Posts Tagged ‘retina’


Age-related macular degeneration, diabetic retinopathy and glaucoma were all associated with a higher risk of developing Alzheimer’s disease in a new study.

by Rich Haridy

A new study has found an interesting correlation between several degenerative eye diseases and the onset of Alzheimer’s disease. No mechanism explaining the connection has been proposed at this stage but it is thought these eye conditions may help physicians identify patients at risk of developing Alzheimer’s at a stage before major symptoms appear.

The five-year study followed almost 4,000 patients over the age of 65, all without clinically diagnosed Alzheimer’s disease at the time of enrolment. After five years, 792 subjects were officially diagnosed with Alzheimer’s. The study found that those subjects with age-related macular degeneration, diabetic retinopathy or glaucoma, were 40 to 50 percent more likely to develop Alzheimer’s compared to patients without those specific conditions. No correlation between cataracts and an increased risk of Alzheimer’s were found.

“We don’t mean people with these eye conditions will get Alzheimer’s disease,” cautions Cecilia Lee, lead researcher on the study. “The main message from this study is that ophthalmologists should be more aware of the risks of developing dementia for people with these eye conditions and primary care doctors seeing patients with these eye conditions might be more careful on checking on possible dementia or memory loss.”

The researchers are clear that there are no definable causal connections between these eye conditions and Alzheimer’s at this stage, but the study does highlight the potential of using the eye as a way to better understand what is going on in the brain. Intriguingly, this isn’t the first bit of research that has found correlations between signs detected in the eye and the onset of Alzheimer’s disease.

Last year, a team from Cedars-Sinai Medical Center revealed that the same type of amyloid protein deposits found in the brain, and hypothesized as a major pathogenic cause of Alzheimer’s, can also be detected on the retina. That research suggested a possible investigational eye scan could become an effective early screening device for the disease.

While this new study does not at all cross over with last year’s research, and there is no implication that amyloid proteins play a part in these degenerative eye diseases, it does add to a fascinating growing body of work that highlights the eye’s role in helping offer a deeper insight into the cognitive health of our brain.

The research was published in the journal Alzheimer’s & Dementia.

https://newatlas.com/eye-disease-alzheimers-connection/55823/

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An array of semitransparent organic pixels on top of a ultrathin sheet of gold. The thickness of both the organic islands and the underlying gold is more than one-hundred times thinner than a single neuron.

SUMMARY: A simple retinal prosthesis is under development. Fabricated using cheap and widely-available organic pigments used in printing inks and cosmetics, it consists of tiny pixels like a digital camera sensor on a nanometric scale. Researchers hope that it can restore sight to blind people.

Researchers led by Eric Glowacki, principal investigator of the organic nanocrystals subgroup in the Laboratory of Organic Electronics, Link√∂ping University, have developed a tiny, simple photoactive film that converts light impulses into electrical signals. These signals in turn stimulate neurons (nerve cells). The research group has chosen to focus on a particularly pressing application, artificial retinas that may in the future restore sight to blind people. The Swedish team, specializing in nanomaterials and electronic devices, worked together with researchers in Israel, Italy and Austria to optimise the technology. Experiments in vision restoration were carried out by the group of Yael Hanein at Tel Aviv University in Israel. Yael Hanein’s group is a world-leader in the interface between electronics and the nervous system.

The results have recently been published in the scientific journal Advanced Materials.

The retina consists of several thin layers of cells. Light-sensitive neurons in the back of the eye convert incident light to electric signals, while other cells process the nerve impulses and transmit them onwards along the optic nerve to an area of the brain known as the “visual cortex.” An artificial retina may be surgically implanted into the eye if a person’s sight has been lost as a consequence of the light-sensitive cells becoming degraded, thus failing to convert light into electric pulses.

The artificial retina consists of a thin circular film of photoactive material, and is similar to an individual pixel in a digital camera sensor. Each pixel is truly microscopic — it is about 100 times thinner than a single cell and has a diameter smaller than the diameter of a human hair. It consists of a pigment of semi-conducting nanocrystals. Such pigments are cheap and non-toxic, and are commonly used in commercial cosmetics and tattooing ink.

“We have optimised the photoactive film for near-infrared light, since biological tissues, such as bone, blood and skin, are most transparent at these wavelengths. This raises the possibility of other applications in humans in the future,” says Eric Glowacki.

He describes the artificial retina as a microscopic doughnut, with the crystal-containing pigment in the middle and a tiny metal ring around it. It acts without any external connectors, and the nerve cells are activated without a delay.

“The response time must be short if we are to gain control of the stimulation of nerve cells,” says David Rand, postdoctoral researcher at Tel Aviv University. “Here, the nerve cells are activated directly. We have shown that our device can be used to stimulate not only neurons in the brain but also neurons in non-functioning retinas.”

https://www.sciencedaily.com/releases/2018/05/180502104043.htm

Schizophrenia is associated with structural and functional alterations of the visual system, including specific structural changes in the eye. Tracking such changes may provide new measures of risk for, and progression of the disease, according to a literature review published online in the journal Schizophrenia Research: Cognition, authored by researchers at New York Eye and Ear Infirmary of Mount Sinai and Rutgers University.

Individuals with schizophrenia have trouble with social interactions and in recognizing what is real. Past research has suggested that, in schizophrenia, abnormalities in the way the brain processes visual information contribute to these problems by making it harder to track moving objects, perceive depth, draw contrast between light and dark or different colors, organize visual elements into shapes, and recognize facial expressions. Surprisingly though, there has been very little prior work investigating whether differences in the retina or other eye structures contribute to these disturbances.

“Our analysis of many studies suggests that measuring retinal changes may help doctors in the future to adjust schizophrenia treatment for each patient,” said study co-author Richard B. Rosen, MD, Director of Ophthalmology Research, New York Eye and Ear Infirmary of Mount Sinai, and Professor of Ophthalmology, Icahn School of Medicine at Mount Sinai. “More studies are needed to drive the understanding of the contribution of retinal and other ocular pathology to disturbances seen in these patients, and our results will help guide future research.”

The link between vision problems and schizophrenia is well established, with as many as 62 percent of adult patients with schizophrenia experience visual distortions involving form, motion, or color. One past study found that poorer visual acuity at four years of age predicted a diagnosis of schizophrenia in adulthood, and another that children who later develop schizophrenia have elevated rates of strabismus, or misalignment of the eyes, compared to the general population.

Dr. Rosen and Steven M. Silverstein, PhD, Director of the Division of Schizophrenia Research at Rutgers University Behavioral Health Care, were the lead authors of the analysis, which examined the results of approximately 170 existing studies and grouped the findings into multiple categories, including changes in the retina vs. other parts of the eye, and changes related to dopamine vs. other neurotransmitters, key brain chemicals associated with the disease.

The newly published review found multiple, replicated, indicators of eye abnormalities in schizophrenia. One of these involves widening of small blood vessels in the eyes of schizophrenia patients, and in young people at high risk for the disorder, perhaps caused by chronic low oxygen supply to the brain. This could explain several key vision changes and serve as a marker of disease risk and worsening. Also important in this regard was thinning of the retinal nerve fiber layer in schizophrenia, which is known to be related to the onset of hallucinations and visual acuity problems in patients with Parkinson’s disease. In addition, abnormal electrical responses by retinal cells exposed to light (as measured by electroretinography) suggest cellular-level differences in the eyes of schizophrenia patients, and may represents a third useful measure of disease progression, according to the authors.

In addition, the review highlighted the potentially detrimental effects of dopamine receptor-blocking medications on visual function in schizophrenia (secondary to their retinal effects), and the need for further research on effects of excessive retinal glutamate on visual disturbances in the disorder.

Interestingly, the analysis found that there are no reports of people with schizophrenia who were born blind, suggesting that congenital blindness may completely or partially protect against the development of schizophrenia. Because congenitally blind people tend to have cognitive abilities in certain domains (e.g., attention) that are superior to those of healthy individuals, understanding brain re-organization after blindness may have implications for designing cognitive remediation interventions for people with schizophrenia.

“The retina develops from the same tissue as the brain,” said Dr. Rosen. “Thus retinal changes may parallel or mirror the integrity of brain structure and function. When present in children, these changes may suggest an increased risk for schizophrenia in later life. Additional research is needed to clarify these relationships, with the goals of better predicting emergence of schizophrenia, and of predicting relapse and treatment response and people diagnosed with the condition.”

Dr. Silverstein points out that, to date, vision has been understudied in schizophrenia, and studies of the retina and other ocular structures in the disorder are in their infancy. However, he added, “because it is much faster and less expensive to obtain data on retinal structure and function, compared to brain structure and function, measures of retinal and ocular structure and function may have an important role in both future research studies and the routine clinical care of people with schizophrenia.”

http://www.eurekalert.org/pub_releases/2015-08/tmsh-rcm081715.php