Most of the time, we don't notice which eye is our dominant one because when we use both eyes to look at something, our brain combines the information from each eye to create a single, unified image. This means that we're not aware that we're seeing two separate images at the same time.
Sighting dominance becomes even more critical when considering information that is not directly in front of us, but rather to the sides of our visual field. Each eye has an independent visual field of about 155 degrees. When we look straight ahead, the area immediately in front of us, between 60deg to the right and left of the center, is covered by both eyes. This overlap of vision allows us to perceive depth, as objects in this area are viewed at slightly different angles by each eye. However, there is a range of about 30 to 40 degrees on the periphery (between 60-95 degrees eccentricity) that is only observed by each eye separately. In cases of strong eye dominance, the peripheral area covered by the stronger eye may be prioritized. In extreme cases, information from the non-sighting-dominant eye is ignored. These areas are illustrated in the video.
The animation illustrates the greater significance of the information received by our dominant eye, compared to our non-dominant eye. This is represented by the respective length of the arrows. It's interesting to observe how the resulting combined view, known as the binocular view, is affected by the weighting of the information from each eye. In fact, the field of view is slightly more extended on the side of the dominant eye
Identifying which eye is the sighting-dominant one is crucial for a range of activities. In cases where there is a significant imbalance in dominance, visual information from the periphery of the weaker eye may not be easily accessible. However, even in cases where the dominance is not extreme, it can still have significant implications, particularly in activities that require good eye-hand coordination and sports that rely on it, such as archery, golf, shooting, and baseball. These and other sports require precision and coordination between the eyes and hands.
There are cases when one eye is more dominant than the other due to simple reasons. For instance, one eye may have poorer visual acuity than the other. In such cases, the brain compensates by relying more heavily on the information arriving at the eye with better acuity, making it more dominant over time. A study by
Griffiths and colleagues (2003) reports the case of an elite archer who experienced a change in eye dominance due to aging and loss of acuity in one eye, resulting in the archer shooting less accurately and hitting the target farther away from the center, though still with highly clustered shots.
However, in many ordinary situations, both eyes have the same acuity, meaning that they can focus equally well on objects. Yet, one eye is still more dominant than the other. In such cases, the dominance is determined by how the brain processes the information received by each eye.
Griffiths, G. W. (2003). Eye dominance in sport: a comparative study.
Optometry today,
43, 16-20.
Measuring Sighting eye dominance
For those with good vision or corrective lenses, identifying the dominant sighting eye can be done through a simple test. One such test is called the Porta test. To perform this test, extend your arm in front of your face and hold your thumb upright while focusing on a distant object with both eyes open. Close one eye at a time, and the eye that keeps your thumb in front of the object is the dominant eye. Another test involves forming a small hole with your hands and viewing a distant object through that hole with both eyes open. Close one eye at a time and note if the object remains in the hole or shifts to the side. If it stays in the hole, you are viewing it with the dominant eye, but if it moves to the side, you are using the non-dominant eye.
