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The Aging of the Retina

Caren Bellmann and José A. Sahel

CONTENTS

INTRODUCTION

MORPHOLOGICAL ALTERATIONS

RETINAL FUNCTION CHANGES

AGE-RELATED MACULAR DISEASE

CONCLUSIONS

REFERENCES

INTRODUCTION

Aging has been defined as “the progressive accumulation of changes with time that are associated with or responsible for the ever-increasing susceptibility to disease and death which accompanies advancing age” [1]. Age-related degeneration of the retina is among the most prevalent and feared complications of aging. Although little is known about trigger and accelerating mechanisms, the amount of knowledge generated over the past few years in this field has increased exponentially. The retina is a highly differentiated neuroectodermal tissue. The retina consists of two distinct regions: the central retina (the macular area, which is specialized for detailed vision) and the peripheral retina. Microscopic examinations show that the macular area can be further subdivided into the fovea (a depression in the inner retinal surface) and the foveola (the central floor of the fovea). Vertical sections of all vertebrate retinas are composed of three layers of nerve cell bodies and two layers of synapses. The outer nuclear layer contains photoreceptor cell bodies; the inner nuclear layer contains the cell bodies of the bipolar, horizontal, and amacrine cells; and the ganglion cell layer contains the cell bodies of ganglion cells and displaced amacrine cells. The human adult retina includes two types of photoreceptor named rods and cones. Cone density is highest in the fovea and decreases rapidly from the fovea to the peripheral retina. Cones are adapted to photopic conditions and allow us to percept colors as well as to resolve fine details. Rods are the major component of the peripheral retina, with a maximal density in the perimacular region (5 mm from the macular center) [2]. These cells are sensitive to dim monochromatic light, allowing night and contrast vision as well as motion detection.

From: Ophthalmology Research: Visual Transduction and Non-Visual Light Perception

Edited by: J. Tombran-Tink and C. J. Barnstable © Humana Press, Totowa, NJ

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