retina Archives - Amazing Health Advances

Morning Exposure to Deep Red Light Improves Declining Eyesight

AHA Publisher — Fri, 03 Dec 2021 08:00:11 +0000

University College London via Newswise – Just three minutes of exposure to deep red light once a week, when delivered in the morning, can significantly improve declining eyesight, finds a pioneering new study by UCL researchers. Published in Scientific Reports, the study builds on the team’s previous work*, which showed daily three-minute exposure to longwave deep red light ‘switched on’ energy producing mitochondria cells in the human retina, helping boost naturally declining vision. For this latest study, scientists wanted to establish what effect a single three-minute exposure would have, while also using much lower energy levels than their previous studies. Furthermore, building on separate UCL research in flies** that found mitochondria display ‘shifting workloads’ depending on the time of day, the team compared morning exposure to afternoon exposure. In summary, researchers found there was, on average, a 17% improvement in participants’ colour contrast vision when exposed to three minutes of 670 nanometre (long wavelength) deep red light in the morning and the effects of this single exposure lasted for at least a week. However, when the same test was conducted in the afternoon, no improvement was seen. Scientists say the benefits of deep red light, highlighted by the findings, mark a breakthrough for eye health and should lead to affordable home-based eye therapies, helping the millions of people globally with naturally declining vision. Lead author, Professor Glen Jeffery (UCL Institute of Ophthalmology), said: “We demonstrate that one single exposure to long wave deep red light in the morning can significantly improve declining vision, which is a major health and wellbeing issue, affecting millions of people globally. “This simple intervention applied at the population level would significantly impact on quality of life as people age and would likely result in reduced social costs that arise from problems associated with reduced vision.” Naturally Declining Vision and Mitochondria In humans around 40 years old, cells in the eye’s retina begin to age, and the pace of this ageing is caused, in part, when the cell’s mitochondria, whose role is to produce energy (known as ATP) and boost cell function, also start to decline. Mitochondrial density is greatest in the retina’s photoreceptor cells, which have high energy demands. As a result, the retina ages faster than other organs, with a 70% ATP reduction over life, causing a significant decline in photoreceptor function as they lack the energy to perform their normal role. In studying the effects of deep red light in humans, researchers built on their previous findings in mice, bumblebees and fruit flies, which all found significant improvements in the function of the retina’s photoreceptors when their eyes were exposed to 670 nanometre (long wavelength) deep red light. “Mitochondria have specific sensitivities to long wavelength light influencing their performance: longer wavelengths spanning 650 to 900nm improve mitochondrial performance to increase energy production,” said Professor Jeffery. Morning and Afternoon Studies The retina’s photoreceptor population is formed of cones, which mediate colour vision, and rods, which adapt vision in low/dim light. This study focused on cones*** and observed colour contrast sensitivity, along the protan axis (measuring red-green contrast) and the tritan axis (blue-yellow). All the participants were aged between 34 and 70, had no ocular disease, completed a questionnaire regarding eye health prior to testing, and had normal colour vision (cone function). This was assessed using a ‘Chroma Test’: identifying coloured letters that had very low contrast and appeared increasingly blurred, a process called colour contrast. Using a provided LED device all 20 participants (13 female and 7 male) were exposed to three minutes of 670nm deep red light in the morning between 8am and 9am. Their colour vision was then tested again three hours post exposure and 10 of the participants were also tested one week post exposure. On average there was a ‘significant’ 17% improvement in colour vision, which lasted a week in tested participants; in some older participants there was a 20% improvement, also lasting a week. A few months on from the first test (ensuring any positive effects of the deep red light had been ‘washed out’) six (three female, three male) of the 20 participants, carried out the same test in the afternoon, between 12pm to 1pm. When participants then had their colour vision tested again, it showed zero improvement. Professor Jeffery said: “Using a simple LED device once a week, recharges the energy system that has declined in the retina cells, rather like re-charging a battery. “And morning exposure is absolutely key to achieving improvements in declining vision: as we have previously seen in flies, mitochondria have shifting work patterns and do not respond in the same way to light in the afternoon – this study confirms this.” For this study the light energy emitted by the LED torch was just 8mW/cm2, rather than 40mW/cm2, which they had previously used. This has the effect of dimming the light but does not affect the wavelength. While both energy levels are perfectly safe for the human eye, reducing the energy further is an additional benefit. Home-Based Affordable Eye Therapies With a paucity of affordable deep red-light eye-therapies available, Professor Jeffery has been working for no commercial gain with Planet Lighting UK, a small company in Wales and others, with the aim of producing 670nm infra-red eye ware at an affordable cost, in contrast to some other LED devices designed to improve vision available in the US for over $20,000. “The technology is simple and very safe; the energy delivered by 670nm long wave light is not that much greater than that found in natural environmental light,” Professor Jeffery said. “Given its simplicity, I am confident an easy-to-use device can be made available at an affordable cost to the general public. “In the near future, a once a week three-minute exposure to deep red light could be done while making a coffee, or on the commute listening to a podcast, and such a simple addition could transform eye care and vision around the world.” To read the original article click here.

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Could a Tiny Fish Hold the Key to Curing Blindness?

AHA Publisher — Wed, 30 Sep 2020 07:00:45 +0000

NIH, National Eye Institute (NEI) via Newswise – Imagine this: A patient learns that they are losing their sight because an eye disease has damaged crucial cells in their retina. Then, under the care of their doctor, they simply grow some new retinal cells, restoring their vision. Although science hasn’t yet delivered this happy ending, researchers are working on it – with help from the humble zebrafish. When a zebrafish loses its retinal cells, it grows new ones. This observation has encouraged scientists to try hacking the zebrafish’s innate regenerative capacity to learn how to treat human disease. That is why among the National Eye Institute’s 1,200 active research projects, nearly 80 incorporate zebrafish. The retina is a layer of tissue in the back of the eye that responds to light. But many scientists think of the retina as part of the brain. Like other neurons of the central nervous system, retinal neurons typically don’t replicate in adult humans. Loss of retinal neurons typically results in irreversible vision loss. Image credit: National Eye Institute However, zebrafish, like newts, frogs, and a strange fish-like salamander called the axolotl, can regrow a variety of body parts – not only retinal neurons, but also the heart, fins, pancreas, brain, spinal cord, and kidney. Zebrafish have a variety of traits that make them a great model for studying tissue regeneration: They’re capable of reproducting hundreds of offspring at a time. They’re cheap to maintain and express about 70% of the same genes that humans do. Unlike mice, which develop in a womb, zebrafish develop externally where scientists can easily observe them. And their flesh is nearly transparent during development, enabling researchers to observe their internal organs. Scientists have long known that when zebrafish retinas are damaged, neuronal support cells called Müller glia start dividing to create neuronal precursor cells, which go on to become replacement retinal neurons. More recently, scientists have been trying to unravel the biological factors that initiate this process. Progress in that effort is detailed in several NEI-supported research projects over the past three years. Studying zebrafish, James Patton of Vanderbilt University and colleagues found that when levels of the neurotransmitter GABA decrease, neural stem cells activate. These cells then migrate to damaged retina and develop (differentiate) into whatever cell type is needed for repair. Patton’s findings help identify cues that stimulate zebrafish regeneration. Jeff Mumm, Johns Hopkins University, reported that immune cells in the retina called microglia are necessary for zebrafish Müller glia to initiate regeneration after injury. After selectively knocking out microglia with a toxic enzyme, Mumm found that the Müller glia showed almost no regenerative activity after three days of recovery, compared with approximately 75 percent regeneration in control zebrafish. However, when an immunosuppressant was applied to inhibit microglia reactivity a day after retinal cell loss had begun, the pace of retinal neuron replacement accelerated. This observation suggests that microglia play different roles at different stages of injury/regeneration. Jeff Mumm, Johns Hopkins, and collaborators, fluorescently labeled immune cells in zebrafish larvae to track immune system activity in a model of retinal degeneration. Image credit: Credit: David White, Mumm Lab, Johns Hopkins University School of Medicine Findings in zebrafish by these other groups led Tom Reh at the University of Washington to unlock the regenerative potential of cells in the mouse retina. In newborn mice, the gene regulatory factor Ascl1 can direct Muller glia to become retinal neurons. This gene goes dormant when mice mature. By artificially expressing the Ascl1 gene in adult mouse Muller glia, Reh’s team turned the gene program back on, showing for the first time that Müller glia in the adult mouse can give rise to new functional neurons after injury. These neurons have the gene expression pattern, the morphology, the electrophysiology, and the epigenetic program to look like interneurons instead of glia, according to the report, and connect with the existing retinal circuitry and respond to light. A second major challenge of regenerating the visual system is figuring out how replacement neurons in zebrafish find their way back to visual centers of the brain. The light-sensing photoreceptors connect to retinal ganglion cells (RGCs). RGC cell fibers called axons coalesce within the optic nerve where they exit the eye and disperse throughout the brain. Beth Harvey, a postdoctoral researcher working with Michael Granato at the University of Pennsylvania, has developed a model for studying this process.1 She uses zebrafish at the late larval stage so that she can observe RGC axons navigate to their appropriate brain target after injury, using a technique called confocal microscopy. Interestingly, she found that axons are more likely to innervate appropriate targets when the optic nerve is only partially cut—like leaving a trail of breadcrumbs for regenerating axons to follow. Illustration of zebrafish head showing optic nerve, eye, and brain. Image courtesy of Beth Harvey, University of Pennsylvania. To accelerate progress, the NEI funded a consortium of scientists as part of its Audacious Goals Initiative to identify biological factors that affect the restoration of functional connections within the retina and between the eye and brain. Projects within the consortium have used various models to evaluate hundreds of genes for their role in regeneration as well as compounds that modify their activity. In partnership with Michael Dyer from St. Jude’s Children’s Hospital, the NEI is uploading consortium data to an online database to help future investigations. References 1. Harvey, B. M., Baxter, M. & Granato, M. Optic nerve regeneration in larval zebrafish exhibits spontaneous capacity for retinotopic but not tectum specific axon targeting. PLoS One 14, e0218667, doi:10.1371/journal.pone.0218667 (2019). To read the original article click here.

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