Looks like this could be a much more complicated topic than I thought. Banks, M.S., Ghose, T.,and Hillis, J. (2004).
Relative image size, not eye position, determines eye dominance switches. http://www.sciencedirect.com/science/article/pii/S0042698903006424
Found that … “When eye position and relative image size were varied independently, there was no consistent effect of eye position. Relative image size appears to be the sole determinant of the switch.”
After thinking about all these findings I now wonder of what use is the idea of a dominant eye as a general term (this idea is expanded on in my next post). Apparently one eye dominates in visual image processing. However which eye dominates depends upon the situation. Apparently, while we have a ”preferred” way to look at the world, our need to view things stereoscopically requires a shift in eye dominance for the best picture and is partially determined by the situation. This means that exact amount of eye dominance is only of use in specific situations. Thus a basketball players preferred eye dominance is of little use because the player is constantly and rapidly moving around the court. Tennis players and basketball players probably should not intentionally use a dominant eye preference to learn to play or shoot well because their visual demands change rapidly.
I think that for pool players this shift in dominance takes on a different meaning. Unlike the aforementioned, we do shoot from a static position. The eye dominance in this situation has historically been thought to be the same. However, as the distance to the object ball changes and the size of the object on the retina changes, eye dominance can actually switch. Banks et al worked with a 40 degree off azimuth angle and distances from 23 to 90 inches. They found that eye dominance changed and even switched over these distances. This is an interesting finding for pool players as these are related to the distances we often use.
The conclusion is that eye dominance changes as a function of distance to the target because the image size changes. While it may feel comfortable to place the cue under some predetermined position relative to the eyes, the eyes will shift dominance as demanded by the retinal image.
When the player begins with the cue closer to the right eye as a part of their PSR, eye dominance will shift as needed for the size of the target viewed. In some cases (?) the opposite eye may become dominant. This means that there is more work for the brain to do because the eye is in the wrong place for this situation.
This possible shift in eye dominance can be determined by using the Miles test over at least two distances. To conduct the test a hole was punched in a 5 X 7” sheet of paper with a pencil. Two pencils we placed on a flat surface. One pencil was about four feet away. The other pencil was about 12 feet away. I sat in one chair and used the back of a second chair as an arm rest. I held the paper rested on the second chair at arms length and then sighted the pencil tips through the hole cut in the paper.
When my face was squared to the paper and I sighted both pencil tips I found that ocular dominance did not change. I am right eye dominant and both targets looked about the same.
When I turned my face at about a 40 degree angle to the paper and sighted both objects there was a shift in dominance that is generally consistent with Banks et al findings. Eye dominance did not switch but it was different.
Many more replications by other people are needed. I shoot with the cue stick centered between my eyes and the pool table visual simulation had the least amount of change when I sighted in my usual way. When I changed my face placement to favor the right eye the ocular dominance appeared to change over distance.
I cannot know if this change is do to a change in my usual way of sighting or as result of a changed perspective. More tests with different people are needed.
It would appear that however one places a cue stick under their eyes it is probably important to be consistent. Banks et al concludes that distance and the subsequent target size does has some effect on ocular dominance when there are changes in viewing angle. My N of one study supports this finding. Though I am not sure why it supports this change in ocular dominance. Is the change a function of training or more simply the way the eyes work together.