EyeMark Newsletters

A list of all our EyeMark Newsletter Articles

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Optical Illusions


Are you seeing what is actually out there, or is your brain processing information that is not quite the same as what you are looking at? Can you trust that what you see is in fact what is meant to be seen? An optical or visual illusion is a perceived image that is different from objective reality. The illusion arises when what we perceive is in conflict with reason and the facts regarding the image. There are various explanations for this, and various types of optical illusions.   PHYSIOLOGICAL ILLUSIONS Physiological illusions are the effects on the eyes and brain of excessive stimulation of specific types, e.g. brightness, colour, size or movement. One example of these is the afterimage we see following exposure to bright lights. In the following diagram, we perceive spots at the intersection of the squares, although these spots are not actually part of the diagram.     COGNITIVE ILLUSIONS Cognitive illusions are the result of the interaction between what we see and unconscious inferences of what we know about the world around us. For example, we know that a door is rectangular in shape, so even if we see an image of a door of different shapes, e.g. open or half-closed, we will still see the image as a rectangle. There are different types of cognitive illusions. With ambiguous illusions we see a switch between alternative interpretations of an image, for example, in this image, we see alternating images of a rabbit and a duck.   DISTORTING...
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Turn Any Specs Into 3D Glasses


If you wear glasses, 3D movies can be quite a challenge! Either you have to wear two pairs of glasses, your own plus 3D, or you spend a couple of hours squinting at a screen while those around you enjoy a movie in 3D! Designers Lucy Jung and Daejin Ahn came up with a solution, a simple set of polarizing filter stickers that can be placed directly on the lenses of a prescription pair of glasses, effectively turning them into 3D specs. Now everyone can relax and enjoy 3D movies!
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668 Hits

Glaucoma

Glaucoma refers to a category of eye disorders often associated with a buildup of internal eye pressure (intraocular pressure or IOP), which can damage the eye's optic nerve. Glaucoma typically affects your peripheral vision first, so that you can lose a great deal of vision before you are aware that something is wrong. If uncontrolled or left untreated, glaucoma can eventually lead to blindness. Signs and symptoms of glaucoma Glaucoma is often referred to as the "silent thief of sight," because most types typically cause no pain and produce no symptoms. But there are other forms of the disease where symptoms of blurry vision, halos around lights, intense eye pain, nausea, and vomiting occur suddenly. If you have these symptoms, make sure you immediately see an eye care practitioner or doctor. What causes glaucoma? Just as a ball needs air pressure to maintain its shape, the eye needs internal fluid pressure to maintain its shape and ability to see. The cause of glaucoma is generally a failure of the eye to maintain an appropriate balance between the amount of fluid produced inside the eye and the amount that drains away. Reasons for this imbalance vary depending on the type of glaucoma. Types of glaucoma There are various types of glaucoma, some of which develop gradually without the patient being aware of it, others which occur suddenly, and some being present at birth. How is glaucoma detected? During routine eye exams, a tonometer is used to measure your intraocular pressure (IOP). An...
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658 Hits

Vision Therapy for Children


Many children have vision problems other than refractive errors such as shortsightedness, farsightedness and astigmatism. These include amblyopia (“lazy eye), eye teaming problems, focusing problems, and visual perceptual disorders. Left untreated, these non-refractive vision problems can cause eyestrain, fatigue, and headaches, and can underlie learning problems at school. What is vision therapy? Vision therapy (also called vision training) is an individualised program of eye exercises and other methods to treat non-refractive vision problems. The optometrist is usually specially trained to deal with children’s vision problems. The therapy is usually performed in an optometrist’s office, but most treatment plans also include visual tasks and eye exercises to be practised at home. Can vision therapy eliminate the need for glasses? Vision therapy is NOT the same as prescription lenses for refractive errors, and doing eye exercises does NOT eliminate the need for glasses if there is a refractive error. In contrast, vision therapy is the treatment of non-refractive vision problems, and there are many studies that demonstrate its effectiveness. Not every vision problem can be resolved with vision therapy. The degree of success depends on factors such as the type and severity of the vision problem, the patient’s age and motivation, and whether the patient performs all visual tasks as directed. Vision therapy is customised and specific The activities and eye exercises prescribed as part of a vision therapy program are tailored to the specific vision problems of the child. Vision therapy and learning disabilities Vision therapy does NOT correct learning difficulties. However,...
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629 Hits

Interesting facts about your eyes

Your eyes: Are the most complex organs you possess except for your brain. Are composed of more than two million working parts. Can process 36,000 bits of information every hour. Under the right conditions, can discern the light of a candle at a distance of 14 miles. Utilize 65% of all the pathways to the brain. Can instantaneously set in motion hundreds of muscles and organs in your body. In a normal life-span, will bring you almost 24 million images of the world around you. The external muscles that move the eyes are the strongest muscles in the human body for the job that they have to do. They are 100 times more powerful than they need to be. The eye is the only part of the human body that can function at 100% ability at any moment, day or night, without rest. Your eyelids need rest, the external muscles of your eyes need rest, the lubrication of your eyes requires replenishment, but your eyes themselves "never" need rest. But please rest them!
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667 Hits

Tell me what I am

A snake and a rabbit were racing along a pair of intersecting forest pathways one day, when they collided at the intersection. They immediately began to argue with one another as to who was at fault for the mishap. When the snake remarked that he had been blind since birth, and thus should be given additional leeway, the rabbit said that he, too, had been blind since birth. The two animals then forgot about the collision and began commiserating concerning the problems of being blind. The snake said that his greatest regret was the loss of his identity. He had never been able to see his reflection in the water, and for that reason did not know exactly what he looked like, or even what he was. The rabbit declared that he had the same problem. Seeing a way that they could help each other, the rabbit proposed that one feel the other from head to toe, and then try to describe what the other animal was. The snake agreed, and started by winding himself around the rabbit. After a few moments, he announced, "You've got very soft, fuzzy fur, long ears, big rear feet, and a little fuzzy ball for a tail. I think that you must be a bunny rabbit!" The rabbit was much relieved to find his identity, and proceeded to return the favor to the snake. After feeling about the snake's body for a few minutes, he asserted, "Well, you're scaly, you're slimy, you've got beady little...
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Did you know?

On average, you blink 15 000 times a day. Women blink twice as much as men. A process NASA developed while refining helmet visors for astronauts led to scratch-resistant lenses for eyeglasses and sunglasses. We can see up to 500 different shades of any colour, even grey. If you count them all up, you'll get to over 10 million colours! Women generally have better night vision than men – but are still more likely to give up night driving, while men will just use brighter lights. The retina contains 120 million rods for "night vision", and 8 million cones that are colour sensitive and work best under daylight conditions?
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633 Hits

Hook, Line and Sinker

A pirate walks into a bar and the bartender says, "Hey, I haven't seen you in a while. What happened, you don't look so good!" "What do you mean?" the pirate replies, "I'm fine." The bartender says, "Well, to start off, what about that wooden leg? You didn't have that before." "Well," says the pirate, "We were in a battle at sea and a cannon ball hit my leg but the surgeon fixed me up, and I'm fine, really." "Ok," says the bartender, "But what about that hook? Last time I saw you, you had both hands." "Well," says the pirate, "We were in another battle and we boarded the enemy ship. I was in a sword fight and my hand was cut off but the surgeon fixed me up with this hook, and I feel great, really." "Oh," says the bartender, "What about that eye patch? Last time you were in here you had both eyes." "Well," says the pirate, "One day when we were at sea, some birds were flying over the ship. I looked up, and one of them made a deposit in my eye." "So?" replied the bartender, "what happened? You couldn't have lost an eye just from some bird dropping!" "Well," says the pirate, "I really wasn't used to the hook yet."
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626 Hits