prescribing for presbyopia
The Monovision vs. Multifocal Debate
BY THOMAS G. QUINN, OD, MS, FAAO
Which works better, monovision or multifocals? After reviewing the charts of successful presbyopic contact lens wearers in my practice, I believe the best response may be...a bit of both!
Monovision (one eye corrected for distance vision, one eye near) has been a proven performer for many years. The criticism hurled at it is lack of binocularity.
Multifocal lenses strive to provide clear vision at distance and near in each eye. Detractors claim there is no clear image at either distance in either eye due to the simultaneous optics of most soft and many GP designs. As the difference between the distance power and near power increases, so does the potential for the two to interfere with one another.
Modified Multifocal Approach
We get around this problem by mixing multifocals with a bit of monovision philosophy. When working with high add patients, select multifocal lens powers that bias one eye for distance and the other for near. This is called the modified multifocal approach.
For lenses that allow you to choose from a variety of add powers, such as Vistakon Acuvue Bifocal, place a low add lens on the dominant eye. The weaker add will have less potentially deleterious effects on distance vision in this eye. On the non-dominant eye, place a lens with the full add to provide good near vision.
For lenses with a single, nominal add, such as CIBA Progressives, add +0.50D or +0.75D to the distance prescription of the non-dominant eye to boost near vision with this eye. Frequency 55 Multifocal (CooperVision) utilizes the modified multifocal approach by employing a center- distance lens on the dominant eye and a center-near lens on the non-dominant eye.
Reviewing My Charts
The majority of my patients (68 percent) with a spectacle add of +1.00D or +1.25D are successful wearing a multifocal lens with the full distance prescription and full add on each eye. Those in this group wearing a modified prescription tend to have a very low distance prescription, making them more susceptible to distance blur from the bifocal add. Generally, in these cases a single vision lens is worn in the dominant eye, and a multifocal lens is worn on the non-dominant eye.
Most patients (79 percent) with a spectacle add of +2.00D, +2.25D or +2.50D are fit with a modified multifocal approach. Some 60 percent of my presbyopic patients fall into this group.
The most interesting group consists of those patients with spectacle adds of +1.50D and +1.75D. What approach to take depends on their visual demands at distance or near. If distance vision is most important, go with the approach that's biased in that direction, and vice versa. If you are not sure, apply lenses with full distance correction and equal adds and modify from there.
The bottom line is: if you want to be successful fitting simultaneous vision multifocal contact lenses, get comfortable employing unequal adds. It works!
Thanks to Maggie Vance for her assistance with this article.
1: Recommended Initial Multifocal Fitting
|SPECTACLE ADD||INITIAL APPROACH|
|+1.00D, +1.25D||Full distance Rx, equal add|
|+1.50D, +1.75D||Start with full prescription and freely modify if symptoms exist|
|+2.00D, +2.25D, +2.50D||Modified multifocal approach|
Dr. Quinn is in group practice in Athens, Ohio, and has served as a faculty member at The Ohio State University College of Optometry.