June 2013

 

COVER FEATURE

 

Presbyopia

Monovision revisited


by Erin L. Boyle EyeWorld Senior Staff Writer

   
Dominant eye test

A patient in Dr. Chu's office is tested for her dominant eye.

Source: Y. Ralph Chu, MD

Some patients can adapt to the reverse of the usual dominant eye for distance

Monovision remains a viable option as a less expensive treatment for presbyopia, with dominance important for achieving best results.

"Monovision offers a less costly option for patients who want to have a good functional spectacle-free life or reduced spectacle dependence, and I recommend that anyone consider doing it," said John A. Hovanesian, MD, clinical instructor, Jules Stein Eye Institute, University of California, Los Angeles. He said monovision can be an excellent way for surgeons to accustom themselves to the premium IOL surgery market. "For the surgeon who's new to refractive cataract surgery, offering monovision is a comfortable, easy way to use familiar lens implants and techniques that allow them to give patients great functional vision at less cost to the patient," he said.

When targeting monovision, the nondominant eye is usually targeted for near and the dominant eye for distance. However, some patients are able to have the reverse, he said.

"There are some [patients] who can tolerate, very comfortably, using the opposite from the usual," Dr. Hovanesian said. "The usual is to use the dominant eye for distance, but many patients can do the opposite and do just fine with it." Y. Ralph Chu, MD, clinical professor of ophthalmology, John A. Moran Eye Center, University of Utah, Salt Lake City; adjunct associate professor of ophthalmology, University of Minnesota, Minneapolis; and medical director, Chu Vision Institute, Bloomington, Minn., said that monovision is an important option for patients who are 40 years and older who want refractive surgery or presbyopia correction. "I do tell patients that a majority of patients do not tolerate the imbalance between their eyes but that I want them to hear about this as an option. I think it's important to determine the best situation for patients, whether it's through a contact lens trial or a discussion of past experience with monovision. I think following those general guidelines will help you be successful with monovision in your patients," said Dr. Chu. Vance Thompson, MD, Vance Thompson Vision, Sioux Falls, S.D., said that he offers the option of monovision to all patients 38 years and older. "I love monovision, so I offer it to all presbyopes, even if they have never tried it. They are comforted by the fact that we can fine-tune the near eye to distance if they do not like it. They are also comforted that we can fine-tune the near eye to [a] stronger near if they tolerate monovision well but hoped near would be better," he said.

Targeting monovision

There are a variety of ways to determine the dominant eye, physicians say, with each aiming to establish a patient's natural choice for the eye that should receive distance vision. Dr. Thompson is a strong advocate of monovision simulation, which he calls an important step when evaluating monovision as an option for patients. He said the "both eyes open" simulation technique is key to helping choose the eye that is best, or most "comfortable," for monovision. "I do this test at distance and near," said Dr. Thompson. "My main concern is distance comfort, and thus I simply hold a +1.25 lens in front of each eye with both eyes open and ask them which one feels more comfortable, which basically means which one is least noticeable at a distance. Most of the time patients like their dominant eye as the distance eye and the nondominant eye as the near eye, but this test helps them understand how tolerable monovision is and also uncovers if they are going to like their dominant eye as their near eye."

Dr. Thompson added that the best test for monovision is contact lenses, minimizing for cylinder for best results.

"For some folks, this means a toric lens. A lot of my patients do not want to invest in a toric lens. So I basically put them in a soft disposable and say, 'If you like that (without treating the cylinder), you are probably going to like true laser vision monovision even better,'" he said. Dr. Chu said his practice employs several methods of determining dominance in patients, including targeting through a small aperture and asking the patient to point.

"We use one of the standard wayswe do it a couple of different ways on a couple of different visits to confirm, especially for these patients who can switch dominance, if possible," he said.

Dr. Hovanesian said in his practice, he uses a disposable film camera to determine dominance. Patients are asked to hold up the camera to simulate taking a photo of themselves in a mirror, which allows them to show which eye is dominant without thought, he said.

"It's simple and it's quick, and patients don't think twice about it. Patients almost always show you their dominant eye that way. But if we choose their dominant eye to do certain tasks, we basically force them to pick an eye," he said.

Pearls

Monovision revisited article summary

Dr. Hovanesian said that in monovision, measurements for refractive accuracy are important, especially in the dominant or distance eye because of the importance of uncorrected distance vision.

"One of the pearls we learned from any type of refractive/cataract surgery is that without good, clear uncorrected distance vision, patients are generally not happy," he said. "No matter what you give them as near, you've got to give them distance."

He recommended that when performing monovision, the near eye could be a quarter to half a diopter off, as slight error can be tolerated in the near eye. But the distance eye must be as perfect a possible.

"In the distance eye, you've got to hit emmetropia, you've got to correct the astigmatism, because that's the only eye they're depending on to see the television clearly, to see road signs clearly," he said.

He said that when the target is not in monovision, physicians should be aware that an enhancement will most likely be necessary.

"If they say, 'I can't see road signs. I had this surgery so I could see far, and I could see near,' they are going to be unhappy," he said. Dr. Chu said establishing patients' needs with a preoperative discussion about lifestyle is critical. He said patients need a great deal of education on monovision's strengths and weakness. One potential strength of monovision is improved near vision, while two weaknesses are a slight loss in depth perception and an intermediate blur zone, he said.

Dr. Thompson said bothersome blur at a distance from the near eye that may require distance lenses is not the only problem patients might face with monovisionthe distance eye might also create near blur for some patients. If they can't ignore this near blur they may need reading glasses for longer, more intense reading times. "That is why I tell monovision patients that the goal is to minimize dependency on glasses, but when they need both eyes at a distance or both eyes up close, having their bifocals to help when necessary is very acceptable. If they can accept this fact, they are more likely to be good candidates to start the monovision journey," he said.

"This is all about setting up pre-experience expectations and then being willing to repeat postop what you said preop [because] they often do not remember everything you said," he continued. "Being patient and a quality educator sets you up for great success in monovision care."

Editors' note: Drs. Chu, Hovanesian, and Thompson have no financial interests related to this article.

Contact information

Chu: 952-835-0965, yrchu@chuvision.com
Hovanesian: 949-951-2020, drhovanesian@harvardeye.com
Thompson: 605-361-3937, vance.thompson@vancethompsonvision.com

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