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Ocular aberrations and contrast sensitivity after cataract surgery with AcrySof IQ intraocular lens implantation
ARTICLE
Ocular aberrations and contrast sensitivity after cataract surgery with AcrySof IQ intraocular lens implantation Clinical comparative study Patrick F. Tzelikis, MD, Leonardo Akaishi, MD, Fernando C. Trindade, MD, Joel E. Boteon, MD
PURPOSE: To determine whether implantation of an intraocular lens (IOL) with a modified posterior aspherical surface (AcrySof IQ, Alcon Surgical Laboratories) results in reduced ocular aberrations (spherical aberration) and improved contrast sensitivity after cataract surgery. SETTING: Brasilia Ophthalmologic Hospital, Brasilia, and Sao Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil. METHODS: In an intraindividual randomized prospective study of 25 patients with bilateral cataract, an IOL with a modified posterior surface (AcrySof IQ) was compared with a biconvex IOL with spherical surfaces (AcrySof Natural, Alcon). Ocular aberrations with a 5.0 mm and 6.0 mm pupil were measured with a Hartmann-Shack aberrometer. Quality of vision was measured by visual acuity and contrast sensitivity under mesopic and photopic conditions. All patients were followed for 3 months. RESULTS: There were no statistically significant differences between eyes in postoperative uncorrected and best corrected distance visual acuities after a follow-up of 1 month and 3 months. Postoperatively, there was a statistically significant between-group difference in contrast sensitivity under photopic conditions without glare at 18 cycles per degree (cpd) (P Z .04) and under mesopic conditions without glare at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd; P Z .03, P Z .009, P Z .003, and P Z .003, respectively) and with glare at 3 cpd and 6 cpd (P Z .001 and P Z .02, respectively). The difference in higher-order aberration (HOA) values between groups was statistically significant with a 5.0 mm and 6.0 mm pupil, with the AcrySof IQ IOL inducing less HOA than the AcrySof Natural IOL. Eyes with an AcrySof IQ IOL also had statistically significant less spherical aberration than eyes with an AcrySof Natural IOL with both pupil diameters (P<.001). CONCLUSIONS: The AcrySof IQ IOL with a modified posterior surface induced significantly less HOA and spherical aberration than the AcrySof Natural IOL. Contrast sensitivity was better under mesopic conditions with the AcrySof IQ IOL. J Cataract Refract Surg 2007; 33:1918–1924 Q 2007 ASCRS and ESCRS
With advances in intraocular lens (IOL) and phacoemulsification technology, cataract surgery has evolved from a procedure for the safe removal of the cataract to one aimed at achieving the best possible postoperative refractive result. Although surgical technique as well as IOL materials and designs have improved significantly, limited attention has been given to improving the optical quality provided by the IOL. Snellen visual acuity does not sufficiently describe the quality of the eye’s optics before and after cataract surgery.1–3 Many scientific studies have shown that 1918
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contrast sensitivity is a robust indicator of functional vision.4–7 The contrast sensitivity function, measured under varying conditions of luminance and glare, establishes the limits of visual perception across the spectrum of spatial frequencies. Studies have also shown a nearly linear decline in image quality with age, suggesting a significant increase in optical aberrations in the eye over time.8,9 Guirao et al.10 found that the positive spherical aberration of the cornea increases with age but that the increase is too small to account for the measured 0886-3350/07/$dsee front matter doi:10.1016/j.jcrs.2007.06.053
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reduction in the retinal image quality with age. In the young human eye, the positive spherical aberration induced by the cornea is partially compensated for by the negative spherical aberration of the youthful lens. This spherical aberration increases with age, becoming positive around the age of 40 years. Because a spherical IOL has inherent positive spherical aberration, there is no correction of the positive spherical aberration of the cornea. Based on these findings, IOLs that introduce negative spherical aberration were developed to compensate for the increasing spherical aberration in older eyes. One such IOL, the AcrySof IQ (model SN60WF, Alcon Surgical Laboratories), is a single-piece foldable acrylic IOL with a posterior aspherical surface (negative spherical aberration) designed to decrease the total amount of ocular spherical aberration after cataract surgery. The purpose of this study was to determine whether implantation of an IOL with a modified posterior aspherical surface (AcrySof IQ) results in reduced spherical aberration and improved contrast sensitivity after cataract surgery. PATIENTS AND METHODS This double-blind prospective randomized study included patients with age-related cataract, no indication of existing ocular pathology, unsatisfactory correction with spectacles, and less than 2.50 diopters (D) of cylinder on topography. Written informed consent was obtained from all patients before surgery, and the study was approved by the local ethics committee. Exclusion criteria were previous ocular surgery, central endothelial cell count less than 1800 cells/mm2, glaucoma or intraocular pressure greater than 21 mm Hg, amblyopia, retinal abnormalities, diabetes mellitus, steroid or immunosuppressive treatment, and connective tissue diseases. Patients had cataract surgery with implantation of an AcrySof aspherical IOL (AcrySof IQ) in 1 eye and an AcrySof spherical IOL (AcrySof Natural IOL, model SN60AT) in the fellow eye; the IOL type was randomly allocated. Table 1 shows the characteristics of the 2 IOLs. To protect patient safety, patients were asked after first-eye surgery whether they wished to have the same IOL type implanted in the second eye.
Accepted for publication June 21, 2007. From Brasilia Ophthalmologic Hospital (Akaishi, Tzelikis), Brasilia, and Sao Geraldo Eye Hospital (Tzelikis, Trindade, Boteon), Federal University of Minas Gerais, Belo Horizonte, Brazil. No author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Dr. P.F. Tzelikis, SQN 203, Bloco G, Apartamento 405, Brasilia DF 70833-070, Brazil. E-mail: tzelikis@terra. com.br.
Table 1. Characteristics of the 2 IOLs in the study.
IOL Characteristic Type Overall length (mm) Optic diameter (mm) Optic material
AcrySof IQ (SN60WF)
1 piece 13.0 6.0 Hydrophobic acrylic Angle (degrees) 0 Refractive index 1.55 Optic shape Biconvex, aspherical posterior surface Estimated A-constant 118.7
AcrySof Natural (SN60AT) 1 piece 13.0 6.0 Hydrophobic acrylic 0 1.55 Biconvex 118.4
IOL Z intraocular lens
Preoperative and postoperative evaluations included uncorrected distance visual acuity, best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE), slitlamp biomicroscopy, applanation tonometry, fundus examination, B-scan biometry, specular microscopy, and corneal topography. Clinical data were collected preoperatively and 1 and 3 months postoperatively. All patients were operated on by the same surgeon (P.F.T.) using the same technique. After topical anesthesia of lidocaine 2% gel was administered, a 2.75 mm temporal self-sealing clear corneal incision was made. Sodium hyaluronate 3%–chondroitin sulfate 4% (Viscoat) was used to reform and stabilize the surgical planes and protect the endothelium. A 5.00 to 5.25 mm continuous curvilinear capsulorhexis was begun with a 26-gauge needle and completed with a forceps. The nucleus was removed, with phacoemulsification performed with an Infiniti (Alcon Surgical) or Sovereign (Allergan Surgical) unit. All IOLs were inserted in the capsular bag with an injector system. The Viscoat was completely removed at the end of the procedure. No sutures were used in any case. After 1 week, patients had surgery in the fellow eye. Postoperative medications included moxifloxacin (Vigamox) or gatifloxacin (Zymar) 4 times a day for 2 weeks, diclofenac sodium 0.1% (Voltaren) 3 times a day for 4 weeks, and prednisolone acetate eyedrops (Pred Forte) 4 times a day for 6 weeks. Postoperative follow-up evaluations were at 1 day and 1 and 3 months. At 1 and 3 months, visual acuity, refraction, contrast sensitivity, and wavefront analysis were performed. Contrast sensitivity was measured using the CSV-1000 HGT instrument (Vector Vision, Inc.), which presents a translucent chart divided into 4 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 and is automatically calibrated to 85 candelas/m2 (cd/m2). All measurements were obtained under mesopic (5 cd/m2) and photopic (85 cd/m2) conditions. Each cycle contains 17 round patches that are 1.5 inches in diameter. The first patch has a high-contrast grating and presents the sample. The test patches are arranged in 2 rows with 8 levels of contrast. The levels decrease 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
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examinations were performed unilaterally at a distance of 2.5 m with BSCVA and an undilated pupil. All measurements were performed under the same conditions by an examiner who was unaware of the type of IOL implanted. Wavefront analysis was performed with the Zywave aberrometer (Bausch & Lomb). This aberrometer uses the Hartmann-Shack method of analyzing the outgoing wavefront that measures up to 5th-order Zernike aberration including coma, trefoil, and spherical aberrations. For statistical analysis of visual acuity, logarithm of minimum angle of resolution (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 SPSS, version 13.0 programs (SPSS, Inc.). The 2 IOLs were compared between eyes intraindividually. The analysis was based on a non-normal distribution of the data. The nonparametric Mann-Whitney U test was used to compare data between the 2 IOL groups. A P value less than 0.05 was considered statistically significant.
Uncorrected Distance Visual Acuity
RESULTS
Best Spectacle-Corrected Visual Acuity
Fifty eyes of 25 patients were included in the study; in all cases, an AcrySof IQ IOL was implanted in 1 eye and an AcrySof Natural IOL in the other eye. Fifteen patients (60.0%) were men, and 10 (40.0%) were women. The mean age of the patients was 68 years G 5.3 (SD) (range 59 to 82 years). All patients completed the 3-month follow-up. There were no intraoperative complications such as posterior capsule rupture.
Preoperative The mean logMAR BSCVA (Snellen equivalent) before surgery was 0.20 G 0.11 (20/32) in the AcrySof IQ group and 0.27 G 0.13 (20/40) in the AcrySof Natural group; there was no statistically significant difference between groups (P Z .06).
Preoperative The mean logMAR uncorrected distance acuity (Snellen equivalent) before surgery was 0.50 G 0.30 (20/63 Snellen equivalent) in the AcrySof IQ IOL group and 0.60 G 0.38 (20/80) in the AcrySof Natural IOL group; there was no statistically significant difference between groups (P Z .20). Postoperative Table 2 shows the uncorrected distance acuity 1 month and 3 months postoperatively. There was no statistically significant difference between the 2 IOL groups at either time. At 3 months, uncorrected distance acuity was 20/25 or better in 16 eyes (64.0%) with an AcrySof IQ IOL and 14 eyes (56.0%) with an AcrySof Natural IOL. The uncorrected distance acuity was 20/40 or better in 23 eyes (92.0%) and 22 eyes (88.0%), respectively.
Postoperative Table 2 shows the BSCVA 1 month and 3 months postoperatively; there were no statistically significant differences between groups.
Table 2. Postoperative visual acuity and refraction. Parameter UCDVA I month Mean logMAR G SD Snellen equivalent 3 months Mean logMAR G SD Snellen equivalent BSCVA I month Mean logMAR G SD Snellen equivalent 3 months Mean logMAR G SD Snellen equivalent SE (D) I month Mean G SD Range 3 months Mean G SD Range
AcrySof IQ (SN60WF)
AcrySof Natural (SN60AT)
P Value
.22 0.09 G 0.09 20/25
0.12 G 0.09 20/26
0.16 G 0.14 20/28
0.19 G 14 20/23
0.00 G 0.07 20/20
0.03 G 0.06 20/20
0.01 G 0.06 20/20
0.04 G 0.06 20/21
0.20 G 0.36 0.75 to C0.50
0.32 G 0.30 1.00 to C0.50
0.30 G 0.44 1.00 to C0.50
0.45 G 0.29 1.00 to C1.00
.51
.13
.17
.16
.28
BSCVA Z best spectacle corrected visual acuity; SE Z spherical equivalent; UCDVA Z uncorrected distance visual acuity
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Spherical Equivalent Preoperative The mean SE before surgery was 0.55 G 2.25 D (range 7.50 to C2.50 D) in the AcrySof IQ group and 0.65 G 3.00 D (range 9.00 to C4.00 D) in the AcrySof Natural group; there was no statistically significant difference between groups (P Z .91). Postoperative Table 2 shows the SE 1 month and 3 months postoperatively; there were no statistically significant differences between groups. Other Preoperative Data There was no statistically significant difference between the 2 IOL groups in preoperative mean corneal curvature, IOL power, or wavefront maps. Contrast Sensitivity Postoperative contrast sensitivity was statistically significantly different between the 2 IOL groups under photopic conditions without glare at 18 cpd (P Z .04). The differences also reached statistical significance under mesopic conditions without glare at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd; P Z .03, P Z .009, P Z .003, and P Z .003, respectively) and with glare at 2 spatial frequencies (3 cpd and 6 cpd; P Z .001 and P Z .02, respectively) (Table 3) (Figure 1). Wavefront Analysis One Month Postoperatively The mean total aberration root-mean-square (RMS) with a 5.0 mm pupil was 0.94 G 0.38 mm in the AcrySof IQ group and 1.03 G 0.31 mm in the AcrySof Natural group and with a 6.0 mm diameter, 1.34 G 0.54 mm and 1.95 G 0.44 mm, respectively. The mean higher-order aberration (HOA) with a 5.0 mm pupil was 0.39 G 0.20 mm in the AcrySof IQ group and 0.45 G 0.16 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.55 G 0.20 mm and 0.80 G 0.16 mm, respectively. The mean spherical aberration with a 5.0 mm pupil was 0.012 G 0.012 mm in the AcrySof IQ group and 0.087 G 0.044 in the AcrySof Natural group and with a 6.0 mm pupil, 0.028 G 0.035 mm and 0.22 G 0.10 mm, respectively. There was no statistically significant difference in total aberration with a 5.0 mm pupil between the 2 IOL groups (P Z .22). However, with a 6.0 mm pupil, the AcrySof IQ group had statistically less total aberration than the AcrySof Natural group (P!.001). The difference in HOA between groups was statistically significant with a 5.0 mm and 6.0 mm pupil (P Z .019 and P!.001, respectively); the AcrySof IQ IOL induced less HOA than the AcrySof Natural IOL. The AcrySof IQ group also had statistically significantly less
Table 3. Contrast sensitivity scores (logMAR) in the 2 IOL groups at 3 months. Mean Contrast Sensitivity Condition
AcrySof IQ
AcrySof Natural
P Value
1.58 1.76 1.28 0.82
1.55 1.69 1.23 0.72
.69 .19 .40 .04*
1.56 1.68 1.19 0.76
1.49 1.56 1.02 0.64
.10 .08 .12 .06
1.59 1.72 1.28 0.89
1.47 1.58 0.98 0.53
.03* .009* .003* .003*
1.51 1.57 1.03 0.73
1.30 1.39 0.98 0.60
.001* .02* .70 .30
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 cpd Z cycles per degree *Statistically significant
spherical aberration than the AcrySof Natural group with both pupil diameters (P!.001). Three Months Postoperatively The mean total aberration RMS with a 5.0 mm pupil was 0.99 G 0.45 mm in the AcrySof IQ group and 1.06 G 0.33 mm in the AcrySof Natural group and with a 6.0 mm pupil, 1.41 G 0.59 mm and 1.97 G 0.48 mm, respectively. The mean HOA with a 5.0 mm pupil was 0.41 G 0.24 mm in the AcrySof IQ group and 0.51 G 0.19 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.66 G 0.37 mm and 0.90 G 0.27 mm, respectively. The mean spherical aberration with a 5.0 mm pupil was 0.014 G 0.02 mm in the AcrySof IQ group and 0.078 G 0.049 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.026 G 0.034 mm and 0.19 G 0.10 mm, respectively (Figures 2 and 3). There was no statistically significant difference in total aberration with a 5.0 mm pupil between the 2 IOL groups (P Z .29). However, with a 6.0 mm pupil, the AcrySof IQ group had statistically less total aberration than the AcrySof Natural group (P Z .001). The difference in HOA between groups was statistically significant with 5.0 mm and 6.0 mm pupils (P Z .016 and P Z .002, respectively); the AcrySof IQ IOL induced less HOA than the AcrySof Natural IOL. The AcrySof
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Photopic Contrast Sensitivity Values - Glare - 3 months
Photopic Contrast Sensitivity Values - No Glare - 3 months Lente intra-ocular AcrySof IQ
1,8000
Lente intra-ocular AcrySof Natural
1,4000
1,2000
1,0000
1,2000
1,0000
0,8000
0,6000
0,6000 6
12
3
18
6
12
Spatial Frequence (cycles/degree)
Spatial Frequence (cycles/degree)
A
B
Mesopic Contrast Sensitivity Values - No Glare - 3 months
1,4000
Contrast Sensitivity
1,0000
0,7500
Lente intra-ocular AcrySof IQ Lente intra-ocular AcrySof Natural
1,6000
1,5000
1,2500
18
Mesopic Contrast Sensitivity Values - Glare - 3 months
Lente intra-ocular AcrySof IQ Lente intra-ocular AcrySof Natural
1,7500
Contrast Sensitivity
1,4000
0,8000
3
Lente intra-ocular AcrySof Natural
1,6000
Contrast Sensitivity
Contrast Sensitivity
1,6000
Lente intra-ocular AcrySof IQ
1,8000
1,2000 1,0000 0,8000 0,6000 0,4000
0,5000 3
6
12
18
3
6
12
Spatial Frequency (cycles/degree)
Spatial Frequency (cycles/degree)
C
D
18
Figure 1. (A, C) Contrast sensitivity in 2 patients at 3 months under photopic and mesopic conditions without (A, C) and with (B, D) glare at 3, 6, 12, and 18 cpd.
IQ group also had statistically significantly less spherical aberration than the AcrySof Natural group with both pupil diameters (P!.001). DISCUSSION Our initial clinical results with the AcrySof IQ modified prolate acrylic IOL indicate significant improvement over the AcrySof Natural IOL at some, but not all, spatial frequencies of contrast sensitivity under mesopic and photopic conditions. Thus, the AcrySof IQ IOL appears to provide an advantage over a standard spherical IOL by correcting spherical aberration in the human eye. Our study also evaluated and compared the refractive and aberrometric outcomes with the 2 IOLs. Postoperative contrast sensitivity testing showed significant differences between the 2 groups, indicating the AcrySof IQ IOL performed better than the
AcrySof Natural IOL. Differences in contrast sensitivity were most pronounced (reached statistical significance) under mesopic conditions at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd) without glare and at 3 cpd and 6 cpd with glare. Under photopic conditions, the only statistically significant difference was at 18 cpd without glare. Other studies report that an aspherical IOL with a prolate surface provided higher contrast sensitivity than standard spherical IOLs.11–13 For example, Mester et al.13 found that the aspherical Tecnis Z9000 IOL (Pharmacia) significantly decreased whole-eye spherical aberration compared with a standard spherical IOL. This reduced spherical aberration resulted in a significant improvement in contrast sensitivity. Packer et al.11 compared the contrast sensitivity of 10 patients with a Tecnis Z9000 IOL and 11 patients with an AR40e spherical IOL (AMO) and found a statistically
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Figure 2. Wavefront maps of a patient 3 months after surgery. A: Maps of right eye with an AcrySof Natural IOL. B: Maps of left eye with an AcrySof IQ IOL. Note the difference in HOA between the right eye and left eye.
significant improvement in contrast sensitivity with the Z9000 IOL at spatial frequencies of 6 cpd, 12 cpd, and 18 cpd under photopic conditions and at 1.5 cpd and 3 cpd under mesopic conditions. In a prospective study by Kennis et al.,14 98 eyes of 71 patients were randomly allocated to receive 1 of 3 IOLs (Tecnis Z9000, Sensar AR40e, or AcrySof Natural SN60AT). Contrast sensitivity was significantly better at almost all spatial frequencies in the Tecnis Z9000 group. Contrary to the findings of Mester et al.,13 Packer et al.,11 and Kennis et al.,14 a study by Mun˜oz et al.15 of spherical aberration and contrast sensitivity with the Tecnis Z9000 IOL found a significant reduction in spherical aberration after Tecnis Z9000 IOL implantation compared with that after implantation of a standard spherical IOL (AR40e); however, they found no statistically significant differences between the AR40e IOL and Z9000 IOL in photopic and mesopic contrast sensitivity. Wavefront technology was first used to evaluate lower-order aberrations and HOAs in normal phakic eyes. This was followed by its use in pseudophakic eyes.16,17 In our study, postoperative wavefront
Figure 3. Wavefront maps of another patient 3 months after surgery. A: Maps of right eye with an AcrySof Natural IOL. B: Maps of left eye with an AcrySof IQ IOL. Note the difference in HOA between the right eye and left eye.
analysis showed significant differences in total aberration, HOA, and spherical aberration between eyes with an AcrySof IQ IOL and eyes with an AcrySof Natural IOL, with the former having less aberration than the latter. Mun˜oz et al.15 observed a significant reduction in spherical aberration with an aspherical IOL (Tecnis Z9000) compared with 2 spherical IOLs (AR40e; Stabibag, Ioltech). Kasper et al.16 also found significantly reduced spherical aberration with an aspherical IOL (Tecnis Z9000) compared with a spherical IOL (Sensar). We made a significant effort to reduce the bias that can occur in comparative clinical studies by making our study an intraindividual comparison, using the same IOL material manufactured by the same company, and having the same surgeon perform bilateral surgery within 1 week using an identical surgical
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technique. When patients were asked after bilateral surgery to identify the eye with better vision, 55.6% (10 patients) said there was no difference and 44.4% preferred the vision in the eye with the AcrySof IQ IOL. Therefore, it remains questionable whether the significant differences in HOA and contrast sensitivity have clinical relevance and what it means for the patient. Evidence from several well-conducted clinical studies 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. Our study showed that visual quality can be improved by implantation of an IOL with a modified prolate surface. Patients will generally be more satisfied after implantation of an aspherical IOL because they will have better contrast sensitivity and less HOA. REFERENCES 1. Arden GB. The importance of measuring contrast sensitivity in cases of visual disturbance. Br J Ophthalmol 1978; 62:198–209 2. Elliott DB. Evaluating visual function in cataract. Optom Vis Sci 1993; 70:896–902 3. Rubin GS, Adamsons IA, Stark WJ. Comparison of acuity, contrast sensitivity, and disability glare before and after cataract surgery. Arch Ophthalmol 1993; 111:56–61 4. Ginsburg AP. Spatial filtering and visual form perception. In: Boff KR, Kaufman L, Thomas JP, eds, Handbook of Perception and Human Performance. New York, NY, John Wiley & Sons, 1986; vol. 2, chapt 34 5. Ginsburg AP, Evans DW, Sekuler R, Harp SA. Contrast sensitivity predicts pilots’ performance in aircraft simulators. Am J Optom Physiol Opt 1982; 59:105–109 6. Rubin GS, Bandeen Roche K, Huang G-H, et al. The association or multiple visual impairments with self-reported visual disability; SEE Project. Invest Ophthalmol Vis Sci 2001; 42:64–72 7. Packer M, Fine IH, Hoffman RS. Wavefront technology in cataract surgery. Current Opin Ophthalmol 2004; 15:56–60
8. Glasser A, Campbell MCW. Presbyopia and the optical changes in the human crystalline lens with age. Vision Res 1998; 38:209– 229 9. Guirao A, Gonza´lez C, Redondo M, et al. Average optical performance of the human eye as function of age in a normal population. Invest Ophthalmol Vis Sci 1999; 40:203–213 10. Guirao A, Redondo M, Artal P. Optical aberrations of the human cornea as a function of age. J Opt Soc Am A Opt Image Sci Vis 2000; 17:1697–1702 11. Packer M, Fine IH, Hoffman RS, Piers PA. Prospective randomized trial of an anterior surface modified prolate intraocular lens. J Refract Surg 2002; 18:692–696 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. 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 Ophtalmol 2004; 294:49–58 15. Mun˜oz G, Albarra´n-Diego C, Monte´s-Mico´ R, et al. Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens. J Cataract Refract Surg 2006; 32:1320–1327 16. Kasper T, Bu¨hren 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 17. 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
First author: Patrick F. Tzelikis, MD Brasilia Ophthalmologic Hospital, Brasilia, and Sao Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil
J CATARACT REFRACT SURG - VOL 33, NOVEMBER 2007
Ocular aberrations and contrast sensitivity after cataract surgery with AcrySof IQ intraocular lens implantation Clinical comparative study Patrick F. Tzelikis, MD, Leonardo Akaishi, MD, Fernando C. Trindade, MD, Joel E. Boteon, MD
PURPOSE: To determine whether implantation of an intraocular lens (IOL) with a modified posterior aspherical surface (AcrySof IQ, Alcon Surgical Laboratories) results in reduced ocular aberrations (spherical aberration) and improved contrast sensitivity after cataract surgery. SETTING: Brasilia Ophthalmologic Hospital, Brasilia, and Sao Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil. METHODS: In an intraindividual randomized prospective study of 25 patients with bilateral cataract, an IOL with a modified posterior surface (AcrySof IQ) was compared with a biconvex IOL with spherical surfaces (AcrySof Natural, Alcon). Ocular aberrations with a 5.0 mm and 6.0 mm pupil were measured with a Hartmann-Shack aberrometer. Quality of vision was measured by visual acuity and contrast sensitivity under mesopic and photopic conditions. All patients were followed for 3 months. RESULTS: There were no statistically significant differences between eyes in postoperative uncorrected and best corrected distance visual acuities after a follow-up of 1 month and 3 months. Postoperatively, there was a statistically significant between-group difference in contrast sensitivity under photopic conditions without glare at 18 cycles per degree (cpd) (P Z .04) and under mesopic conditions without glare at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd; P Z .03, P Z .009, P Z .003, and P Z .003, respectively) and with glare at 3 cpd and 6 cpd (P Z .001 and P Z .02, respectively). The difference in higher-order aberration (HOA) values between groups was statistically significant with a 5.0 mm and 6.0 mm pupil, with the AcrySof IQ IOL inducing less HOA than the AcrySof Natural IOL. Eyes with an AcrySof IQ IOL also had statistically significant less spherical aberration than eyes with an AcrySof Natural IOL with both pupil diameters (P<.001). CONCLUSIONS: The AcrySof IQ IOL with a modified posterior surface induced significantly less HOA and spherical aberration than the AcrySof Natural IOL. Contrast sensitivity was better under mesopic conditions with the AcrySof IQ IOL. J Cataract Refract Surg 2007; 33:1918–1924 Q 2007 ASCRS and ESCRS
With advances in intraocular lens (IOL) and phacoemulsification technology, cataract surgery has evolved from a procedure for the safe removal of the cataract to one aimed at achieving the best possible postoperative refractive result. Although surgical technique as well as IOL materials and designs have improved significantly, limited attention has been given to improving the optical quality provided by the IOL. Snellen visual acuity does not sufficiently describe the quality of the eye’s optics before and after cataract surgery.1–3 Many scientific studies have shown that 1918
Q 2007 ASCRS and ESCRS Published by Elsevier Inc.
contrast sensitivity is a robust indicator of functional vision.4–7 The contrast sensitivity function, measured under varying conditions of luminance and glare, establishes the limits of visual perception across the spectrum of spatial frequencies. Studies have also shown a nearly linear decline in image quality with age, suggesting a significant increase in optical aberrations in the eye over time.8,9 Guirao et al.10 found that the positive spherical aberration of the cornea increases with age but that the increase is too small to account for the measured 0886-3350/07/$dsee front matter doi:10.1016/j.jcrs.2007.06.053
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reduction in the retinal image quality with age. In the young human eye, the positive spherical aberration induced by the cornea is partially compensated for by the negative spherical aberration of the youthful lens. This spherical aberration increases with age, becoming positive around the age of 40 years. Because a spherical IOL has inherent positive spherical aberration, there is no correction of the positive spherical aberration of the cornea. Based on these findings, IOLs that introduce negative spherical aberration were developed to compensate for the increasing spherical aberration in older eyes. One such IOL, the AcrySof IQ (model SN60WF, Alcon Surgical Laboratories), is a single-piece foldable acrylic IOL with a posterior aspherical surface (negative spherical aberration) designed to decrease the total amount of ocular spherical aberration after cataract surgery. The purpose of this study was to determine whether implantation of an IOL with a modified posterior aspherical surface (AcrySof IQ) results in reduced spherical aberration and improved contrast sensitivity after cataract surgery. PATIENTS AND METHODS This double-blind prospective randomized study included patients with age-related cataract, no indication of existing ocular pathology, unsatisfactory correction with spectacles, and less than 2.50 diopters (D) of cylinder on topography. Written informed consent was obtained from all patients before surgery, and the study was approved by the local ethics committee. Exclusion criteria were previous ocular surgery, central endothelial cell count less than 1800 cells/mm2, glaucoma or intraocular pressure greater than 21 mm Hg, amblyopia, retinal abnormalities, diabetes mellitus, steroid or immunosuppressive treatment, and connective tissue diseases. Patients had cataract surgery with implantation of an AcrySof aspherical IOL (AcrySof IQ) in 1 eye and an AcrySof spherical IOL (AcrySof Natural IOL, model SN60AT) in the fellow eye; the IOL type was randomly allocated. Table 1 shows the characteristics of the 2 IOLs. To protect patient safety, patients were asked after first-eye surgery whether they wished to have the same IOL type implanted in the second eye.
Accepted for publication June 21, 2007. From Brasilia Ophthalmologic Hospital (Akaishi, Tzelikis), Brasilia, and Sao Geraldo Eye Hospital (Tzelikis, Trindade, Boteon), Federal University of Minas Gerais, Belo Horizonte, Brazil. No author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Dr. P.F. Tzelikis, SQN 203, Bloco G, Apartamento 405, Brasilia DF 70833-070, Brazil. E-mail: tzelikis@terra. com.br.
Table 1. Characteristics of the 2 IOLs in the study.
IOL Characteristic Type Overall length (mm) Optic diameter (mm) Optic material
AcrySof IQ (SN60WF)
1 piece 13.0 6.0 Hydrophobic acrylic Angle (degrees) 0 Refractive index 1.55 Optic shape Biconvex, aspherical posterior surface Estimated A-constant 118.7
AcrySof Natural (SN60AT) 1 piece 13.0 6.0 Hydrophobic acrylic 0 1.55 Biconvex 118.4
IOL Z intraocular lens
Preoperative and postoperative evaluations included uncorrected distance visual acuity, best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE), slitlamp biomicroscopy, applanation tonometry, fundus examination, B-scan biometry, specular microscopy, and corneal topography. Clinical data were collected preoperatively and 1 and 3 months postoperatively. All patients were operated on by the same surgeon (P.F.T.) using the same technique. After topical anesthesia of lidocaine 2% gel was administered, a 2.75 mm temporal self-sealing clear corneal incision was made. Sodium hyaluronate 3%–chondroitin sulfate 4% (Viscoat) was used to reform and stabilize the surgical planes and protect the endothelium. A 5.00 to 5.25 mm continuous curvilinear capsulorhexis was begun with a 26-gauge needle and completed with a forceps. The nucleus was removed, with phacoemulsification performed with an Infiniti (Alcon Surgical) or Sovereign (Allergan Surgical) unit. All IOLs were inserted in the capsular bag with an injector system. The Viscoat was completely removed at the end of the procedure. No sutures were used in any case. After 1 week, patients had surgery in the fellow eye. Postoperative medications included moxifloxacin (Vigamox) or gatifloxacin (Zymar) 4 times a day for 2 weeks, diclofenac sodium 0.1% (Voltaren) 3 times a day for 4 weeks, and prednisolone acetate eyedrops (Pred Forte) 4 times a day for 6 weeks. Postoperative follow-up evaluations were at 1 day and 1 and 3 months. At 1 and 3 months, visual acuity, refraction, contrast sensitivity, and wavefront analysis were performed. Contrast sensitivity was measured using the CSV-1000 HGT instrument (Vector Vision, Inc.), which presents a translucent chart divided into 4 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 and is automatically calibrated to 85 candelas/m2 (cd/m2). All measurements were obtained under mesopic (5 cd/m2) and photopic (85 cd/m2) conditions. Each cycle contains 17 round patches that are 1.5 inches in diameter. The first patch has a high-contrast grating and presents the sample. The test patches are arranged in 2 rows with 8 levels of contrast. The levels decrease 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
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examinations were performed unilaterally at a distance of 2.5 m with BSCVA and an undilated pupil. All measurements were performed under the same conditions by an examiner who was unaware of the type of IOL implanted. Wavefront analysis was performed with the Zywave aberrometer (Bausch & Lomb). This aberrometer uses the Hartmann-Shack method of analyzing the outgoing wavefront that measures up to 5th-order Zernike aberration including coma, trefoil, and spherical aberrations. For statistical analysis of visual acuity, logarithm of minimum angle of resolution (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 SPSS, version 13.0 programs (SPSS, Inc.). The 2 IOLs were compared between eyes intraindividually. The analysis was based on a non-normal distribution of the data. The nonparametric Mann-Whitney U test was used to compare data between the 2 IOL groups. A P value less than 0.05 was considered statistically significant.
Uncorrected Distance Visual Acuity
RESULTS
Best Spectacle-Corrected Visual Acuity
Fifty eyes of 25 patients were included in the study; in all cases, an AcrySof IQ IOL was implanted in 1 eye and an AcrySof Natural IOL in the other eye. Fifteen patients (60.0%) were men, and 10 (40.0%) were women. The mean age of the patients was 68 years G 5.3 (SD) (range 59 to 82 years). All patients completed the 3-month follow-up. There were no intraoperative complications such as posterior capsule rupture.
Preoperative The mean logMAR BSCVA (Snellen equivalent) before surgery was 0.20 G 0.11 (20/32) in the AcrySof IQ group and 0.27 G 0.13 (20/40) in the AcrySof Natural group; there was no statistically significant difference between groups (P Z .06).
Preoperative The mean logMAR uncorrected distance acuity (Snellen equivalent) before surgery was 0.50 G 0.30 (20/63 Snellen equivalent) in the AcrySof IQ IOL group and 0.60 G 0.38 (20/80) in the AcrySof Natural IOL group; there was no statistically significant difference between groups (P Z .20). Postoperative Table 2 shows the uncorrected distance acuity 1 month and 3 months postoperatively. There was no statistically significant difference between the 2 IOL groups at either time. At 3 months, uncorrected distance acuity was 20/25 or better in 16 eyes (64.0%) with an AcrySof IQ IOL and 14 eyes (56.0%) with an AcrySof Natural IOL. The uncorrected distance acuity was 20/40 or better in 23 eyes (92.0%) and 22 eyes (88.0%), respectively.
Postoperative Table 2 shows the BSCVA 1 month and 3 months postoperatively; there were no statistically significant differences between groups.
Table 2. Postoperative visual acuity and refraction. Parameter UCDVA I month Mean logMAR G SD Snellen equivalent 3 months Mean logMAR G SD Snellen equivalent BSCVA I month Mean logMAR G SD Snellen equivalent 3 months Mean logMAR G SD Snellen equivalent SE (D) I month Mean G SD Range 3 months Mean G SD Range
AcrySof IQ (SN60WF)
AcrySof Natural (SN60AT)
P Value
.22 0.09 G 0.09 20/25
0.12 G 0.09 20/26
0.16 G 0.14 20/28
0.19 G 14 20/23
0.00 G 0.07 20/20
0.03 G 0.06 20/20
0.01 G 0.06 20/20
0.04 G 0.06 20/21
0.20 G 0.36 0.75 to C0.50
0.32 G 0.30 1.00 to C0.50
0.30 G 0.44 1.00 to C0.50
0.45 G 0.29 1.00 to C1.00
.51
.13
.17
.16
.28
BSCVA Z best spectacle corrected visual acuity; SE Z spherical equivalent; UCDVA Z uncorrected distance visual acuity
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Spherical Equivalent Preoperative The mean SE before surgery was 0.55 G 2.25 D (range 7.50 to C2.50 D) in the AcrySof IQ group and 0.65 G 3.00 D (range 9.00 to C4.00 D) in the AcrySof Natural group; there was no statistically significant difference between groups (P Z .91). Postoperative Table 2 shows the SE 1 month and 3 months postoperatively; there were no statistically significant differences between groups. Other Preoperative Data There was no statistically significant difference between the 2 IOL groups in preoperative mean corneal curvature, IOL power, or wavefront maps. Contrast Sensitivity Postoperative contrast sensitivity was statistically significantly different between the 2 IOL groups under photopic conditions without glare at 18 cpd (P Z .04). The differences also reached statistical significance under mesopic conditions without glare at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd; P Z .03, P Z .009, P Z .003, and P Z .003, respectively) and with glare at 2 spatial frequencies (3 cpd and 6 cpd; P Z .001 and P Z .02, respectively) (Table 3) (Figure 1). Wavefront Analysis One Month Postoperatively The mean total aberration root-mean-square (RMS) with a 5.0 mm pupil was 0.94 G 0.38 mm in the AcrySof IQ group and 1.03 G 0.31 mm in the AcrySof Natural group and with a 6.0 mm diameter, 1.34 G 0.54 mm and 1.95 G 0.44 mm, respectively. The mean higher-order aberration (HOA) with a 5.0 mm pupil was 0.39 G 0.20 mm in the AcrySof IQ group and 0.45 G 0.16 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.55 G 0.20 mm and 0.80 G 0.16 mm, respectively. The mean spherical aberration with a 5.0 mm pupil was 0.012 G 0.012 mm in the AcrySof IQ group and 0.087 G 0.044 in the AcrySof Natural group and with a 6.0 mm pupil, 0.028 G 0.035 mm and 0.22 G 0.10 mm, respectively. There was no statistically significant difference in total aberration with a 5.0 mm pupil between the 2 IOL groups (P Z .22). However, with a 6.0 mm pupil, the AcrySof IQ group had statistically less total aberration than the AcrySof Natural group (P!.001). The difference in HOA between groups was statistically significant with a 5.0 mm and 6.0 mm pupil (P Z .019 and P!.001, respectively); the AcrySof IQ IOL induced less HOA than the AcrySof Natural IOL. The AcrySof IQ group also had statistically significantly less
Table 3. Contrast sensitivity scores (logMAR) in the 2 IOL groups at 3 months. Mean Contrast Sensitivity Condition
AcrySof IQ
AcrySof Natural
P Value
1.58 1.76 1.28 0.82
1.55 1.69 1.23 0.72
.69 .19 .40 .04*
1.56 1.68 1.19 0.76
1.49 1.56 1.02 0.64
.10 .08 .12 .06
1.59 1.72 1.28 0.89
1.47 1.58 0.98 0.53
.03* .009* .003* .003*
1.51 1.57 1.03 0.73
1.30 1.39 0.98 0.60
.001* .02* .70 .30
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 cpd Z cycles per degree *Statistically significant
spherical aberration than the AcrySof Natural group with both pupil diameters (P!.001). Three Months Postoperatively The mean total aberration RMS with a 5.0 mm pupil was 0.99 G 0.45 mm in the AcrySof IQ group and 1.06 G 0.33 mm in the AcrySof Natural group and with a 6.0 mm pupil, 1.41 G 0.59 mm and 1.97 G 0.48 mm, respectively. The mean HOA with a 5.0 mm pupil was 0.41 G 0.24 mm in the AcrySof IQ group and 0.51 G 0.19 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.66 G 0.37 mm and 0.90 G 0.27 mm, respectively. The mean spherical aberration with a 5.0 mm pupil was 0.014 G 0.02 mm in the AcrySof IQ group and 0.078 G 0.049 mm in the AcrySof Natural group and with a 6.0 mm pupil, 0.026 G 0.034 mm and 0.19 G 0.10 mm, respectively (Figures 2 and 3). There was no statistically significant difference in total aberration with a 5.0 mm pupil between the 2 IOL groups (P Z .29). However, with a 6.0 mm pupil, the AcrySof IQ group had statistically less total aberration than the AcrySof Natural group (P Z .001). The difference in HOA between groups was statistically significant with 5.0 mm and 6.0 mm pupils (P Z .016 and P Z .002, respectively); the AcrySof IQ IOL induced less HOA than the AcrySof Natural IOL. The AcrySof
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Photopic Contrast Sensitivity Values - Glare - 3 months
Photopic Contrast Sensitivity Values - No Glare - 3 months Lente intra-ocular AcrySof IQ
1,8000
Lente intra-ocular AcrySof Natural
1,4000
1,2000
1,0000
1,2000
1,0000
0,8000
0,6000
0,6000 6
12
3
18
6
12
Spatial Frequence (cycles/degree)
Spatial Frequence (cycles/degree)
A
B
Mesopic Contrast Sensitivity Values - No Glare - 3 months
1,4000
Contrast Sensitivity
1,0000
0,7500
Lente intra-ocular AcrySof IQ Lente intra-ocular AcrySof Natural
1,6000
1,5000
1,2500
18
Mesopic Contrast Sensitivity Values - Glare - 3 months
Lente intra-ocular AcrySof IQ Lente intra-ocular AcrySof Natural
1,7500
Contrast Sensitivity
1,4000
0,8000
3
Lente intra-ocular AcrySof Natural
1,6000
Contrast Sensitivity
Contrast Sensitivity
1,6000
Lente intra-ocular AcrySof IQ
1,8000
1,2000 1,0000 0,8000 0,6000 0,4000
0,5000 3
6
12
18
3
6
12
Spatial Frequency (cycles/degree)
Spatial Frequency (cycles/degree)
C
D
18
Figure 1. (A, C) Contrast sensitivity in 2 patients at 3 months under photopic and mesopic conditions without (A, C) and with (B, D) glare at 3, 6, 12, and 18 cpd.
IQ group also had statistically significantly less spherical aberration than the AcrySof Natural group with both pupil diameters (P!.001). DISCUSSION Our initial clinical results with the AcrySof IQ modified prolate acrylic IOL indicate significant improvement over the AcrySof Natural IOL at some, but not all, spatial frequencies of contrast sensitivity under mesopic and photopic conditions. Thus, the AcrySof IQ IOL appears to provide an advantage over a standard spherical IOL by correcting spherical aberration in the human eye. Our study also evaluated and compared the refractive and aberrometric outcomes with the 2 IOLs. Postoperative contrast sensitivity testing showed significant differences between the 2 groups, indicating the AcrySof IQ IOL performed better than the
AcrySof Natural IOL. Differences in contrast sensitivity were most pronounced (reached statistical significance) under mesopic conditions at all spatial frequencies (3 cpd, 6 cpd, 12 cpd, and 18 cpd) without glare and at 3 cpd and 6 cpd with glare. Under photopic conditions, the only statistically significant difference was at 18 cpd without glare. Other studies report that an aspherical IOL with a prolate surface provided higher contrast sensitivity than standard spherical IOLs.11–13 For example, Mester et al.13 found that the aspherical Tecnis Z9000 IOL (Pharmacia) significantly decreased whole-eye spherical aberration compared with a standard spherical IOL. This reduced spherical aberration resulted in a significant improvement in contrast sensitivity. Packer et al.11 compared the contrast sensitivity of 10 patients with a Tecnis Z9000 IOL and 11 patients with an AR40e spherical IOL (AMO) and found a statistically
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Figure 2. Wavefront maps of a patient 3 months after surgery. A: Maps of right eye with an AcrySof Natural IOL. B: Maps of left eye with an AcrySof IQ IOL. Note the difference in HOA between the right eye and left eye.
significant improvement in contrast sensitivity with the Z9000 IOL at spatial frequencies of 6 cpd, 12 cpd, and 18 cpd under photopic conditions and at 1.5 cpd and 3 cpd under mesopic conditions. In a prospective study by Kennis et al.,14 98 eyes of 71 patients were randomly allocated to receive 1 of 3 IOLs (Tecnis Z9000, Sensar AR40e, or AcrySof Natural SN60AT). Contrast sensitivity was significantly better at almost all spatial frequencies in the Tecnis Z9000 group. Contrary to the findings of Mester et al.,13 Packer et al.,11 and Kennis et al.,14 a study by Mun˜oz et al.15 of spherical aberration and contrast sensitivity with the Tecnis Z9000 IOL found a significant reduction in spherical aberration after Tecnis Z9000 IOL implantation compared with that after implantation of a standard spherical IOL (AR40e); however, they found no statistically significant differences between the AR40e IOL and Z9000 IOL in photopic and mesopic contrast sensitivity. Wavefront technology was first used to evaluate lower-order aberrations and HOAs in normal phakic eyes. This was followed by its use in pseudophakic eyes.16,17 In our study, postoperative wavefront
Figure 3. Wavefront maps of another patient 3 months after surgery. A: Maps of right eye with an AcrySof Natural IOL. B: Maps of left eye with an AcrySof IQ IOL. Note the difference in HOA between the right eye and left eye.
analysis showed significant differences in total aberration, HOA, and spherical aberration between eyes with an AcrySof IQ IOL and eyes with an AcrySof Natural IOL, with the former having less aberration than the latter. Mun˜oz et al.15 observed a significant reduction in spherical aberration with an aspherical IOL (Tecnis Z9000) compared with 2 spherical IOLs (AR40e; Stabibag, Ioltech). Kasper et al.16 also found significantly reduced spherical aberration with an aspherical IOL (Tecnis Z9000) compared with a spherical IOL (Sensar). We made a significant effort to reduce the bias that can occur in comparative clinical studies by making our study an intraindividual comparison, using the same IOL material manufactured by the same company, and having the same surgeon perform bilateral surgery within 1 week using an identical surgical
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technique. When patients were asked after bilateral surgery to identify the eye with better vision, 55.6% (10 patients) said there was no difference and 44.4% preferred the vision in the eye with the AcrySof IQ IOL. Therefore, it remains questionable whether the significant differences in HOA and contrast sensitivity have clinical relevance and what it means for the patient. Evidence from several well-conducted clinical studies 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. Our study showed that visual quality can be improved by implantation of an IOL with a modified prolate surface. Patients will generally be more satisfied after implantation of an aspherical IOL because they will have better contrast sensitivity and less HOA. REFERENCES 1. Arden GB. The importance of measuring contrast sensitivity in cases of visual disturbance. Br J Ophthalmol 1978; 62:198–209 2. Elliott DB. Evaluating visual function in cataract. Optom Vis Sci 1993; 70:896–902 3. Rubin GS, Adamsons IA, Stark WJ. Comparison of acuity, contrast sensitivity, and disability glare before and after cataract surgery. Arch Ophthalmol 1993; 111:56–61 4. Ginsburg AP. Spatial filtering and visual form perception. In: Boff KR, Kaufman L, Thomas JP, eds, Handbook of Perception and Human Performance. New York, NY, John Wiley & Sons, 1986; vol. 2, chapt 34 5. Ginsburg AP, Evans DW, Sekuler R, Harp SA. Contrast sensitivity predicts pilots’ performance in aircraft simulators. Am J Optom Physiol Opt 1982; 59:105–109 6. Rubin GS, Bandeen Roche K, Huang G-H, et al. The association or multiple visual impairments with self-reported visual disability; SEE Project. Invest Ophthalmol Vis Sci 2001; 42:64–72 7. Packer M, Fine IH, Hoffman RS. Wavefront technology in cataract surgery. Current Opin Ophthalmol 2004; 15:56–60
8. Glasser A, Campbell MCW. Presbyopia and the optical changes in the human crystalline lens with age. Vision Res 1998; 38:209– 229 9. Guirao A, Gonza´lez C, Redondo M, et al. Average optical performance of the human eye as function of age in a normal population. Invest Ophthalmol Vis Sci 1999; 40:203–213 10. Guirao A, Redondo M, Artal P. Optical aberrations of the human cornea as a function of age. J Opt Soc Am A Opt Image Sci Vis 2000; 17:1697–1702 11. Packer M, Fine IH, Hoffman RS, Piers PA. Prospective randomized trial of an anterior surface modified prolate intraocular lens. J Refract Surg 2002; 18:692–696 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. 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 Ophtalmol 2004; 294:49–58 15. Mun˜oz G, Albarra´n-Diego C, Monte´s-Mico´ R, et al. Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens. J Cataract Refract Surg 2006; 32:1320–1327 16. Kasper T, Bu¨hren 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 17. 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
First author: Patrick F. Tzelikis, MD Brasilia Ophthalmologic Hospital, Brasilia, and Sao Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil
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