Why are there rings or halos around lights when you drive at night?

1 ANSWERS

1. Amit bang
   

   This phenomenon falls under the category of "spherical aberration"—just one of several examples of how the human eye is optically imperfect. In daylight, the pupil narrows to a very small opening, allowing light to hit the very center of the lens. At night, when the pupil dilates dramatically to allow maximum light to enter, your eye is using a much larger swath of its lens to see. "The farther out on the lens you go, the less perfect the optics are," says Duffner. "And as you get off center, those light rays won't be focused to the center of the eye." You see circles, well, because your lens is round. Almost everyone sees these rings, and if you've always seen them, you're probably just fine, he says. But halos can also be caused by opacities in the lens—a sign of cataracts. So if seeing halos is new to you, see a doctor for a cataract exam.

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