Mini- and Micro-incision Cataract Surgery – A Critical Review of Current Technologies

Abstract

Modern cataract surgery is striving for smaller and smaller incisions with the aim of making clear corneal incisions that are as safe and topographically stable as possible. Recent innovations in both phacoemulsification (phaco) and intraocular lens (IOL) technology have made micro-incision cataract surgery, defined as <2mm incision, safe and effective. Bi-axial sleeveless micro-phaco has recently been joined by sleeve-armed micro-co-axial micro-phaco, made possible by the development of slim-shaft strong-bevel phaco needles armed with micro-sleeves that run flush with an enlarged needle head. Such tip technology allows for a highly efficient and safe high-flow, high-vacuum phaco through incisions as small as 1.4mm by providing high influx and suppressing surge while avoiding mechanical and thermal tissue damage. Two tips have so far been made available for mini- (2.2–2.4mm) and micro-incision cataract surgery (MICS) (1.4–1.6mm, depending on the incision architecture used). With the micro-tip supplemented by additional flow through an infusion spatula (‘infusion-assisted’ or ‘hybrid’ phaco), excessive flow and vacuum rates may be used, resulting in a two-fold efficiency as mirrored by the reduced phaco power required. IOL technology is lagging behind phaco technology. The challenge is to avoid trade-offs with regard to implant stability and aftercataract formation, as well as optical performance. Current MICS-IOLs are mostly hydrophilic acrylic one-piece constructions with insufficiently sharp posterior optic edges and broad haptic–optic junctions, both of which features compromise the optic-edge barrier effect. Recently, a hydrophobic three-piece IOL has been made available, which features a slim haptic junction and an exquisitely sharp optic edge and also allows for optional optic entrapment into a posterior capsulorhexis for lasting eradication of after-cataracts.