18. Subject currently on any systemic medication [i.e., beta-blocker, carbonic anhydrase inhibitors, corticosteroids (including dermal), etc.], that may have an effect on the subject's IOP, or who will require its use during the study period (Note: an inhaled steroid, systemic beta-blocker or β-adrenoceptor antagonist may be permitted, providing the subject has maintained a stable dosage regimen for at least the last three months)