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Focusing on Night Vision



You wake from a dream in the middle of the night, or you're searching for the light switch or door in the dark. We've all found ourselves in the dark before. It takes a couple of minutes for your eyes to adjust to the dark. This process, called ''dark adaptation,'' allows us to see even when it's really dark.

Night vision requires a whole assortment of biochemical, physical and neural mechanisms - for granted. But how does this work? The retina is a layer of cells at the back of the eye. The section of the retina directly across from the pupil which produces the point of focus is called the fovea. The retina is made up of rod-shaped and cone-shaped cells. The rods are able to function even in low light conditions but they are not found in the fovea. As you may know, the cones contribute to color vision, while the rods are sensitive to light.

Considering these facts, if you want to see something in the dark, like the edge of the last stair in a dark basement, instead of looking right at it, try to use your peripheral vision. 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.

Another method by which your eye responds to darkness is by your pupils dilating. It requires fewer than sixty seconds for the pupil to fully enlarge but your eyes will keep adapting over a half hour time frame.

Here's an example of dark adaptation: if you exit a bright area and enter a dim one, for instance, walking inside after sitting in the sun. It'll always require a few moments for your eyes to adapt to normal indoor light. Then if you go back outside, those changes will disappear in a moment.

This is actually why a lot people have trouble driving their cars at night. When you look directly at the headlights of an oncoming car in traffic, you are briefly blinded, until that car is gone and your eyes once again adjust to the night light. A helpful way to prevent this sort of temporary blindness is to avoid looking right at headlights, and learn to try to allow peripheral vision to guide you.

If you're beginning to find it challenging to see at night or in the dark, call us to schedule an appointment with our doctors who will explore the reasons this might be occurring, and eliminate other and perhaps more severe causes for poor night vision, like cataracts and macular degeneration.