PURPOSE. To determine the effects on the electroretinogram (ERG) of retinal capillary closure induced in the pig by embolization with microspheres. METHODS. Fourteen Yorkshine Landrace pigs of 25-to 45-kg body weight were used. With a customized cannula introduced into the external carotid artery, 10-lm diameter microspheres were delivered to the origin of the vessel that supplies blood to the eye in the pig. Fundus fluorescein angiography and electroretinography were performed between days 7

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... d 28 post injection. The ERG responses of embolized eyes were compared with those of the contralateral nonembolized eyes. RESULTS. The amplitudes of the scotopic b-wave (P = 0.002), the maximal b-wave (P < 0.010), the photopic a-wave (P < 0.001) and b-wave (P < 0.001), and the scotopic oscillatory potentials (OPs) (P = 0.025) and photopic OPs (P = 0.036) were significantly reduced in embolized eyes. The reduction of these ERG amplitudes was significantly correlated with the number of microspheres in the retina. There was no significant difference in the combined rod-cone bright flash (maximal) ERG a-wave amplitude between eyes with and without microspheres. Implicit times, however, were similar in embolized and control eyes. Animals Yorkshine Landrace pigs of 25-to 45-kg body weight were used in this study. Animals were sedated with ketamine intramuscularly (10 mg/kg body weight) and anesthetized with a 5% to 10% halothane/oxygen mixture for induction and a 2% mixture for maintenance, delivered via an endotracheal tube. Heart rate and blood pressure were monitored and oxygenation assessed by ear oximetry. Pupils were dilated with 3 drops of tropicamide 1% (Alcon Laboratories, Inc., Fort Worth, TX) instilled into each eye at 5-minute intervals. From the