Experimental glaucoma in primates: Changes in cytochrome oxidase blobs in V1 cortex

PURPOSE. To evaluate the effects of ganglion cell depletion from experiment al glaucoma on the relative metabolic activities of neurons in the cytochro me oxidase blobs of V1 cortex in the macaque visual system. METHODS. Monocular experimental glaucoma was induced in adult monkeys (Maca ca mulatta and Macaca fascicularis) by laser application to the trabecular meshwork, increasing the intraocular pressure. After other experiments, the primary visual cortices were analyzed for functional excitation from survi ving ganglion cells, as indicated by cytochrome oxidase histochemistry. RESULTS. Cytochrome oxidase reactivity was uniformly reduced in blobs with input from the glaucomatous eye in a manner consistent with loss of known a fferent inputs. The average size of glaucomatous blobs in layers 2 and 3 of V1 cortex was reduced by half. CONCLUSIONS. Experimental glaucoma in monkeys reduces retinal input to the central nervous system, thereby reducing the metabolic drive to downstream targets, as indicated by the reduction in the size of cytochrome oxidase bl obs in layers 2 and 3 of V1 cortex. The pattern of cytochrome oxidase loss within the blob was uniform, suggesting that all sources of afferent input to the blobs were affected by experimental glaucoma.