Low-tech test is effective for determining eye dominance

A laminated card with a hole in it is the eye dominance test one physician has used for 20 years.

Issue: April 1, 2006

ByKatrina Altersitz

Daniel S. Durrie

A simple laminated card with a hole in it is the most reliable way to test ocular dominance and to explain to patients what eye dominance means in their daily life, according to Daniel S. Durrie, MD. He has been using this low-tech tool for 20 years in his practice.

Dr. Durrie and his colleagues did a study several years ago to determine the best way to discern eye dominance so that doctors and staff knew, and that patients comprehended, its importance.

“What we found is that it’s the most consistent test that we can use and it’s easy for staff to administer as long as they know the process,” he said in an interview with Ocular Surgery News. “And the extra thing it gives you is the ability for the patient to understand what dominance is about.”

Conducting the test

“One of the things that’s becoming much more important for ophthalmologists, especially for cataract and refractive surgeons, is to understand more about eye dominance,” Dr. Durrie said. Dominance is especially important in patients for whom a monovision correction is planned, he said.

In his simple test, patients are shown a 5-by-8 inch laminated card with a hole in the center. The hole is large enough to allow the patient to see the 20/400 E on a Snellen eye chart or to focus on an object across the room (Figure 1). Patients must have their best corrected vision in place so refractive error does not affect the outcome.

“I don’t say, ‘We’re going to test your eye dominance.’ I just say, ‘Look in the distance with both eyes; take this card,’” Dr. Durrie said. “Then I actually show them myself so they understand what we’re doing before they do the test.” See Figure 2.

Then, patients take the card and Dr. Durrie instructs them to focus on the large E or the object across the room with both eyes (Figure 3).

“That’s kind of the key – to keep telling patients, ‘With both eyes, look at this object in the distance,’” Dr. Durrie said.

As a patient focuses on the object, he or she brings the card upward, at arm’s length, until the object is centered within the hole (Figure 4). Once it is in the center, the patient brings the card toward his or her face, keeping the target in the center of the hole the entire time (Figure 5).

The patient ends up pulling the card toward the eye that is dominant for distance (Figure 6), Dr. Durrie said.

The 20/400 E is used as a target focal point. Any object, such as a light switch that is across the room, can also be used.

Dr. Durrie demonstrates to a patient the proper way to hold the laminated card at arm’s length in order to center the target in the hole.

The patient holds the eye dominance tester at arm’s length as she focuses with both eyes on the 20/400 E, which she sees just above the card.

The patient holds the card to her face, having kept the E in the center. Note that the hole is over her right eye, determining that she is right-eye dominant.

The patient centers the 20/400 E in the hole. Seen from the view of the patient.

The patient begins to pull the card toward her face, maintaining the E in the center of the hole.

Images: Durrie DS

Patient understanding

“It not only shows me or the staff person which is their dominant eye because that’s the eye they chose to focus at the distant target, but, after they pull it in, I tell them to hold it there,” Dr. Durrie said. “Then I tell the patients, ‘Tell me which eye you’re using.’ So they close one eye and close the other eye and say, ‘Oh, I’m using my right eye.’”

Dr. Durrie explains to his patients that the eye they use in this test is their distant-dominant eye, and that this eye has always been dominant for distance viewing situations.

“Your brain suppresses your nondominant eye,” he said. “The reason it does that is so you can make really quick decisions at distance so your brain only has to process half the data to make those safety quick decisions,” such as when to swerve a car to avoid an object.

Patients, and most doctors, are not aware of this life-long suppression process in the brain, Dr. Durrie said. “It’s important to educate the patient about what it really means, too, because many people will take that information about which eye is dominant and take that into the treatment plan.”

Doctor understanding

Dr. Durrie said he “constantly” runs into surgeons who do not perform monovision refractive surgical procedures because they “don’t believe in it.” He said monovision is an “extremely good treatment” for presbyopia, but only if a surgeon can accurately assess dominance in patients.

“There’s a reason for dominance and … you should see which eye they’re preferring to use at distance when they have their full correction in place,” Dr. Durrie said. “It’s part of good documentation, good discussion.”

Patients who have their dominance determined incorrectly can encounter major problems after monovision refractive surgery, Dr. Durrie said. He mentioned patients he has treated who have undergone LASIK surgery and are “backwards,” requiring additional surgery to reverse the treatment.

“Their question is: ‘Well, why didn’t my doctor measure that? Why didn’t I have that discussion before my surgery?’” Dr. Durrie said.

With the exception of rare cases, Dr. Durrie said it is best to maintain distance dominance as it occurs naturally, because patients do not adapt well to changing it in the creation of monovision.

If patients are left-eye dominant, “They’re not going to learn to be right-eye dominant,” Dr. Durrie said. “It doesn’t change over time.”

Whether an ophthalmologist is planning to perform monovision LASIK, conductive keratoplasty or implantation of mixed IOLs, dominance should be considered prior to surgery so the surgeon is aware which eye should be focused for distance.

It comes back to one question, Dr. Durrie said. “Are we accurately testing dominance in the clinic?”

For Your Information:

Daniel S. Durrie, MD, can be reached at Durrie Vision, 5520 College Blvd., Suite 200, Overland Park, KS 66211; 913-491-3330; e-mail: ddurrie@durrievision.com.

Katrina Altersitz is an OSN Staff Writer who covers all aspects of ophthalmology.