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If you treat presbyopes, I am sure you are familiar with the term “dominant eye.” This term can mean different things to different professionals, making some days more entertaining than others.
To a marksperson (trying to be politically correct here), “dominant eye” is the eye used to sight a target. For a photographer, it is the eye used to view an image through a camera’s viewfinder. For an astronomer, it is the eye used to look through the microscope to see Mars. To a patient who had cataract surgery-and one eye is slight better than the other for reading-I hope it is the better for eye distance for the patient’s sake and my sanity.
An engineer recently came to see me for his annual exam. He is an emerging presbyope interested in changing his contact lenses to enable him to read his phone and computer more comfortably.
I tested for his dominant eye and determined it was his right. He said, “No, Doc, that is not correct. My left is dominant.”
Me: Well, with my test, it is your right.
Him: I don’t think that is correct.
Me: How do you know what eye is dominant? (Sighing inwardly but maintaining my best smile. I have at least one patient ready, and two are being worked up in adjacent lanes.)
Him: When I look at the clock at night, I shut my right eye.
Me: OK, that may be the case, but for what I am about to do, I want to say your right is the dominant eye. (Tapping my foot.)
Him: If you make the left eye for reading, how will I read the clock in the middle of the night?
Me: You will have removed the lenses before you went to bed, unless you want to see me in the morning with a red, painful eye.
Patients may have preconceived notions of which eye their brain predominantly uses. This is especially true if they perform tasks using only one eye.
But I have found that the eye patients use may be determined by the instrumentation used or how they were taught. I have stopped telling patients, “I am going to test to see which eye is dominant.”
I have far fewer arguments before the testing, and it is surprising how many patients follow my gestures, complete the test, and do not know for what I am testing. When I tell them which eye is dominant, they may agree or disagree based upon their preconceived idea. If they disagree with my expert assessment, I will repeat the testing and stick with my opinion. I am fitting contact lenses-not sighting a rifle, looking in a single-lens reflex camera, or looking at the moon.
Determining ocular dominancy can be conducted several ways. I did what every patient would do, and I Googled it. Here is what I found:
1. Extend your arms out in front of you. Create a triangular opening between your thumbs and forefingers by placing your hands together at a 45-degree angle.
2. With both eyes open, center this triangular opening on a distant object.
3. Close your left eye.
4. If the object stays centered, your open, right eye is your dominant eye. If the object is no longer framed by your hands, your left eye is your dominant eye.
5. Close your right eye.
6. If the object stays centered, your open, left eye is your dominant eye. If the object is no longer framed by your hands, your right eye is your dominant eye.1
My concern with this method is that the opening is large, and the patient may not be able to tell which is “off center.”
Point your finger at a distant object and close one eye. If your finger appears to move, then you closed your dominant eye.2
When I tried this method, I picked the wrong eye. (Sorry, wikiHow-not the best advice.)
WikiHow goes on to explain how to determine the dominant eye for near work (because apparently in Wikiworld, they may be different):
“To find out which eye is dominant at close distances, write a small letter on a piece of paper and tape it to the end of a ruler. Hold the ruler out at eye level and move it toward your nose. As you move it down, your non-dominant eye will stop focusing on the letter.”
When I tried this, I was not able to tell a difference between my eye’s view. Maybe the website is referring to a break with near-point convergence. But that would require someone else’s eyes look at mine. Either way, I give that method an “F.”
A riflery website suggested this method:
Hold your arms straight out at eye level, with fingers up, palms out, thumbs and forefingers overlapping, leaving a small hole through which you sight a faraway object. Slowly bring your hands to your face, keeping the object in sight, until they wind up over one eye or the other. That’s your master eye.3
Calling it a “master eye” rather than “dominant eye” seems much more “ninja-like,” and I think I may start doing this in the office. But I digress.
When I tried this method, my hands were on my nose, which was described as center dominant. That was fine for shooting but not useful in presbyopic correction-unless the patient is a Cyclops. We don’t see much of them outside Camp Half-blood.
Try the “hole in the card” method:4
1. Cut a hole 1.5 inches in diameter in a piece of paper.
2. Hold the paper with the hole at arm’s length with both hands straight in front of your body.
3. Look through the hole at a small target 10 feet away.
4. While looking at the target, close one eye, then the other. Don’t move or adjust your position.
5. The eye that can see the letter is your dominant eye.
When I perform this method, my left eye is dominant.
The “optometry” method5 uses loose lenses to determine which eye is prominently used for distance vision or which eye is best used for near. Instruct the patient to look at a distance target, such as the 20/25 line. Place a +1.50D lens over the right eye, then the left eye.
Is the line clearer and more comfortable with the lens over the right eye or the left eye?
If the answer is the right eye, then this is the “master eye.” Use this eye for distance.
I love this method because it lends itself directly to the task at hand, blurring the distance vision slightly to increase flexibility at near. Because it is highly unlikely your patient has loose lenses at home or at the shooting range, she is less likely to argue with the result.
Most importantly, this is an efficient way to determine if a patient will tolerate monovision. If she is averse to the loose lens test, you should jump right to multifocals and maintain binocularity.
1. Heiting G. Dominant eye test: How to find your dominant eye. All About Vision. Available at: https://www.allaboutvision.com/resources/dominant-eye-test.htm. Accessed 2/28/19.
2. Leng T. How to determine your dominant eye. wikiHow. Available at: https://www.wikihow.com/Determine-Your-Dominant-Eye). Accessed 2/28/19.
3. Bourjaily P. An easy way to find your dominant eye. Range365. Available at: https://www.range365.com/an-easy-way-to-find-your-dominant-eye. Accessed 2/28/19.
4. Rice ML, Leske DA, Smestad CE, Holmes JM. Results of ocular dominance testing depend on assessment method. J AAPOS. 2008 Aug;12(4): 365–369.
5. Quinn TG. Presbyopic contact lenses: From selection to success. Rev of Optom. Available at: https://www.reviewofoptometry.com/article/presbyopic-contact-lenses-from-selection-to-success. Accessed 3/4/19.