Face to face with IOLs

The virtues of phacoemulsification lens surgery are manifold: small self-sealing incision, easier astigmatism management, and closed-eye and controlled capsule surgery. Where phacosurgery has lagged for many years is in our inability to use the small incision for intraocular lens (IOL) implantation. Foldable IOL technology has now caught up with lens extraction techniques and thereby solves some, although not all, the demands of lens surgery. For example, low- and high-power IOLs require the use of larger, rigid IOLs and wider incisions. Thus, when hyperopic eyes require more than 30 diopters (D) of IOL power, either a poly(methyl methacrylate) (PMMA) IOL has to be used, with the disadvantage of an extended incision, or 2 or more foldable IOLs can be implanted in the capsular bag in piggyback fashion.1 Some new issues arise from the second stratagem. In this issue, Findl and coauthors describe a “Newton ring” phenomenon as a consequence of the face-to-face contact of acrylic IOLs. The serendipitous outcome is a multifocal effect, which appears to be quite beneficial for the recipient. They note that the contact zone is dependent on IOL curvature, mechanical properties of the IOL material, and the contact pressure, a consequence of capsular bag shrinkage. They suggest that the IOL surfaces will be fractionally flattened at the central contact zone and therefore of slightly less refractive power than the surrounding zone, yielding a multifocal effect. Does this affect visual acuity? Is there a price to be paid for the potential multifocal gain? A separate issue not yet reported with piggyback IOLs is the presence of rogue cells (pearls?) in the interface between the IOLs. How do lens epithelial cells or other cells gain access? Even if they do, how can they grow between the compressed surfaces? One has only to observe broken walls and sidewalks from tree roots to appreciate the “muscular” power of growing cells and tissues and realize that pearls can thrive and disrupt the optical continuity of piggyback IOLs (Figure 1). Such a phenomenon does exist and thereby raises a therapeutic challenge. With capsular bag shrinkage, how can we gain access to the pearl to remove it? The neodymium:YAG laser surely has no part in management for its application would disrupt the IOL surfaces.Figure 1.: (Rosen) A pearl disrupting the optical continuity of piggyback IOLs (Staar plate-haptic IOL) 12 months after implantation.New techniques raise new if rare issues. Reporting them is important to enable a wider audience to contemplate the next set of solutions.