retina

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It really gets me how your brain completes what you see. The first picture shows what your brain tells you that you see. But in reality, your retina is covered by blood vessels and you see them all the time. Also, there’s a blind spot on your eye that your brain erases and completes for you by averaging the light conditios around it. And your cornea and lens twist the picture so it is both horizontally and vertically flipped. 

So the second picture shows what is really projected on your retina.

sixpenceee, you might be slightly interested.

Retinal changes may serve as measures of brain pathology in schizophrenia

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.”

Early Retina Cell Changes in Glaucoma Identified
Mouse study points to the specific structural features and cell types in the retina that may act as key factors in glaucoma progression

Glaucoma, the second leading cause of blindness, usually stems from elevated eye pressure, which in turn damages and destroys specialized neurons in the eye known as retinal ganglion cells. To better understand these cellular changes and how they influence the progression and severity of glaucoma, researchers at University of California, San Diego School of Medicine and Shiley Eye Institute turned to a mouse model of the disease. Their study, published Feb. 10 in The Journal of Neuroscience, reveals how some types of retinal ganglion cells alter their structures within seven days of elevated eye pressure, while others do not.

“Understanding the timing and pattern of cellular changes leading to retinal ganglion cell death in glaucoma should facilitate the development of tools to detect and slow or stop those cellular changes, and ultimately preserve vision,” said Andrew D. Huberman, PhD, assistant professor of neurosciences, neurobiology and ophthalmology. Huberman co-authored the study with Rana N. El-Danaf, PhD, a postdoctoral researcher in his lab.

Retinal ganglion cells are specialized neurons that send visual information from the eye’s retina to the brain. Increased pressure within the eye can contribute to retinal ganglion cell damage, leading to glaucoma. Even with pressure-lowering drugs, these cells eventually die, leading to vision loss.

In this study, Huberman and El-Danaf used a mouse model engineered to express a green fluorescent protein in specific retinal ganglion cells subtypes. This tool allowed them to examine four subtypes of retinal ganglion cells. The different cell types differ by the location in the eye to which they send the majority of their dendrites (cellular branches). Within seven days of elevated eye pressure, all retinal ganglion cells that send most or all of their dendrites to a region of the eye known as the OFF sublamina underwent significant rearrangements, such as reductions in number and length of dendritic branches. Retinal ganglion cells with connections in the ON part of the retina did not.

“We are very excited about this discovery,” Huberman said. “One of the major challenges to the detection and treatment of glaucoma is that you have to lose a lot of cells or eye pressure has to go way up before you know you have the disease. These results tell us we should design visual field tests that specifically probe the function of certain retinal cells. In collaboration with the other researcher members of the Glaucoma Research Foundation Catalyst for a Cure, we are doing just that and we are confident these results will positively impact human patients in the near-future.” 

Pictured: Example of retinal ganglion cells with dendrites in the retina of a healthy eye.

The brain works as a ‘cyclops,’ compensating the optical differences between the eyes

The eyes differ in their optical properties what results in a blur projected in each retina, despite we see sharp images because the visual system calibrates itself. An international research performed by the Consejo Superior de Investigaciones Científicas has discovered that when each eye separately has a different level of blur, our brain uses as sharp reference the image projected through the less aberrated eye. The research has been published in Current Biology.

“Our impression about what is sharp is colossal and it is determined by the sharper image among those which are projected through both eyes”, explain the CSIC researcher Susana Marcos of the Instituto de Óptica Daza de Váldes. The research reveals that, despite these blur differences, the perception of each eye separately about the sharper image is the same, regardless of the eye we use to make the test and coincides with the blur image projected through the less aberrated eye.

The nature of these visual calibrations is important in order to understand the different consequences referred to the refractive errors between both eyes. “For instance, an available solution to correct the presbyopia is monovision, in which different refractive corrections are provided for both eyes. One eye, the dominant eye, is corrected for distance viewing and the other one is corrected for vision viewing. It is essential to understand the visual calibration with different levels of blur to understand the visual processing of the patients, the main objective is to provide the best possible correction”, conclude the researcher.

Nerve Cell Nurturing

The umbilical cord provides a growing baby with blood and nutrients from mum. But after this job is complete, cells from the cord can be extracted and re-employed to help fix damaged nerve tissue. Indeed, umbilical cord tissue cells (UTCs) have been shown to boost regeneration and recovery in animal models of stroke and retinal degeneration, and are currently being investigated clinically as a possible treatment for age-related macular degeneration. It’s thought that factors secreted from the UTCs might somehow be responsible for their beneficial effects, and new research supports that theory. UTCs cultured in the same dish but physically separated from neurons (green) promoted the growth and survival of the neurons as well as the development of cell-to-cell connections, or synapses (yellow). Scientists are also starting to identify some of the secreted UTC factors, suggesting that, in the future, regenerative cocktails may replace the use of the cells themselves.

Written by Ruth Williams

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New insights into the circuits of sight: Study reveals cortical circuits that encode black and white

While some things may be ‘as simple as black and white’, this has not been the case for the circuits in the brain that make it possible for you to distinguish black from white. The patterns of light and dark that fall on the retina provide a wealth of information about the world around us, yet scientists still don’t understand how this information is encoded by neural circuits in the visual cortex—a part of the brain that plays a critical role in building the neural representations that are responsible for sight. But things just got a lot clearer with the discovery that the majority of neurons in visual cortex respond selectivity to light vs dark, and they combine this information with selectivity for other stimulus features to achieve a detailed representation of the visual scene.

Scientists have long known that neurons in the retina that provide information to higher centers in the brain respond selectively to light vs dark stimuli. ‘ON’ cells that respond selectively to light stimuli and ‘OFF’ cells that respond selectively to dark stimuli were known to form separate parallel channels relaying information to circuits in visual cortex. But here is where the picture got murky. Based on recording the responses of single cortical neurons with electrodes, it appeared that as soon as the ON and OFF channels entered the cortex, they converged onto single neurons, a convergence necessary for the emergence of a novel cortical response property: selectivity for the orientation of edges. Further stages in cortical processing were thought to lead to more and more mixing of the ON and OFF signals, so that individual neurons responded similarly to both dark and light stimuli. These results raised an obvious question: If the responses of single cortical neurons to dark and light are ambiguous, how is it that the brain allows us to perceive these differences?

Drs. Gordon Smith and David Whitney in David Fitzpatrick’s lab at Max Planck Florida Institute for Neuroscience decided it was time to revisit this question. Using new imaging technologies that make it possible for the first time to visualize the activity of hundreds of neurons simultaneously in the living brain, they quantified the responses of neurons in ferret visual cortex to light and dark stimulation.

The first surprise for the team happened when they looked at cortical responses to the presentation of uniform dark or light stimuli. Although previous studies had not observed responses to uniform luminance changes, Smith et al. were not only able to visualize neurons that responded to these stimuli, they discovered patches of neurons that responded preferentially to dark vs light stimulation. Even more surprising, they found that the cortical neurons that responded selectively to the orientation of edges or to the direction of stimulus motion also responded preferentially to dark vs light stimuli. In short, the Max Planck Florida scientists discovered that information about dark and light is preserved in the responses of most neurons in visual cortex, and it is an integral part of the neural code that cortical circuits use to represent our visual world.

The next challenge for Max Planck Florida scientists is to understand the precise patterns of synaptic connections that enable cortical circuits to construct this modular representation of black and white. Stay tuned for more exciting discoveries that promise to reshape our understanding of cortical function.

As you know I've been in and out of the hospital,

Nothing life threatening of course, just dehydration among other things.
Well on top of all of that, I recently have suffered retinal detachment in my right eye, it is a potentially sight-threatening condition in which the retina becomes detached from its normal position and is separated from supporting blood vessels.   Without prompt treatment, the condition can cause blindness.

I have my surgery date planned, but unfortunately the surgery will cost me $5,583 out of pocket.

I am at high risk of a second detachment in my other eye which could cost a second round of over 5 thousand dollars.

I’m so desperate for help.  We just moved into our new home and have house payments on top of this.

Any help is appreciated.  Thank you for listening!  I HAVE SET UP A GOFUNDME PAGE IF ANYONE HAS A DOLLAR OR TWO TO SHARE.

I will promote anyone who donates as well <3