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Cataracts
Figure 6: Early Primary Barrier Failure Along the Broad co-axial phaco techniques, these limitations are the main reason why
Optic–Haptic Junction of Hydrophilic Micro-incision
sleeveless bi-axial phaco has not gained widespread usage.
Cataract Surgery Intraocular Lenses
Barrier failure at one year post-operatively
Micro-incision Cataract Surgery Intraocular Lenses
A critical issue is IOL technology for micro-incisions. Currently, several
IOL designs are available that may be inserted through incisions
between 1.5 and 2.0mm. The MI60 IOL by Bausch & Lomb is a one-piece
acrylic IOL with four solid flanges and an ‘enhanced’ edge that runs
beneath the broad junctions to provide a barrier effect. A strong
angulation will press the optic posteriorly in order to minimise the
Zeiss-Acri.Tech
Acrismart optic–capsule interspace for LEC immigration and pearl formation. The
Micro AY by PhysIOL is another one-piece acrylic with four fenestrated
haptics. Both lenses are designed to fit through a 1.8mm CCI with the
injector tip docked to it. The Acri.Smart IOL by Zeiss-Acri.Tec is a one-
piece IOL with two broad solid flanges similar to earlier plate lens styles.
In addition to aspherical optics, it is also available with toric and bi-focal
optics, or a combination of both. An incision size of only 1.5mm is
claimed to be sufficient for implantation. All three MICS IOLs are made
of hydrophilic acrylics, allowing the lens to be compressed and, thus, to
B&L MI60
pass through a micro-cartridge, and all are delivered by docking the
Source: M Möglich. Source: T Amzallag.
injector tip to the incision entrance. By contrast, the Y-60H iMICS IOL by
HOYA features a three-piece design with polymethylmethacrylate loops
Figure 7: Hydrophobic HOYA iMICS Three-piece
Intraocular Lens – Optic Entrapment in Posterior
bonded to an optic made of hydrophobic acrylic. The optic features an
Capsulorhexis Opening (‘Posterior Optic Button-holing’)
exquisitely sharp posterior optic edge, which is also functional beneath
Excludes Retro-optical Opacification the slim optic–haptic junctions. The IOL comes with a special micro-
cartridge to allow implantation with the tip inserted through incisions as
Posterior optic button-holing
small as 1.8mm if designed accordingly.
In principle, IOLs with a broad haptic–optic junction suffer from
deficiencies in the barrier effect against migrating LECs. Although
attempts have been made to counterbalance this by implementing a
so-called enhanced edge running beneath the flange haptics, thus
bridging the posterior optic sharp edges outside the haptic junctions,
this concept has been shown to be ineffective. This is not surprising as
it is not the sharp edge per se but rather the capsular bend that blocks
LEC migration. In the course of capsular-bag closure, the posterior
capsule is pulled around and up to the anterior capsule to be finally
sealed to the latter through collagen depletion by transforming
anterior LECs.
8
Simply implementing a ridge beneath a broad haptic
does not allow for bending of the posterior capsule, which is made
impossible by a peripherally extending flange haptic, even if
fenestrated. In addition, the edges of these hydrophilic IOLs are not as
sharp as claimed and the barrier effect is therefore limited.
14
It is not
surprising that as early as one year post-operatively, a significant
needle head, which counteracts forward-directed flow. The infusion percentage of eyes implanted with hydrophilic flange-haptic MICS-IOLs
enters the chamber through the lateral openings of the sleeves and is exhibit signs of primary barrier failure (see Figure 6).
8
The HOYA iMICs
re-attracted by the frontal opening of the phaco needle. The high IOL complies with the standard of a slim haptic design and exhibits the
fluidics allowed with this particular needle design and the incisional sharpest posterior optic edge of all hydrophobic acrylic IOLs on the
tightness provided by the sleeve minimise uncontrolled turbulences in market,
15
thereby allowing optimum circumferential capsular bending.
the chamber by confining the fluid stream between the sleeve and Since the injector tip is inserted into the incision, unfolding and
needle openings to the tip of the handpiece. With infusion and delivering into the capsular bag is perfectly controlled. The HOYA iMICS
aspiration separated, the fluid stream changes according to the three-piece IOL may also be used in conjunction with posterior optic
relative positioning of the instrument openings and is superimposed button-holing for permanent eradication of any form of after-cataract
by turbulences caused by the wound leak, which varies as the formation (see Figure 7).
9
Considering the high rate of barrier failures,
instruments manipulate the corneal wound. Also, the advantages of a even with hydrophobic acrylic IOLs, this IOL feature may gain
slim-shaft needle cannot be fully exploited, since the outer wall of a increasing importance in the future. In consideration of the market
needle used with sleeveless phaco must run flush with the head for trend towards one-piece IOLs, which are most easily handled and
proper wound sealing. In order to be efficient, needles for sleeveless inserted, HOYA is currently developing a single-piece IOL with a similar
phaco must be thicker, or they will be less efficient if down-sized in design to the Acrysof SX60 platform, but with sharper edges and a
diameter for use in micro-incisions. Apart from the familiarity with the glistening-free hydrophobic acrylic optic.
56 EUROPEAN OPHTHALMIC REVIEW
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