion to postural challenge to be a continous process which takes place over several minutes.  

 

Keywords: blood supply • optic disc • optic flow