Prescribing for Presbyopia
What’s the Deal with Monovision?
BY DOUGLAS P. BENOIT, OD, FAAO
Despite having bifocal and multifocal contact lenses since the late 1940s, they are an underutilized presbyopic vision correction option (Morgan et al, 2011). Could it be fear of using a more complex design? The perceived increase in chair time? The familiarity with monovision? A lack of motivation to try something else? Predominantly older practitioners seem to perpetuate the use of monovision, while younger fitters seem willing to try multifocal designs. Some continued use of monovision is due to practitioners not educating patients on all of the options we have to correct presbyopia.
Monovision leads to a loss of depth perception and contrast sensitivity, suppression, and night driving issues, such as light spray (Rajagopalan et al, 2006). Visual acuities at distance and near might be better in monovision, but, subjectively, patients prefer the visual performance of a multifocal contact lens (Woods et al, 2015). So why the hesitance to use multifocal lenses?
What’s the Appeal?
Monovision is simple (at least for emerging presbyopes), and it works with spherical and astigmatic lenses. Once the dominant eye is determined, the distance power is modified in the nondominant eye to enhance near vision. Distance vision is generally still good, and early on, intermediate vision may also be good.
Unfortunately, as patients age and the presbyopia advances, visual compromise develops. Often, intermediate vision is lost first. Because many people use electronic devices throughout their work day, the loss of intermediate vision is a significant problem. Later, the vision at other distances also degrades, and patients sometimes drop out of contact lenses and revert to glasses.
Multifocal contact lenses provide good vision at all distances—not “perfect” vision, but adequate to perform daily tasks without straining. Some designs and materials are better than others at creating this good visual outcome; Rajagopalan et al (2006) found that there was better contrast sensitivity at all frequencies, better high- and low-contrast visual acuity, and less disabling glare with GP versus soft multifocals and that both multifocal designs outperformed monovision.
Note that many multifocal contact lenses are designed to work via an enhanced, or modified, monovision approach. Some use actual differences in the size of the zones for the add, with a smaller add intrusion on the dominant eye and a larger one on the nondominant eye. Others use a central distance power zone for the dominant eye and a central near power zone for the nondominant eye. Still others use the same zone size/type for each eye and advise “pushing plus” on the nondominant eye to enhance vision. In truth, a combination of all of these design concepts seems to find its way into our treatment of these presbyopic patients.
Where does that leave us? The science would tell us that the multifocal design is the better choice in most instances. So, we all need to stay current on the latest innovations in multifocal lenses and present these options to every presbyopic patient. While it may move some of us out of our comfort zone, it can make day-to-day practice more satisfying. CLS
For references, please visit www.clspectrum.com/references and click on document #249.
Dr. Benoit is the senior optometrist with Concord Eye Center, a multi-subspecialty ophthalmology group in Concord, NH. He is a Diplomate of the American Academy of Optometry’s Section on Cornea, Contact Lenses and Refractive Technologies, currently the Special Advisor for the Section. Dr. Benoit is a Distinguished Practitioner and Fellow in the National Academies of Practice-Optometry Section and is a Diplomate of the American Board of Optometry. He is also on the Advisory Board of the GPLI and is the 2016 GPLI Practitioner of the Year. Dr. Benoit is a consultant to, and clinical investigator for, Alcon and Visioneering Technologies.