After Images
Have you ever experienced this? When you stare at bright light for few seconds then you shut your eyes or look into a dark space, you’d still see a brief image (inverted image ) of that bright light or object you were staring at or when you stare at an object with bright colors, when you look at something else, you’d see some images of those colors very briefly. This effect is called after images.
WHAT IS AFTER IMAGE?
An afterimage is a type of optical illusion ( they are actually not real images) in which an image continues to appear in the eye after exposure to the real image (original image) has ended. This phenomenon may be normal(physiologic) or pathological ( a disorder called Palinopsia).
Afterimages occur because photochemical (rods and cones) activity in the retina continues even when the eyes are no longer experiencing the original stimulus, they are basically overstimulated initially i.e they are actively stimulated afterwards they are then desensitized. This simple process is what avails us to experience after images.
THERE ARE 2 TYPES OF AFTER IMAGE.
Positive After image – The colours you see in the after image are same colours with the real image. They occur very fast ( from a few seconds to a minute).
Negative After image – The colours seen in the after image are inverted ( reversed colour) to the original image seen, they also occure briefly.
As explained earlier, after images are just illusionary images that last few seconds and they fade away, however, there is Palinopsia which is actually a neurological and visual disorder. People with palinopsia see images which may appear immediately or following a time interval and images are long lasting or intense compared to the physiologic after image which is briefly seen.
When you experience brief after images, now you know have an idea of what is happening in the eye however then your after images are lasting for a long period such that it is disturbing your vision, you should not hesitate to visit the clinic and get examined.
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