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Cataracts
Mini- and Micro-incision Cataract Surgery –
A Critical Review of Current Technologies
Rupert Menapace
Professor, and Head, Day Surgery Centre and Intraocular Lens Service, University of Vienna Medical School and Vienna General Hospital
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 after-
cataract 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.
Keywords
Micro-incision cataract surgery (MICS), micro-co-axial microphacoemulsification, high-flow high-vacuum phaco, surge suppression,
mechanical and thermal tissue damage, MICS lenses, optic-edge barrier effect, sharp posterior optic edge, slim haptic–optic junction, posterior
optic ‘button-holing’
Disclosure: The author has no conflicts of interest to declare.
Received: 28 July 2009 Accepted: 20 September 2009
Correspondence: Rupert Menapace, Professor of Ophthalmology, Intraocular Lens Service, Department of Ophthalmology, Waehringer Guertel 16-18, A 1090 Vienna,
Austria. E:
rupert.menapace@meduniwien.ac.at
Recent developments in cataract surgery have been dominated by • Topographic neutrality (corneal stability): incisions must not induce
efforts to further down-size the incision for phaco-emulsification corneal shape changes. Smaller incisions cause asymmetrical
(phaco) and intraocular lens (IOL) implantation. This article changes, which are properly picked up only with corneal
demonstrates and discusses the benefits and downsides of further topography. Topographical stability may be considered relevant
down-sizing the cataract incision, the requirements regarding phaco within a pupillary zone of 5mm.
and IOL technology, the pros and cons of the co-axial and bi-axial
approaches and the currently available state-of-the-art co-axial We have demonstrated that temporally located tunnel incisions with
instrumentation and implants. a scleral portion (temporal sclero-corneal incisions [SCIs]) are the best
option to provide both adequate deformation resistance
1
against
Is There a Need for Further digital massage and topographical neutrality within a 5mm zone.
2
This
Down-sizing of the Cataract Incision? is true for incision sizes up to 4mm.
3
Cataract incisions must fulfil two requirements:
If temporally located sclero-corneal incisions up to a size of 4mm
• Deformation resistance (wound stability): to be safe, an incision fulfil the requirements, why then should we struggle to further
must not open when manipulated. In practice, a patient may rub minimise the cataract incision? The answer is that the
the eye with a finger tip. Temporally located incisions are aforementioned is true only for sclero-corneal incisions. We have also
particularly exposed to such deformation and must be designed demonstrated that 3mm-wide clear corneal incisions (CCIs) are not
accordingly. Deformation resistance depends on the size and safe enough and induce asymmetrical corneal flattening adjacent to
construction of the incision; it increases as it gets smaller and the incision that encroaches on the 5mm optical zone.
4
With
longer and when it incorporates a scleral portion. temporal-superiorly or superiorly located incisions, this sectorial
52 © TOUCH BRIEFINGS 2009
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