Neuronal density in the human retinal ganglion cell layer from 16–77 years

Abstract

Literature assessing whether or not neurons (retinal ganglion cells and displaced amacrine cells) are lost from the retinal ganglion cell layer in mammals with age is still controversial, some studies finding a decrease in cell density and others not. To date there have been no studies estimating the total number of neurons in the retinal ganglion cell layer of humans throughout life. Recent studies have concentrated on the macular region and examined cell densities, which are reported to decrease during aging. In a study of the human retinal pigment epithelium (RPE), we showed that, while RPE cell number does not change, cell density increases significantly in central temporal retina (macular region) as the retina ages. We speculated that the increase in density represents a "drawing together" of the retinal sheet to maintain high cell densities, in this region of the neural retina, in the face of presumed cell loss from the ganglion cell layer due to aging. Here, therefore, we have sampled the entire ganglion cell layer of the human retina and estimated total neuron numbers in 12 retinae aged from 16 to 77 years. Human retinae, fixed in formalin, were obtained from the Queensland Eye Bank and whole-mounted, ganglion cell layer uppermost. The total number of neurons was lower in the older than younger retinae and neuronal density was lower in most retinal regions in older retinae. Retinal area increased with age and neuronal density fell throughout the retina with a mean reduction of 0.53% per year. However, the percentage reduction in density was much lower for the macular region, with a value of 0.29% per year. It is possible that this lesser reduction in cell density in the macula is a result of the drawing together of the retinal sheet in this region as we speculated from RPE data.

Quantification of Neuroretinal Rim Loss Using Digital Planimetry in Long-term Follow-up of Normals and Patients With Ocular Hypertension

“…Neuronal density in the ganglion cell layer showed a mean reduction of 0.53% per year in this study. 35 The results of the presented study are also consistent with the clinical observation that morphologic glaucomatous damage frequently precedes visual field loss by several years. [36][37][38][39] Histologic studies confirmed that up to 40% of retinal nerve fibers might be lost before visual field defects occur.…”

“…Even if the measured neuroretinal rim loss in the control group of the presented study is very low-data is comparable to large cross-sectional studies 8 and histologic examinations. 28,35 The results of the presented study support evidence for the presence of age-related neurodegeneration in the eye and might change the view of interpretation of morphometric change in the context of determination progressive disease.…”

Modeling the effects of aging on retinal ganglion cell density and nerve fiber layer thickness

“…The studies based on axon counts [3,30,32,36,43] generally indicate lower age-related losses than those based on cell body counts [7,19], probably arising from differences in sampling strategies [14]. In addition, there is uncertainty in defining the slopes of the aging functions, because they are based on relatively few samples due to the formidability of obtaining suitable post-mortem material, and in many of the studies the variability across eyes was large.…”

Rapid Contrast Adaptation in Glaucoma and in Aging

“…28 We particularly investigated performance in the time window that is most relevant for natural visual tasks (within a few hundred milliseconds). Because normal aging may also affect the anatomical substrates involved in contrast adaptation [30][31][32] (such as a reduction in RGC density 30 ), and because neurological alterations contribute to contrast deficits in older adults, 33 an additional group of young observers were included in the study to investigate the effects of aging on rapid contrast adaptation.…”