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Home » What's New » The Mechanics of Night Vision

The Mechanics of Night Vision

Everyone’s found themselves in the dark, at some point in their lives. At first you can’t see, but gradually the things in the room begin take shape. This process, ”dark adaptation,” allows our vision to see even when there’s very little light.

In order for night vision and dark adaptation to happen, many physiological, neurological and biochemical mechanisms must take place behind the scenes. Let’s have a look at how this works. The retina is a layer of cells at the back of the eye. The section of the retina behind the pupil which produces sharp focused vision is called the fovea. The retina is made up of cone cells and rod cells, named for their respective shapes. The rod cells have the capacity to function even in low light conditions. They are not found in the fovea. What’s the functional difference between these two cell types? Basically, details and colors we see are sensed by the cones, and the rods allow us to see black and white, and are light sensitive and detect movement.

So, if you’re trying to get a glimpse of an object in the dark, instead of focusing right on it, try to use your peripheral vision. That way, you’re avoiding the use of the fovea, which only has cells that are less sensitive to low light.

Another way your eye responds to the dark is by your pupils dilating. It requires approximately one minute for the pupil to completely dilate; however, it takes approximately 30 minutes for your eyes to fully adapt.

Dark adaptation occurs when you walk into a dark cinema from a bright lobby and have trouble finding somewhere to sit. After a while, you adapt to the dark and see better. You’ll experience the same thing when you’re looking at stars at night. At the beginning, you probably won’t be able to actually see that many. As you keep staring, your eyes will dark adapt and millions of stars will gradually appear. Even though you need several moments to adapt to the dark, you’ll always be able to re-adapt to exposure to bright light, but if you return to the darker setting, your eyes will need time to re-adjust again.

This is actually one reason behind why so many people prefer not to drive at night. When you look at the ”brights” of opposing traffic, you may find yourself briefly blinded, until that car is gone and you once again adjust to the night light. A helpful way to avoid this is to avoid looking right at the car’s lights, and instead, try to allow your peripheral vision to guide you.

If you’re having trouble seeing when it’s dark, call us to schedule a consultation with your eye doctor who will see if your prescription needs updating, and eliminate other reasons for decreased vision, such as macular degeneration or cataracts.

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