Inside the human eye, at the back of the eyeball, is a tissue lining called the retina, which contain photoreceptors (a type of sensor nerve that can take in light) called rods and cones, and they are "wired" to the optic nerve that sends electrical signals (neuro impulses) containing that information to the brain, which gives you sight.

There are approximately 7 million cones in an eye, and they are for seeing in bright light conditions or in the daytime (photopic vision). This is how you get your high-resolution vision, and the ability to distinguish colors (red, green, and blue wavelengths). The bottom line is that with a lot of white light you can see things clearly.

There are approximately 120 million rods in the eye, and they are for seeing in low light conditions or at night (scotopic vision). The good news is that there are more rods than cones, and they are 1000 times more sensitive to light than cones. The bad news is that rods interpret the world for you in black and white only, which means less spatial acuity because things seem a bit "flat" and images tend to blend into each other. It's like watching an old black and white television screen compared to a new high-resolution color monitor. Not good in a fight.

There are two things that will always determine how you will fight:

1. Situation.

2. Environment.

So, imagine this scenario. The situation is a hostile coming straight at you, and you can't see his hands clearly. The environment you're in is a flat hard surface you're standing on, there are no objects or barriers nearby, and it's low-light conditions. Essentially, you're in the dark. So, how are you going to use the rods in your eyes to your advantage? Well, I'm going to teach you how to deal with this very situation, and its information that just may save your life one day.

Wear Shades

Have you ever wondered why police officers or combat soldiers wear sunglasses all the time? That's because a week of being exposed to direct sunlight, without wearing sunglasses, can reduce night vision by 50%. Oh sure, the night vision will come back to 100% if you stay out of direct sunlight, but it will take the same amount of time, a week, of being in darkness to accomplish that.

When buying sunglasses make sure that the lenses block 99% or 100% of UVB and UVA rays. Even when you are in the shade you get a significant amount of UV exposure. Prolonged exposure to UV rays can harm your eyesight, and these rays are linked to cataracts, macular degeneration, and other eye conditions.

From Light to Dark

Unless you've been walking around in the dark for several hours before you're attacked, which is unlikely, your eyes will not have fully adapted to the darkness (dark adaptation). It takes at least 20 to 30 minutes for your eyes to adjust to the change going from a lit area into a dimly lit area. Think of the last time you walked into a movie theater when you were late, it was dark when you walked in, and it took some time for your eyes to adjust before you could even see where the empty seats where. You just stood at the back wall waiting for your eyes to adjust. However, if you go from a dimly lit room into a bright room or outdoors, the cones in your eyes adjust to light much faster than the rods to dark. Yes, you may have to squint or put up your hand in front of your eyes for a few seconds at first, due to the sudden light saturation, but not for long.

Have you noticed in pirate movies that some pirates have an eye patch on? You'd think it was due to losing an eye in battle, which I'm sure some pirates did, but some historians believe that the eye patch was intentionally worn by navigators (those who piloted the wooden ships), who had two good eyes, so they could have optimum night vision in one eye when darkness fell, and that was because they navigated by the stars in those days. Keep in mind they didn't have sunglasses in those days.

One law enforcement and military technique, which is reminiscent of the days of the navigation eye patch, is to close and cover one eye with your cupped hand if you must go out from a low light environment to a well-lit area, and then go back into the low light environment again. Using the movie theater example again, let's say you've been waiting for your eyes to adjust, but you want to poke your head outside for a moment to see if your friend is coming with the popcorn, and to let him or her know where you are inside the theater. So that you don't completely lose your night vision, and must start the clock all over again, you cover the one eye until you are back int the low light environment. Now that you understand the technique you can do the same for other environments as well: a bar situation where you may end up going into a brightly lit restroom, going from a dark back alley to a street with streetlights, et cetera.

Above: The security agent (the female on the left) heard gun shots in the library. When she enters the room, she sees a man down on the floor, possibly injured or dead, and a person sitting in a chair facing away from her in a low light situation.

Above: The security agent, who has the suspect at gunpoint yells out, "Put your hands up! Put your hands up!" However, he just sits in the dark for a few seconds not obeying the commands.

Red Light

For military operations at night, either inside a vehicle or an aircraft, or when reading a map or the instruments on equipment out in the field, red light is used. Since the rods in the eye do not respond to red, warriors can maintain full dark-adapted vision after using red light and then immediately looking up at the low light terrain. On the other hand, if you use a regular white light flashlight, let's say shining it on something in the dark, and then look out into the darkness again, you just lost your night vision.

​Zig Zag Observation Pattern

The trick to seeing all the telltale signs of your attacker's intent, provided you have some reaction time, is not to stare directly at anything for too long. Yes, you are going to look at the attacker's eyes, for they are the "window to the soul," but only for a moment. You're going to look at the hands, because "it is the hands that kill," but only for a moment. Remember, in the dark you can't look at something the way you would when there is sufficient light, because you are only seeing a black and white image. You're missing a lot of information that you are used to when there is light. Therefore, you are deprived of key details that may contribute to your survival. To overcome this deficiency, you're going do the Zig Zag Observation Pattern:

1. Your first look at the overall threat, which is instinctive.

2. Your second look must be a zig zag pattern over the threat area, which is not instinctive. For example, a man is coming at you in a threatening manner. You see him coming at you, but to see if he has a weapon in his hand or not, you look at the hand directly for just a moment, then visually scan from side to side over and around the hand. The scientific reason for this is because your cones (what makes you see in a lit area or in the daytime) are concentrated in the fovea centralis (the inside center of your retina). In other words, at night you have a blind spot there when you are looking directly at an object (5˚ to 18˚ central). Therefore, by using your peripheral vision instead, which begins beyond 18˚ (near peripheral), and extends as far as 110˚ (far peripheral), the rods that are absent from the fovea centralis can pick up the shape and contrast of a weapon. Plus, rods also can detect motion better than cones, which means your peripheral vision is also needed to track that incoming weapon. However, another human instinct, what is known as "Tunnel Vision," makes you want to focus on the immediate threat. The only way you are going to override this tendency is with lots of good training.

Train in Low Light Environments

To train your eyes to depend more on the rods than the cones during conflict in a low light environment, you need to do a lot of realistic training in a simulated environment.

For many of the self-defense courses that I teach I manipulate the lighting. Sometimes I'll turn off half the lights in a room or all of them. This is why I'm a firm believer in making a school more like a theater stage rather than the traditional martial arts school, which are bright. I, and several of my certified Reality-Based Personal Protection instructors, have blacked out all the windows and painted the walls, ceiling, and floors flat black in our training rooms. This is to make the room as light proof as possible, and the light can be precisely controlled. Taking it a step further, if you turn on a police light bar in the corner, then you have a law enforcement scenario. Have a little night light off to the side, place a female student on the mat with a blanket over her, and you now have a rape scenario in a bedroom. Have a student walk the length of the room with a light overhead shining down through a black tube to make a spotlight, and you have an instant street crime scene at night. It can be a robber, gang attack, or any number of scenarios.

If most crimes happen at night, and in low light situations, doesn't it stand to reason that most of your training should be in a low light environment. Not only do you need muscle memory (to perform a task automatically through repetition) for your body, but also for your eyes (to rely on peripheral vision more than central vision).

So important is training at night that when I was in the police academy, we had an entire testing process called "Night Problems." When I was training to be a sniper at 1st Marine Division Scout Sniper School at Camp Pendleton, we did a lot of the shooting at night. In fact, it was from my Marine instructors where I first learned, in detail, all about the rods and cones of the eye. Therefore, if you want to make your training "reality-based" you've got to do it in low light.

Above: This is a Knife Survival course that I am teaching in Cologne, Germany. It is a Reality-Based Personal Protection training room with the ceilings, walls, and floor painted flat black. Although the mats on the floor don't make it all black, that's okay. I then turned off half of the lights in the room so that half of the students would experience a low light environment. For the next exercise I had the second group experience the same thing.

If you're not cheating, you're not trying

If you really want to see in the dark, then there is nothing better than Night Vision Goggles (NVG). This is why combat soldiers and S.W.A.T. officers wear them for various night operations. However, a military grade NVG cost over $10,000 and they are rather bulky because they are worn on the head or a helmet. You can get civilian NVG at a reasonable price (from $100 and up), but it is nowhere near the clarity of military grade. It's better than nothing, but I wouldn't want my life to depend on a civilian version.

When I was training German counterterrorist GSG9 in Sankt Augustin, Germany I had the opportunity to try out their newest NVG. It was amazing! I could see facial features perfectly at a distance, and then look down and read a newspaper just as if the lights were on. The clarity was unbelievable. Then when I took them off, everything was pitch black. It's a weird sensation. Of course, NVG are not very practical for everyday life, and it is unlikely you'll have them on you when attacked.

There is a more practical device that you may want to consider for making yourself safer at nights, and it plugs directly into the phone's Lightning connector. Plus, it's only around $300. It is the FLIR ONE Pro – iOS – Professional Grade Thermal Camera for Smartphones. It's basically a Thermal Imaging Night Vision device, and it detects heat. For example, let's say you're out camping or just looking around at night on your property, and you think that an intruder is hiding nearby in some vegetation in the dark. That's an unnerving situation. Therefore, you turn on your phone and the thermal imaging device, and a human body, which the naked eye would not be able to see if it were too dark, will stand out instantly on the screen. Yes, it would work for you walking down a dark alley, but in this situation, there's also a disadvantage. Once the attacked is launched, you were just looking at a lit screen, so a lot of your night vision for fighting is gone.

Above: This photo of me was taken only a month ago in Southern California, with a FLIR One Pro Thermal Camera for Smartphones, when I was teaching a shooting course on a live-fire pistol range. The yellow and orange colors represent different degrees of heat coming from my body, and the person on the left changing out his target. Because I am wearing a ballistic vest, which does not give off heat, the color is purple (not a heat source). Notice that my neck and face are yellow, which means nothing is blocking the emanating heat, whereas my clothes reduce the heat signature slightly. This is a great device to "see in the dark."

Taking care of your eyes

You've probably heard that carrots are good for your eyes. Well, it's true. That's because Vitamin A (all-trans-retinol) is needed for healthy rods. Vitamin A is found in carrots, broccoli, sweet potato, and it's highly concentrated in the livers of beef, pork, and fish. Of course, Vitamins C and E are good for eye health, along with zinc, zeaxanthin (found in corn, saffron, and most green plants) and omega-3 fatty acids.

If you wear contact lenses, take them out at the end of the day and let them soak in solution overnight. Never sleep with them in. Contact lenses block the flow of oxygen to the eyes.

Women who have tactical jobs should not wear make-up while on duty. Make-up can cause the pores around the eyes to become clogged, which can lead to hordeolum (bacterial infection), and it can potentially scratch the cornea.

Allergen-reducing eye drops can affect your vision because it constricts the blood flow to the cornea, which means less oxygen. Yes, the drops stop the itchiness, and eyes are no longer inflamed, but it also can result in swelling and scarring.

Prevent eye fatigue by getting enough sleep each night, limit your time on devices, and if you feel that you must rub your eyes do so only after you have washed your hands to prevent foreign contaminates from entering. Speaking of devices, phones emit light, and light shined in the eyes is not good if you need your night vision. Therefore, if you must look at your phone, prior to going into a low light high risk area, you may want to do the pirate thing – close and cup one eye so you'll at least have one eye for night vision.

BE A HARD TARGET

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