Perhaps you recall hearing about "ocular dominance" or a person's "dominant eye," but remain uncertain about what these terms really mean. It could be that you are interested in performing a test to determine your own dominant eye. If so, the paragraphs that follow can fill in the gaps.
What Is The Dominant Eye?
The dominant eye is simply that which sends a slightly better quality of information to the visual processing portion of the brain and transmits details of the true location of discrete objects with greater accuracy.
Generally speaking, this terminology is employed when discussing the typical visual function in which both eyes function properly and in tandem, rendering essentially the same visual acuity, but where one of the eyes takes the role of "preferred" or "leading" eye.
Testing For The Dominant Eye
There is a straightforward test that can be used to ascertain which is the dominant eye:
- First, extend the arms outward, producing a triangular shape between the forefingers and thumbs. The hands simply need to be placed together at an angle of 45 degrees.
- Keeping both eyes in an open position, center the triangle on an object that is some distance away. This could be a door handle or perhaps a clock on the wall.
- Shut the left eye fully.
- If the chosen object remains centered, the open right eye can be declared the dominant eye. However, if the object no longer remains within the triangle created with the hands, the left eye is dominant.
An alternative test for the dominant eye is as follows:
- Extend one of the arms outward, keeping the thumb on the extended hand upright. It is also possible to use that hand's index finger.
- With both eyes still open and intentionally focusing on an object in the distance, the thumb should be superimposed onto it. If the thumb seems to partially disappear, this is okay.
- Close only one of the eyes at a time.
- The dominant eye is the one in which the thumb appears to remain directly in front of the chosen object during the period the other eye stays closed.
Each of these testing procedures represents a "sighting" test, as they both require the subject to align a makeshift device with a visual target. This is akin to the sight of a rifle.
There has been research to suggest that these types of dominant eye tests are essentially accurate and simple to conduct, but can be impacted by non-visual circumstances and handedness.
In order to mitigate the effects of such factors, some believe that non-sighting tests are more effective in determining ocular dominance and are therefore preferable.
These tests require the subject to keep both right and left eyes open. Visual stimuli will then be put before each of the eyes in turn, utilizing specialized devices for that purpose. The use of such tools is indicative of the natural limitations of non-sighting types of tests. Equipment of this type tends to be available mainly in clinical or research settings.
Ultimately, however, simplified eye tests such as those initially described are sufficient to determine which is the dominant eye.