Information contained within this article will give firearm instructors and marksmanship students a better understanding of how vision significantly contributes to shooting ability and success.
Appreciating the dominant role vision plays in directing and monitoring most of the skills used during shooting will prove useful in updating training methodology. The ultimate result of incorporating useful scientific models and research into a training curriculum should result in shooting performance enhancement.
A comprehensive definition of vision goes beyond the classic 20/20 sight definition. A limited concept of vision is often defined as the ability to see a sharp, clear, 20/20 or better visual acuity image. However, defining vision as a dynamic, learned process of deriving meaning and directing action from light energy establishes a scientific model to better appreciate the importance of vision for accurate and safe shooting.
Visual skills provide intelligent information to shooters concerning where targets are located, what details and characteristics constitute the target, as well as target speed and direction of movement. This type of spatial, temporal and labeling information is used to make a decision whether or not to coordinate a response to shoot the target. Understanding how visual abilities dominate the process of shooting targets accurately and quickly will provide a framework to improve firearms instruction.
An overview of the basic anatomy and physiology of how the eye responds to light to begin the visual process establishes a framework of reference. The amount and intensity of light entering the eye dictates what neurological information is sent via the optic nerve to the brain for processing and interpretation. Generally, basic vision function is divided into three levels of light intensity; daylight (photopic), twilight (mesopic) and low light, night (scotopic) vision function.
Photopic vision functions during bright light levels. Specific neuroreceptors called cones dominate the eye’s response to bright levels of light. The inner photosensitive part of the eye, called the retina, has approximately 7 million cones. Cones are concentrated in the area of the retina that corresponds to straight ahead vision. This anatomical area of the retina is called the macula, and within the macula is a depression called the fovea consisting almost entirely of cones. Cones convert light energy into neural energy sending information via the optic nerve to the brain. Reflected light from targets stimulates cones to send information to the brain about forms, shapes, textures, colors and high contrast sensitivity detection of various line forms. This information is then combined and analyzed by the brain to form an impression of the target.
From a practical perspective, only in daylight vision can very precise detail and color of a target be seen. Also, precise 3-D depth perception (stereopsis) is only possible during cone-dominated daylight viewing conditions. The highest degree of depth perception occurs when the central, straight ahead fixation point in each eye sends information to the brain in a highly coordinated fashion. During low light conditions, the cones are unable to send precise signals for the brain to process depth.
Daylight vision enables the eyes to maintain the highest degree and control of eye fixation, the ability to maintain steady and accurate eye position upon a stationary target. Also, the ability to follow a moving target (called pursuit eye movements) functions optimally during photopic viewing conditions. A different type of eye movement of looking from one separated target to another target to another target, etc. (called saccadic eye movements) function much better during bright light conditions than during low light conditions. The voluntary act of allowing the extraocular muscles of the eye to position the eye such that images fall on the retina where cone density is highest is an important component of establishing visual attention on targets.
The ability to maintain accurate focus (accommodation) on a target requires sufficient light to activate the eye focusing system. The accommodative response functions most efficiently when the target reflects sufficient light to stimulate accurate eye focus. Cones have the best ability to receive the refracted light that the lens inside the eye alters during the act of focusing clearly on a target. When light diminishes, the cone function is suppressed and the quality of the eye focusing ability declines.
Once bright light declines and darkness emerges, there is a period of light transition (seen during dusk) defined as mesopia. During mesopia there is a shift from cone domination of vision to rod domination of vision. However, during mesopic vision, both rods and cones are partially active. The 120 millions rods are located throughout the entire peripheral retina. The main functions of rods are to send visual information to the brain about movement detection, organizing spatial orientation of where targets may be located in space, and responding to low levels of light that may be present in the environment. During mesopia there is a gradual loss of color perception, gradual loss of discerning target detail, gradual loss of the ability to maintain accurate eye focus upon target, contrast sensitivity losses, and a diminishing ability to maintain accurate three dimensional depth perception. From a practical viewpoint, mesopia is complete when color perception is eliminated, and at this point, the visual system begins to function in scotopia.
When light levels fall into darkness, the human eye functions in a state of scotopia. Rod physiology does not allow for color vision nor the ability to discern detail. It is estimated that the best visual acuity during scotopia is 20/200. When you change from day vision to darkness immediately (e.g. entering a dark room during the day), the dark adaptation of cones is complete in five minutes, while full rod adaptation takes about 30 minutes. However, rods are more sensitive than cones at the seven-minute mark. Complete dark adaptation requires about 30 minutes for the rods to reach their highest level of sensitivity while in darkness.
The ability to maintain accurate eye focus upon a target is greatly reduced during scotopic vision function. Other important visual changes that accompany scotopic vision include increased awareness of peripheral light and movement, increased pupil size resulting in less depth of field, reduction in contrast sensitivity, loss of texture perspective, altered target search strategies and variability of eye focus control increases. It follows that detection of the fine details of an object of attention is greatly reduced. Unless there is added light source directed at a target, the human visual system is unable to judge accurately target characteristics such as size, shape, contour, texture and color.
Above and beyond the basic visual functions that are operational at various lighting conditions, there are specific visual changes that occur when a shooter is threatened by a dangerous situation. The Body Alarm Reaction (BAR) is the body’s response to an unexpected and sudden change in the environment, most commonly initiated during the early stages of a life threatening attack. The BAR is often associated with combat or violent encounters. The most immediate visual change in response to the BAR is that the eye focusing system (accommodation) loses it ability to maintain clear focus on targets at close distances. It is not possible during the first few seconds after entering into the BAR to clearly focus upon the front sights of a gun. A shooter’s visual focusing and attention is drawn to focus toward far distant viewing, toward infinity. This focusing change toward far distant focus is a direct result of the change from parasympathetic nervous system control to sympathetic nervous system control. This shift in the autonomic nervous system balance is responsible for changing how the crystalline lens inside the eye changes it shape and optical power. During the immediate stages of the BAR, the lens becomes less convex in shape and this results in an optical shift of focus resulting in clear focus only while viewing distant targets.
The autonomic nervous system has two major branches; the parasympathetic and sympathetic branches. Generally speaking, the sympathetic nervous system prepares the body for direct action and confrontation by increasing heart pulse rate and bringing blood supply to large muscle groups. Also, eye pupil diameter increases, and the ciliary muscle relaxes, forcing a shooter to focus the eyes at far distances, perhaps to be behaviorally better prepared for a perceived oncoming threat. There is a slight bulging of the eyes associated with sympathetic nervous system dominance.
The parasympathetic nervous system allows you to maintain a more relaxed, balanced state of readiness by slowing an accelerated heart rate, decreasing pupil size, and allowing the eye’s accommodative system to focus at increasingly close distances of up to inches from your eyes. The parasympathetic nervous system aims to bring neural physiology back to a state of balance or relative homeostasis.
When the BAR is activated, along with the neural changes, there are hormonal and other biochemical channels activated concurrently by a part of the brain called the hypothalamus. These chemical mediators are useful in helping maintain the influence of the autonomic nervous system response by either encouraging the body to stay in ‘high alert’ or by reversing this high intensity response to strong stimuli and resume a more normal relaxed controlled state of neural balance. However, during the early stages of the BAR, adrenalin is released in the body to further enhance the excitatory component of the BAR. (see flow chart)
It is important to remember that the sympathetic nervous system can exert its neural messengers either in a focal manner (through secretion of noradrenalin or norepinephrine) at local end organs (as is the case at the ciliary muscle of the eye’s focusing system), or through releasing noradrenalin or norepinephrine directly into the bloodstream to prepare the body for combat.
It is worthwhile to note that during the BAR there are a series of other biochemical and hormonal changes that are activated throughout the body. One example is that the adrenal glands secrete a group of hormones called glucocorticoids. Cortisol is the most prevalent of these hormones. Cortisol increases blood sugar levels to contribute energy for muscle function. Research has also correlated decreased learning and decreased memory function, as well as attention anomalies with increased cortisol levels in the body. These changes in response to cortisol levels increasing during the BAR help explain, in part, why visual memory and visual attention is narrowed during the BAR. These types of physiological changes that accompany the BAR begin to explain the perceptual changes called “tunnel vision” and “perceptual narrowing”. Humans have an innate tendency to narrow attention upon a threat during extreme stress. It can be argued that learning how to expand peripheral awareness of space can minimize the effects of “tunnel vision” during the BAR. Other strategies to overcome the tunneling effects of perceptual narrowing will be outlined in the visual training section of this bulletin.
From a behavioral perspective, Dr. A. M. Skeffington, the father of behavioral optometry, theorized that during stress, the human ability to center on a task and identify and maintain meaningful awareness on a specific target is severely hampered. BAR type of stress causes a decline in your ability to derive meaning from your visual memory image due to a perceptual narrowing that accompanies the breakdown of optimal human performance. His theory postulated in the 1940s has gained strength and understanding during the last half century as much current neurological and psychological research has proven the bulk of his intuitive understanding of human responses to stress.
Other behavioral and performance changes have been reported to be associated with “perceptual narrowing”. The theory of perceptual narrowing suggests that as the level of demand increases on a central, straight ahead target, there will be a corresponding decrease in the visual area surrounding the central area from which peripheral information can be extracted. Increased arousal causes increased narrowing of the attentional focus, with a progressive elimination of input from the more peripheral aspects of the visual field. Another way of viewing “tunnel vision” is that as stress increases, there is a reduction of cues used to regulate performance. When stress levels are further increased, there is a further restriction in the range of visual cues used to sample visual space. Under stress, the useful field of view shrinks, and the amount of processing of visual information is narrowed.
A summary of behavioral changes that are associated with high levels of stress, such as seen during the BAR, include;
1. Narrowing of attention span and range of perceived alternatives
2. Reduction in problem-solving capabilities
3. Oversight of long-term consequences
4. Inefficiency in information search strategies
5. Difficulties in maintaining attention to fine detail discrimination
6. With intense fear, there is also temporary loss of fine visual-motor (e.g. eye-hand) coordination
With the possibility of some of the above mentioned changes affecting shooter’s during high stress encounters, it follows that a person involved in a combat situation may have difficulty accurately recording and remembering all the details of an encounter. During the active stages of the BAR, it may be quite difficult to recall with high accuracy and detail the events that just occurred during a shooting exchange. However, once the high stress has been relieved and a shooter returns to a state of more controlled relaxation, there may be recall of more visual images related to a specific previous combat situation.
Contemporary visual research describes a parallel, dual processing visual system that is useful to further understand the complex nature of how visual information travels from the retina to the brain. One pathway (M-pathway) is more sensitive to coarse visual forms and images that move quickly. The other pathway (P-pathway) is more sensitive to fine spatial details of forms that are stationary or move at very slow rates.
It appears that the P-pathway processing visual information that is dominated by central, detailed labeling of information, whereas the M-pathway processes information dominated by peripheral vision awareness of movement, orientation and location of visual images. It may be that these pathways work in a synchronous manner to efficiently process visual information. Under high stress there seems to be an imbalance between the P and M pathways such that one pathway overrides the other. “Tunnel vision” appears to be related to P-pathway dominance and M-pathway inhibition during the BAR.
There are certain visual attributes that relate to object visibility that help shooters better understand why certain targets are easier to see that other targets. For example, size of a target is related to visibility because relatively larger image sizes have the potential to stimulate more retinal cells resulting in more information sent to the visual areas of the brain for processing. This increases the chances of a more accurate visual interpretation of the details of the target of interest.
Contrast of a target is a critical variable directly related to ease of visibility. Contrast corresponds to the ability to discriminate a dark visual image from a lighter visual image within a total visual surround. In general terms, contrast is the relationship between the lighting intensity of two adjacent areas. A dark target, approaching black (having no reflected light) is most easily seen next to a white (reflecting all light) background. Shades of gray that have similar light reflective intensities are most difficult to visually discriminate and separate because the contrast values are most similar. Shading differences, reflective light patterns and texture gradients are learned behaviors that improve a shooter’s ability to recognize contrast.
Colors of objects have a direct influence on visibility in daylight (photopic) conditions. In low light (scotopic) conditions, color has no influence on visibility of a target because rod cell physiology operates during scotopic conditions and rod cells do not have color discrimination ability. The colors white and yellow have the highest visibility potential, followed by orange, red, green and blue. Since white reflects all wavelengths of light visible to the human eye, white is highly visible during daylight conditions.
Another visual attribute related to color and contrast is brightness (luminance) of a target. When light falls upon a target, it is absorbed or reflected. The light reflected by a target is what the eye senses if the light is of sufficient intensity to stimulate the cones and rods. Materials that reflect or radiate the highest amount of light are most easily seen by the human visual system. Brightness is a shooter’s subjective appreciation of the intensity of light entering the eye. However, glare, an excessive amount of light that serves no purpose, can be counterproductive to ease of visibility.
Although movement of a target improves the ability to detect a figure from its surroundings, at the same time, as speed of a target increases, the ability to distinguish details of the target decreases. It follows that once you fixate upon a target, the chances of engaging and discerning details of the target with precise eye-hand-mind coordination improves as the target speed slows towards becoming stationary. Fixation control is the ability to maintain steady and accurate eye position upon a stationary target. Many visual factors influence improved fixation control such as high contrast of target, color and size of target, as well as flexible eye focusing skills. Fixation control begins to deteriorate after a few seconds of steady fixation because the eye has an innate tendency to continually scan and move to change retinal areas of stimulation. Also, the ability to follow a moving target (pursuit movements) uses other neurological controls than do fixation control. Pursuit movements, as well as fixation control, improve as the quality of the target’s contrast and brightness increases.
The following visual skills are important for shooter speed and accuracy of aim;
A. Visual acuity: Both static (discerning detail of a stationary target) and dynamic visual acuity (discerning detail of a moving target) is important to a marksman. Good dynamic acuity will enhance a shooter’s visual reaction time and eye tracking abilities.
B. Peripheral vision: Skillful shooters have reported a visual ability of maintaining an awareness of a central target while simultaneously maintaining a vast amount of peripheral visual awareness. A fully functioning visual system is capable of responding to objects located within a total visual field (which for each eye is approximately 40 degrees up, 60 degrees toward the nose, 70 degrees down and 90 degrees towards the temple measured from a central point of fixation). It is critical that shooters are aware of what is beyond and around the target to insure safety, and peripheral vision awareness is crucial to achieve this task.
C. Depth perception: An essential skill for the shooter who needs to judge relative distances between targets.
D. Eye motility: Eye tracking abilities are crucial to maintain accurate detail and awareness of any moving target. This skill is highly critical if a marksman needs to shoot a moving target.
E. Eye-hand-body-mind coordination: A necessary set of visual coordinated abilities that are used in developing precise trigger control while maintaining precise aim on target.
F. Visualization: The ability to use your “mind’s eye” to create a mental visual picture when direct view of a target may not be possible. This highly developed visual skill is useful to anticipate where a target or adversary is most likely to be located during episodes of lack of direct vision.
G. Speed of recognition time: Extremely important when a target may be only visible for a brief moment in time. The ability to accurately recognize as much of a target in as little as 0.01 seconds can be critical in deciding to shoot, or not shoot, a target.
H. Eye focusing flexibility: This ability plays an extremely important part of a shooter’s ability to quickly adjust focus upon targets that are located in different distances in space. The speed and flexibility of quickly changing eye focus from one point in space to another point in space has a direct influence on maintaining clear, single binocular vision while in shooting competition or in combat.
I. Color perception: May prove to be a useful skill when confronted with the need to engage targets of specific coloring.
J. Fixation ability: Necessary to establish ‘sight picture’ awareness and consistency.
K. Visual memory: Used to embed the learning elements of training to help skills reach the point of automaticity. Training to the point of automaticity implies that the speed of processing and performing a set of skills is fast, there is a relative lack of effort to perform a skill, and the skill is autonomous such that it may be initiated and run completely on its own without an active voluntary conscious thought process. The automaticity realization of shooting skills is useful in avoiding visual perceptual overload resulting in confusion in target recognition.
L. Central-peripheral awareness: The ability to have awareness of central details of a target and simultaneously be aware of the visual space surrounding the target (the peripheral space around the target). This skill helps a shooter avoid getting locked into “tunnel vision” for extended periods of time.
What is exciting to report to shooters concerning the above mentioned visual skills is that most all the skills (except for color vision) have a learned component involved in the acquisition of the skill, and this learned component can be trained to improve. Not only are there testing procedures to determine how well these skills have developed and how efficiently they function, but there is emerging a growing body of visual training techniques which may enhance performance in the visual skills important for shooting. Sports visual training is the optometric art and science of fine tuning and enhancing visual skills and abilities. Sports vision practitioners are designing exercises and learning opportunities to enhance and fine tune visual skills used during shooting.
Why are some shooters able to maintain visual-motor (eye-hand) accuracy despite high arousal, as seen during the BAR, leading to lower visual focusing control? There are various models to help explain this paradoxically confusing relationship of visually monitored marksmanship control during the BAR. The one consistent thread that is part of most explanations is professional, comprehensive firearms sports training, and knowing when and how to implement this training with confidence. Current neurobiological biofeedback research has clearly demonstrated that humans can be trained to control certain autonomic nervous system functions. This implies that with proper training, particularly under stressful conditions, a well established image of proper visual spatial alignment can be maintained as a consistent eye-hand-body-mind coordinate system. Shooters that can maintain sufficient and efficient eye-hand-body-mind coordination control and adequate visual attention during the BAR will be capable of accurate marksmanship during high combat stress. It is becoming increasingly evident that you can learn to “visualize” a visual image even without having direct accommodation (direct focus) on the object of regard. The ability to visualize and develop improved eye-hand-body-mind coordination skills can be trained using a variety of visual training techniques.
An example of a sports visual training exercise is ‘flash recognition training’. This type of training is designed to improve a shooter’s ability in the areas of speed of visual recognition time and short term visual memory. The goal of this technique is to accurately perceive and retain visual information in increasingly shorter and shorter periods of time. One behavioral outcome of this type of training may be increased visual attention to increasingly complex visual stimuli.
During World War II optometrists used flash recognition training to teach U.S. Navy Pilots airplane recognition. This training reinforced optimal “visual posturing” (includes the posture of every body part whose adjustment affects vision) adjustments the pilots made to improve their visual perception of targets.
A 1995 research report discussed a three month visual training program conducted with the Catalan Government Special Intervention Squad at the Olympic Training Center in Spain. Pre-test and post-test results were compared for pistol shooting performance and visual function. Statistical analysis revealed significant gains in visual function and pistol shooting scores after the visual training program.
Another example of visual training is biofeedback training. Using an instrument that allows you feedback as the relative stimulation or relaxation of the eye focusing muscle (ciliary muscle) can exert a carry over effect during intense shooting competition. A learned behavior of voluntarily stimulating a positive accommodation (parasympathetic response) during the BAR can act as a counter force to the negative accommodation response to the sympathetic nervous system stimulation during the BAR.
Sports vision training has developed effective exercises to enhance and fine- tune depth perception, eye motility and movement speed and accuracy, eye-hand-body coordination, visualization, speed and flexibility of eye focus and visual memory skills. More information concerning visual training for shooters, and practitioners that offer these services, is available by contacting organizations listed below.