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--- health:screen-brightness [2019/07/20 08:34]
john [References]
+++ health:screen-brightness [2020/04/27 01:48] (current)
marcos
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-Under construction
-====== The effect of screen brightness ======
-Lower the screen brightness of your phone, TVs, laptop, or tablet. It will be good for your eyes. Research shows that screen brightness affects your eyes. This is because the pupils of your eyes dilate (enlarge) and constrict (shrink) depending on the level of screen brightness (Mathôt & Van der Stigchel, 2015). If the level is high, it shrinks to reduce the amount of light that enters your eyes.
-On the other hand, if the brightness level is low, the pupils enlarge to allow more light to get in. In low ambient light and high screen brightness, the pupils shrink to reduce the amount of light entering the eyes. This is not dangerous to your eyes. However, if the ambient light is high, and the screen brightness is low, it can have damaging effects on your eyes. This is because the pupils will dilate to allow more light from the screen, but this will also allow more ambient light. The amount of ambient light will be too high and thus damage your eyes. The best life hack is regulated the screen brightness to be in tune with the ambient light. One way of doing this is by reducing ambient light and increasing display brightness (Beutel, Kundel, Metter, Kim, & Horii, 2000, p. 408).
+====== Screen Brightness ======
-Another life hack is to reduce screen brightness so that you can avoid glare. Glare can be very damaging to your eyes. So make sure you reduce the screen brightness to a level where there is no glare. For most people having a very bright screen is disturbing, but for some, they spend hours and hours of computer use at a high brightness level. This is very damaging to their eyes. A research conducted by Lanum (1978) showed that long hours of computer use at a high brightness level damages the retina of the human eye. The best life hack is to have the brightness level at a medium level.
+===== Bright Screens are Harmful to Your Eyes =====
-How do you calibrate the best screen brightness for you? In modern computers using windows operating system, you can open the control panel, and search, “calibrate.” Then under the display, click “Calibrate.” This will enable you to calibrate the best screen brightness, gamma, color balance, and contrast for your monitor. According to Shui (2012, p. 16), if the screen of your computers is really bright, your eyes become tired after a few hours, and if it is too dim, it takes you longer to focus on objects on the screen (leading to eyestrain—which can damage your eyes). The best life hack is for you to adjust the brightness of your screen relative to ambient light. Better yet, make it as bright as a page from your favorite magazine (Shui, 2012, p. 16). The trick here is to have a balance between your screen brightness and ambient light levels.
+==== Blue Light Photons ====
-====== References ======
+Screens may look nicer when their brightness is up, but the high intensity of light is harmful for your eyes. ((https://pubs.rsc.org/en/content/articlelanding/2017/IB/c7ib00032d))\\
-Beutel, J., Kundel, H. L., Metter, R. L. V., Kim, Y., & Horii, S. C. (2000). Handbook of Medical Imaging: Display and PACS. SPIE Press.
+https://www.chemistryworld.com/news/phone-screen-light-kills-human-eye-cells/3007113.article\\
+http://www.eyecarefun.com/bad-for-eyes-to-use-computer-in-dark
-Lanum, J. (1978). The damaging effects of light on the retina. Empirical findings, theoretical and practical implications. Survey of Ophthalmology, 22(4), 221–249. https://doi.org/10.1016/0039-6257(78)90070-X
+Especially high frequency blue/violet light that carries more energy per photon. ((https://en.wikipedia.org/wiki/Visible_spectrum)).  Human eyes are designed to block UV light from reaching the retina.  Thus, the danger of creating reactive oxygen species (ROS) on the retina is highest from the blue light frequency range. ((https://www.allaboutvision.com/cvs/blue-light.htm))
-Mathôt, S., & Van der Stigchel, S. (2015). New Light on the Mind’s Eye. Current Directions in Psychological Science, 24(5), 374–378. https://doi.org/10.1177/0963721415593725
+In order to reduce retinal nerve damage, the goal is to let in as little light into your eyes as possible, where you can still see the detail you need to see.
-Shui, S. (2012). Speaking Computer: Learning the Foreign Language of Technology. Speaking Computer.
+==== Reducing Concentrated Regions of Retinal Light Intensity ====
+The eyes can regulate the amount of incoming light through the [[https://en.wikipedia.org/wiki/Pupillary_light_reflex |pupillary light reflex]], where the pupil contracts or dilates according to the summation of light intensity onto both retina. ((https://www.quora.com/Does-peripheral-light-affect-the-pupillary-light-reflex-such-that-pupils-watching-TV-in-a-dark-room-will-be-slightly-wider-than-pupils-watching-TV-in-a-lit-room))
+Eyes evolved to have a relatively even intensity of light from the entire visual field, as obtained from sunlight's [[https://en.wikipedia.org/wiki/Atmospheric_optics |dispersion through the atmosphere]].
+While working at your monitor, light comes in through both ambient and monitor sources.  The summation of the light from the entire visual field contribute to how much your pupils contract.  The retinal nerve cells responsible for pupillary-light-reflex are the [[https://en.wikipedia.org/wiki/Intrinsically_photosensitive_retinal_ganglion_cells |Photosensitive Ganglion Cells]].
+If the light distribution reaching the retina is uneven, some cells may receive an unhealthy amount of radiation which can lead to cell death.  In the case of electronic displays, the distribution of retinal light intensity can be uneven if the ambient light and screen brightness are not balanced.
+For example, if you are watching a bright TV in a dark room.  As an extreme example, staring at the sun.  The opposite would be too dim of a display with intense ambient light, where peripheral nerves of the retina may be stressed.
+==== Improving Visual Acuity ====
+"As in a photographic lens, visual acuity is affected by the size of the pupil. Optical aberrations of the eye that decrease visual acuity are at a maximum when the pupil is largest (about 8 mm), which occurs in low-light conditions. When the pupil is small (1–2 mm), image sharpness may be limited by diffraction of light by the pupil (see diffraction limit). Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm." ((https://en.wikipedia.org/wiki/Visual_acuity))
+The best situation is where the monitor light and the ambient light have matching intensity.  But it's still not optimal if both sources are extremely bright.  A low ambient light and a matching low screen brightness, which still allows you to see the detail you need to see, is the best option for eye healh.
+In practice, with most computer monitors and most indoor lighting, you will be dialing the brightness level to zero.  Monitors are just too bright, unless sunlight is shining through your window in the background.  You can also play with the contrast to optimize image clarity and readability.
+If you practice this from an early age, you will find that most people in the era-of-screens have limited vision in low light.  Manufacturers are starting to take note, with now common features such as screens with automatic brightness, and a blue-light cycle that follows the [[health:circadian-rhythm|circadian rhythm]].
+==== Eye Strain (Asthenpia) ====
+The physiology of eye strain, or asthenopia, is not fully understood. ((https://scholar.google.com/scholar?q=related:9epKqfJgBQUJ:scholar.google.com/&scioq=cause+of+asthenopia&hl=en&as_sdt=0,33))
+Asthenopia has been categorized into eye surface and internal symptoms. ((https://www.tandfonline.com/doi/abs/10.1080/09500340600855460)) ((https://journals.lww.com/optvissci/Abstract/2003/11000/Is_all_Asthenopia_the_Same_.8.aspx))  Explanations for internal eye strain include muscular ache from [[https://en.wikipedia.org/wiki/Accommodation_%28eye%29 |accomodative]], [[https://en.wikipedia.org/wiki/Vergence |convergent]] and pupillary contractions.  External eye strain consists of "sensations of dryness and irritation on the front of the eye and caused by compromised conditions in the viewing environment."  ((https://www.tandfonline.com/doi/abs/10.1080/09500340600855460))

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