This month's cover focus discusses the various models, potential benefits, and selection process of aspheric IOLs on the market. With the current trend of emphasizing the refractive outcome of cataract surgery, aspheric IOLs have become a major focus of attention in recent years. The IOL guide found on page 60 of this issue provides a sampling of aspheric IOLs available in Europe.
It is quite easy for ophthalmologists to understand that spherical IOLs induce additional spherical aberration in the eye. Personally, I have always questioned our use of spherical IOLs, as we have already been using aspheric optics for diagnostic ophthalmoscopy for many years. As Milind V. Pande, DO, FRCS, FRCOphth, of the United Kingdom, suggests in his article, perhaps those IOLs that have not yet transitioned to an aspheric design will do so in the future. Logically, the market share of aspheric IOLs is growing rapidly. In my own clinic, we switched to the aspheric version of our usual implant as soon as it became available. The thinner profile of the aspheric AcrySof SN60WF (Alcon Laboratories, Inc., Fort Worth, Texas) compared with its spherical predecessor was an extra motivation to make the switch.
Where all authors in this series of articles describe the advantageous principles of aspheric designs, one large question remains: What is the optimal desired amount of spherical aberration to be corrected? Although some surgeons prefer an aspheric zero aberration design and others prefer the negative aberration designs, we cannot be sure which type of lens offers the most accurate correction and best contrast sensitivity. It is not very likely that this debate will cease in the near future. The new concept of the Light Adjustable Lens (LAL; Calhoun Vision, Inc., Pasadena, California), described by José L. Güell, MD, PhD, of Barcelona, Spain, which may be precisely adjusted by UV light might be an interesting option in the future.
In my opinion, it is very doubtful that any specific spherical aberration correction strategy will prove to be significantly superior to the others. Although I am convinced that we should implant aspheric IOLs into our patients when possible, I also recognize that variables like individual corneal shape, pupil size, IOL decentration, and tilt greatly determine the clinical relevance of using an aspheric design. Moreover, when a patient has a minor residual refractive error—corrected or uncorrected—the influence of spherical aberration correction is minimal.
Other differences between the existing aspheric IOL models on today's market may be more important than the minor differences in spherical aberration correction such as material, sharpness of the optic edge, haptic design, minimal required incision size, related induced astigmatism, ease of injection, and axial and rotational stability.
As technology continues to advance and our patients broaden their demands for optimal visual quality after surgery, the customized selection of an IOL with respect to toricity, spherical aberration, multifocality, and color (selective light filtering) will become more important. This will become a large but exciting challenge for both surgeons and the ophthalmic industry. Regrettably, I foresee a future problem in the way that European health care systems will be reluctant to accept the ever-increasing additional cost involved with this progress.
I trust that not only these cover focus articles, but also the other cataract and refractive surgery topics found in this issue, will help and inspire you in your daily practices. As always, we encourage your comments and letters to the editor.
