question: Color-blindness glasses filter out colors, but wouldn't that make the problem worse?
comment: Normally, people's eyes have three color receptors, for red, green, and blue light. However, there's some overlap. Orange light, for example, will excite both the red and the green receptors a little bit. For some people, *red* light will excite both the red and green receptors, which is a problem because then it seems really similar to when orange light is received, since both receptors respond similarly. The glasses take out a section of light that's most overlapped. This means that a chunk of the red and a chunk of the green light is simply filtered out, but *some* of the red light (the "redder" light) remains, and *some* of the green light (the "bluer" green light) remains. As such, when someone wearing the glasses sees a red balloon, they'll only see the reddest light coming from that balloon. So it will appear definitely red. Whereas when they see an orange balloon, it will no longer make the red receptors respond since the reddest light from the orange balloon will have been filtered out, allowing the green receptor to respond a little bit to it, and the red receptor to respond a little bit to it (due to the orange balloon still having *some* red light that gets through on the reddest side of the spectrum) and so the orange balloon can be seen as distinct from the red balloon. Meanwhile, blue balloons look blue, since they never had as much red or green light reflecting from them to begin with.
passages: Different models of sunglasses exist, according to the color deficiency the person suffers from.
  
  Section::::Products incorporating EnChroma lenses.:Indoor glasses.
  
  This version of the glasses for people with CVD can be used indoors, but they work best in bright lighting and have applications for people who spend a lot of time facing a computer monitor. 
  
  Students with color blindness can have a benefit from the glasses, because they can understand particular color-coded information better at their school or at university.
  
  Section::::Products incorporating EnChroma lenses.:Children, industrial safety and sports glasses.
   Lenses that filter certain wavelengths of light can allow people with a cone anomaly, but not dichromacy, to see better separation of colors, especially those with classic "red/green" color blindness. They work by notching out wavelengths that strongly stimulate both red and green cones in a deuter- or protanomalous person, improving the distinction between the two cones' signals. As of 2012, sunglasses that notch out color wavelengths are available commercially.
  
  Section::::Management.:Apps.
   The research involved 48 color blindness volunteers, four were women and 44 were men, aged between 14 and 64. These participants were already aware of their own condition of CVD. The study concluded that, although an improvement in color vision has been accomplished since the colors are enhanced by the effect of the glasses, the technology could not be considered completely effective because the color vision it offers ws not identical to the non-colour blind individuals.
   Optometrists can supply colored spectacle lenses or a single red-tint contact lens to wear on the non-dominant eye, but although this may improve discrimination of some colors, it can make other colors more difficult to distinguish. A 1981 review of various studies to evaluate the effect of the X-chrom contact lens concluded that, while the lens may allow the wearer to achieve a better score on certain color vision tests, it did not correct color vision in the natural environment. A case history using the X-Chrom lens for a rod monochromat is reported and an X-Chrom manual is online.
   At no time should the goggles be used to help assess the visibility.
  
  Section::::Concept.
  
  Dark adaptor goggles were invented by Wilhelm Trendelenburg in 1916.
  
  The concept is based on the work by Antoine Béclère on dark adaptation of the eye, where it is noted that fluoroscopy relies on the use of the retinal rods of the eye. 
   In 2015 Dr. Blake Porter of the University of Otago conducted an experiment with 406 participants, of whom 42 already used EnChroma glasses. The participants were asked questions about their color blindness, their personal experience with the lens and the effects of those on their life and on the way they saw the colors.
   The Pacific University College of Optometry's experiment tested whether the glasses helped people with particular deficiencies improve the way they see colors. The study involved ten individuals with hereditary deficiencies (nine males and one female from age 19 to 52).
  
  The EnChroma Cx-14 filters did not significantly influence the vision of CVD subjects but, for two of them, the error score was improved.
  
  Section::::University experiments.:University of Granada.
   In 2018, researchers from the University of Granada studied EnChroma lenses and proved that they merely helped color blind people to see the same colors in a different way since the colored filter altered the way colors appeared in their eyes.
   While some blue blocking sunglasses (see above) are produced as regular sunglasses for exposure to bright sunlight, others—especially for macular degeneration patients—do not block light or other colors in order to function well in regular daylight and even dim sunlight. The latter allow the passage of enough light so normal evening activities can continue, while blocking the light that prevents production of the hormone melatonin. Blue-blocking tinted glasses, i.e. amber or yellow, are sometimes recommended to treat insomnia; they are worn in artificial lighting after dark, to reestablish the circadian rhythm and treat delayed sleep phase disorder.
   Sunglasses were the first product to use EnChroma lenses. They can be used in various lighting conditions, even in bright indoor environments, and assist people affected by deuteranopia and protanopia. They protect those who are affected by color blindness from solar ultraviolet and blue light and do not let solar radiation with a wavelength shorter than 450 nanometers pass through. They block just one or two colors (usually green and blue), permitting people to see colors such as dull brown or yellow. This is due to a specific coat that increases the brightness of colors and provides protection from UV rays. 
   Aggressive advertisements may contribute to the public perception of the dangers of blue light. A sponsored post on NewGradOptometry promoted sales training from Essilor and their product range (including the moral benefits), then segued into the amoral nature of upselling unnecessary lenses, finishing by arguing that patients will go blind without blue-filtering lenses. Essilor provided a pair of free glasses to a fashion blogger who did not need prescription glasses but nonetheless quoted a large number of Essilor marketing pitches including the blindness-preventing promises of their blue-light filtering technology. The Essilor website claims that one may experience vision loss without their special filtering lenses, whether one requires prescription glasses or not. Zeiss offers a similar product yet does not make nearly as extreme claims.
   Some of the newly-launched IOLs are able to provide ultraviolet and blue light protection. The crystalline lens of the eye filters these potentially harmful rays and many premium IOLs are designed to undertake this task as well. According to a few studies though, these lenses have been associated with a decrease in vision quality.
  
  Another type of intraocular lense is the light-adjustable one which is still undergoing FDA clinical trials. This particular type of IOL is implanted in the eye and then treated with light of a certain wavelength in order to alter the curvature of the lens.
   Due to the widespread implementation of surveillance cameras, glasses are being built which can defeat CCTV cameras. In December 2016 a form of anti-CCTV and facial recognition sunglasses called 'reflectacles' were invented by a custom-spectacle-craftsmen based in Chicago named Scott Urban. They reflect infrared and, optionally, visible light which makes the users face a white blur to cameras. The project easily surpassed its funding goal of $28,000 and reflectacles became commercially available in June 2017.
  
  Section::::See also.
  
  BULLET::::- Artificial intelligence for video surveillance
  
  BULLET::::- Bugging
  
  BULLET::::- Closed-circuit television camera
  
  BULLET::::- Documentary practice
  
  BULLET::::- Eye in the sky (camera)
   Yellow tinted glasses are a type of glasses with a minor yellow tint. They perform minor color correction, on top of reducing eyestrain due to lack of blinking. They may also be considered minor corrective unprescribed glasses. Depending on the company, these computer or gaming glasses can also filter out high energy blue and ultra-violet light from LCD screens, fluorescent lighting, and other sources of light. This allows for reduced eye-strain. These glasses can be ordered as standard or prescription lenses that fit into standard optical frames. Due to the ultra-violet light blocking nature of these lenses, they also help users sleep at night along with reducing age-related macular degeneration.
   More recently, high-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration; before, debates had already existed as to whether "blue blocking" or amber tinted lenses may have a protective effect. Some manufacturers already design glasses to block blue light; the insurance company Suva, which covers most Swiss employees, asked eye experts around Charlotte Remé (ETH Zürich) to develop norms for blue blocking, leading to a recommended minimum of 95% of the blue light. Sunglasses are especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
   Section::::Management.
  
  There is generally no treatment to cure color deficiencies. ″The American Optometric Association reports a contact lens on one eye can increase the ability to differentiate between colors, though nothing can make you truly see the deficient color.″
  
  Section::::Management.:Lenses.
   The optical filter used in EnChroma lenses can improve or modify aspects of color vision deficiency (CVD). EnChroma lenses focus on the most common color vision deficiency which is caused by the red and green retinal cone cells that, when responding to light, coincide. The most common form of color blindness is known as deuteranomaly, it is genetic and an X-linked trait that affects up to one in every 12 men (8%) and one in 200 women (0.5%). To eliminate the overlapping of the wavelengths of light, there is an optical material called a 'multi-notch' filter, is capable of removing the exact wavelengths of light in the location where it overlaps, getting a simplified differentiation of colors. The glasses block specific wavelengths to create a clearer separation of different color signals so that they can be better calculated by the brain. The separation of signals allows most people with CVD to distinguish colors, but the glasses will have little to no effect on the 20% of color blind people who have severe color impairment.
   ChromaGen contact lenses have been used and shown to have some limitations with vision at night although otherwise producing significant improvements in color vision. An earlier study showed very significant improvements in color vision and patient satisfaction.
  
  Later work that used these ChromaGen lenses with dyslexics in a randomised, double-blind, placebo controlled trial showed highly significant improvements in reading ability over reading without the lenses. This system has been granted FDA approval for use in the United States.
   Smart sunglasses which are able to change their light filtering properties at runtime generally use liquid crystal technology. As lighting conditions change, for example when the user goes from indoors to outdoors, the brightness ratio also changes and can cause undesirable vision impairment. An attractive solution for overcoming this issue is to incorporate dimming filters into smart sunglasses which control the amount of ambient light reaching the eye. An innovative liquid crystal based component for use in the lenses of smart sunglasses is PolarView by LC-Tec. PolarView offers analog dimming control, with the level of dimming being adjusted by an applied drive voltage.
   Section::::Scotopic sensitivity syndrome.
  
  Scotopic sensitivity syndrome, also known as Irlen Syndrome, is said to be a visual-perceptual defect related to difficulties with light source, glare, luminance, wavelength and black/white contrast. According to Irlen, these difficulties lead to reading problems, eye-strain, headaches, migraines, and other physical difficulties that can be alleviated by the use of person specific tinted lenses, known as Irlen Spectral Filters, worn as glasses or contact lenses.
  
  The syndrome has six characteristics:
  
  BULLET::::1. photophobia
  
  BULLET::::2. eye strain
  
  BULLET::::3. poor visual resolution
  
  BULLET::::4. a reduced span of focus
  
  BULLET::::5. impaired depth perception
  
  BULLET::::6. poor sustained focus
   Sunglasses allow for better vision in bright daylight, and may protect one's eyes against damage from excessive levels of ultraviolet light. Typical sunglasses lenses are tinted for protection against bright light or polarized to remove glare; Photochromatic glasses are clear in dark or indoor conditions, but turn into sunglasses when in they come in contact with Ultraviolet light. Most over the counter sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be made.
   A 2009 report by the American Academy of Pediatrics (AAP) does not believe that there is conclusive scientific evidence for the use of coloured lenses (one treatment used to relieve symptoms of scotopic sensitivity syndrome) although it acknowledges anecdotal evidence to the contrary. When discussing its scientific basis, the AAP mentions that "[t]he method used to select the lens or filter color has been highly variable, the color selection has also shown considerable variability, and the test-retest consistency has been poor" (p. 843).
   Even though some of these glasses are proven good enough for driving at night, it is strongly recommended not to do so, due to the changes in a wide variety of light intensities, especially while using yellow tinted protection glasses. The main purpose of these glasses are to protect the wearer from dust and smog particles entering into the eyes while driving at high speeds.
  
  Section::::Special-use.:Aircraft piloting.
   90% of the participants said they would recommend them to other people, and more than 50% of those people stated that EnChroma glasses improved their life. 10% of the remaining participants reported that the glasses did not have any impact on their life. 40% of the participants identified green as the color range that changed the most.
   The glasses are available in single vision lenses, bifocals, and progressive lens. The sunglasses are also used by some senior citizens to help with sunlight sensitivity or due to medical conditions such as diabetes, glaucoma, macular degeneration, cataracts, multiple sclerosis, and eye cancer.
  
  Section::::University experiments.
  
  Section::::University experiments.:Pacific University and Qassim University.
  
  The Qassim University and the Pacific University conducted joint experiments.
  
  The Qassim University experiment involved 25 males aged from 20 to 25 years. Two of those 25 were excluded because of a vision disease that may affect the CVD deficiency.
  