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  2. Refractive error - Wikipedia

    en.wikipedia.org/wiki/Refractive_error

    It is estimated that at least 2 billion people in the world have refractive errors. [4] The number of people globally with refractive errors that have not been corrected was estimated at 660 million (10 per 100 people) in 2013. [9] Refractive Errors are the first common cause of Visual Impairment and second most common cause of visual loss . [45]

  3. Keratoconus - Wikipedia

    en.wikipedia.org/wiki/Keratoconus

    Keratoconus ( KC) is a disorder of the eye that results in progressive thinning of the cornea. [ 3] This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, [ 4] and light sensitivity leading to poor quality-of-life. [ 3][ 5] Usually both eyes are affected. [ 3] In more severe cases a scarring or a circle may be ...

  4. Upside down goggles - Wikipedia

    en.wikipedia.org/wiki/Upside_down_goggles

    Upside down goggles. Upside down goggles, also known as "invertoscopes" by Russian researchers, [ 1] are optical instruments that invert the image received by the retinas upside down. They are used to study human visual perception, particularly psychological process of building a visual image in the brain. Objects viewed through such a device ...

  5. Biological effects of high-energy visible light - Wikipedia

    en.wikipedia.org/wiki/Biological_effects_of_high...

    Blue light, a type of high-energy light, is part of the visible light spectrum. High-energy visible light (HEV light) is short-wave light in the violet/blue band from 400 to 450 nm in the visible spectrum, which has a number of purported negative biological effects, namely on circadian rhythm and retinal health (blue-light hazard), which can lead to age-related macular degeneration.

  6. Invisible disability - Wikipedia

    en.wikipedia.org/wiki/Invisible_disability

    People may see someone with an invisible disability as lazy, weak, or antisocial. A disability may cause someone to lose connections with friends or family due to this lack of understanding, potentially leading to a lower self-esteem. Individuals with invisible disabilities may experience guilt and feeling misunderstood when asking for support ...

  7. Pinhole glasses - Wikipedia

    en.wikipedia.org/wiki/Pinhole_glasses

    Pinhole glasses, also known as stenopeic glasses, are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens. Similar to the workings of a pinhole camera , each perforation allows only a very narrow beam of light to enter the eye which reduces the size of the circle of confusion on the ...

  8. Binocular vision - Wikipedia

    en.wikipedia.org/wiki/Binocular_vision

    Principle of binocular vision with horopter shown. In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an animal has eyes on opposite sides of its head and ...

  9. Cosmic ray visual phenomena - Wikipedia

    en.wikipedia.org/wiki/Cosmic_ray_visual_phenomena

    Cosmic ray visual phenomena, or light flashes ( LF ), also known as Astronaut's Eye, are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program. While LF may be the result of actual photons of visible light being sensed by the retina, [1] the LF discussed here ...