JUNE
2003 CATARACT & REFRACTIVE SURGERY TODAY Page 1
Can
an
Improve Visual Performance?
Comparing
the results obtained with three IOLs.
BY
ROBERT M. KERSHNER, MD, FACS
COVER
STORY
In
2002, the FDA approved the Tecnis Z-9000 lens
(Pfizer
Inc., New York, NY), which features an anterior,
modified
prolate, aspheric surface. The aim of
the
IOL’s design is to restore the balance between
the
positive spherical aberration of the cornea and the
negative
spherical aberration of the youthful crystalline
lens
that is lost upon the development of a cataract. At
the
ASCRS annual meeting in San Francisco in April
2003,
I presented the results of my study to determine
whether
the the aspheric optic of the Tecnis lens can
improve
retinal image contrast and functional visual
performance.1
METHODOLOGY
For
the prospective study, 221 eyes of 156 patients
were
randomized to receive either the STAAR AA4207-
VF
Silicone IOL (STAAR Surgical Company, Monrovia,
CA),
an Alcon SA60AT acrylic IOL (Alcon Laboratories,
Inc.,
Fort Worth, TX), or a three-piece Tecnis IOL. I performed
all
of the lens extractions and IOL implantations.
Observers
and I collected data while blinded as to IOL
identity,
and we followed subjects for 6 months. We
measured
patients’ visual acuity preoperatively and at
1
day, 1 week, 3 weeks, 1 month, 3 months, and 6
months
postoperatively. We performed fundus photography
and
functional acuity contrast testing under photopic
and
mesopic conditions preoperatively and at
3
months postoperatively. I analyzed the photographs via
Adobe
Photoshop 7.0 image software (Adobe Systems
Incorporated,
San Jose, CA) using the L*a*b color model,2
an
international standard for color measurement de-signed
to
be consistent no matter which device is used to
produce
the image.
RESULTS
No
surgical or postoperative complications occurred
during
the course of this study. Thirty-one patients (7%)
experienced
a rise in postoperative IOP (>24 mm Hg)
that
was unassociated with lens style. The increase in
pressure
resolved with the release of aqueous and the
application
of one drop of 0.5% Timolol (Merck and Co.,
Inc.,
West Point, PA) to achieve IOPs below 18 mm Hg.
The
YAG capsulotomy rate at 6 months was 0.9% for the
silicone
group and 0% for the aspheric and acrylic
groups.
I
found no statistically significant difference between
subject
groups in pre- and postoperative spherical, astigmatic
refractive
error or BCVA. Patients who received
the
aspheric IOL, however, achieved the best UCVA during
the
first postoperative month. Under photopic conditions,
they
demonstrated a 38% to 47% increase in
contrast
sensitivity, whereas I found little difference in
contrast
sensitivity under these lighting conditions between
the
preoperative cataract, silicone, and acrylic IOL
groups.
The aspheric IOL also performed best under
mesopic
conditions (an improvement of 9% to 100% vs
25%
to 50% in the acrylic group and 0% in the silicone
group)
(Figure 1). Subjects who received the spherical
silicone
IOL experienced no increase in contrast sensitivity
as
compared with preoperative cataract levels. My
digital
analysis of retinal imaging showed an increase in
threshold
luminance levels in the aspheric group, as well
as
in image contrast, when compared with the preoperative
cataract,
silicone, and acrylic groups (Figure 2).
At
the 1-month visit, the UCVA of subjects who
received
acrylic IOLs matched that of those who received
the
aspheric IOL. A statistically significant difference
in
UCVA continued after the 3- to 6-month visits,
however,
between the aspheric group (20/25 ±2) and
the
silicone (20/36 ±1) and acrylic (20/30 ±1) groups
(results
at 6 months). This difference could not be explained
on
the basis of pre-existing or postoperative refractive error.
CONCLUSIONS
All
three IOLs improved patients’ UCVA after cataract
surgery,
but the greatest improvement occurred in the
aspheric
group during the first month. Patients who received
the
silicone IOL did not demonstrate improved
contrast
testing despite an improvement in visual acuity.
The
acrylic IOL improved patients’ contrast testing under
some
lighting levels when compared with preoperative
levels,
but the increased values were significantly less
than
those experienced by subjects who received aspheric
IOLs.
Although the clarity of the retinal imaging improved
in
all subject groups when compared with the
preoperative
images, the retinal image contrast markedly
improved
in the patients who received aspheric IOLs as
compared
with those who received either silicone and
acrylic
IOLs (Figure 3).
These
data demonstrate that implanting the aspheric
IOL
significantly enhances patients’ objective retinal
image
contrast and functional visual performance. This
lens
technology may represent a new standard in IOL
visual
quality.
Robert M. Kershner, MD, FACS, is Director of the Eye
Laser Center in Tucson, Arizona, and Clinical Professor
of
Ophthalmology at the Moran Eye Center, University of
Utah School of Medicine, Salt Lake City. He has no
proprietary
or financial interest in the products described herein
.
Dr. Kershner may be reached at (520) 797-2020;
1.
Kershner RM. A prospective evaluation of aspheric (Tecnis), silicone, and
acrylic IOLs on
retinal
image contrast and functional visual performance. J Cataract Refract Surg.
In press.
2.
Adobe Systems Incorporated. Adobe Photoshop Users Manual. San Jose, CA;
2002.
Figure
1. Functional acuity contrast testing compares the
aspheric,
silicone, and acrylic IOLs.
Figure
2. The author analyzed retinal image contrast with pre-operative
(left)
and postoperative (right) fundus photography.
Note
the marked improvement in image quality and contrast.
Figure
3. Threshold luminance displays the difference between
the
lightest edge (bottom of graph) and the darkest
edge
(top of graph) for the pooled image data of each subject
group.
Note that the widest range of contrast data for the
retinal
images was taken through the aspheric IOLs.
Figure
4. The TECNIS IOL in position.
JUNE
2003 CATARACT & REFRACTIVE SURGERY TODAY Page 2