System and method for ocular iontophoresis with buffering

A delivery device for transferring a therapeutic substance across and/or through a surface of an ocular globe, comprising:

• an iontophoretic chamber configured to store the therapeutic substance;
• an electrode disposed relative to the iontophoretic chamber, the electrode configured to provide an electromotive force, when energized, to transfer of at least a portion of the therapeutic substance stored within the iontophoretic chamber across and/or through the surface of the ocular globe;
• a buffer system disposed at least partially within the at least one iontophoretic chamber, the buffer system does not contain the therapeutic substance, the buffer system configured to maintain a pH at the surface of the ocular globe within a range of about 3 to 8 during iontophoretic transfer of the therapeutic substance;
• and
• the iontophoretic chamber further comprises a first layer and a second layer, the first layer including the buffer system and the second layer including a therapeutic substance, wherein the first layer is disposed closest to the electrode and has a higher buffering capacity than the second layer.