April 2019

REFRACTIVE

Presentation spotlight
Choosing between monovision and multifocals


by Stefanie Petrou Binder, MD EyeWorld Contributing Writer


To determine the dominant eye, the patient should make a circle with the pointer finger and thumb and extend the arm.
After spotting a distant object through the circle, each eye should be closed one at a time to determine which one the object can still be viewed through.
Source: Scott Greenbaum, MD

Monovision is a proven and trustworthy option to attain spectacle independence in patients undergoing cataract surgery. According to Ehud Assia, MD, the best results are attained by waiting for the outcomes of the first-eye surgery before moving on the create monovision.
“I will often set the second eye for monovision once I have the first-eye outcomes, even if the patient did not intend to have it to begin with,” Dr. Assia said in a presentation at the 36th Congress of the European Society of Cataract and Refractive Surgeons. “In my personal experience, –1.75 D is optimal, and although monovision may be slightly less effective than multifocals, there are also far fewer side effects.”
In conventional monovision, the dominant eye is targeted for distance and the nondominant eye for near. In crossed monovision, the dominant eye is targeted for near and nondominant eye for distance. Hybrid monovision refers to the use of both monofocal and multifocal lenses, in which one eye (usually the dominant eye) is set for distance using a monofocal IOL and the second eye with the multifocal lens to achieve good near and intermediate distances.
Ophthalmic surgeons distinguish between two types of monovision. Conventional monovision is set for less than or equal to –1.50 D, or somewhere between –1.0 and –2.0 D. Mini-monovision allows a maximum of –0.75 D anisometropia, or between –0.25 and –0.75 D. “Conventional monovision aims for far and near vision, while with mini-monovision, the focus is on intermediate vision,” Dr. Assia said.
“The potential candidate for monovision would be any patient who has good vision in both eyes, who desires spectacle independence and understands how monovision works,” Dr. Assia said.
Contraindications to monovision include ocular disease that affects or threatens vision and astigmatism that cannot be surgically corrected. Severe eye dominance, exophoria, and pediatric patients whose eyes are still growing constitute relative contraindications to monovision.

Monovision versus multifocality

“In most studies, unaided distance is very similar between multifocal vision and monovision. The difference is in the intermediate and near,” Dr. Assia said. “As for unaided intermediate vision, often times monovision does even better than multifocals, but slightly at the expense of near vision. As for unaided near vision, it is improved whether we use monovision or multifocals, but some studies show superiority of multifocals. But one word of caution: Most of the studies in the literature today used bifocals, not trifocals. Also, multifocal torics were not available for earlier studies, despite one third of the population having astigmatism of at least 1.0 D. We need to look at past studies with the perspective that they did not use the best lenses, compared to today.”
Monovision and multifocal IOLs have their drawbacks, despite reports of high patient satisfaction in both categories. Stereoacuity is decreased by monovision because one eye is set for distance and the other for near. Multifocal lenses, on the other hand, are associated with photic phenomena, like halos, glare, and difficulties in night driving. In most studies, multifocal lenses achieved better spectacle independence, somewhere between 65 and 95%, according to Dr. Assia, while this rate is lower for monovision, achieving between 35 and 90% spectacle freedom.

Choosing

“When deciding on multifocal correction, the decision must be made before the first operation—we do either both eyes or neither of the eyes. Monovision is often times a decision made on the second operation. If the distance vision is good after the first operation, we can do the second eye for near. If the patient is not happy after the first operation, we do the second eye for distance, for example, and this patient would use reading glasses,” Dr. Assia said.
The decision comes down to the visual preferences of the individual patient. “If the patient wants to cover all distances or the patient’s occupation requires good binocularity, multifocals are probably superior. They are independent of eye dominance and provide better stereoacuity,” he said. “Monovision has no extra cost, however. The decision is delayed for the second eye, and it can be simulated with contact lenses prior to surgery. Monovision is reversible, not only by lens exchange, but with the use of bioptics, add-on lenses, contact lenses, or glasses.”

Pearls

Dr. Assia advises patients with good vision on all the options. “If the patient desires to be spectacle independent, my first choice would be trifocal lenses. With astigmatism in excess of 0.75 D, especially if it is against the rule, it must be corrected. We do expect to have some photic phenomena with trifocals, but usually it improves with time and rarely interferes clinically,” he said.
“If the patient needs good intermediate vision, an EDOF or low monovision, about 1.0 D, both work well. But if the patient does not desire or cannot afford multifocal lenses, I would choose to target the first eye for emmetropia and aim for distance, regardless of which eye is dominant. If vision is good, I would recommend monovision for the second eye between 1.5 and 2.0 D, typically 1.75, even if the patient did not ask for near vision correction,” he said.

About the doctor
Ehud Assia, MD
Director of the Center for
Applied Eye Research
Department of Ophthalmology Meir Medical Center
Kfar Saba, Israel

Contact information
Assia
: assia@netvision.net.il

Choosing between monovision and multifocals Choosing between monovision and multifocals
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