Usually when they refer to neuroadaptation they are referring to adapting to the different type of optics in a premium lens. Since you mention monovision, there is adaptation that goes on with that as well if you haven't been using monovision already, but that usually isn't what they are referring to.
Natural human eyes can differ in their focal point and the brain is able to sort out which eye to pay attention to for what distance. Most people can adapt to a certain level of monovision, though when the difference is too high people can have trouble. Ideally people should to trials with contact lenses of monovision, and multifocal contacts, to see what they like and can adapt to before their cataracts get too advanced to interfere with the experiemtn.
Thanks for the response.
Don't you think concept of neuroadaptation goes against idea of monovision ? People should not be comfortable at all with monovision, since one eye is set for near vision and other for far ?
I should say that in someone much younger, like say a 19 year old, having a monofocal in one eye might lead to a bit more difficulty adapting due to how much accommodation the natural eye has. When focused at near with the natural eye, there might be several diopters difference between that eye and the monofocal eye. There was a young poster on this site who did seem to have some difficulty dealing with an IOL in only one eye. However you are old enough that you don't have that much accommodation left, so even at near there won't be a huge difference between the monofocal and the natural eye. I suspect most people don't have a problem with it, and if you did then you could decide to get the other eye done.
There isn't much of a concern about neuroadaptation with a monofocal lens since there isn't anything majorly different about its optics compared to a natural lens, other than that it doesn't change focus like the natural eye can (in someone with some accommodation left). If anything, the difficult issue in the case of a monofocal for someone young is that they lose near vision, and so it is likely easier to adapt if the other eye retains its ability to see near.
Thanks for the detailed response. But shouldn't neuroadaptation thing apply in the case of monofocals as well ? That was my question. In other words why, if I go for only one monofocal in my right eye and leave left one as it is, neuroadaptation wont be of any concern ?
reg
The reason some doctors suggest getting both eye's done at around the same time is that they feel it speeds neuroadaptation, the process of the brain getting used to seeing through a lens that is different than the natural lens. They feel that having both eyes using the new optics forces the brain to need to learn how to handle it faster, whereas with only 1 eye with a premium lens the brain may fall back on the natural eye that it is used to and take longer to get used to using the new lens. However the brain would still adapt to having a lens in only 1 eye, even if it takes a bit longer, so I'm not sure it is worth getting both eyes done if the vision in the other eye is still good.
At your age you likely don't have much presbyopia yet (though that varies with each person). It is possible you would lose a bit of near vision compared to your natural eye even with the Symfony or a multifocal so you might not have as good vision in that eye as you do now (though its possible they'd be comparable to what you have now, again it depends on the person). If you can wait until you have a problem cataract before getting your other eye done, they may have even better lenses on the market by then. That said, there is a sense of relief from getting both eyes done and not needing to worry about the issue any more. You will be losing near vision over the next few years in your natural eye if you don't get surgery in it, and getting a Symfony or multifocal now would prevent needing to worry about that.
Some people have great vision right away after getting a premium lens, whereas others only have ok vision at first at some distances (often they have great distance but the near isn't as sharp as it could be at first), and their vision improves over time as their brains get used to how the lenses work. e.g. multifocals provide the eye 2 or 3 different images, one for each focal point, and the brain needs to get used to choosing the best one for the particular distance you are trying to see. Its not something you think about or are aware of, you don't know there are multiple images, , the brain just does it automatically. The Symfony extends depth of focus beyond what you ordinarily have, so it also may require a different sort of adaptation process. (though to me it seems its likely something closer to what the brain needs to deal with anyway than multifocals are, since people have different natural depths of focus so brains need to adapt to whatever an eye has, and the depth of focus of a natural eye changes with the pupil size, so its used to some variability).
Read this carefully:
http://www.medhelp.org/user_journals/show/1648102/Consider-ALL-the-Options-Before-Your-Cataract-Surgery-Working-Through-Whats-Best-For-You Then read all the many posts about the pros/cons of monofocal vs multifocal. Educate yourself as its reasonably complex. Read the postings by Software Developer.