Sometimes, in a very myopic eye, the desired IOL power will calculate to zero diopters. An IOL of zero diopters has no refractive effect, so should we implant an IOL at all? The resounding answer is yes, you should always implant an IOL (if there are no other contraindications) because it acts as an important barrier.
If we leave the eye aphakic, then the net refractive result will be identical to implanting a zero power IOL. In the immediate post-op period, both methods will result in excellent and identical vision. But then the eyes will develop posterior capsule opacification (PCO) which will likely be more pronounced in the aphakic eye. The IOL edge has an ability to limit the migration of the lens epithelial cells which lead to PCO.
When you perform a YAG laser capsulotomy in the aphakic eye, there is no longer a barrier and the vitreous can prolapse into the anterior segment. If there is the zero power IOL, it acts as a barrier and prevents this occurrence. In addition, the IOL has a built-in UV blocker which can aid in preventing photo-toxicity to the retina.
For this reason, I encourage all surgeons to implant the IOL, even if the power is zero. In some rare cases, such as post-vitrectomy eyes, implanting an IOL may not be necessary. In this case, I would perform a posterior capsulorhexis at the time of the original cataract surgery, prior to leaving the eye aphakic.
click below to see cataract surgery in this highly myopic eye with a zero power IOL: