Methods

This prospective, randomized, bilateral, double-masked clinical study included 50 eyes of 25 patients with visually significant bilateral cataracts. Patients randomly received an aspherical IOL Akreos AO in one eye (25 eyes) and a spherical IOL Akreos Fit (25 eyes) in the fellow eye. Table 1 shows the characteristics of the 2 IOLs.

Patients with visually significant bilateral cataract and corneal astigmatism lower than 2.0 diopters (D) were eligible for inclusion in the study. Exclusion criteria included any ocular disease, such as corneal opacities or irregularity, dry eye, amblyopia, anisometropia, glaucoma, retinal abnormalities, surgical complications, IOL tilt, IOL decentration of more than 0.4 mm (estimated by retroillumination), or incomplete follow-up. The primary outcome measures of the study were contrast sensitivity and wavefront data.

Patients were examined before surgery and at 1, 7, 30, and 90 days after surgery. At 30 and 90 days after surgery, the best-corrected visual acuity (BCVA) and distance uncorrected visual acuity (UCVA) were measured as well as HOA values. At 90 days, contrast sensitivity test was performed under photopic and mesopic conditions in all patients.

Visual acuity was measured using the Early Treatment Diabetic Retinopathy Study charts under photopic conditions (target luminance of 85 cd/m ² ). The visual acuity values were converted to the logarithm of the minimal angle resolution units for statistical analysis. All eyes were targeted for emmetropia. Distance-corrected, near (33.3 cm), and intermediate (100 cm) visual acuity were studied as a measurement of depth of focus.

Wavefront analysis was carried out using the OPD-Scan aberrometer (Nidek Co, Gamagori, Japan), which uses dynamic retinoscopy technology to obtain wavefront data. All aberrations were measured up to the sixth Zernike order. Measurements were repeated at least 3 times to obtain a well-focused and aligned image of the eye. Measurements were analyzed for 5- and 6-mm pupils. Pupils were dilated with 2 drops of cyclopentolate 1% given 15 minutes apart. Measurements were obtained 45 minutes after the last cyclopentolate drop was instilled. Pupil diameter was measured using the Colvard pupillometer (Oasis Medical, Glendora, California, USA).

Contrast sensitivity was measured with VCTS 6000 (Vistech Consultants Inc, Dayton, Ohio, USA) with best spectacle correction under photopic (85 cd/m ² ) and mesopic (3 cd/m ² ) conditions. Light conditions were controlled with a luxometer (Gossen-Starlite, Nürnberg, Germany). The log base 10 contrast sensitivity values were used to construct a graphic for each spatial frequency tested and then presented in the original test scale. At the same visit, the Pelli-Robson contrast sensitivity test (Pelli-Robson chart; Clement Clarke International, London, United Kingdom) was performed using a distance of 1 m (corresponding to a spatial frequency of approximately 1 cycle/degree) and a luminance of 85 cd/m ² . Pupil size (in millimeters) was measured under scotopic (1.5 cd/m ² ), mesopic (3 cd/m ² ), and photopic (85 cd/m ² ) conditions ( Table 2 ). Pupil diameter in millimeters was measured using the same Colvard pupillometer mentioned before.

At 90 days after surgery, a subjective questionnaire also was applied. It was the same as that used in a previous study conducted by Tester and associates. All interviews were conducted by the same masked investigator (A.P.C.G.). The questionnaire is targeted to evaluate patient perception of overall bilateral vision, and therefore it is not specific about how each eye is deemed to be working.

All surgeries were performed by the same experienced surgeon (M.R.S.) with standardized small-incision phacoemulsification with IOL implantation in the capsular bag. Continuous curvilinear capsulorrhexis with an approximate 5.0-mm diameter was created. No adverse event has occurred.

Statistical analysis was performed using SPSS for Windows (version 115; SPSS, Inc, Chicago, Illinois, USA). For primary outcome measures, the statistical tests were conducted at an α level of 0.05. For the remaining analyses, a Bonferroni correction was applied and the P value therefore was reduced to .003. For statistical analysis of visual acuity, the logarithm of the minimal angle of resolution acuity value was used. The analysis was based on a nonnormal distribution of the data. The 2 IOLs were compared between eyes intraindividually. The nonparametric Wilcoxon paired test was used to compare data between the 2 IOL groups. For our analysis, a sample size of at least 21 eyes per group allowed effect size of 0.85 and also the sample sizes took into account a significance level of 5% and a power of 95% for the Wilcoxon test.

Results

Fifty eyes of 25 patients (12 men [48.0%] and 13 women [52.0%]) were enrolled in this study. Mean age of the patients was 56.80 ± 6.48 years. No significant difference was found between IOLs groups for mean IOL power in diopters ( P = .736) and mean axial length in millimeters ( P = .431). No significant difference was found between groups for mean preoperative corneal spherical aberration ( P = .321). There was also no statistical difference between groups in mean best spectacle-corrected visual acuity, spherical equivalent, and corneal curvature before surgery.

No eye had intraoperative complications. At 3 months after surgery, all the lenses were well centered and there was no evidence of posterior capsule opacity. There were no problems with follow-up with any patients.

At 1 month after surgery, all eyes showed improvement in UCVA. The spherical equivalent was 0.02 ± 0.38 in the Akreos AO group and 0.07 ± 0.43 in the Akreos Fit group ( P = .197). The mean distance UCVA was 0.07 ± 0.07 in the Akreos AO group and 0.09 ± 0.08 in the Akreos Fit group. There was no significant difference between the IOL groups for distance UCVA ( P = .289). The mean distance BCVA was 0.00 ± 0.12 in the Akreos AO group and 0.02 ± 0.07 in the Akreos Fit group. There was no significant difference between the IOL groups for distance BCVA ( P = .431). Table 3 shows the results of mean distance-corrected near and intermediate visual acuity. No significant difference was found between the Akreos AO and Akreos Fit groups for distance-corrected near ( P = .083) and intermediate ( P = .102) visual acuity.

Figures 1 and 2 show contrast sensitivity results under photopic and mesopic conditions. Under photopic conditions, the Akreos AO IOL presented statistically better contrast sensitivity than the Akreos Fit IOL only at 12 cycles per degree (cpd) spatial frequency ( P = .028). Under mesopic conditions, the Akreos AO IOL presented statistically better contrast sensitivity than the Akreos Fit IOL at all spatial frequencies (1.5, 3, 6, 12, and 18 cpd; P = .004, P = .042, P = .017, P = .0017, and P < .001, respectively). Mean pupil diameter was similar between the groups under photopic, mesopic, and scotopic conditions ( Table 2 ). Mean contrast sensitivity values, measured by the Pelli-Robson test, were 1.57 ± 0.03 in the Akreos AO group and 1.56 ± 0.03 in the Akreos Fit group ( P = .041).

Graph showing contrast sensitivity under photopic conditions in the Akreos AO group and the Akreos Fit group. The difference between the aspherical intraocular lens (IOL; Akreos AO) and the spheric IOL (Akreos Fit) was statistically significant only at 12 cycles per degree.

Graph showing contrast sensitivity under mesopic conditions in the Akreos AO group and the Akreos Fit group. The difference between the aspherical intraocular lens (IOL; Akreos AO) and the spheric IOL (Akreos Fit) was statistically significant at all spatial frequencies.

Table 4 shows wavefront data at 1 and 3 months after cataract surgery. At 1 month after surgery, the Akreos AO group had statistically significantly lower values of mean HOA compared with the Akreos Fit group with 5.0- and 6.0-mm pupil diameters ( P = .005 and P = .007, respectively).

TABLE 4

Wavefront Data of Eyes Implanted with Akreos AO and Akreos Fit

Wavefront Data	Akreos AO (Mean ± SD)	Akreos Fit (Mean ± SD)	P Value
5-mm pupil, 1 mo
HOA RMS	0.81 ± 0.35	1.27 ± 0.68	.005 a
Coma	0.50 ± 0.19	0.57 ± 0.42	.342
Spherical aberration	0.21 ± 0.42	0.37 ± 0.16	.040 a
6-mm pupil, 1 mo
HOA RMS	0.89 ± 0.18	1.34 ± 0.39	.007 a
Coma	0.51 ± 0.18	0.59 ± 0.26	.483
Spherical aberration	0.28 ± 0.07	0.47 ± 0.17	<.001 a
5-mm pupil, 3 mos
HOA RMS	0.79 ± 0.18	1.24 ± 0.39	.015 a
Coma	0.49 ± 0.21	0.55 ± 0.43	.366
Spherical aberration	0.20 ± 0.07	0.37 ± 0.17	0.002 a
6-mm pupil, 3 mos
HOA RMS	0.96 ± 0.19	1.39 ± 0.39	.004 a
Coma	0.51 ± 0.19	0.57 ± 0.28	.412
Spherical aberration	0.26 ± 0.08	0.45 ± 0.17	<.001 a

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