If you wear glasses, you need to choose binoculars with a long eye-relief (over 15mm) to get a full field of view (if you want to know more about eye-relief, please see this article: Glossary Of Binoculars: Eye Relief).
At times, however, eyeglass wearers might want to use binoculars without their glasses for the following reasons.
First, the reflections from your glasses can be annoying. Secondly, external light can negatively influence contrast. Finally, oils on the rubber eyecups (fold-up/down type) can leave marks on your glasses especially if you share your binoculars with non-eyeglass wearers.
So, in this article, I will answer the question; ”Can nearsighted people see clearly with binoculars?”
Can nearsighted people use binoculars?
I’m sometimes asked, “Can nearsighted people see clearly with binoculars?” Before I had LASIK surgery, I wore glasses because of my poor eyesight.
In those days, I gave up using binoculars with my naked eyes because I couldn’t focus on objects in the infinity range. I’ll explain why this happened.
Most binoculars are optimized for people with 20/20 (normal) vision. (20/20 means you can see clearly at 20 feet what should be seen clearly at 20 feet.)
With binoculars, those with normal vision can focus on objects in the infinity range. They can also focus on the “beyond infinity” range. The closest focus distance is usually around 2.5m, depending on the specifications.
A person with 20/40 vision still can use most binoculars although the range beyond infinity is more limited. The closest focusing distance also becomes shorter.
Then, what would happen if a person with 20/120 vision looks through the same binoculars?
In this case, they cannot focus on infinity as their focusing range runs out. On the other hand, the closest focusing distance gets much shorter.
If you are still confused, here is a flowchart for nearsightedness.
Basically, a nearsighted person can see objects clearly through binoculars as long as the focusing range covers infinity. Otherwise, you need to use your glasses or contact lenses together with the binoculars.
What does “diopter” mean?
It is useful to know what your diopters are to determine whether or not a particular pair of binoculars will cover your vision. Diopters can be calculated as follows:
If you can see an object clearly at 50cm away but no further, your diopter is as follows:
So, your diopter is written as “-2D”.
The focal range of most binoculars is within ±2.5～4.0D. I suggest that you check the specifications carefully to see if your vision is within the range of that particular pair.
- You may ask, “What if I have astigmatism?”
If you have astigmatism, you should wear glasses or contact lenses when using binoculars. For eyeglass wearers, this article “How To Choose Binoculars For Glass Wearers” is helpful.
Magnification varies slightly depending on your vision.
Interestingly, magnification varies slightly depending on your vision, which is not widely known. Magnification is a little higher for nearsighted people and a little lower if you are farsighted.
It’s easier to understand if you think of your eyes as convex or concave lenses.
A nearsighted person has virtual convex lenses in their eyes, which will make magnification slightly higher. In contrast, farsighted people have virtual concave lenses, which make the magnification a little lower.
The lenses in our eyes affect what we see in various ways. For nearsighted people, the infinity range of binoculars might be out of focus. It depends on your vision, so you should check your diopters and the focusing range of the binoculars you want.
Those who have astigmatism should wear glasses or contact lenses to get a sharp image with binoculars.
Magnification varies depending on your vision: magnification becomes slightly higher for nearsighted people. In contrast, magnification is a little lower for farsighted people.