Purpose: To investigate the effect of topical iganidipine, a new dihydropyridine derivative calcium channel blocker, on impairment of the ocular circulation caused by endothelin-1 (ET-1), we examined modification of the effect of ET-1 on visual-evoked potential (VEP) in albino rabbits.
Methods: To clarify whether VEP could be used to indicate the extent of ocular circulatory impairment, we evaluated the dose dependency of changes in VEP over 2 hours after intravitreal injection of 3 ET-1 doses (1.0, 3.3, or 10 pmol) and the vehicle. Then modification of the effect of ET-1 on the VEP by iganidipine was examined. One hour after the topical instillation of 0.1% iganidipine (20 microl) or its vehicle, 10 pmol of ET-1 was injected into the vitreous in rabbits. The VEP was measured for 2 hours after ET-1 application, and the response was compared between the eyes with iganidipine and vehicle pretreatment.
Results: Intravitreal injection of ET-1 dose-dependently reduced the VEP amplitude. Topical administration of 0.1% iganidipine significantly suppressed the reduction of VEP amplitude for the entire 2-hour monitoring period after intravitreal injection of 10 pmol ET-1. There was no significant change of the systemic blood pressure as well as intraocular pressure after topical administration of iganidipine.
Conclusions: Iganidipine eyedrops may be useful for the treatment of ischemic retinal and optic nerve disorders related to abnormal ET-1 production for the maintenance of visual function.