Alzheimers Disease and Retinal Neurodegeneration

Abstract

Alzheimer's disease (AD) is the major cause of dementia in the world. Although the entorhinal cortex and hippocampal complex are best known as the sites of early pathology in AD, increasing evidence shows that the eye, particularly the retina, is also affected. The AD-related changes in the retina are associated with degeneration and loss of neurons, reduction of the retinal nerve fibres, increase in optic disc cupping, retinal vascular tortusity and thinning, and visual functional impairment. Given the fact that evaluating pathologic changes in the brain during life has always been an indirect process, largely shielded from view by the barrier of the skull, the eye can be used as a window into diseases of the brain. Using modern techniques, the changes in the retina can be visualized in real-time. In addition to the changes in the eyes of AD patients, similar mechanisms of neurodegeneration in the brain have also been demonstrated in the eye. Targeting AD-liked changes in the retina has been recently shown to be effective in the reduction of retinal neuronal degeneration and loss in eye diseases. This review will cover recent findings on retinal degeneration in AD, pathological similarities between AD and eye diseases, and highlight the potential of modern technologies for the detection of prospective biomarkers in the eye in early AD.

Ocular Manifestations of Alzheimer’s Disease in Animal Models

“…A side effect of this research, however, has been the finding that A β deposition occurs in the lenses of AD subjects [61] and has been found in lenses and corneas of single and double transgenic animal models [111]. A β deposition and hyperphosphorylated tau have also been detected in the lenses and corneas of triple transgenic mice [81] raising the slightly unexpected but equally welcome possibility that an ocular biomarker for AD may exist that is not connected with the CNS.…”

The current research status of normal tension glaucoma

“…Both NTG and POAG are prevalent in senile populations 61,93. Some studies showed evidence that the anti-Alzheimer agents exhibit benefit to POAG patients 106,107. Thus, presently, more and more researchers consider glaucomas as a group of aging-related disease similar to neurodegenerative disease in the central nervous system 108,109…”

Ocular indicators of Alzheimer’s: exploring disease in the retina

“…Since then, the reports of retinal pathology in patients with AD have grown to include RGC loss, NFL atrophy, thinning of the macular ganglion cell complex, and widespread axonal degeneration in the optic nerve [17, 19, 21, 22, 38, 73, 81, 92, 97, 147, 174]. Other changes, such as blood flow rate [19, 50, 59, 183], signs of inflammation [20, 21], and varied cellular degeneration mirroring those observed in the AD brain may reflect cerebral pathology [21, 76, 128, 186], but do not indicate AD as strongly as disease hallmarks.…”