Posts Tagged ‘ophthalmology’

By Jim Dryden

It may be possible in the future to screen patients for Alzheimer’s disease using an eye exam.

Using technology similar to what is found in many eye doctors’ offices, researchers at Washington University School of Medicine in St. Louis have detected evidence suggesting Alzheimer’s in older patients who had no symptoms of the disease.

Their study, involving 30 patients, is published Aug. 23 in the journal JAMA Ophthalmology.

“This technique has great potential to become a screening tool that helps decide who should undergo more expensive and invasive testing for Alzheimer’s disease prior to the appearance of clinical symptoms,” said the study’s first author, Bliss E. O’Bryhim, MD, PhD, a resident physician in the Department of Ophthalmology & Visual Sciences. “Our hope is to use this technique to understand who is accumulating abnormal proteins in the brain that may lead them to develop Alzheimer’s.”

Significant brain damage from Alzheimer’s disease can occur years before any symptoms such as memory loss and cognitive decline appear. Scientists estimate that Alzheimer’s-related plaques can build up in the brain two decades before the onset of symptoms, so researchers have been looking for ways to detect the disease sooner.

Physicians now use PET scans and lumbar punctures to help diagnose Alzheimer’s, but they are expensive and invasive.

In previous studies, researchers examining the eyes of people who had died from Alzheimer’s have reported that the eyes of such patients showed signs of thinning in the center of the retina and degradation of the optic nerve.

In the new study, the researchers used a noninvasive technique — called optical coherence tomography angiography — to examine the retinas in eyes of 30 study participants with an average age in the mid 70s, none of whom exhibited clinical symptoms of Alzheimer’s.

Those participants were patients in The Memory and Aging Project at Washington University’s Knight Alzheimer’s Disease Research Center. About half of those in the study had elevated levels of the Alzheimer’s proteins amyloid or tau as revealed by PET scans or cerebrospinal fluid, suggesting that although they didn’t have symptoms, they likely would develop Alzheimer’s. In the other subjects, PET scans and cerebrospinal fluid analyses were normal.

“In the patients with elevated levels of amyloid or tau, we detected significant thinning in the center of the retina,” said co-principal investigator Rajendra S. Apte, MD, PhD, the Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Sciences. “All of us have a small area devoid of blood vessels in the center of our retinas that is responsible for our most precise vision. We found that this zone lacking blood vessels was significantly enlarged in people with preclinical Alzheimer’s disease.”

The eye test used in the study shines light into the eye, allowing a doctor to measure retinal thickness, as well as the thickness of fibers in the optic nerve. A form of that test often is available in ophthalmologist’s offices.

For this study, however, the researchers added a new component to the more common test: angiography, which allows doctors to distinguish red blood cells from other tissue in the retina.

“The angiography component allows us to look at blood-flow patterns,” said the other co-principal investigator, Gregory P. Van Stavern, MD, a professor of ophthalmology and visual sciences. “In the patients whose PET scans and cerebrospinal fluid showed preclinical Alzheimer’s, the area at the center of the retina without blood vessels was significantly larger, suggesting less blood flow.”

Added Apte: “The retina and central nervous system are so interconnected that changes in the brain could be reflected in cells in the retina.”

Of the patients studied, 17 had abnormal PET scans and/or lumbar punctures, and all of them also had retinal thinning and significant areas without blood vessels in the centers of their retinas. The retinas appeared normal in the patients whose PET scans and lumbar punctures were within the typical range.

More studies in patients are needed to replicate the findings, Van Stavern said, but he noted that if changes detected with this eye test can be used as markers for Alzheimer’s risk, it may be possible one day to screen people as young as their 40s or 50s to see whether they are at risk for the disease.

“We know the pathology of Alzheimer’s disease starts to develop years before symptoms appear, but if we could use this eye test to notice when the pathology is beginning, it may be possible one day to start treatments sooner to delay further damage,” he said.

O’Bryhim BE, Apte RS, Kung N, Coble D, Van Stavern GP. Optical coherence tomography angiography findings in pre-clinical Alzheimer’s disease. JAMA Ophthalmology, Aug. 23, 2018.

https://source.wustl.edu/2018/08/alzheimers-one-day-may-be-predicted-during-eye-exam/

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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

A new treatment has successfully changed the color of people’s eyes in Latin America, but the procedure isn’t approved in the U.S. yet.

For years, a California-based company called Stroma Medical has been publicizing a laser procedure that turns brown eyes blue. Theoretically, this would give brown-eyed individuals the choice to change the tint of their irises, not unlike the way many decide to use surgery to alter the noses or chests they were born with.

Now Stroma Medical claims that it has conducted 37 successful treatments on patients in Mexico and Costa Rica. It also says that it would likely charge about $5,000 for anyone wanting the procedure. That is, of course, only if and when American medical safety regulators give the surgery the green light in the United States.

Company chairman Gregg Homer says the procedure works by disturbing the thin layer of pigment that exists on the surfaces of all brown irises.

“The fundamental principle is that under every brown eye is a blue eye,” Homer told CNN. “If you take that pigment away, then the light can enter the stroma—the little fibers that look like bicycle spokes in a light eye—and when the light scatters it only reflects back the shortest wavelengths and that’s the blue end of the spectrum.”

Although the treatment lasts only 20 seconds, the patient’s eye color isn’t changed right away. Instead, it takes a few weeks for the human body to remove the pigmented tissue, resulting in blue eyes.

Given that light eyes are increasingly rare, with less than a fifth of Americans boasting blue peepers, it’s easy to see how there might be demand for this procedure. A preference for blue eyes in Western societies has been documented in many unscientific ways, though controlled studies suggest that the blue-eyes-are-more-attractive stereotype is more a product of culture than unconscious preference.

Whether or not you feel this procedure is a net good—or bad—thing for society, a bigger concern might be safety.

Though Stroma claims the surgery is safe, at least one ophthalmologist cautioned that the shedding of pigment could clog up drainage channels in the eye, increasing pressure and the risk for glaucoma.

http://time.com/money/3733372/surgery-turn-brown-eyes-blue/