The diffractive type cataract lenses are lenses that are on the surface of the artificial crystalline lens. Small micro-grooves have been impressed on them, which, are of a few microns high, have the ability to make a diffractive effect on light, that dignifies the additional foci. Therefore, the lens has a focus for distance vision and because of the diffractive circles, it is possible to also create additional focuses for intermediate and near distances.
Basically, the most used diffractive lens, more popular in this period, is the trifocal lens, which has a focus for distance vision, for intermediate (which can be around 60-70-80 cm) and for near which is around 35 cm, so it allows you to drive, to see your computer or dashboard and allows you to read a book up close. This type of lens works very well and gives a definitive correction of the vision defect, therefore it does not need maintenance, does not break, does not get dirty, it is not to be changed and is therefore a product that can be given for a lifetime. After the cataract surgery is done, a trifocal lens is implanted and there is no longer any need to do anything for life, so it is a product that works a lot in the long term. We have to think about an investment that we make in our lives, on the quality of our vision.
The defect of this lens is that it may create halos around lights at night because these micro-grooves create aberrations that the patient perceives as halos. This type of disorder is always present after cataract surgery, even with a normal lens, but it is a disorder that the brain gradually cancels out. Therefore, the patient, after the implantation of a trifocal diffractive lens, has an excellent quality of vision during daytime, has an excellent intermediate and near vision, but may complain of a nocturnal nuisance of halos around lights.
This tends to go away after six months of surgery, but it is not guaranteed that it will disappear completely. Many patients accept it very well, so they do not complain too much and report that they can do whatever they want in their life and therefore have no limitations of any kind. On the other hand, there are patients (and they are a small part) who report a medium-important discomfort, so it is very serious, on our part, to tell the patients themselves before the surgery and then explain that the implantation of a diffractive trifocal lens create this type of discomfort and at that point, the patient can choose whether to implant this type of lens or another one.