Roughly 250 years after Tadini1 proposed the use of a high-diopter lens implanted into the eye to remedy aphakia, his ideas have been realised imany variations. Intraocular lenses (IOLs), first implanted by Ridley2 in 1949, have become indispensable in the treatment of cataract or very high myopia. Today’s surgeons have myriad lenses to choose from:
• refractive multifocal and diffractive multifocal IOLs (mIOLs);
• lenses with square or round optics edges;
• IOLs with two, three or four haptics or a plate haptic;
• hydrophilic, hydrophobic or silicon lens materials; and
• fully transparent lenses and lenses with ultraviolet (UV) and even blue blocking filters.
Each of these choices will have an influence on the post-operative wavefront result and will be discussed in the following article.
Emergence of Wavefronts
The concept of wavefronts refers to waves of light like flat waves on a surface of water. A perfect lens will transform these flat waves into spherical waves with a centre in the focal point, and vice versa. An imperfect lens, on the other hand, will distort these wave patterns and superimpose distortions on these perfect patterns. These distortions are called the wavefront aberrations of the optical system. In order to measure wavefront aberrations in the eye, devices called aberrometers have been developed that use the above principle to quantify the ocular optical distortions. Many different types of aberrometers exist; the most common is the Hartmann-Shack method.3 Comparisons between the different methods and devices have been described in the literature.4,5 Wavefront aberrations are usually well explained within the context of refractive surgery, but remain largely unknown in other fields of ophthalmology because until recently there was no apparent need for it. However, cataract patients have become more demanding and are less willing to accept any post-operative spectacle correction, either for reading or for ametropia. This result can be achieved by a rigorous pre-operative biometry of the cornea, the anterior chamber and the eye as a whole, as well as the implantation of an IOL that remains immobile within the eye after implantation. Only a limited number of IOLs are on the market that can claim such a stable result. However, even with a stable IOL the need to educate the patient about a realistic outcome of the surgery is not eliminated. As an important part of the ocular optics is replaced during the cataract procedure, pre-operative aberrometry is perceived as not being very useful. Wavefront measurements come into play only to evaluate the result after the operation has been performed.