Presbyopia is an undesirable certainty for those of us who have reached our mid-forties. Whilst it is also true that the potential market for a successful surgical treatment for presbyopia is significant, the optimal surgical treatment for those wishing to reduce dependency on glasses remains less than crystal clear.
The benefit of any surgical intervention must significantly outweigh the risks. There must also be evidence-based medicine in the form of peer-reviewed literature to back up this conclusion. Without such evidence, any surgical intervention remains “investigational” or even “experimental”.
Glasses and Contact Lenses
Spectacles are and will remain the mainstay of presbyopia treatment until we can successfully replace the crystalline lens with a substance that remains clear and mimics its accommodative properties. Multifocal contact lenses, and monofocal contact lenses used in a blended vision setting are the other non-surgical options.
What is often overlooked in the promotion of surgical solutions for presbyopia is that spectacles will still be required for many patients in certain conditions after surgery. It is more accurate to state that these procedures can reduce the need for reading glasses rather than necessarily eliminate it.
Spectacles will still be required for many patients after surgery…these procedures can reduce the need for reading glasses rather than necessarily eliminate it
Corneal Versus Lenticular
Surgical treatment options for presbyopia can be divided into lenticular and corneal. The lenticular options are used in the setting of cataract extraction or refractive lens exchange and include multifocal intraocular lenses (IOLs), pseudo-accomoodative IOLs and blended vision with monofocal IOLs. Corneal options include LASIK blended vision, ‘Presbylasik’ Corneal Inlays such as the Acufocus, and femtosecond procedures such as ‘Intracor’.
The fact that there is such a diversity of options reflects the fact that none are perfect. Many however are able to significantly reduce dependency on spectacles without significant associated risk. The difficulty is in distinguishing those with good evidence-based medicine to support their use from those that are unproven or associated with unacceptable risk.
Multifocal IOLs (Zeiss, Alcon, AMO) have been around for many years. Numerous published studies support their efficacy, however, all have potential problems. Unfortunately for some people, night vision degradation can be problematic, requiring IOL extraction. It is the relative frequency and occasional severity of these symptoms that have limited more widespread use of these lenses.
Pseudo accommodative IOLs such as the Crystalens (B+L) also have their advocates. These lenses can improve patient function significantly but occasional issues such as IOL movement, weeks or month postoperatively, have prevented their widespread uptake. More recent versions include the Synchrony from Visiogen, recently released in Australia.
In my opinion, there is no evidence that these IOLs are superior to a well planned blended (mono) vision in most patients. I use the Alcon Restor multifocal lens when patients are not suitable for blended vision and find it a good alternative but would like to see a well designed prospective trial comparing these two options.
I believe LASIK blended vision is suitable for appropriately selected patients and have also had it myself. I enjoy binocular unaided vision of 6/4.5 and N5 at age 48 with normal stereopsis. While it is not for everyone, it is a safe option.
The history of corneal refractive surgery contains many ironies. For many years, we have tried to improve visual quality following LASIK by performing wavefront guided ablations and changing algorithms that minimise induced aberrations, such as spherical aberration. Some surgeons are now trying to deliberately induce it to increase depth of focus, thereby providing some near vision.
Presbylasik is a relatively new treatment in which corneal excimer ablation patterns are manipulated to increase multifocality, spherical aberration, or asphericity to improve near vision (Alcon, AMO, B+L). The fact that there are many different approaches again should ring alarm bells, and suggests that this technology has not yet been refined. I would classify it as investigational – meaning patients should only be treated with Presbylasik as part of a clinical trial with appropriate ethics committee approval and informed consent.
Intracorneal implants are not new. The latest manifestation is the Acufocus (Figure 2). It is basically a pinhole that is placed over the entrance pupil within a corneal pocket. I believe this technology is at best unproven and requires long term study to prove efficacy and safety.
Finally and more recently, there have been attempts to change corneal shape with the femtosecond laser. One of these treatments is ‘Intracor’. Again, there are no prospective long term studies to support its use and the potential for loss of visual quality is significant.
Presbyopia is a fact of life. Complete dependence on reading spectacles is not. There is a plethora of other new surgical options but many are unproven despite being aggressively marketed. A cautious approach and a demand for peer-reviewed evidence that they not only work, but are safe for our patients, should remain mandatory.
Dr. Gerard Sutton is the inaugural Sydney Medical School Foundation Professor of Corneal and Refractive Surgery at Sydney University and has his private practice at Vision Eye Institute Chatswood.