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Night Vision

Everyone has found themselves in the dark, at some point in their lives. It takes a couple of minutes for your eyes to adjust to the dark. This impressive process is ''dark adaptation''.

Many people don't know that night vision is dependent upon the cooperation of physical, neural and biochemical mechanisms. So how does this work? The human eye contains photoreceptors that can be classified as two kinds of cells: cones and rods, which are found on the retina at the back of the eye. Together they make up the sensory layer. This is the part that gives your eye the ability to detect light and color. Cones and rods are spread throughout the retina, except for in the small area opposite the pupil known as the fovea. The fovea has only cone cells, and its primary function involves focusing on detail. As you may know, the cones enable us to see color and detail, while rod cells are sensitive to light.

So, if attempting to focus on an object in the dark, like the dresser in a darkened room, instead of looking right at it, try to look just beside it. You want to maximize the use of the rod cells in low light, and avoid relying on your cone-rich fovea, even though it seems counter-intuitive to look away from the object you want to see.

Another process your eye undergoes is pupil dilation. It takes less than a minute for the pupil to completely dilate; however, it takes approximately half an hour for your vision to fully adapt. During this time, your eyes become 10,000 times more sensitive to light.

Dark adaptation occurs if you leave a bright area and enter a dim one, for example, walking inside after sitting in the sun. While you need a few noticeable moments to begin to see in the darker conditions, you'll quickly be able to re-adapt to exposure to bright light, and this resets any dark adaptation that had developed where it was darker.

This is why many people don't like to drive at night. If you look directly at the lights of a car heading toward you, you are briefly blinded, until that car is gone and you readjust to the night light. A good way to prevent this sort of temporary blindness is to avoid looking right at the car's lights, and learn to use peripheral vision in those situations.

There are numerous things that could potentially lead to difficulty seeing at night, including: a nutritional deficiency, cataracts, glaucoma, or some other visual obstruction. Should you begin to notice that you experience problems with night vision, schedule an appointment with one of our eye care professionals who will be able to shed some light on the issue.

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