Binocular Vision

[johnyandell]

Let's discuss Chris Lewit's article, "Binocular Vision"

[ralph]

Is the old dominant eye test of which eye one look through when using a camera valid!

[johnyandell]

No idea! Chris?

[clewit]

Is the old dominant eye test of which eye one look through when using a camera valid!

Hi Ralph,

Thank you, I have not asked the experts specifically about that test but I can. I would assume it suffers from similar flaws as the triangle test. There is a camera test used in a lab but the camera “field test” you are describing is likely invalid. That test would not allow for co-dominance or gradations of dominance. Dr. Laby stressed that tests should be able to measure both of those factors.

[clewit]

Is the old dominant eye test of which eye one look through when using a camera valid!

I asked Dr. Laby. Lets see what he thinks.

[nickw]

Hi Chris,

I haven't read the new article yet, but will do very soon. The subject is interesting for me personally, and my coaching, and I do have a couple of questions based from the first article:

I'm cross-dominant, right handed, but also have a lazy right eye. If I shut my left eye, everything is blurry. If I shut my right eye, nothing changes and I have sharp vision. My first question is does this affect the importance of eye dominance, when vision in one eye is significantly stronger than the other, compared to someone with equal vision quality in both eyes?

I experimented a bit the other day, by hitting balls with my right eye shut. I expected there to be no difference but was surprised to find I couldn't focus on the ball, though I could still hit it ok. That's conclusive proof for me that despite my right eye being lazy, it still plays a crucial role in my ability to see and hit the incoming ball. When I shut my left eye, I couldn't see clearly but was also surprised that I could make clean contact with the ball most of the time.

From my own experience previously, I'm most susceptible to framing the ball when running down a wide forehand, unless I consciously keep my eye on the ball until contact, and this would seem to make sense as my dominant eye is furthest away from the ball in that situation. Based on that, I have believed that there is something in this eye dominance thing, but I totally agree that any intervention with stances or technique based on eye dominance, doesn't make any sense at all.

As a coach, I have always asked players to be aware of which is their dominant eye, and have only offered them the following advice: If they are cross-dominant, then it's more important for them to watch the ball onto the strings of the racket (like Roger Federer does so famously), and if they are same side dominant, it's less important to do this. As we know, some players watch the ball onto the strings, whilst others clearly don't. How would you rate the value of this advice?

[clewit]

Hi Chris,

I haven't read the new article yet, but will do very soon. The subject is interesting for me personally, and my coaching, and I do have a couple of questions based from the first article:

I'm cross-dominant, right handed, but also have a lazy right eye. If I shut my left eye, everything is blurry. If I shut my right eye, nothing changes and I have sharp vision. My first question is does this affect the importance of eye dominance, when vision in one eye is significantly stronger than the other, compared to someone with equal vision quality in both eyes?

I experimented a bit the other day, by hitting balls with my right eye shut. I expected there to be no difference but was surprised to find I couldn't focus on the ball, though I could still hit it ok. That's conclusive proof for me that despite my right eye being lazy, it still plays a crucial role in my ability to see and hit the incoming ball. When I shut my left eye, I couldn't see clearly but was also surprised that I could make clean contact with the ball most of the time.

From my own experience previously, I'm most susceptible to framing the ball when running down a wide forehand, unless I consciously keep my eye on the ball until contact, and this would seem to make sense as my dominant eye is furthest away from the ball in that situation. Based on that, I have believed that there is something in this eye dominance thing, but I totally agree that any intervention with stances or technique based on eye dominance, doesn't make any sense at all.

As a coach, I have always asked players to be aware of which is their dominant eye, and have only offered them the following advice: If they are cross-dominant, then it's more important for them to watch the ball onto the strings of the racket (like Roger Federer does so famously), and if they are same side dominant, it's less important to do this. As we know, some players watch the ball onto the strings, whilst others clearly don't. How would you rate the value of this advice?

Thanks very much!

1. How did you confirm you are cross-dominant. One of the main thrusts of my article is that the common field tests used are not valid according to research. They are often flawed.

2. My understanding is that visual acuity is not related to eye dominance. The dominant eye is based on sighting, not acuity. Both eyes are crucial for depth perception of the incoming ball.

3. It doesn’t make sense to me that your dominant eye would be farther away from a running forehand. If you are left eye dominant, your left eye would be closer to the incoming ball.

[nickw]

Thanks very much!

1. How did you confirm you are cross-dominant. One of the main thrusts of my article is that the common field tests used are not valid according to research. They are often flawed.

2. My understanding is that visual acuity is not related to eye dominance. The dominant eye is based on sighting, not acuity. Both eyes are crucial for depth perception of the incoming ball.

3. It doesn’t make sense to me that your dominant eye would be farther away from a running forehand. If you are left eye dominant, your left eye would be closer to the incoming ball.

Thanks Chris

1. I've always used the method that involves placing a distant object in a circle made from your thumb and index finger, and then shutting each eye in turn. Whichever eye is open when the object doesn't move out of the circle is the dominant eye. It produces the same result every single time, as it does with my students. Is this method definitely not valid based on the research? if so, is there any estimate as to what % of people this test is accurate for?

2. Thanks that makes sense.

3. You're right, on a running forehand, my left eye is actually marginally closer to the ball! It doesn't feel that way when I'm running out to them, and I never thought to question what I felt. What's very clear is that the difference in distance between the ball and each of the eyes is so small, which would suggest it has little or no relevance to the outcome of the shot.

4. You didn't answer my last question Chris, please do if you have an answer; Do you believe there is anything in the idea that there is a link between ocular dominance and the importance of head position at contact (looking at contact point like Fed or slightly in front of contact point like Djokovic)? Or does the research (if there is any) simply suggest this is not a thing?

I've certainly never been of the mindset that eye dominance is crucially important in tennis, and would never tamper with technique or positioning based on it. I've only worked with the (perhaps totally flawed) theory already mentioned. I'm very happy to be converted to the idea that there is little or nothing in this eye dominance thing, but it does also seem to be a subject that needs a lot of further research in order to get conclusive answers to every question.

Thanks for your time Chris, both your articles have been an interesting and enjoyable read!

[clewit]

Thanks Chris

1. I've always used the method that involves placing a distant object in a circle made from your thumb and index finger, and then shutting each eye in turn. Whichever eye is open when the object doesn't move out of the circle is the dominant eye. It produces the same result every single time, as it does with my students. Is this method definitely not valid based on the research? if so, is there any estimate as to what % of people this test is accurate for?

2. Thanks that makes sense.

3. You're right, on a running forehand, my left eye is actually marginally closer to the ball! It doesn't feel that way when I'm running out to them, and I never thought to question what I felt. What's very clear is that the difference in distance between the ball and each of the eyes is so small, which would suggest it has little or no relevance to the outcome of the shot.

4. You didn't answer my last question Chris, please do if you have an answer; Do you believe there is anything in the idea that there is a link between ocular dominance and the importance of head position at contact (looking at contact point like Fed or slightly in front of contact point like Djokovic)? Or does the research (if there is any) simply suggest this is not a thing?

I've certainly never been of the mindset that eye dominance is crucially important in tennis, and would never tamper with technique or positioning based on it. I've only worked with the (perhaps totally flawed) theory already mentioned. I'm very happy to be converted to the idea that there is little or nothing in this eye dominance thing, but it does also seem to be a subject that needs a lot of further research in order to get conclusive answers to every question.

Thanks for your time Chris, both your articles have been an interesting and enjoyable read!

4. I'm sorry but I don't see a link. Research shows that head position should be still to develop the "quiet eye" to enhance concentration, etc. regardless of whether an athlete is cross-dominant or not. Teaching the quiet eye technique like Federer will help all your players, regardless of their eye dominance. Hope that helps amigo.

[clewit]

Thanks Chris

1. I've always used the method that involves placing a distant object in a circle made from your thumb and index finger, and then shutting each eye in turn. Whichever eye is open when the object doesn't move out of the circle is the dominant eye. It produces the same result every single time, as it does with my students. Is this method definitely not valid based on the research? if so, is there any estimate as to what % of people this test is accurate for?

2. Thanks that makes sense.

3. You're right, on a running forehand, my left eye is actually marginally closer to the ball! It doesn't feel that way when I'm running out to them, and I never thought to question what I felt. What's very clear is that the difference in distance between the ball and each of the eyes is so small, which would suggest it has little or no relevance to the outcome of the shot.

4. You didn't answer my last question Chris, please do if you have an answer; Do you believe there is anything in the idea that there is a link between ocular dominance and the importance of head position at contact (looking at contact point like Fed or slightly in front of contact point like Djokovic)? Or does the research (if there is any) simply suggest this is not a thing?

I've certainly never been of the mindset that eye dominance is crucially important in tennis, and would never tamper with technique or positioning based on it. I've only worked with the (perhaps totally flawed) theory already mentioned. I'm very happy to be converted to the idea that there is little or nothing in this eye dominance thing, but it does also seem to be a subject that needs a lot of further research in order to get conclusive answers to every question.

Thanks for your time Chris, both your articles have been an interesting and enjoyable read!

1. This is a great question. Don Tieg recommends this field test in his book but Dr. Laby is adamant that the test is invalid. The research supports the lack of validity. I would have to go back and find the journal articles to review the specifics. You can search on Pubmed to find the Mayo Clinic study, for example. I agree with you that the field test seems like a simple way to get a rough estimate of sighting preference, but research casts doubt on this test. I would urge caution if using this test to make assumptions about a player's eye dominance characteristics. If the test is not accurate, coaches should find a better test to use in practice or refer out to a specialist. Dr. Laby makes this same point. These types of tests are all over youtube and the internet and are all flawed. That's a major point Dr. Laby makes. And that's one of the reasons the research out there is a mess because researchers are all using flawed tests from the beginning!

3. Dr. Tieg says left eye in that situation, if dominant, might give a fraction of a second faster input to the brain and could give an advantage. Dr. Laby insists it's not an advantage and stresses that both eyes need to watch the ball for maximum vision performance in all situations.

[clewit]

4. I'm sorry but I don't see a link. Research shows that head position should be still to develop the "quiet eye" to enhance concentration, etc. regardless of whether an athlete is cross-dominant or not. Teaching the quiet eye technique like Federer will help all your players, regardless of their eye dominance. Hope that helps amigo.

4. In addition, I would add that keys to the quiet eye technique are a steady head and gaze, whether looking at the impact like Federer or looking slightly in front like Djokovic--both are effective. There is no benefit in terms of actual vision or tracking of the incoming ball at that stage. The human eye cannot track the ball at high speeds during the final moment before impact. John has also made that point. At slower speeds the eyes could track the ball into the actual impact point. Thus the reason you see so many pros keeping the head still is likely for the concentration and mental/emotional benefits rather than for visual enhancement.

[nickw]

Beautiful Chris, thanks for your thoughts and insight, very helpful. I’ve always been a big advocate of head still during the contact phase, because the results in students are clear and obvious, and the quiet eyes idea makes a lot of sense. Thankfully I’ve never got too bothered about eye dominance related ideas, as I’ve never seen much clear evidence that it helps anyone. Therefore, I’m quite happy with the idea there might be nothing in it! I’ll adjust my teaching accordingly, and for me personally, I’ll enjoy not worrying about eye dominance, and trusting both my eyes to work together, even though one is a bit crap! Thanks again mate

[clewit]

Beautiful Chris, thanks for your thoughts and insight, very helpful. I’ve always been a big advocate of head still during the contact phase, because the results in students are clear and obvious, and the quiet eyes idea makes a lot of sense. Thankfully I’ve never got too bothered about eye dominance related ideas, as I’ve never seen much clear evidence that it helps anyone. Therefore, I’m quite happy with the idea there might be nothing in it! I’ll adjust my teaching accordingly, and for me personally, I’ll enjoy not worrying about eye dominance, and trusting both my eyes to work together, even though one is a bit crap! Thanks again mate

Thank you amigo