Can an Aspheric IOL

Improve Visual Performance?

Comparing the results obtained with three IOLs.



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




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.



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


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.




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.