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Picture this: there's a power outage and you need to locate a flashlight or the fuse box. Your eyes normally require a few minutes to adjust to the dark and then you can see again. This remarkable process is ''dark adaptation'' and it's what lets our eyes get used to the dark.

A person with a healthy set of eyes probably takes night vision - and the biochemical, physical and neural mechanisms - for granted. So how does it really happen? Firstly, let's examine some eye anatomy. Your eye has, in addition to other cells, rod cells and cone cells, which are found at the back of the eye; or, to be precise, on the retina. Together they form the sensory layer. This is the part that helps the eye pick up light and color. These cells are distributed evenly throughout your retina, save for the small area opposite the pupil known as the fovea. This is made up of only cone cells, and its main function involves focusing on detail. What's the difference between these two cell types? Basically, cones contribute to color vision, and the rods are sensitive to light and detect movement.

This information is significant because, when you're trying to find something in the dark, like the edge of the last stair in a dark basement, instead of looking directly at it, try to look just beside it. When you do that, you use the part of the eye that has rods, which, as mentioned above, are more responsive to light, even if there isn't much of it.

Your pupils also dilate when it's dark. Your pupil reaches its largest diameter within a minute but dark adaptation keeps enhacing your vision for the next half hour.

You'll experience dark adaptation when you first enter a darkened movie theatre from a well-lit area and have a hard time finding somewhere to sit. But after a couple of minutes, your eyes get used to the situation and see better. This same thing occurs when you're looking at the stars in the sky. Initially, you can't see very many. Keep looking; as you dark adapt, the stars will become visible. Despite the fact that you need a few noticeable moments to begin to see in the darker conditions, you'll quickly be able to re-adapt upon your return to bright light, but then the dark adaptation process will have to begin from scratch if you go back into the dark.

This is why many people prefer not to drive at night. If you look at the headlights of an oncoming car, you may find yourself momentarily unable to see, until that car is gone and your eyes once again adjust to the night light. A helpful way to avoid this is to avoid looking right at headlights, and instead, try to allow peripheral vision to guide you.

If you're beginning to find it challenging to see at night or in the dark, schedule an appointment with your eye doctor who will confirm that your prescription is up to date, and rule out other reasons for decreased vision, such as macular degeneration or cataracts.

Welcome to Texas State Optical Katy Fry

Welcome to Texas State Optical Katy Fry

Welcome to Texas State Optical Katy Fry

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