Binocular Vision

What are we to make of the conflicting information about how to use the eyes in tennis?

On the face of it we have confusion. Vision experts like Drs. Don Teig, Daniel Laby and elite tennis coaches and trainers like Patrick Mouratoglou, Jofre Porta, and Paul Dorochenko seem to have many conflicting views regarding vision and eye dominance.

The science available on eye dominance is scarce, inconsistent, and inchoate, and the latest research is inconclusive. And we certainly don't have clear answers or definite refutations the claims about eye dominance in tennis by Mouratoglou, Porta, and Dorochenko.

Some older studies in baseball showed that cross-dominant athletes had better batting performances than same-side athletes at little league and major league levels. But recent studies disagree.

In a study of 410 major league baseball players, researchers found that ocular dominance patterns had no influence on batting average. In another study of 215 professional baseball players, researchers found that same-side or cross-dominant eye/hand combinations showed no correlation with hitting ability, pitching success, or fielding.

These studies certainly suggest that ocular dominance characteristics would have little to no impact on success in hitting the tennis ball. But it's still possible—if unlikely--that there may be elements of eye dominance not yet discovered that affect tennis technique, or possibly motion in certain directions on the tennis court.

Does ocular dominance have an effect in baseball?

Daniel Laby holds the opinion that eye dominance plays no role in tennis performance. But Don Teig says that there may be a subtle advantage to tennis athletes on the groundstroke side where the dominant eye is closer to the ball.

Any claims about pro players and their eye dominance have to be viewed skeptically because of the flawed nature of the field tests used to measure eye dominance. And even more skeptically, claims by some coaches they can tell eye dominance just by watching players hit tennis balls.

Can you tell eye dominance just by watching?

If we cannot know for certain the eye dominance of athletes, we cannot make conclusions about how their games and techniques reflect that eye dominance. There needs to be more precise testing of tennis players to demonstrate what percentage of them are cross-dominant, same-side dominant, or non-dominant. Laby makes a strong case that the sighting field tests used by most researchers and coaches are highly flawed. Teig also agrees that many commonly used tests are inaccurate.

The entire subject of eye dominance is a hot mess because virtually all of the research out there is based on non-standardized and often flawed testing of athletes. A 2022 systematic review study on eye dominance and sports performance stated that many of the studies in the review were based on flawed methodologies and differing testing protocols.

Laby documents several recent studies that show poor validity of eye dominance field tests and that these tests can give different results based on the distance of the object and angle of vision. Laby has developed a more precise computerized test that determines eye dominance based on gradations, which he says is much better than simple field tests that force a right or left dominance conclusion.

What's real and what's speculation?

To state the obvious, it's impossible to know the truth scientifically when the basic identification tests used in most research studies are inaccurate or compromised from the onset.

Says respected sports scientist, teaching pro, and Tennisplayer contributor Doug Eng, PhD: “What Mouratoglou is saying is highly speculative. Much of what he says is almost definitely incorrect but we cannot say he is entirely wrong since there is hardly any evidence."

Elite coaches and trainers in the tennis world simply do not agree. The scientific research is scarce, non-concurrent, and inconclusive. So we are left with an unsteady foundation of conjecture and anecdotal stories. Due to this lack of conclusive research in this area, I avoid using eye dominance as a factor in my technique building with players. Instead I focus on binocular vision.

Based on the limited research that is available and trustworthy—and my own extensive professional coaching experience—here are my conservative bottom-line conclusions and recommendations about eye dominance and sports vision to help guide tennis players and coaches during the technique building process:

Heads still but often in different positions.

I have always encouraged my players to keep their head relatively still at impact and to minimize excessive head and neck rotation during the groundstrokes and serve. A steady head is a key ingredient for building world-class and pretty technique even though different players hold the head still in quite different positions.

It's debatable whether this has any benefit on the actual vision of the incoming ball, but I believe a stable head helps to minimize swing-path disruptions and improve the accuracy of the shots.

With good technique neither eye is obscured.

It is common sense that a still head can help with control of the shot versus a head with a wild rotation or movement during the critical impact phases of the shot. A steady head is also the foundation for the Quiet Eye approach, a term first coined by researcher Joan Vickers, discussed further below.

A very important takeaway is to ensure both eyes are tracking the ball with a binocular field of vision. Tennis players should be careful not to obscure either one of their eyes because athletes need both eyes to give the best possible vision. But as Jeff Counts and others have stated, this should not be a problem when a player has good stroke technique.

The health of the eyes, visual acuity, contrast sensitivity, depth perception, and reaction are more important areas of sports vision than the dominant sighting eye. These aspects of sports vision are backed by trustworthy research showing they are the most important contributors to performance in a sport with high visual demands like tennis.

For coaches and players looking to improve their vision to help their tennis game, focusing on ocular health and performance basics and watching the ball with both eyes should be the priority. Positioning the head to allow both eyes to consistently track the ball is a major component of the Winning Pretty approach.

There are many reasons to keep the head still.

The quiet eye is a term used by researchers to describe the control of the gaze at the moment of skill execution in a sport. A better term would probably be quiet eyes plural, to emphasize the importance of binocular vision in sports.

In tennis, it is critical to keep a steady head position while executing a stroke for myriad reasons. As mentioned previously, keeping the head still helps with overall balance and can improve the accuracy of the shot because the racquet is delivered to the ball without any artifact caused by extraneous head movement.

Research shows that keeping the head still during a sports movement, whether that is a golf swing, free throw, or tennis stroke, has additional benefits, not only for ball tracking but for focus and calming the nervous system. Practicing the quiet eye technique will improve focus while ensuring better balance and body control, and will improve the accuracy of the tennis shot.

Eye dominance plays no role in trunk rotation.

In the winning pretty approach, creating efficient power by optimizing the kinetic chain is more important than eye dominance. Trunk rotation needs to be maximized whenever possible for power development while maintaining a binocular vision field by turning the head and neck. Barring any range of motion issues or orthopedic limitations that prevent turning the head fully to see the ball binocularly, eye dominance should not play a role in determining the amount of trunk rotation used.

Eye dominance does not correlate to timing of contact points.

In order to develop winning, efficient, and pretty technique, players should strive to meet the ball early for better extension of the racquet at impact, which optimizes the kinetic chain and transfers more energy to the ball. Brian Gordon has also argued that greater extension of the arm to 150 degrees or more at impact can optimize ball rotation rates without sacrificing ball speed on the forehand groundstroke. Coaches should emphasize meeting the ball early for better extension in their teaching.

Eye dominance does not correlate to earlier or later contact points or power or control.

Later contact points do not allow players to hold the ball on the strings longer, presuming that would even be an advantage in an event with duration measured in milliseconds. According to the laws of physics, meeting the ball earlier or later has no correlation with the time the ball spends on the string bed at impact.

My recommendation is to not change groundstroke shoulder angles based on eye dominance. Shoulder angles at impact are likely a result of technical training and player preference rather than because of eye dominance. Research has shown that, at the distances near impact, the human eye is not capable of tracking the incoming ball at higher speeds.

Shoulder angle at contact can vary.

The theory that Federer turns his head and keeps his shoulders more closed at impact so that his dominant left eye tracks the ball better does not make logical sense considering the human eye cannot see the ball at high speeds at close distances. It's more likely that this is a quiet eye practice by Federer, which helps his balance and focus during the execution phase of the stroke.

In the winning pretty system, the shoulders should rotate into the incoming ball comfortably and the shoulder angle at impact will vary somewhat based on the player preference, grip, stance, and direction of the shot.

According to John Yandell, world-class players use every stance situationally--closed, open, and semi-open. Unless a player has a restricted range of motion in the spine, he or she should be able to rotate the neck and head to perceive the ball binocularly, even when preparing with a closed stance and maximum shoulder/trunk rotation.

Stance preference is not based on eye dominance.

It's true that players sometimes have a preferred stance but this phenomenon is likely due to their technical training or player preference--not related to their eye dominance. As Don Teig and Daniel Laby advise, players and coaches should ensure the head is positioned to optimize tracking the ball using both eyes for optimal vision, regardless of the stance or amount of shoulder turn.

Using both eyes to read the incoming ball should be the focus--not using the dominant eye. Turning the head to focus both eyes on the ball should not be difficult for elite tennis players who generally have excellent range of motion in the spine. In rare cases where players have restricted cervical and/or thoracic spine rotation, perhaps due to previous injury, it may be beneficial to use an open or semi-open stance in certain instances or sacrifice shoulder turn to ensure binocular vision of the ball.

On the serve, head position should be trained so that both eyes can track the toss. There may be some benefit to having the head facing forwards, as Mouratoglou advises, to see peripherally any movement the returner makes during the tossing phase of the serve, but this benefit is likely due to optimal binocular vision and not dominant eye sighting.

Players and coaches should be cautious about changing stances or shoulder positions on the serve according to their dominant eye, if they even know what it is. Players and coaches should strive to maximize the kinetic chain through optimal trunk rotation while ensuring the head is in a position to see the ball and the court binocularly.

Another key takeaway is that sighting field tests used by trainers and coaches like Mouratoglou, Porta, and Dorochenko should not be used to determine eye dominance. Especially the hand triangle test. Laby gives a very strong and clear warning against this type of test because of its inherent flaws in validity.

Research by the Mayo Clinic supports the inconsistency in the results of various field tests for eye dominance. The sighting field tests can show changing dominance results based on the angle and distance of the object in the visual field. Orthopedic issues like upper extremity pain and range of motion can skew the test results. If a coach or player wants to test for eye dominance, there are more accurate computer guided tests, and a pointing field test with a camera that can give non-binary results with gradations of dominance. These tests also allow for a non-dominance result. Experts like Drs. Laby recommend using these more accurate binocular tests that allow for finer gradations of eye dominance.

But in the end the whole issue of eye dominance could be viewed as an irrelevant distraction. No one can change their eye dominance and it is questionable whether it even possibly has an effect on stroke development.

So here is a list of my suggestions about vision in tennis.

Binocular Vision

Chris Lewit