Goggles are helpful for keeping the cleaning chemicals that are used to keep swimming pools clean out of your eyes. Many people react to chlorine or other chemicals. They also have the added benefit of helping you see more clearly underwater. Let's take a look at why this works.
The swim goggles function is to keep water away from and out of the eye. Swim goggles also have a layer of air between the eye and the goggles plastic or glass viewing surface. It's this bit of air that is all important in making goggles work to improve your vision. If your swim goggles were leaky, for example, you would soon find the goggles become just as blurry as sticking your head under water.
How the Eye Works
The eyes are able to see clearly when they can focus the incoming light to a point that centers on the optic nerve. Those who are nearsighted or farsighted have eyes whose natural shape focuses the light in front or behind the optic nerve. This results in blurring at some distances. Most eyes will have a point where they can focus. The owner of the eye soon learns where he or she needs to be in order to provide a clear focus. Thus, we see people reading very close to their eyes or moving things far away from their eyes. When one obtains middle age, the eyes become less accommodating to bending light, and so another vision problem begins.
The eye has two parts that need to work together to focus light properly. The amount of light bending these two areas can do depends on the use of attached muscles and ligaments in the eye. In fact, the eye is always adjusting your vision to the light. Your eye muscles can become tired just like any other set of muscles can fatigue. This is why most of us cannot read or do close work for too long a time.
The eye has two set of lenses. One is on the cornea or at the front of the eye. The other is at the back of the eye. Lenses focus light in unusual ways. They always focus light to a point, but the image is always shown upside down and usually there is a size difference as well. Fortunately, it was observed many years ago when the telescope was discovered that adding a second lens to the system would correct the fault and allow the original object to be viewed correctly. Fortunately, for us, our eye does this on its own.
Fluid in the Eye
The eye also has fluid inside it. This fluid nourishes the eye and assists with focusing light. The water and the fluid in your eye are almost the same thickness. Thus, the eye is not able to bend the light coming from the water the way it is used to doing. This is why what you see in the pool is blurry. There are people, due to vision problems, can actually see better underwater than in the air. But most of us enter a blurry world underwater that many people don't enjoy.
What Goggles Can Do
Once we put on swim googles, we add a layer of air to the picture. This essentially creates a system of viewing that is the same as that above water. This returns your vision to its normal state. Of course, if you don't see well without glasses or lenses, you will in fact need prescription swim goggles to see clearly in the water. One benefit is today's prescription swim goggles are much lighter than the old glass ones were. So, if you need glasses out of the water, simply adding a pair of swim goggles won't fix all of your blurring problems.