Structure–Function Relations of Parasol Cells in the Normal and Glaucomatous Primate Retina

Abstract

Ganglion cells in the glaucomatous eye retain most of their normal intrinsic electrical properties, but are less responsive, both spatially and temporally, to visual stimuli. The reduction in visual responsiveness most likely results from significant changes in dendritic architecture, which affects their level of innervation by more distal retinal neurons.

Retinal Ganglion Cell Death Postponed: Giving Apoptosis a Break?

“…Den-dritic structural changes in primate and murine models of glaucoma have confirmed that such changes have functional consequences, e.g. the generation of action potentials is more stochastic [5,6] .…”

“…Action potential generation is more disorganised, while contrast sensitivity and receptive field size are reduced, contributing to a reduction in the efficiency of spatial summation [5,6] . These changes have a clear clinical correlate in glaucoma, in which variability in visual field sensitivity (rather than loss of field per se) is an early feature of disease.…”

Adaptive Changes in the Retina and Central Visual Areas in Glaucoma

“…This increase in soma size can be attributed as a precursor to their death. Another possibility is derived from developmental studies on the retina that points to the fact that increase in [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] in glaucomatous eye that are almost doubled in size when compared to normal. In these topographic mapping there was no overlap of receptive fields in the normal eye mapping, however, experimental glaucomatous eye showed numerous overlapping receptive fields.…”

“…In monkey glaucomatous retina, there was no increase in RGC soma size or dendritic arborization (26); however, a decrease in the dendritic field sizes of the RGC was reported within 3-6 months of induced glaucoma. In monkeys, Smith et al (27) reported visual deficits in long-term glaucoma as a consequence of RGC loss with no changes in the functional property of the surviving neurons. In addition, loss of some lateral geniculate neurons and reduction in the soma sizes of others were observed.…”

Oxidative Stress in Anterior Segment of Primary Open Angle Glaucoma

“…In glaucoma free radicals may damage the trabecular meshwork (TM) (Saccà et al 2005) while in the posterior segment of the eye the process of apoptotic retinal ganglion cell death starts with exposure of glial cells to elevated concentrations of free radicals (Nakazawa et al 2006). The final neurological damage results in progressive RGCs death, axon atrophy and degeneration also extending to the brain cortex (visual areas) finally leading to the characteristic optical-cup neuropathy and irreversible visual loss (Weber and Harman 2005) (Yucel et al 2000). In addition to the loss of the ganglion cells, the most of glaucoma types is characterized by having a high intraocular pressure (IOP).…”