Eye training: Where to look, and how
Where to look, and how to look are extremely important in martial arts. Every style, and every teacher has an opinion. Some use tunnel vision and focus on looking directly into the eyes. Others use peripheral vision. There are other practitioners that use both. Each approach has it’s reasons.
Those that look you in the eye, do so because they believe the eyes to be the windows to the soul. There is much truth in this. You can see their intent, sometimes before they realize it themselves. You can see if they are confident, or afraid. Some like to look into their opponents eyes, to see their pain and suffering as they destroy them. There are considerations you must take into account if this is the method used. There are Philosophical issues with this approach, but my intention is to discuss functional issues. Functionally, if you are this focused you lose awareness of your surroundings. You are susceptible to attack by outside forces. If your fighting a skilled opponent, he may be able to use his eyes to feint, fake, and otherwise deceive you. In such a case it could be a weakness your opponent can exploit in you. Looking directly and focusing increases reaction time compared to peripheral vision.
Peripheral vision is used by many. Some will use unfocused eyes and generally look at the chest, or another body part, others will look off to the side. Using different head positions, and postures, you can increase your peripheral vision from 180 degrees, to virtually 360 degrees around yourself. Using it lets you see without looking. It also lets you be more aware of your surroundings. Another reason to use peripheral vision is that reaction time is quicker then tunnel vision. To understand why, you need to understand a bit of how the eye works. The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their distinct shapes. Cones are concentrated in the center of the retina, in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details. Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night. Since we want to move on motion, we want the information from the rods, without also having to process extra information from the cones, slowing down our reaction time.
I once heard a taiji master explain that in the classics when they say to look left, and gaze right they are referring to tunnel vision, and peripheral vision. In other words they use both, as do many others. I certainly think you need to use both. Specifically you need to know when and how to use each.