Explaining eye dominance

by Linda K. Miller & Keith A. Cunningham | December 19, 2023

We are often asked two questions. First, should I shoot with both eyes open? Second, why does my sight picture get blurry? It turns out, the answers to these questions can be related.

Eye dominance

One of the main reasons people often close one eye when shooting is eye dominance. The dominant eye wants to deliver an image to your brain, and if you aim with the other eye, there’ll be a conflict of images.

For example, a right-handed shooter who is right-eye dominant has no trouble. You’ll bring the rifle to your right shoulder and the rifle sight will be aligned with your dominant eye. You can likely keep both eyes open and still see a clear image through your scope.

However, a right-handed shooter who is left- eye dominant may not be able to easily acquire the image through the sight. In this case, you’ll want to close your left eye to force the right eye to align with your scope. This so-called “cross dominance” is common, about 25% of the population.

The same is true of left-handed shooters who’ve gone to the trouble of getting a left-handed rifle…if you’re left eye dominant, no problem. If you’re cross dominant, you may have to close one eye to make the other take over.

So what’s the problem

The eyes are made to work together. When they are both open, the pupils dilate to accommodate the available light. If you close one eye, it’s kind of dark in there behind the eyelid, so the pupil dilates to let in more light. And the pupils are made to work together, so the other pupil dilates as well…and if it gets too much light, you’ll have a blurry image.

So, if you must close an eye, do so for only the shortest time it takes to shoot a good shot. And if your vision blurs, relax your eyes. The best thing is to look at shady grass one to two metres away. (Competition shooters keep their non-aiming eye open while occluding the image with a well- positioned piece of translucent plastic.)

My dominance is fine…why do I still get a blurry image?

Shooters are very fussy about their vision. While sugar, some drugs, and some health conditions can cause vision problems (and it’s worth having your doctor check into it), two common causes of temporary blurry vision are eye fatigue and dehydration.

Eye fatigue is common among target shooters. Little muscles control the lenses in the eyes, and they can tire. If they won’t contract enough to focus for the distance you’re trying to see, you can get a blurry image.

Dehydration is also common among target shooters and hunters. If your body is dehydrated, the aqueous film on your eyes can be too dry, which can result in blurry vision. If you’re severely dehydrated, your blood pressure can drop below normal levels and one of symptoms can be blurry vision.

So, stay healthy, stay hydrated, and when your eyes tire, let them rest.

Originally published in the Nov.-Dec. 2022 issue of Ontario OUT of DOORS

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