Optical quality and retinal quality are essential elements of the performance of any IOL. Physicians can define success by determining how much of each issue is involved in any procedure.
This article was reviewed by Dr. Jorge Alio, MD, PhD
Presbyopia-correcting IOLs are among the most important recent innovations in cataract and refractive surgery. A number of options are available to satisfy a growing patient population that demands spectacle-independent intermediate vision in addition to distance vision.
“These technologies have resulted in tremendous changes in clinical practice,” said Jorge Alio, MD, PhD. “Selecting the appropriate presbyopia-correcting IOL is now a challenge for most ophthalmologists.”
Presbyopia-correcting IOL choices
The current trends in the new multifocals (mf) IOLs presbyopic IOLs are diffractive and refractive models. The former have reached a high standard of clinical performance and are designed to eliminate halos and glare by decreasing the near optical power, according to Dr. Alito, professor and chairman of ophthalmology, VISSUM, Instituto Oftalmologico de Alicante, Universidad Miguel Hernandez, Alicante, Spain.
“The new models combine manipulation of aberrations with multifocality and are referred to as a new hybrid mfIOL,” he explained.
Extended-depth-of-focus (EDOF) IOLs
This is the most recent technologic advance to become available for treating presbyopia.
According to Dr. Alio, these lenses manipulate the IOL’s spherical aberration (SA) so that the incoming light waves are elongated, which eliminates both the overlap of near and far images and the halos. These IOLs were designed to improve the intermediate vision. An associated limitation is the decreased retinal image quality, and for this reason the near vision add is limited to about 1 D.
A number of companies have investigated this approach. Dr. Alio mentioned the Wichterle IOL (Medicem), a continuous-focus model that manipulates SAs. The idea behind this single-piece polyfocal hyperbolic optic with no haptics was that it mimicked the natural young crystalline lens, with the possibility of accommodation; however, poor visual quality forced the company to abandon this model. The Mini Well monofocal IOL (Sifl), another EDOF IOP, induces SAs in specific areas of the optic to increase the depth of focus and generate multifocality.
Another way of achieving the EDOF effect is use of the pinhole effect. The IC-8 (AcuFocus, Inc.), which uses a small aperture, achieves an extended and continuous range of vision using an embedded opaque annular mask of 1.36 mm that blocks unfocused paracentral light rays and permits paraxial light rays to enter. The XtraFocus Pinhole Implant (Morcher) is based on the same principle using a smaller pinhole of 1.3 mm.
The EDOF IOLs are approved only for distance and intermediate vision. Patients will need at least 1 D of correction for near vision. Postoperative patient dissatisfaction is attributed to intolerance of the total induced aberrations. If there is excessive EDOF, the quality of vision is affected. The explantation rate is higher.