Loss of neurons in magnocellular and parvocellular layers of the lateral geniculate: Nucleus in glaucoma

Objective: To determine whether there is loss of lateral geniculate nucleus relay neurons, which convey visual information to the visual cortex, in ex perimental glaucoma in monkeys. Methods: Four cynomolgus monkeys with experimentally induced glaucoma in th e right eye (referred to as the glaucoma group) and 5 control monkeys were studied. In both groups, the same conditions of fixation, tissue processing , staining, and measurement were used. in each monkey, the left lateral gen iculate nucleus target neurons in magnocellular layer 1 and parvocellular l ayers 4 and 6, connected to the right glaucomatous eye, were studied. Immun ocytochemistry with antibody to parvalbumin was used to specifically label relay neurons connecting to the visual cortex. The number of parvalbumin-im munoreactive neurons was estimated using an unbiased 3-dimensional counting method. The t test was used to compare the experimental and control groups . Results: The mean (+/-SD) number of neurons in magnocellular layer 1 was si gnificantly decreased in the glaucoma group compared with the control group (20 692 +/- 9567 vs 37 687 +/- 8017; P = .02). The mean (+/-SD) number of neurons in parvocellular layers 4 and 6 was significantly decreased in the glaucoma group compared with the control group (100 141 +/- 44 906 vs 174 0 90 +/- 39 136; P = .03). Data are given as the mean +/- SD. Conlusion: Significant loss of lateral geniculate nucleus relay neurons ter minating in the primary visual cortex occurs in the magnocellular and parvo cellular layers in an experimental monkey model of glaucoma. Clinical Relevance: Knowledge of the fate of neurons in the central visual system may lead to a better understanding of the nature and progression of visual loss in glaucomatous optic neuropathy.