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 |
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