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  • Category: Science

    Why do we get blinded for a while when we move into a dark room from a bright lighted area?


    Interested in knowing the scientific reason behind change in vision when you move from a light to dark area? Find the reasons to your queries from experts on this page.

    So many times we might have experienced this phenomenon in our real life. When we move into a theatre for matinee show during midday time from outside bright light, first we get blinded for a while but slowly we are able to view things one by one. Similarly when we move from dark room into bright lighted area we get blinded for a while but slowly we recover to normalcy. How can we explain these phenomena scientifically?
    Experts: do advice.
  • #139007
    The simple explanation can be given as follows.
    When you are in the dark, the pupil gets dilated to allow more light into the retina so that you can see. When you are in a bright area, the pupil constricts so that not much light than that needed reaches the retina. Our retina will need a definite amount of light for proper vision.

    When you are in a bright room, the pupil has constricted itself, and on sudden darkness, it would take certain time for the pupil to dilate so that you will be able to see.

    The rods and cones in our eye are less sensitive and send lesser amount of neural impulses to the brain when we are in a bright area. On entering the dark room, they will need to become more sensitive, and this adjustment does take some time. That is the sole reason for the momentary difficulty in having a proper vision.

    Live....and Let Live...!

  • #139012
    Our eyes respond to the light sources. And based on the reflection of the light the imagery is printed on the eyes and the response is given to the brain. This process requires the place to have decent amount of light. So this is one reason that makes the eye respond differently to the darkness. And though it appears like blindness, your mind is still in the process of creating the imagery. In case of blindness, the brain has no process that does the imagery processing, that's why the blind person can't as the eyes have lost the ability to do just that. In case of the light source being low or high, not having this capacity is not exactly a type of blindness but inability of brain to process the objects nearby without the light sources. Some animals on the other hand have the capacity to process the imagery despite having low or no light source and so they are nocturnal and can see in the darkness.

  • #139023
    Nice query, let me explain as I have studied. Actually the pupil plays the major role in the eye organ. The eye takes care of our eyes by it self. The retina of our eyes needs some amount of light for us to see any where. So when we enter the dark the light rays will be less that's why the pupil allows more light to go in and thus we can see in dark. Similarly when we move from dark to light area the pupil restricts the light from going in. That's the reason when we move suddenly from dark to light area the pupil takes some time to dilate or get adjusted, it acts very fast but not as fast as human movements. So during the period of dilating from dark to light area we feel blackness and difficulty in vision.

  • #139033
    Our visibility is dependent on the following factors-
    1) The pupil- The pupils may be treated like cameras where in the aperture either expands or contracts depending upon the intensity of light / darkness.
    2) Rod and Cone Cells - Our eyes operate on two different type of cells to see the light and this mechanism is known as Rod and Cones. The Cone - cell can perceive fine detail of an object but this requires light of high magnitude where as the Rod - cells having poor resolution can see the dark.
    3) Photopigments- Both Rods and Cones are full of light sensative chemicals known as Photopigments. On exposure to light, the Photopigments start functioning through chemical reaction and the light energy is converted to electrical one and finally brain can respond to this phenomena.
    Rhodopsin is the Photopigmentation utilised by the Rods and it is the prime source of night - vision. Darkness results in the regeneration in the process known as dark - adaption, where the eyes adjust to see the low intensity of the light.
    Our eyes can adjust to focus a distinct object in both the conditions but it takes a couple of minutes to see the object distinctly in the dark.

  • #139076
    Adaptation:-
    This is the phenomena that takes place when we move from dark room to bright light or else from bright area to dark room. Our eyes take some time to adjust and adapt to the total change of light that it experiences and thus images appearing to us seem unclear with a little bit of darkness or blindness appearing to our eyes.

    This adaptation takes place automatically without our knowledge due to ability of our visual system to adjust to the changing light. It is a complex phenomena which is based on many factors like cone and rods of eyes, pupil size etc..... Adaptation first begins with iris of the eyes whose main function is to control image quality.

    Light Adaptation:-
    When we move from dark room to bright room, this phenomena takes place. Sensitivity of receptors of our eyes is set to dim light and when we suddenly move from dark room to bright room then all that we can see is white light. Resultant glare is due to instant breaking of photo pigments. It is an active defense mechanism. It prevents damage to vision by bright light.

    In this case, sensitivity of retina of our eyes decreases. Rods and cones both gets stimulated. Neurons present in retina here adapts quickly. They favor cones and inhibit rods. Within a few minutes our eyes adapt to the bright light and we no longer feel discomfort in viewing and that is because cones are excited by brightness to take over. In this phenomena, retinal sensitivity goes away. For next few minutes, one can experience more clarity in vision and color.

    Dark Adaptation:-
    When we move from bright room to dark room then adaptation that our eyes have to do to adjust to the darkness is known as dark adaptation. Here, function of cone is inhibited. In the beginning of the phase, rods too seem to lose their functioning as its pigments are bleached by bright light. In this phenomena, sensitivity of retina is not lost unlike light adaptation. In fact it increases. Reflexive changes are seen in pupil.


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