August 2002
Review of Refractive Surgery
A new accommodating IOL(Human Optics AG, Eriangen.
Germay provide patients with good, spectacle-free visual
acuity for both near and distance.
The foldable one-piece
IOL has a central optic of 5.5 mm and an overall diameter
of 9.8 mm. (Figure 1) It is made of a hydrophilic acrylic
material with a UV-inhibitor
and has a refractive index of 1.46. It has four flexible haptics with flexible
joints. The joints of the haptics bend when the capsular bag compresses an
edge; as a result, the proposed mechanism for this IOL is that the haptic moves
forward to increase the distance between the lens and the retina, there by
enabling the eye to achieve accommodation.
We conducted a small
trial of 11 eyes of 11 patients who underwent implantation
with this new lens. Study patients had a mean age of 51.5 years (range: 49
to 72 years). All had cataracts and their mean preoperative uncorrected visual
acuity was 20/150 (range: CF to 20/50) for distance and J7 (range: Jl to J1O)
for near. All
had a scotopic pupil size less than 5 mm.
After a mean follow-up
of seven months (range: five to nine months), all patients
achieved vision sufficient for driving and reading
a newspaper without spectacle correction. All of the
patients are 20/30 or better and they are very happy
because they do not use glasses. Many wore glasses
or contact lenses preop to correct for near and distance.
All were presbyopic.
Surgical technique
Patients underwent phacoemulsification through a 2.75-mm clear comeal incision,
under topical anesthesia achieved by 2% Xylocaine gel. It is important to
note that this lens requires a very central, relatively small (4 to 5 mm),
and curvilinear capsulorhexis. According to the mechanism of accommodative
movement proposed by the manufacturer, it is believed that this is imperative
to achieve postop accommodation, which appears to be driven by the capsular
movement following contraction of the ciliary body. A larger, eccentric and
nonorcular capsulorhexis may reduce this effect significantly.
The IOL is inserted with a shooter. The lens is prefolded
in the shooter cartridge and then injected within the
capsular bag in a slow, controlled fashion. Learning
to unfold the IOL in the bag becomes easier with experience.
(Figure 2) Following insertion of the IOL within the
bag, the surgeon unfolds all four haprics. I perform
this maneuver with a Kuglen hook. The IOL achieves
good centradon despite its relative smaller total diameter,
perhaps due to its multiple points of fixation.
We had no intraoperative complications. At the final
follow-up the mean uncorrected visual acuity was 20/35
(range: 20/15 to 20/50) for distance and J2 (range:
Jl ± J3) for near. The mean postoperative accommodating
index, determined by measuring the prescription of
the eye at cycloplegia and with drop ofpilocarpine,
was +1.50 D (range: +1 D to +2.50 D). One eye with
macular degeneration adversely affected the
mean postoperative visual values.
Visual acuity was
measured one eye at a time and mean postop refraction
was +0.25 D. The mean result of the push-up accommodation
test without pilocarpine was +1.50 D (range: +1 to+3
D).
Capsulorhexis, I/A
The lens is easy to handle, and it is simple to tell the top from the bottom.
It unfolds gently in the eye and has no sharp edges. All of these are concerns
when using a new lens. The implantation is standard for any phaco procedure.
What makes the procedure difficult is the need for a near-perfect phaco through
a 4.5-mm capsulorhexis. If the capsule is torn or the capsulorhexis compromised,
then the accommodating mechanism may not be effective. The small capsulorhexis
provides more tensile strength to the residual capsule for accommodation.
If the capsulorhexis is
decentered or larger, there is less tension is placed on the lens haptics,
and the lens will have less maneuverability for accommodation.
Capsule opacification is another issue-a YAG laser
capsulotomy may also disable the accommodating mechanism.
We have not needed to perform a capsulotomy in these
II eyes. We were, however, very careful to perform
meticulous aspiration of all the residual cortex to
reduce the possibility of capsule opacification. Although
none of our
patients reported problems with night vision, the lens may not be ideal for
patients with very large pupils.
Two other IOLs that have been designed to afford improved
uncorrected near vision are in clinical studies in
the United States-AMO's Array multifocal IOL (Irvine,
CA) and C&C Vision's CrystaLens (Aliso Viejo, CA).
The first provides pseudo-accommodation via concentric
biconvex rings while the latter employs a hinged design
to move the optic forward.
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