As multifocal contact lenses continue to improve, the question arises, Should a monovision patient be refit with multifocal contact lenses or simply be left alone?

Many practitioners would advocate keeping a happy monovision patient in monovision. How can you ascertain whether a patient is truly pleased with monovision or is simply putting up with it for fear they would otherwise have to give up contact lens wear?

Three questions can provide insight into a patient's level of satisfaction.

Question 1: Do you have problems with night vision?

Perhaps the most common complaint expressed by monovision patients is difficulty seeing at night, which results from halos induced by distance blur in the eye corrected for near vision. This phenomenon tends to become more problematic as presbyopia advances and more plus is needed in the near eye.

Refitting symptomatic patients with a multifocal lens on the near eye allows them to maintain clear near vision while improving distance vision.

More advanced presbyopes often perform best with a multifocal lens when you bias the add power low but overplus distance power by 0.25D to 0.50D. This approach tends to reduce complaints of ghosting when viewing near print.

Although this modification may reduce distance vision somewhat in this eye, it will still be a significant improvement over the 20/200 acuity that's often present in the monovision near-corrected eye.

Question 2: Do you have problems with intermediate vision?

Many early presbyopes perform well with monovision because the low effective add power allows for a wide range of focus, providing adequate vision at most distances. As presbyopia advances and patients need additional plus to maintain good near vision, an associated reduction in near focus range evolves, resulting in blur at the intermediate range.

When exploring visual performance at the intermediate distance, ask patients about viewing detail on the grocery store shelf, the speedometer and, of course, the computer. If patients complain about vision with any of these, recommend switching to a multifocal.

Question 3: Do you have problems with depth perception?

This area can be a little tricky to get a handle on. Rather than literally asking about depth perception, ask the patient if he has difficulty turning corners or pulling into parking spaces. I often have symptomatic patients tell me they bump the front end of their car when pulling into the garage.

Enhanced binocularity at distance will help performance. Recommend a multifocal lens to solve this problem.

When refitting symptomatic monovision patients with multifocal lenses, I've found it helpful to keep some monovision bias in the system. Striving for full and equal binocular vision in these patients often results in complaints of shadow images and blur.

Remember that most of these patients have adapted fairly well to monovision and have only developed problems as their presbyopia has progressed. Therefore, these patients generally tolerate some imbalance between the eyes when wearing multifocal lenses.

Biasing the dominant eye for distance and the non-dominant eye for near will cure the ills induced by monovision while providing satisfactory crispness of vision to keep patients happy.