Download HydROPHOBIc AcRylIc IOl

contacts
Update
cataract & refractive
HYDROPHOBIC ACRYLIC IOL
Novel material and design aim to bring optimised
optical and anatomic performance
by Cheryl Guttman Krader in Vienna
C
ataract surgeons report
favourable early experiences
with a new, single-piece
IOL constructed of a novel
hydrophobic acrylic material (enVista
MX60, Bausch+Lomb).
In a free paper session during the XXIX
ESCRS Congress, Roberto Bellucci MD,
Department of Ophthalmology, Hospital
and University of Verona, Italy, and
Richard Packard MD, Prince Charles Eye
Unit, Windsor, UK described the features
of the new IOL, reviewed its handling
characteristics, and reported postoperative
outcomes.
The IOL has a 6.0mm optic with an
aspheric (aberration-free) design and
360-degree square edge. It has modified
C-haptics, an overall length of 12.5mm,
lies flat on the bench, and has a five-degree
posterior vault when compressed.
Its hydrophobic acrylic material is a
highly cross-linked acrylic copolymer
designed specifically for IOL use. It has an
optimised refractive index (1.54), a high
Abbe number (40.5), and low silicone
oil affinity. The IOL is hydrated to an
equilibrium water content of four per cent
and packaged in physiological sterile saline
so that its water content is maintained.
“The refractive index of this novel
acrylic material allows for a thin lens and is
similar to that of the acrylic of the AcrySof
IOLs, but it has a higher Abbe number.
Hydration of the material to equilibrium
prior to implantation should eliminate the
driving force for water diffusion into the
IOL in the eye, theoretically eliminating
the potential for haze, glistenings and other
material defects,” said Dr Bellucci.
“Surface hardness is also excellent,
making it resistant to damage from surgical
instruments, and the surface properties of
the IOL are more stable after implantation
compared to other hydrophobic IOLs that
are packaged dry,” said Dr Bellucci.
Design features Dr Packard also
commented on the unique material and
design features. “The Abbe value of this
material is important because the higher
the number, the less the chromatic
aberration and therefore the better the
retinal image quality. Its four per cent
equilibrium water content, which is much
higher than the 0.35 per cent to 0.5 per
EUROTIMES | Volume 16/17 | Issue 12/1
EnVista lens in cartridge
“
The refractive index
of this novel acrylic
material allows for
a thin lens and is
similar to that of the
acrylic of the AcrySof
IOLs, but it has a
higher Abbe number
Roberto Bellucci MD
EnVista lens emerging into eye with elbow of haptic forward
cent water content of other hydrophobic
acrylic IOLs, should allow the material
to remain stable in the eye without water
exchange, which is believed to cause
glistenings,” he said.
The hydrophobic acrylic is not as sticky
as some lens materials, but it does have a
good contact angle and with its 360-degree
square posterior edge, it should have good
PCO characteristics, he added.
Dr Bellucci reported that the BCVA
outcome in his series of 10 patients was
“very satisfying”. At six months, logMAR
BCDVA was -0.02 ±0.06. Slit-lamp
examinations performed throughout the
follow-up period confirmed continued
centration and absence of any internal
vacuoles or surface scratches.
Findings from wavefront aberrometry
showed a pattern consistent with that of
neutral aspheric IOLs. Optical quality was
investigated by determining the pointspread function (Strehl ratio) measured
using both Hartmann-Shack (Topcon) and
double-pass (OQAS) aberrometers, and the
results were satisfactory.
Richard Packard – [email protected]
Roberto Bellucci – [email protected]
“These first optical and anatomical
results are encouraging, and because
the IOL could have absorbed water in
its packaging prior to surgery, even this
short-term study is important as initial
confirmation of its potential to remain
glistening-free. Longer observation is
needed,” said Dr Bellucci.
Dr Packard’s study included 20 patients,
10 of his own and 10 operated on by
David Spalton MD, St Thomas’ Hospital.
The surgeries were done under topical
anaesthesia through a 2.75mm clear
corneal incision. Ease of insertion using a
proprietary injection device was rated
with an overall score of four (best possible
= five).
“The injector system worked well
through a 2.75mm incision, and the IOL
unfolded slowly, which made it easy to
position. Now, a new injector system is
available allowing implantation through a
2.2mm incision,” Dr Packard said.
Courtesy of Richard Packard MD
18
No adverse events He also reported
that consistent with the surface hardness
of the hydrophobic acrylic material, he
observed no markings from instrument
handling in slit-lamp examination, and
there were no adverse events during a
mean follow-up of 17.3 days.
Mean Snellen UDVA improved
from 21.9/6 to 10.4/6 and mean CDVA
improved from 14.3/6 to 8.2/6. However,
Dr Packard observed the results were
skewed because visual prognosis was
guarded in two patients with ocular
co-morbidities. Mean MRSE was +0.4 ±0.9
D compared with a formula predicted
target of -0.27 ± 0.2 D.
Power calculations were performed using
the SRK/T formula with the manufacturer’s
original recommended A-constant of 118.7
for optical biometry. However, based on
the refractive outcomes, the manufacturer
has revised the A-constant to 119.1, Dr
Packard said.
Dr Packard also presented a video to
demonstrate IOL loading and implantation
through a 2.2mm incision.
After the IOL is placed in the cartridge
with the haptics tucked under the edge, the
implant is rotated to align its long axis, ie,
along the optic-haptic junction, with the
long axis of the cartridge. This causes the
leading haptic to turn into an elbow on
the top of the lens and assures that when
the lens is released, the leading haptic is
properly positioned and the IOL can be
pushed directly into the capsular bag.
“Proper loading of the IOL in the
cartridge is important for ease of
positioning. In addition, to enable pushing
the lens into the bag, surgeons should fill
the whole capsular bag with viscoelastic
before filling the rest of the anterior
chamber,” Dr Packard said.