Over the last few years I have experimented with delivering "monovision" to my surgical patients using monofocal lens implants in a similar way that one would use monovision contact lenses. I won't go into detail regarding how I select the best candidates for this or the testing that it involves. The key concept here is that unlike contact lenses, lasik or the natural lens of a presbyopic eye, IOL's provide a pseudoaccomadation of approximately 1 diopter. This means that if I use my IOL master to plan for a post-refractive outcome of -1.75, the majority of my 65+ year old patients will be able to read uncorrected with that eye (as if they were -2.75). This of course would not be the case for seniors who are given +1.75 add reading glasses or contact lenses. Because I can target the reading eye for -1.75 it means that I can target the "distance" eye for -0.50. Even with only a -0.5 in that eye most of them can see not only distance but also intermediate (because of the 1D pseudoaccomodation). Lastly, because the spread between the two eyes is only 1.25 diopter (the difference between -0.50 and -1.75) it is very well tolerated.
This leads to some interesting issues which I am still experimenting with . For example, some of these people will still require spectacle correction to eliminate the monovision at certain times ie: at the baseball game, at the movies, driving at night, doing fine near work. However, when designing near spectacles for them I no longer go the obligatory +2.50 add that one usually uses. For example, my patient above with the monovision implants will NOT need a +2.00 add to supplement his residual -0.50 myopia. His pseudoaccomodation is already helping him significantly. He will probably need about +1.50 or less. The other eye (-1.75) needs no additional add at all.
Likewise, in a patient who I have only done one eye (and targeted -0.5), I will give them an add of +2.00 in the pseudophakic eye, and the full add of +2.50 in their phakic eye.
The concept of pseudoaccomodation is so powerful that I have even begun experimenting with targeting -0.75 postop. I have found that although this leads to somewhat blurry distance vision at night, it completely opens up the intermediate world. Patients can use their cell phones, PDA's, computers, see their food and even read print at hand's length. This may ultimately be the best overall compromise.
I would be quite interested in finding out if others have noted and experimented with this pseudoaccomodation phenomena? If not, you will be pleasantly surprised to see how well it works. I would also be interested in seeing if this works for all lens implants (I use the Acrysof wavefront acrylic implants)
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