Spherical Aberration and Contrast Sensitivity in Eyes Implanted with ...

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May 1, 2008 - tive study of 25 patients with bilateral cataract, an IOL with a modified anterior surface (Tecnis Z9001; Ad- vanced Medical Optics, Santa Ana, ...

Spherical Aberration and Contrast Sensitivity in Eyes Implanted with Aspheric and Spherical Intraocular Lenses: A Comparative Study PATRICK F. TZELIKIS, LEONARDO AKAISHI, FERNANDO C. TRINDADE, AND JOEL E. BOTEON ● PURPOSE:

To determine whether implantation of an intraocular lens (IOL) with a modified anterior aspheric surface results in reduced spherical aberration and improved contrast sensitivity after cataract surgery. ● DESIGN: Prospective, comparative, interventional case series. ● METHODS: In an intraindividual randomized prospective study of 25 patients with bilateral cataract, an IOL with a modified anterior surface (Tecnis Z9001; Advanced Medical Optics, Santa Ana, California, USA; group 1) was compared with biconvex lens with spherical surfaces (ClariFlex; Advanced Medical Optics; group 2). Ocular aberrations for a 5.0-mm pupil and 6.0-mm pupil were measured with Hartmann-Shack aberrometer. Quality of vision was measured by visual acuity and contrast sensitivity under mesopic and photopic conditions. All patients were followed up for three months. ● RESULTS: No statistically significant difference in postoperative uncorrected and best-corrected distance vision acuity after a follow-up of three months existed between the groups. Postoperative contrast sensitivity testing revealed significant differences between the groups under photopic and mesopic conditions. These differences reached statistical significance under photopic conditions at three spatial frequencies and under mesopic conditions at all spatial frequencies. When analyzing higher-order aberrations, the difference between the groups was statistically significant at the 5.00-mm and 6.00-mm pupil diameters, with the group 1 inducing less higher-order aberration and also less spherical aberration compared with group 2. ● CONCLUSIONS: Results show the Tecnis Z9001 IOL with a modified anterior aspheric surface induced significantly less higher-order aberration and spherical aberration compared with the ClariFlex IOL. Contrast sensitivity revealed better values under photopic and mesopic conditions with the Tecnis Z9001 IOL. (Am J Ophthalmol 2008;145:827– 833. © 2008 by Elsevier Inc. All rights reserved.)

Accepted for publication Dec 20, 2007. From the Brasília Ophthalmologic Hospital, HOB, Brasília, Brazil (L.A., P.F.T.); and the São Geraldo Eye Hospital, Federal University of Minas Gerais–UFMG, Belo Horizonte, Brazil (P.F.T., F.C.T., J.E.B.). Inquiries to Patrick F. Tzelikis, SQN 203, bloco G, apart 405, Brasilia–DF–Brazil 70833-070; e-mail: [email protected] 0002-9394/08/$34.00 doi:10.1016/j.ajo.2007.12.023

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ITH IMPROVEMENT IN THE QUALITY OF LIFE

and the resulting expansion of the elderly population, the prevalence of cataract cases will continue to rise. The population is on average older, and the environment has become more demanding for older people, who therefore need to regain excellent quality of vision. Advances in both intraocular lens (IOL) and phacoemulsification technology have enabled cataract surgery to evolve from a procedure concerned with the safe removal of the cataract to a procedure refined to achieve the best possible postoperative refractive result. Snellen visual acuity insufficiently describes the quality of the eye’s optics before and after cataract surgery.1–3 Multiple scientific studies have demonstrated that contrast sensitivity represents a robust indicator of functional vision.4 – 6 The contrast sensitivity function, measured under varying conditions of luminance and glare, establishes the limits of visual perception across the spectrum of spatial frequencies.1,2 Studies have demonstrated a nearly linear decline in image quality with age, suggesting a significant increase in the optical aberrations in the eye over time.7–9 Advances in wavefront technology have opened a new door to the measurement of ocular aberrations.9,10 Also, this technology allowed the development of a new type of IOL designed to compensate for the positive spherical aberration of the cornea, which is one of the most important aberrations contributing to visual deterioration of the pseudophakic eye.11–14 Based on these findings, the approach to compensate for increasing spherical aberration in older eyes is to develop an IOL that introduces negative spherical aberration into the system. Such an IOL, the Tecnis Z9001 IOL (Advanced Medical Optics, Santa Ana, California, USA), has been developed. This is a polysiloxane foldable three-piece IOL, with an anterior aspheric surface (negative spherical aberration) designed to decrease the total amount of ocular spherical aberration after cataract surgery.7 The purpose of this study is to determine whether implantation of an IOL with a modified anterior aspheric surface results in reduced spherical aberration and improved contrast sensitivity after cataract surgery.

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recorded for all eyes (noncontact specular microscope; NonCon Robo CA; Konan Medical, Hyogo, Japan). The visual acuity measurements were recorded with logarithm of the minimum angle of resolution (logMAR) UCDVA and BCVA. Clinical data were collected before surgery and one and three months after surgery for each eye. All patients were operated in the same fashion by the same surgeon (P.F.T.). All patients received topical anesthesia by lidocaine 2% gel before surgery. A 2.75-mm self-sealing clear corneal incision was made on the temporal side. Viscoelastic solution of sodium hyaluronate 3% and chondroitin sulfate 4% (Viscoat; Alcon Laboratories, Fort Worth, Texas, USA) was used to reform and stabilize the surgical planes and to protect the endothelium. A 5.00- to 5.25-mm continuous curvilinear capsulorrhexis initially was performed with a 26-gauge needle and was completed with forceps. The nucleus was removed without intraoperative complications such as posterior capsule rupture. Phacoemulsification was performed using the Infinite (Alcon Surgical) or Sovereign (Allergan Surgical; Advance Medical Optics) device. All IOLs were inserted in the capsular bag with the injector system. The viscoelastic material was removed completely at the end of the procedure. No sutures were used in any case. After one week, the patient underwent surgery in the fellow eye. Postoperative medication included moxifloxacin (Vigamox; Alcon) or gatifloxacin (Zymar; Allergan, Irvine, California, USA) four times daily for two weeks, 0.1% diclofenac sodium (Voltaren; Novartis Corp, East Hanover, New Jersey, USA) three times daily for four weeks, and steroid (Predfort; Allergan) eye drops four times a day for six weeks. Postoperative evaluations were performed at one day, one month, and three months. At one and three months, visual acuity, refraction, contrast sensitivity (CSV-1000 HGT; Vector Vision, Inc, Greenville, Ohio, USA), and wavefront analysis with the Zywave aberrometer (Bausch & Lomb, Rochester, New York, USA) were performed. Contrast sensitivity was measured using the CSV-1000 HGT testing instrument, which presents a translucent chart divided into four cycles with spatial frequencies of 3, 6, 12, and 18 cycles per degree (cpd). The background illumination of the translucent chart does not depend on room lighting; rather, it is provided by a fluorescent luminance source of the instrument and is calibrated automatically to 85 candelas (cd)/m2. All measurements were obtained under mesopic (5 cd/m2) and photopic (85 cd/m2) conditions. Each cycle contained 17 round patches that were 1.5 inches in diameter. The first patch had a high-contrast grating and represented the sample. The test patches were arranged in two rows with eight levels of contrast. The levels decreased from left to right along the row in a logarithmic fashion in 0.17 log units for steps 1 through 3 and 0.15 log units for steps 3 through 8. The examinations were performed unilaterally at a distance of 2.5 m with BCVA and an undilated pupil. All measure-

TABLE 1. Characteristic of Two Intraocular Lens in the Study Characteristic

IOL type Overall length (mm) Optic diameter (mm) Optic material Angle (degrees) Refractive index Optic shape Estimated A-constant

Aspheric

Spheric

Three-piece 13.0 6.0 Silicone 6 1.46 Biconvex, aspheric anterior surface 119.1

Three-piece 13.0 6.0 Silicone 10 1.46 Biconvex 118.0

IOL ⫽ intraocular lens.

METHODS THIS DOUBLE-BLIND PROSPECTIVE, RANDOMIZED STUDY IN-

cluded patients with age-related cataract, no indication of existing ocular pathologic features, unsatisfactory correction with glasses, and less than 2.50 diopters (D) of topography cylinder. Patients were offered the opportunity to be part of a clinical trial in which they would be allocated to have cataract surgery with implantation of an aspherical or spherical IOL. Patients were randomized to receive a Tecnis Z9001 aspheric IOL in one eye and a ClariFlex spheric IOL (Advanced Medical Optics) in the fellow eye. To protect patient safety, after the first eye surgery, they were asked whether they wished to have the same lens type implanted in the second eye. Exclusion criteria were previous ocular surgery, central endothelial cell count less than 1800 cells/mm2, glaucoma or intraocular pressure of more than 21 mm Hg, amblyopic eyes, retinal abnormalities, diabetes mellitus, steroid or immunosuppressive treatment, and connective tissue diseases. The selected lenses used in this study were the Tecnis Z9001 and the ClariFlex IOLs (Table 1). Eyes in group 1 (n ⫽ 25) received the Tecnis Z9001 IOL and eyes in group 2 (n ⫽ 25) received the ClariFlex IOL (Table 1). The Holladay formula was used to calculate the IOL power when there was a short axial length (⬍22.0 mm) and the SRK/T formula was used when there was an average axial length (ⱖ22.0 mm). The A-constant used was 119.1 for the Tecnis Z9001 IOL and 118.0 for the ClariFlex IOL. Axial length was measured with the IOL Master (Carl Zeiss Meditec, Inc, Dublin, California, USA), and the targeted postoperative refractive error was 0.0. Preoperative and postoperative evaluation included uncorrected distance visual acuity (UCDVA), best-corrected visual acuity (BCVA), spherical equivalent (SE), slit-lamp biomicroscopy, applanation tonometry, fundus examination, B-scan biometry, specular microscopy, and corneal topography. Topography was performed in all patients using the EyeSys unit version 3.03 (EyeSys Technologies, Houston, Texas, USA). The corneal endothelial cell count also was 828

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ments were conducted under the same conditions by an examiner who was unaware of the type of IOL implanted. Wavefront analysis was performed by the Zywave aberrometer. The Zywave aberrometer uses the HartmannShack method of analysis of the outgoing wavefront that measures up to fifth-order Zernike aberrations, including coma, trefoil, and spherical aberrations. For statistical analysis of visual acuity, logMAR acuity values were used. Similarly, the recorded contrast sensitivity values were transformed into log values as described by Vector Vision. All data analyses were performed using SPSSX statistical programs (SPSS, Inc, Chicago, Illinois, USA). The two IOLs were compared between eyes intraindividually. The analysis was based on a nonnormal distribution of the data. The nonparametric Mann–Whitney U test was used to compare data between the two IOL groups. A P value of less than .05 was considered statistically significant.

TABLE 2. Postoperative Visual Acuity and Refraction

UCDVA one mo UCDVA three mos BCVA one mo BCVA three mos SE ⫾ SD one mo (D) SE ⫾ SD three mos (D)

Spheric

P value

⫺0.10 ⫾ 0.11 ⫺0.12 ⫾ 0.13 0.00 ⫾ 0.05 0.00 ⫾ 0.05 ⫺0.25 ⫾ 0.40 ⫺0.27 ⫾ 0.38

⫺0.12 ⫾ 0.08 ⫺0.17 ⫾ 0.13 ⫺0.01 ⫾ 0.05 ⫺0.02 ⫾ 0.06 ⫺0.38 ⫾ 0.33 ⫺0.43 ⫾ 0.37

.50 .22 .32 .27 .15 .08

BCVA ⫽ best-corrected visual acuity; D ⫽ diopter; mos ⫽ months; SD ⫽ standard deviation; SE ⫽ spherical equivalent; UCDVA ⫽ uncorrected distance visual acuity. Visual acuity measurement in logarithm of the minimum angle of resolution units.

TABLE 3. Contrast Sensitivity Scores (logMAR units) in the Two Intraocular Lens Groups at Three Months

RESULTS FIFTY EYES OF 25 PATIENTS WERE INCLUDED IN THE STUDY.

Contrast Sensitivity

Eleven (44.0%) were men and 14 (56.0%) were women. The mean age of the patients was 65 years (range, 52 to 76 years; standard deviation [SD], ⫾ 6.3 years). All patients were followed up for three months. All patients received the Tecnis Z9001 in one eye (group 1) and ClariFlex in the contralateral eye (group 2). Before surgery, the mean logMAR UCDVA of group 1 was ⫺0.54 (20/70; SD, ⫾ 0.31), and that of group 2 was ⫺0.60 (20/80; SD, ⫾ 0.35), with no statistical difference between groups (P ⫽ .15). There was also no statistical difference between groups in mean best spectacle-corrected visual acuity, SE, corneal curvature, IOL power, and wavefront maps before surgery. After a follow-up of one month after surgery, groups 1 and 2 achieved logMAR UCDVA of 0.10 (20/25; SD, ⫾ 0.11) and 0.12 (20/26; SD, ⫾ 0.08), respectively, with no statistical difference between groups (P ⫽ .50). After a follow-up of three months, groups 1 and 2 achieved a UCDVA of 0.12 (20/26; SD, ⫾ 0.13) and 0.17 (20/30; SD, ⫾ 0.13), respectively, also with no statistical difference between groups (P ⫽ .22). After a follow-up of three months, a UCDVA of 20/25 or better was achieved 15 of 25 eyes (60.0%) in group 1 and 10 of 25 eyes (40.0%) in group 2. A UCDVA of 20/40 or better was achieved 24 of 25 eyes (96.0%) in group 1 and 23 of 25 eyes (92.0%) in group 2. Before surgery, the logMAR BCVA of group 1 was 0.18 (20/30; SD, ⫾ 0.09), and that of group 2 was 0.23 (20/34; SD, ⫾ 0.12), with no statistical difference between groups (P ⫽ .11). After the surgery, with a follow-up of one month, groups 1 and 2 achieved a BCVA of 0.00 (20/20; SD, ⫾ 0.05) and 0.01 (20/20; SD, ⫾ 0.05), respectively (P ⫽ .32). After a follow-up of three months, groups 1 and 2 achieved a BCVA of 0.00 (20/20; SD, ⫾ 0.05) and 0.02 (20/21; SD, ⫾ 0.06), respectively (P ⫽ .27). VOL. 145, NO. 5

Aspheric

VISUAL EFFICACY

Condition

Photopic, no glare 3 cpd 6 cpd 12 cpd 18 cpd Photopic, glare 3 cpd 6 cpd 12 cpd 18 cpd Mesopic, no glare 3 cpd 6 cpd 12 cpd 18 cpd Mesopic, glare 3 cpd 6 cpd 12 cpd 18 cpd

Aspheric (Mean)

Spheric (Mean)

P value*

1.62 1.78 1.37 0.92

1.59 1.67 1.31 0.75

.61 .10 .38 .026*

1.59 1.66 1.29 0.79

1.51 1.60 1.15 0.64

.20 .47 .022* .031*

1.62 1.67 1.27 0.87

1.45 1.53 1.13 0.70

.006* .012* .037* .038*

1.49 1.58 1.21 0.83

1.37 1.44 1.10 0.69

.032* .011* .137 .06

Cpd ⫽ cycles per degree; IOL ⫽ intraocular lens; logMAR ⫽ logarithm of the minimum angle of resolution. *Statistically significant P ⬍ .05.

The average SE at referral for group 1 was 0.35 D (range, ⫺7.50 to 4.00 D; SD, ⫾ 2.31 D), and that of group 2 was 0.27 D (range, ⫺8.50 to 4.50 D; SD, ⫾ 2.87 D), with no statistical difference between groups (P ⫽ .88). After a follow-up of one month after surgery, the SE in group 1 was ⫺0.25 D (range, ⫺1.50 to 0.50 D; SD, ⫾ 0.40 D), and that of group 2 was ⫺0.38 D (range, ⫺1.25 to 0.25 D; SD, ⫾ 0.33 D), with no statistical difference between groups (P ⫽ .15). After a follow-up of three months, the SE was ⫺0.27 OF

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FIGURE 1. Graphs demonstrating the postoperative comparison of contrast sensitivity in photopic and mesopic lighting conditions with and without glare at 3, 6, 12, and 18 cpd between the aspherical and spherical intraocular lens (IOL). (Top left) Postoperative comparison of contrast sensitivity in photopic lighting conditions without glare at 3, 6, 12 and 18 cycles per degree (cpd) between the aspherical and spherical IOL. Statistical difference between groups at 18 cpd (P ⴝ .02). (Top right) Postoperative comparison of contrast sensitivity in photopic lighting conditions with glare at 3, 6, 12, and 18 cpd between the aspherical and spherical IOL. Statistical difference between groups at 12 and 18 cpd (P ⴝ .02 and P ⴝ .03, respectively). (Bottom left) Postoperative comparison of contrast sensitivity in mesopic lighting conditions without glare at 3, 6, 12, and 18 cpd between the aspherical and spherical IOL. Statistical difference between groups at all spatial frequencies of 3, 6, 12, and 18 cpd (P ⴝ .006, P ⴝ .012, P ⴝ .037, and P ⴝ .038, respectively). (Bottom right) Postoperative comparison of contrast sensitivity in mesopic lighting conditions with glare at 3, 6, 12, and 18 cpd between the aspherical and spherical IOL. Statistical difference between groups at 3 and 6 cpd (P ⴝ .032 and P ⴝ .011, respectively).

D (range, ⫺1.25 to 0.50 D; SD, ⫾ 0.38 D) and ⫺0.43 D (range, ⫺1.25 to 0.25 D; SD, ⫾ 0.37 D) in groups 1 and 2, respectively, also with no statistical difference between groups (P ⫽ .08; Table 2). Postoperative contrast sensitivity testing revealed significant differences between the groups under photopic and mesopic conditions. These differences reached statistical significance under photopic conditions at three spatial frequencies: 18 cpd without glare (P ⫽ .02) and at 12 and 18 cpd with glare (P ⫽ .02 and P ⫽ .03, respectively). 830

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These differences also reached statistical significance under mesopic conditions at all spatial frequencies—3, 6, 12, and 18 cpd without glare (P ⫽ .006, P ⫽ .012, P ⫽ .037, and P ⫽ .038, respectively)—and at two spatial frequencies—3 and 6 cpd with glare (P ⫽ .032 and P ⫽ .011, respectively; Table 3; Figure 1). Postoperative wavefront analysis revealed at one month mean total aberration root mean square (RMS) values of 0.91 ⫾ 0.35 ␮m and 1.38 ⫾ 0.58 ␮m (group 1) and 1.09 ⫾ 0.34 ␮m and 2.01 ⫾ 0.57 ␮m (group 2) at 5.00- and OF

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FIGURE 2. Wavefront maps of one patient three months after surgery. (Top) In the right eye, the IOLs implanted was the Tecnis Z9001. (Bottom) In the left eye, the IOL implanted was the ClariFlex. Note the difference between high-order aberration in the (Top) right eye compared with the (Bottom) left eye.

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6.00-mm pupil diameters. Mean higher-order aberration values at one month were 0.33 ⫾ 0.11 ␮m and 0.53 ⫾ 0.19 ␮m (group 1) and 0.42 ⫾ 0.09 ␮m and 0.77 ⫾ 0.15 ␮m (group 2) at a 5.00- and 6.00-mm pupil diameters. Mean spherical aberration values at one month were 0.010 ⫾ 0.013 ␮m and 0.025 ⫾ 0.032 ␮m (group 1) and 0.070 ⫾ 0.042 ␮m and 0.16 ⫾ 0.09 ␮m (group 2) at a 5.00- and 6.00-mm pupil diameter. No statistically significance was found between groups 1 and 2 at one month when looking at total aberration at the 5.00-mm pupil diameter (P ⫽ .07). However, with a pupil of 6.00 mm, group 1 showed statistically less total aberration (P ⬍ .001) than group 2. When analyzing higherorder aberrations, the difference between the groups was statistically significant at 5.00- and 6.00-mm pupil diameters (P ⫽ .007 and P ⬍ .001, respectively), with group 1 inducing less higher-order aberration compared with group 2. Group 1 also obtained statistically significant less spherical aberration when compared with group 2 at the 5.00and 6.00-mm pupil diameter (P ⬍ .001). Postoperative wavefront analysis at three months revealed mean total aberration RMS values of 0.97 ⫾ 0.39 ␮m and 1.41 ⫾ 0.57 ␮m (group 1) and 1.09 ⫾ 0.36 ␮m and 1.99 ⫾ 0.56 ␮m (group 2) at 5.00- and 6.00-mm pupil diameters. Mean higher-order aberration values at three months were 0.35 ⫾ 0.18 ␮m and 0.55 ⫾ 0.26 ␮m (group 1) and 0.46 ⫾ 0.16 ␮m and 0.82 ⫾ 0.23 ␮m (group 2) at 5.00- and 6.00-mm pupil diameters. Mean spherical aberration values at three months were 0.012 ⫾ 0.020 ␮m and 0.024 ⫾ 0.030 ␮m (group 1) and 0.066 ⫾ 0.050 ␮m and 0.15 ⫾ 0.097 ␮m (group 2) at 5.00- and 6.00-mm pupil diameters (Figure 2). No statistically significance was found between groups 1 and 2 at three months when looking at total aberration with a 5.00-mm pupil diameter (P ⫽ .27). However, with a pupil of 6.00 mm, group 1 showed statistically less total aberration (P ⫽ .001) than group 2. When analyzing higher-order aberrations, the difference between the groups was statistically significant at 5.00- and 6.00-mm pupil diameters (P ⫽ .025 and P ⫽ .001, respectively), with group 1 inducing less higher-order aberration compared with group 2. Group 1 also obtained statistically significant less spherical aberration when compared with group 2 at 5.00- and 6.00-mm pupil diameters (P ⬍ .001). At the last follow-up, the subjects were specifically asked to identify the eye with better vision. Fifty-two percent (13 patients) said there was no difference and 48% preferred the vision in group 1.

quality of vision. Contrast sensitivity and wavefront analysis effectively represent the optical quality of vision. These initial clinical results with the Tecnis Z9001 modified prolate IOL indicated significant improvement in some— but not all—spatial frequencies of contrast sensitivity as compared with the ClariFlex IOL under mesopic and photopic conditions. Thus, the Tecnis Z9001 IOL seems to provide an advantage over a standard spherical lens by correcting spherical aberration in the human eye. Our study also evaluated and compared the refractive and aberrometric outcomes of the two IOLs. Postoperative contrast sensitivity testing revealed significance differences between the two groups, indicating a better performance of the Tecnis IOL compared with the ClariFlex IOL. Differences in contrast sensitivity were most pronounced (reached statistical significance) under mesopic conditions at all spatial frequencies: 3, 6, 12, and 18 cpd without glare and 3 and 6 cpd with glare. Under photopic conditions, three spatial frequencies achieved statistically significance: 18 cpd without glare, and 3 and 6 cpd with glare. In others studies, the aspherical IOL with a prolate surface has been shown to provide higher contrast sensitivity than with standard spherical IOLs.15,16 In a study by Mester and associates, they found that the Tecnis Z9000 IOL (Advance Medical Optics) provided a significant decrease in whole eye spherical aberration compared with a standard spherical IOL.13 This reduced spherical aberration resulted in a significant improvement in contrast sensitivity. Packer and associates compared the contrast sensitivity of 10 Tecnis Z9000 patients and 11 AR40e (spherical IOL) patients and found a statistically significant improvement in contrast sensitivity in the Z9000 IOL at spatial frequencies of 6, 12, and 18 cpd under photopic conditions and at 1.5 and 3 cpd under mesopic conditions.11 Kennis and associates conducted a prospective study in which 98 eyes of 71 patients received one of three IOLs (the aspherical IOL Tecnis Z9000, and the spherical IOLs Sensar AR40e (Advance Medical Optics), and the AcrySof Natural SN60AT; Alcon) at random.17 When comparing the Tecnis Z9000 with the AR40e and SN60AT IOL, contrast sensitivity showed significant better results at almost all spatial frequencies in the Tecnis Z9000 group. Contrary to the findings of Mester and associates, Packer and associates, and Kennis and associates, in another study, Muñoz and associates measured spherical aberration and contrast sensitivity with the Tecnis Z9000 IOL and found a significant reduction in spherical aberration after Tecnis Z9000 IOL implantation compared with a standard spherical IOL (AR40e); however, no statistically significant differences between the AR40e and the Z9000 IOL in photopic and mesopic contrast sensitivity were found.14 Wavefront technology was first used to evaluate lower- and higher-order aberrations in normal phakic eyes. However, several studies started to use this technology in pseudophakic eyes.17–20 In our study, postoperative wavefront analysis showed significant differences

DISCUSSION CATARACT SURGERY AND IOL IMPLANTATION IS BECOM-

ing more of a refractive procedure, where results are measured not only by means of visual acuity, but also by 832

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in total aberration, higher-order aberration, and spherical aberration between the Tecnis eyes and ClariFlex eyes, with the Tecnis eyes inducing less aberration compared with the ClariFlex eyes. In a study by Muñoz and associates, the authors observed a significant reduction in spherical aberration after an aspheric IOL (Tecnis Z9000) was implanted compared with a spherical acrylic IOL.14 Kasper and associates also found significantly reduced spherical aberration for an aspherical IOL (Tecnis Z9000) compared with spherical Sensar IOLs.18 A significant effort was made to reduce the bias of the comparative clinical study (i.e., an intraindividual comparative study; same lens material, manufactured by the same company; bilateral surgery performed by the same surgeon

within one week using an identical surgical technique). The results in this prospective study clearly indicate that the theoretical advantages of the Tecnis Z9001 IOL can be measured. Major advances have been seen recently in the creation of increased functional vision and its assessment. Evidence from several well-conducted clinical investigations confirm that correction of spherical aberration using an IOL with a modified prolate surface leads to a significant improvement in quality of vision in pseudophakia, as demonstrated by contrast sensitivity testing and night driving simulation. In conclusion, our investigations show that visual quality can be improved by implantation of an IOL with a modified prolate surface.

THE AUTHORS INDICATE NO FINANCIAL SUPPORT OR FINANCIAL CONFLICT OF INTEREST. INVOLVED IN CONCEPTION AND design (P.F.T., F.C.T.); analysis and interpretation of data and writing the article (P.F.T.); critical revision of the article (L.A., F.C.T., J.E.B.); final approval of the article (F.C.T., J.E.B.); data collection (P.F.T.); provision of materials and patients (L.A.); statistical expertise (P.F.T.); Literature search (P.F.T.); and administrative and technical support (L.A., F.C.T., J.E.B.). The study and data accumulation were carried out with approval from the Institutional Review Board of the Federal University of Minas Gerais (UFMG), Belo Horizonte, Minas Gerais, Brazil. Written informed consent was obtained from all patients before surgery, and the study was approved by the local ethics committee. ClinicalTrials.gov identifier: NCT00576485.

12. Packer M, Fine IH, Hoffman RS, Piers PA. Improved functional visual with a modified prolate intraocular lens. J Cataract Refract Surg 2004;30:986 –992. 13. Mester U, Dillinger P, Anterist N. Impact of a modified optic design on visual function: clinical comparative study. J Cataract Refract Surg 2003;29:652– 660. 14. Muñoz G, Albarrán-Diego C, Montés-Micó R, RodriguezGalietero A, Alió JL. Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens. J Cataract Refract Surg 2006;32:1320 – 1327. 15. Denoyer A, Le Lez ML, Majzoub S, Pisella PJ. Quality of vision after cataract surgery after Tecnis Z900 intraocular lens implantation: effect of contrast sensitivity and wavefront aberration improvements on the quality of daily vision. J Cataract Refract Surg 2007;32:210 –216. 16. Bellucci R, Scialdone A, Buratto L, et al. Visual acuity and contrast sensitivity comparison between Tecnis and AcrySof SA60AT intraocular lenses: a multicenter randomized study. J Cataract Refract Surg 2005;31:712–717. 17. Kennis H, Huygens M, Callebaut F. Comparing the contrast sensitivity of a modified prolate anterior surface IOL and of two spherical IOLs. Bull Soc Belge Ophthalmol 2004;294: 49 –58. 18. Kasper T, Bühren J, Kohnen T. Intraindividual comparison of higher-order aberrations after implantation of aspherical and spherical intraocular lenses as a function of pupil diameter. J Cataract Refract Surg 2006;32:78 – 84. 19. Rocha KM, Chalita MR, Souza CE, et al. Postoperative wavefront analysis and contrast sensitivity of a multifocal apodized diffractive IOL (ReSTOR) and three monofocal IOLs. J Refract Surg 2005;21:S808 –S812. 20. Rocha KM, Soriano ES, Chalita MR, et al. Wavefront analysis and contrast sensitivity of aspheric and spherical intraocular lenses: a randomized prospective study. Am J Ophthalmol 2006;142:750 –756.

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ASPHERIC IOLS

833

Biosketch Dr Patrick F. Tzelikis completed his residency at São Geraldo Eye Hospital, Federal University of Minas Gerais (UFMG), Brazil, followed by a fellowship in cataract and refractive surgery at the same institution. From November 2003 to October 2004, he worked toward a subsequent fellowship in cornea, external disease, and refractive surgery at Wills Eye Hospital in Philadelphia, Pennsylvania. Dr Tzelikis is currently a member of the cataract and refractive service at Hospital Oftalmológico de Brasília (HOB) and the cataract and refractive surgery service at São Geraldo Eye Hospital.

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AMERICAN JOURNAL

OF

OPHTHALMOLOGY

MAY 2008

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