Glaucoma is a major cause of blindness and is characterized by death
of retinal ganglion cells. In a rat model of glaucoma in which intraocular
pressure is raised by cautery of episcleral veins, the somata and
dendritic arbors of surviving retinal ganglion cells expand. To assess
physiological consequences of this change, we have measured visual
receptive-field size in a primary retinal target, the superior colliculus.
Using multiunit recording, receptive-field sizes were measured for
glaucomatous eyes and compared to both those measured for contralateral
control eyes and to homolateral eyes of unoperated animals. Episcleral
vein occlusion increased intraocular pressure. This was accompanied by a
significant increase in receptive-field size across the superior
colliculus. The expansion of receptive fields was proportional to both
degree and duration of the increase of intraocular pressure. We suggest
that this increase in the size of receptive fields of glaucomatous eyes
may be related to the increase in the size of dendritic arbors of the
surviving ganglion cells in retina.