Bad Reflections These odd shapes, nick-named the ‘muffin’ (left) and the ‘potato’ (right), are a real test to our powers of observation. Our brains make sense of the world around us using binocular stereopsis: a process that compares what the left and right eyes see, using small differences between their viewpoints to estimate distance and depth. When looking at shiny things, however, this is much more of a challenge. Human test subjects looking at a 3-dimensional shiny muffin found its curve difficult to judge; their eyes were confused by false dips and bends in the glimmering reflections. The potato’s contours were, oddly, much easier to spot. Psychophysicists believe that when looking at highly irregular shapes, our brains decide to take binocular stereopsis with a pinch of salt and quickly search for other clues to work out shape and depth in the midst of so many brain-bending reflections. Written by John Ankers — Andrew Welchman University of Birmingham, UK Published in PNAS 110(6): 2413-2418
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Bad Reflections

These odd shapes, nick-named the ‘muffin’ (left) and the ‘potato’ (right), are a real test to our powers of observation. Our brains make sense of the world around us using binocular stereopsis: a process that compares what the left and right eyes see, using small differences between their viewpoints to estimate distance and depth. When looking at shiny things, however, this is much more of a challenge. Human test subjects looking at a 3-dimensional shiny muffin found its curve difficult to judge; their eyes were confused by false dips and bends in the glimmering reflections. The potato’s contours were, oddly, much easier to spot. Psychophysicists believe that when looking at highly irregular shapes, our brains decide to take binocular stereopsis with a pinch of salt and quickly search for other clues to work out shape and depth in the midst of so many brain-bending reflections.

Written by John Ankers

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Source: bpod.mrc.ac.uk

Eye Insights The eyes of fish grow larger throughout their lives because stem cells produce new tissue in the retina, the light-sensitive lining at the back of the eye. Humans and other mammals lack these stem cells, so the retina can neither grow nor be repaired naturally. Studies of zebrafish show that the development of stem cells in the retina is controlled by chemicals from nerve cells nearby. This research may lead to a better understanding of degenerative diseases of the eyes and nervous system in humans and the causes of cancer, which can occur when stem cells go out of control. Pictured is a cross-section of a zebrafish eye. The ring stained green with the dark centre is the lens, with the retina appearing as a semi-circle around it. Stem cells are concentrated in the regions at either end of the red-stained arcs of nerve connecting tissue. Written by Mick Warwicker — Kara Cerveny Zebrafish Research, UCL, London
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Eye Insights

The eyes of fish grow larger throughout their lives because stem cells produce new tissue in the retina, the light-sensitive lining at the back of the eye. Humans and other mammals lack these stem cells, so the retina can neither grow nor be repaired naturally. Studies of zebrafish show that the development of stem cells in the retina is controlled by chemicals from nerve cells nearby. This research may lead to a better understanding of degenerative diseases of the eyes and nervous system in humans and the causes of cancer, which can occur when stem cells go out of control. Pictured is a cross-section of a zebrafish eye. The ring stained green with the dark centre is the lens, with the retina appearing as a semi-circle around it. Stem cells are concentrated in the regions at either end of the red-stained arcs of nerve connecting tissue.

Written by Mick Warwicker

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Source: bpod.mrc.ac.uk

Bright Eyes A growing foetus is sheltered from the outside world, but external conditions may still affect it. Only a tiny amount of light manages to get inside the womb, but new evidence suggests this may be essential to ensure eyes develop correctly. Inside each growing eye, a cup-shaped network of blood vessels forms to supply the early retina with oxygen and nutrients. After birth these vessels are no longer needed, so they slowly break down. The left-hand image shows the pattern of vessels (stained blue) in the eye of a healthy eight-day-old mouse. In genetically engineered mice that lack the light-absorbing protein melanopsin (right-hand image) the vessels fail to break down normally post-birth, persisting as a dense, tangled mess. Exactly the same thing happens if a foetus grows in total darkness. This discovery may help to explain certain eye abnormalities, although the influence of light during human pregnancy is still unknown. Written by Emma Stoye — Sujata Rao Cincinnati Children’s Hospital Medical Center, USA Reprinted by permission from Macmillan Publishers Ltd: Nature Copyright 2013 Published in Nature 2013
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Bright Eyes

A growing foetus is sheltered from the outside world, but external conditions may still affect it. Only a tiny amount of light manages to get inside the womb, but new evidence suggests this may be essential to ensure eyes develop correctly. Inside each growing eye, a cup-shaped network of blood vessels forms to supply the early retina with oxygen and nutrients. After birth these vessels are no longer needed, so they slowly break down. The left-hand image shows the pattern of vessels (stained blue) in the eye of a healthy eight-day-old mouse. In genetically engineered mice that lack the light-absorbing protein melanopsin (right-hand image) the vessels fail to break down normally post-birth, persisting as a dense, tangled mess. Exactly the same thing happens if a foetus grows in total darkness. This discovery may help to explain certain eye abnormalities, although the influence of light during human pregnancy is still unknown.

Written by Emma Stoye

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Source: bpod.mrc.ac.uk

Through New Eyes Our vision relies on a multi-layered structure on the inner surface of the eye, the retina, bearing specialised light-sensitive neurons known as photoreceptors. Progressive degeneration of these cells leads to blindness, as in inherited diseases such as retinitis pigmentosa. While this cannot be reversed, transplanting healthy cells into the eye may provide a solution. Photoreceptor precursor cells are injected into the retina, where they mature into functional light detectors. In mice genetically modified to show symptoms of these diseases, transplants can restore normal responses to light. Pictured are donor cells (stained green), successfully integrating into the host retina (stained blue) of healthy mice (top left corner) and of mouse models of three different genetic diseases causing blindness in humans. Though the extent of integration still depends on the nature and progression of the disease, this technique raises hopes of recovering sight from a range of conditions. Written by Emmanuelle Briolat — Rachael Pearson & Robin Ali University College London Institute of Ophthalmology, UK Published in PNAS 110(1): 354-359
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Through New Eyes

Our vision relies on a multi-layered structure on the inner surface of the eye, the retina, bearing specialised light-sensitive neurons known as photoreceptors. Progressive degeneration of these cells leads to blindness, as in inherited diseases such as retinitis pigmentosa. While this cannot be reversed, transplanting healthy cells into the eye may provide a solution. Photoreceptor precursor cells are injected into the retina, where they mature into functional light detectors. In mice genetically modified to show symptoms of these diseases, transplants can restore normal responses to light. Pictured are donor cells (stained green), successfully integrating into the host retina (stained blue) of healthy mice (top left corner) and of mouse models of three different genetic diseases causing blindness in humans. Though the extent of integration still depends on the nature and progression of the disease, this technique raises hopes of recovering sight from a range of conditions.

Written by Emmanuelle Briolat

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Source: bpod.mrc.ac.uk