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September 5, 2017
Ocular dominance (also called eye preference) refers to visual preference in one eye over the other. Most people are unaware they favor one eye for visual input. The brain processes and builds images using slightly different views from the right or left eye. Most people tend to have a dominant eye so that even when both eyes are open, one is processing visual input more than the other. A common question is whether eye dominance and handedness (being right-handed or left-handed) are connected. Although they are not linked scientifically, population studies indicate about 90% of people are right-handed, and of those, 67% are right-eye dominant. Despite these odds, handedness alone is not an accurate predictor of eye dominance.
Rosenbach is credited with being the first author to refer to eye dominance in a German publication, back in 1903. He claimed most individuals have a dominant eye, even when the vision of both eyes is equal. He discovered an inter-ocular difference in vision, meaning the eye with the better vision is not necessarily the dominant eye. This concept has been confirmed in more recent research by Jonathan Pointer, who also showed an individual’s handedness is not predictive of eye dominance. The work of Nobel Prize winners David Hubel and Torsten Wiesel greatly expanded scientific knowledge of visual processing.
Knowing which eye is dominant is useful in sports such as shooting, archery, bow-hunting, darts, baseball, golf, cricket, and basketball. Knowing which eye dominates can help an athlete achieve better head and eye positioning while hitting a baseball or shooting a basket. For example in archery, if you are right-eye dominant, you draw the string with your right hand. If you are left-eye dominant, you draw with your left hand. Shooting a bow that is the reverse of your eye dominance can be frustrating. Let’s say you begin shooting archery as a right-eye shooter, but you are left-eye dominant. Aiming is harder than it should be and you’ll notice the tendency to turn your head to see out of your left eye.
Knowing which eye is dominant has other practical applications. It is important in cataract, refractive, and laser eye surgery, as well as contact lens wear. In a ‘monovision’ approach, the dominant eye is typically corrected for distance and the other eye for near vision. Sight in the dominant eye is less easily suppressed by the relatively blurred image in the non-dominant eye. Interestingly, the dominant eye also matters to clinicians who use monocular instruments such as the microscope and ophthalmoscope. It also applies to photography because using the dominant eye to look through the viewfinder has obvious benefits on focus and composition.
Patching is the standard therapy for children with amblyopia (lazy eye), in which the “good” eye is patched to improve vision in the weaker eye. This approach harkens back to the concept of cortical plasticity corroborated in experiments on the kitten deprived of vision in one eye, and it also works in adults. Ample evidence shows the adult brain retains a degree of neural plasticity. In terms of the visual cortex, this has been confirmed in studies on perceptual learning, noninvasive brain stimulation, and short-term monocular deprivation.
1. Extend arms in front of you and create a triangular opening between your thumbs and forefingers by placing your hands together at a 45-degree angle. Keep both eyes open and center the triangular opening on a distant object (e.g. wall clock), at least 10 to 20 feet away. Close your left eye. If the object stayed centered with your right eye open, the left eye is your dominant eye. If the object moved outside the triangle, your left eye is dominant.
2. Make a circle with your thumb and first finger. Keep both eyes open and look at an object on the wall or in the distance, centering it inside the circle. If one eye is dominant, the object should have moved outside the circle. If the object seemed to move when you closed your left eye, then you have left eye dominance. If the object moved more when your right eye was closed, the right eye is dominant.
Some studies have suggested sighting dominant eye tests (like those above) are impacted by handedness and other non-visual factors. Non-sighting dominant eye tests may be a more accurate way to determine ocular dominance. In a non-sighting test, the subject keeps both eyes open while visual stimuli are presented to each eye separately with the use of special optical devices. The downside is these tests generally require equipment and expertise available only in specialized vision clinics.
Some people may discover during a sighting test that the visual target is not perfectly aligned with the triangular opening between their hands or thumb with either eye. If the sighting test isn’t obvious, mixed ocular dominance (also called alternating ocular dominance) is a possibility. This means one eye is dominant for certain functions or tasks, while the other eye is dominant for other functions. Moreover, ocular dominance exists in different degrees – from minor to extreme. Some experts believe the concept of having a single, unchanging dominant eye may be flawed. Nevertheless, determining your ocular dominance is simple and may change how you approach certain activities.