The arguments for multi-focal IOLs, so-called "premium" devices, are spurious. In every imaginable circumstance where a consumer is asked to spend more money for the best or the deluxe item, the buyer gets not just more of something the lesser item offers, but usually an additional bell or whistle. Multi-focal IOLs are no different in this respect.
The basic offering of all cataract surgery is the elimination of poor vision by the removal of the cataract. The offering of the implanted lens (IOL) is the elimination of the incredibly thick glasses baby boomers' grandparents wore following cataract surgery. Now, in the era of refractive surgery, baby boomers are eager for one more offering: The ability to see far and near following cataract surgery without wearing glasses. This is the bell or whistle, the upgrade that will face every patient having cataract surgery in the future.
In the last twenty years we have all seen some amazing breakthroughs in technology. No where has that change been more exhilarating than in the quality of our video displays - our televisions and computer monitors and the complex signals that carry the data. The term "high definition" abounds in the sale of these items and our cable options. Even our cell phones provide high quality images.
It stands to reason that patients should expect the highest quality of vision from their eyeglasses, contact lenses and IOLs. While eyeglass lenses have undergone revolutionary improvements in optical quality, contact lenses have not. And while IOL optics have certainly improved, the case cannot be made for multi-focal IOLs.
1. Desirability is a given; everyone wants relief from the encumbrance of eyeglasses and contact lenses. The mere mention of such devices generates immediate enthusiasm. Multi-focal IOLs, like multi-focal contact lenses, are an easy sell. But, unlike multi-focal contact lenses, multi-focal IOLs are not disposable; their explantation has definite risks.
2. Inherent in all cataract surgery is some degree of residual refractive error, small amounts of nearsightedness, farsightedness and or astigmatism, the amount of which cannot be known precisely in advance. While a factor in all cataract surgery, residual refractive errors are of particular significance following the promise of (and payment for) glasses-free vision. This is why surgeons are more likely to suggest that multi-focal IOL cataract surgery may need to be augmented with limbal relaxing incisions or ablation. Additional procedures can require additional expense.
3. The highest quality professional-grade cameras combined with the most sophisticated lenses ALL depend on the ability to FOCUS the image. Distant panoramas focus at infinity; pics of the grandchildren require a different focus. If our camera lenses could manage quality images with just one focal length, auto-focus mechanisms would be a thing of the past. But to avoid poor quality photos, our cameras (like youthful eyes) continually shift their focus. So, how can clear, simultaneous distance and near vision be obtained in a non-focusable IOL? Technically, it can't. This is where a few compromises must be made. This is where the shortcomings of multi-focal IOLs must give way to marketing and the concept of neuro-adaptation.
4. One of the contra-indications for multi-focal IOLs is the apparent onset of macular degeneration. Why? Evidently multi-focal IOLs require a sufficient vision quality "buffer" to result in acceptable post-surgical vision. Since every patient has the potential to develop macular degeneration, logic suggests that the reduced image quality and reduced contrast sensitivity of multi-focal IOLs is contra-indicated for all patients.
5. To offset the LOW definition of multi-focal IOLs versus their added expense and desirability of HIGH definition vision, the term neuro-adaptation has been called to the fore. Neuro-adaptation does NOT mean the visual system will, over time, "see" clearly. It does not mean that the brain will focus what is optically out of focus, read between-the-lines, so to speak. Blur is blur. Aberrations are aberrations. It is not neuro-adaptation that is occurring in some patients with MF IOLs but HABITUATION. The successful patient simply becomes tolerant of the lack of sharp, crisp vision.
All of the above is not meant to suggest that multi-focals are a failure. Many patients are pleased with their experience. Many accept the need for supplemental reading glasses. Others may be inhibited from night time driving but content to limit it. Multi-focal IOL quality has its shortcomings just as LASIK and other refractive surgery. But, just like refractive surgery, so much comes down to the patient's expectations. And patient expectations are dependent on the surgeon to under-promise and over-deliver, not the other way around. As always, problems arise when the patient's expectations have not been met and habituation is not acceptable.