Chinese Medical Journal 2009;122(22):2705-2710 2705 Original article Evaluation of long-term visual performance following AcrySof ReSTOR lens implantation ZHAO Yun-e, LI Jun-hua, ZHU Jun, WANG Dan-dan and WANG Qin-mei Keywords: vision; multifocal lens; refraction; posterior capsular opacification D Background Multifocal lens has become popular in cataract surgery. Short-term outcome after AcrySof ReSTOR Lens implantation had been reported by many studies, but long-term visual performance and the effect of posterior capsular opacification (PCO) on visual performance need further investigation. Methods This retrospective study involved 54 eyes from 41 cataract patients implanted with ReSTOR lens, with a follow-up period of 12 to 31 months. Manifest refraction spherical equivalence (MRSE), monocular uncorrected and best-corrected distance visual acuity, uncorrected and distance-corrected near and intermediate visual acuity, contrast sensitivity were assessed. The effect of PCO on visual performance was evaluated by comparing visual parameters between pre and post-capsulotomy. Results Uncorrected distance visual acuity of eyes with MRSE within ±0.5 diopter (D) was better than those with MRSE greater than ±0.5 D (P <0.05). Uncorrected distance and near visual acuity (LogMAR) was 0.10 and 0.17 respectively. Best corrected distance visual acuity and best distance-corrected near visual acuity (LogMAR) was 0.00 and 0.16, a significant improvement was noted after correction (P=0.000, P=0.001, respectively). Contrast sensitivity logarithm was comparable with the normal value at difference spatial frequencies except at 12 cpd. In 5 eyes with mild PCO, post-capsulotomy visual parameters were better than pre-capsulotomy (P <0.05). Conclusion ReSTOR lens provides a good long-term distance and near vision, functional intermediate vision and contrast sensitivity. Mild PCO significantly affects visual performance and needs early intervention. espite advances in cataract surgical techniques and intraocular lenses (IOL), restoration of distance visual performance with spectacle independence for cataract patients is still a goal for ophthalmic surgeons to achieve. Some multifocal intraocular lenses (MIOLs), therefore, have been introduced into the market to provide cataract patients with good distance and near visions. AcrySof ReSTOR (SA60D3) IOL (Alcon laboratories Inc. USA) as a second generation MIOL, has been clinically used for several years. The AcrySof ReSTOR (SA60D3) lens has a biconvex optic that contains an apodized diffractive structure in the central 3.6 mm on the anterior surface. The periphery of this lens is identical to that of monofocal AcrySof Natural (SN60AT) lens manufactured by Alcon Laboratories, Inc, USA. Many published studies confirmed that the AcrySof ReSTOR IOLs provided good distance and near visual performance during 3 6 months follow-up, 1-4 but there were few long-term studies. In a recently published study, de Vries et al 5 reported long-term (3 years) changes in visual performance in patients underwent cataract surgery with bilateral implantation of AcrySof ReSTOR lenses. In this study, distance and near visual acuities as well as contrast sensitivity declined slightly from 6 months to 3 years though no statistically significant difference was found. However, theoretically, visual acuities may improve over time because of selective adaptation. Kaymak et al 6 reported a visual improvement from functional vision training after MIOL implantation. The declined visual acuities in the study of de Vries might be due to PCO. The purpose of the present study was to investigate visual performance after AcrySof ReSTOR lens implantation following a long-term follow up based on distance, near and intermediate functional visions as well as contrast sensitivity. The effect of PCO on visual performance was also evaluated. METHODS Patient inclusion criteria This study was a retrospective visual evaluation of cataract patients with implantation of AcrySof ReSTOR (SA60D3) lenses. It involved 54 eyes from 41 cataract patients including 22 male (31 eyes) and 19 female (23 eyes). Follow-up period was 12 to 31 (20.82±7.18) months. Twenty-six eyes from 13 patients received DOI: 10.3760/cma.j.issn.0366-6999.2009.22.006 School of Optometry and Ophthalmology, Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang 325003, China (Zhao YE, Li JH, Zhu J, Wang DD and Wang QM) Correspondance to: Dr. WANG Qin-mei, School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang 325027, China (Tel: 86-577-88068830. Fax: 86-577-88832083. Email: wqm8@mail.eye.ac.cn; zye@mail.eye. ac.cn)
2706 Table 1. Correlations between UCDVA, UCNVA and the MRSE (median (25th 75th)) Groups MRSE (absolute value) n (%) UCDVA UCNVA UCIVA/50 cm UCIVA/60 cm UCIVA/70 cm A 0.50 D 41 (75.9) 0.10 (0.00 0.10) 0.17 (0.11 0.23) 0.40 (0.30 0.60) 0.32 (0.22 0.52) 0.26 (0.16 0.46) B >0.50 D 13 (24.1) 0.10 (0.10 0.23) 0.20 (0.17 0.25) 0.30 (0.20 0.75) 0.22 (0.12 0.52) 0.26 (0.16 0.46) Z values 2.186 1.128 1.369 1.208 0.550 P values 0.029 0.259 0.171 0.227 0.582 UCDVA: uncorrected distance visual acuity. UCNVA: uncorrected near visual acuity. MRSE: manifest refraction spherical equivalence. bilateral implantation. Patients between 50 and 75 years of age (mean 62±8) and available for long-term postoperative examinations were enrolled into the study. Exclusion criteria included: preoperative corneal astigmatism greater than 1.50 D, a pupil smaller than 2.4 mm, and any ocular pathology other than cataract. Patients with complications during surgical procedure, such as capsule rupture or zonulysis, were also excluded. Preoperative biometry was performed using IOLMaster (Carl Zeiss Meditec, Jena, Germany) or A-scan (Quantel Medical, France). IOL power was calculated using SRK/T formula. Targeted refraction was emmetropia or mild hyperopia. Clinical evaluation Clinical evaluations included MRSE, uncorrected and best-corrected distance visual acuity (UCDVA, BCDVA), uncorrected and distance-corrected near visual acuity (UCNVA, DCNVA), uncorrected and distance-corrected intermediate visual acuity at 50, 60, 70 cm (UCIVA/50 cm, UCIVA/60 cm, UCIVA/70 cm, DCIVA/50 cm, DCIVA/60 cm, DCIVA/70 cm), contrast sensitivity (CS) with and without glare. Then patients were checked for IOL position and posterior capsule condition using slit-lamp after pupil dilation. Monocular uncorrected and best corrected distance visual acuities were measured with an ETDRS LogMAR chart (Precision Vision, USA) at 4 m with 100% contrast and 180 250 cd/m 2. Near visual acuities were measured at the best distance chosen by the patients, using a 40 cm visual acuity chart fixed onto a phoropter (Topcon Co. IS-400, Japan). Intermediate visual acuities were measured at 50, 60 and 70 cm using the same visual acuity chart. The testing illumination for near and intermediate vision was 12 20 cd/m 2. All near and intermediate visual acuity scores were converted to the logmar units as follows: recorded VA= Log (observed distance/(0.4 10 observed VA )). Contrast sensitivity was measured using CSV-1000E (Vector Vision, Inc. USA), a self standardized vision-testing instrument that provides a constant luminance level of 85 cd/m 2. For each examination, 4 spatial frequencies (3, 6, 12, and 18 cycles per degrees (cpd)) were tested with 8 sequences per spatial frequency. With patients sitting at 2.4 meters from the chart, the tests were performed under non-glare and glare conditions with the best optical corrections and the fellow eye closed under the same room luminance conditions. Patients were given 5 minutes before test to adapt to each condition. The tests were performed first under non-glare condition and then glare condition. Results were recorded as logarithm values. Contrast sensitivity curves were constructed for each patient. Biomicroscopic examinations were performed after pupil dilation. Posterior capsule transparency was evaluated. The grades for posterior capsular opacification (PCO) were defined as: 0=none; 1=transparent, visible only in retroillumination; 2=white-gray fibrosis clearly visible in retroillumination; 3=dense white fibrosis or Elschnig pearl formation. 7 Capsulotomy was performed using Nd:YAG laser on all patients with grades 1 to 3. Re-evaluations were performed on these patients one week after capsulotomy and the re-evaluated visual parameters were used for statistical analyses. All measurements were conducted by the same investigator following a strict methodology and the same sequence of tests. Statistical analysis All data were recorded as median (25th 75th), and analyzed using SPSS 13.0 (SPSS Inc., USA). The statistical difference between refraction groups was analyzed using Wilcoxon rank-sum test. Wilcoxon Signed-Rank test was used for other data. The logarithm value of CS was compared with the normal value. 8 P value less than 0.05 represents statistically significant differences. RESULTS Refractions and visual acuity correlations Average MRSE with best distance corrected visual acuity was ( 0.01±0.42) D ( 0.88 to +1.13 D). Patients were divided into two groups according to MRSE, and related uncorrected distance, intermediate and near visual acuities were shown in Table 1. Forty-one eyes (group A, 75.9%) were within ±0.50 D, 13 eyes (group B, 24.1%) were greater than ±0.50 D, respectively. There was statistically significant difference in uncorrected distance visual acuity between the two groups (P <0.05), whereas no significant differences were found in uncorrected near visual acuity and uncorrected intermediate visual acuities (P >0.05). Visual acuities at different distances were summarized in Table 2. Monocular uncorrected distance and near visual acuity was 0.10 (0.00 0.15) and 0.17 (0.11 0.23) respectively. Significant improvement was observed in distance and near visual acuity with best distance corrected (P=0.000 and P=0.001, respectively). Monocular uncorrected intermediate visual acuity was 0.40 (0.30 0.60), 0.32 (0.22 0.52), 0.26 (0.16 0.46), at 50, 60, 70 cm, respectively. There was no significant difference between uncorrected and best distance
Chinese Medical Journal 2009;122(22):2705-2710 2707 Table 2. Monocular visual acuity for distance, near, and intermediate vision n (%) Visual acuity Median (25th 75th) Z values P values 20/40 or better 20/25 or better Distance (4 m) Uncorrected 0.10 (0.00 0.15) 51/54 (94.4) 39/54 (72.2) 5.383 0.000 Best distance corrected 0.00 ( 0.03 0.00) 54/54 (100.0) 51/54 (94.4) Near Uncorrected 0.17 (0.11 0.23) 48/54 (88.9) 8/54 (14.8) 3.298 0.001 Best distance corrected 0.16 (0.11 0.21) 50/54 (92.6) 14/54 (25.9) Intermediate (50 cm) Uncorrected 0.40 (0.30 0.60) 20/54 (37.0) 4/54 (7.4) 1.633 0.102 Best distance corrected 0.40 (0.30 0.60) 21/54 (38.9) 4/54 (7.4) Intermediate (60 cm) Uncorrected 0.32 (0.22 0.52) 18/54 (33.3) 1/54 (1.9) 1.604 0.109 Best distance corrected 0.32 (0.22 0.52) 19/54 (35.2) 1/54 (1.9) Intermediate (70 cm) Uncorrected 0.26 (0.16 0.46) 26/54 (48.1) 2/54 (3.7) 1.826 0.068 Best distance corrected 0.26 (0.16 0.46) 28/54 (51.9) 2/54 (3.7) corrected intermediate visual acuity (P >0.05). Non-glare and glare CS The CS logarithm under non-glare conditions compared with the normal values at difference spatial frequencies was summarized in Table 3. There were no statistical differences in CS at 3, 6 and 18 cpd under non-glare conditions. But at 12 cpd, it was significantly lower than the normal value (P=0.007). There were no statistical differences between glare and non-glare conditions at difference spatial frequencies (P >0.05, Table 4). Table 3. Comparison of non-glare CS (logarithm) and normal value (median (25th 75th)) Variables Non-glare CS (logarithm) Normal values Z values P values 3 CPD 12 CPD 18 CPD 1.63 (1.49 1.78) 1.84 (1.70 1.99) 1.40 (1.00 1.62) 1.00 (0.64 1.25) 1.56 1.80 1.50 0.93 1.965 0.522 2.697 0.865 0.050 0.602 0.007 0.387 Table 4. Comparison of CS (logarithm) between non-glare and glare conditions (median (25th 75th)) Variables CS (logarithm) Z values P values 3 CPD Non-glare 1.63 (1.49 1.78) Glare 1.63 (1.49 1.78) 0.705 0.481 Non-glare 1.84 (1.70 1.99) Glare 1.84 (1.55 1.99) 1.134 0.257 Non-glare 1.40 (1.00 1.62) Glare 1.40 (1.17 1.54) 0.107 0.915 Non-glare 1.00 (0.64 1.25) Glare 0.96 (0.81 1.18) 0.599 0.549 Comparison of visual performance of eyes with bilateral and monocular implants To evaluate the long-term visual function of eyes with bilateral and monocular implantation of AcrySof ReSTOR lens, visual parameters between 26 eyes from 13 patients and 28 eyes from 28 patients were compared. UCDVA and BCDVA were significantly better in bilateral implantation group (Table 5). No statistically significant differences were found in other parameters. Table 5. Comparison of visual parameters between binocular and monocular patients (median (25th 75th)) Variables Binocular Monocular Z values P values n (%) 26 (48.1) 28 (51.9) UCDVA 0.00 ( 0.10 0.10) 0.10 (0.00 0.20) 3.181 0.001 BCDVA 0.00 ( 0.10 0.00) 0.00 (0.00 0.05) 2.271 0.023 UCNVA 0.16 (0.11 0.22) 0.18 (0.12 0.28) 1.314 0.189 DCNVA 0.11 (0.10 0.20) 0.18 (0.11 0.21) 1.741 0.082 Non-glare CS (logarithm) 3 CPD 1.49 (1.49 1.63) 1.63 (1.49 1.78) 1.111 0.267 1.84 (1.70 1.99) 1.84 (1.70 1.99) 0.836 0.403 12 CPD 1.47 (1.25 1.58) 1.40 (0.91 1.54) 1.378 0.168 18 CPD 1.10 (0.81 1.25) 0.96 (0.40 1.25) 1.551 0.121 Glare CS (logarithm) 3 CPD 1.63 (1.49 1.78) 1.63 (1.49 1.78) 0.363 0.717 1.84 (1.70 1.99) 1.70 (1.55 1.99) 1.310 0.190 12 CPD 1.40 (1.25 1.54) 1.25 (0.91 1.54) 0.725 0.468 18 CPD 1.10 (0.81 1.25) 0.96 (0.64 1.10) 1.792 0.073 UCDVA: uncorrected distance visual acuity. BCDVA: best corrected distance visual acuity. UCNVA: uncorrected near visual acuity. DCNVA: distance corrected near visual acuity. PCO and its impact on visual performance All IOLs were implanted successfully without tilt confirmed by slit-lamp check. PCO at grade 1 was found in 5 eyes 18 to 31 months after implantation. Capsulotomy was performed using Nd:YAG laser in all affected eyes with no complications. There was remarkable visual performance improvement one week after treatment (P <0.05 for all evaluations, Table 6). DISCUSSION The AcrySof ReSTOR (SA60D3) lens is an apodized diffractive IOL. The optic consists of a central 3.6 mm apodized diffractive region. Within it is a +4.00 D addition that equates to a +3.20 D addition at the spectacle plane allowing optimal near vision approximately 31 cm from patient s eye. Surrounding it is a refractive area with a distance focal point. When the incoming light passes through the central 3.6 mm region of the optic, the diffractive steps divide the light waves which are focused at both a near and a distant point. While the retina is receiving both the near and distance images, it is the patient s attention that determines which image the brain perceives. Besides providing near and distance vision,
2708 Table 6. Comparison of visual parameters between pre- and post-capsulotomy (median (25th 75th), n=5) Variables Pre-capsulotomy Post-capsulotomy Z values P values UCDVA 0.10 (0.10 0.30) 0.10 ( 0.10 0.05) 2.121 0.034 BCDVA 0.00 (0.00 0.15) 0.10 ( 0.15 to 0.10) 2.041 0.041 UCNVA 0.23 (0.21 0.30) 0.10 (0.04 0.11) 2.023 0.043 DCNVA 0.23 (0.18 0.32) 0.10 (0.05 0.11) 2.023 0.043 Non-glare CS (logarithm) 3 CPD 1.49 (1.26 1.56) 1.63 (1.56 1.86) 2.032 0.042 1.70 (1.15 1.85) 1.99 (1.53 2.29) 2.032 0.042 12 CPD 1.25 (0.70 1.40) 1.69 (1.47 1.99) 2.023 0.043 18 CPD 0.64 (0.17 0.96) 1.10 (0.89 1.40) 2.023 0.043 Glare CS (logarithm) 3 CPD 1.00 (0.70 1.17) 1.63 (1.49 1.86) 2.023 0.043 0.91 (0.76 1.30) 1.84 (1.53 2.14) 2.032 0.042 12 CPD 0.91 (0.46 1.17) 1.54 (1.40 1.62) 2.023 0.043 18 CPD 0.47 (0.02 0.64) 1.10 (0.72 1.25) 2.032 0.042 reduced image contrast and unwanted visual phenomena including glare and halos have been also associated with these multifocal lenses. 9-15 Theoretically, visual performance may improve over time because of selective adaptation. 6 Therefore, long-term visual performance evaluation is necessary after multifocal lens implantation. Some factors may influence long-term visual performance, such as PCO and IOL decentration. These factors should be eliminated before visual performance evaluation. In the present study, visual performance was evaluated more than one year after the AcrySof ReSTOR implantation. All IOLs were well centered. To eliminate the impact of posterior capsular opacification, re-evaluations were performed on those patients treated with capsulotomy for PCO and the re-evaluated visual parameters were used for statistical analyses. Despite advances in biometry measurements and IOL calculating formulas, refractive errors occur occasionally. In this study, the refraction in 75.9% eyes was within ±0.50 D, whereas 24.1% eyes had refractive errors more than ±0.50 D. There was statistically significant worsening with MRSE for distance vision (P=0.029); whereas no significant differences were found between different MRSE for near vision. Possible explanation is that the range of the refractive errors were within 0.88 to +1.13 D in these patients, and the near visual acuity was measured at the best distance chosen by patients. This finding was consistent with the published data on the visual acuity tolerance to residual refractive errors. 16 Regarding intermediate visual acuity, no significant differences were found between different MRSE in this study. Blaylock et al 2 also reported that there was no correlation between postoperative MRSE and uncorrected intermediate vision. In our study, distance visual acuity of eyes with AcrySof ReSTOR implant was good and comparable with those reported in other studies. The uncorrected distance visual acuity was 0.10 (0.00 0.15). There were 93.3% eyes achieving uncorrected distance visual acuity better than 20/40; 72.2% achieving better than 20/25. Similar percentages were found by Alfonso et al 1 (93.7%, 68.9%, respectively). After correction of refractive errors there was a significant improvement in distance vision (P=0.000). The best corrected distance vision was 0.00 ( 0.03 to 0.00). One hundred percent eyes achieved better than 20/40 and 94.4.0% eyes better than 20/25. For near vision, the monocular uncorrected acuity and distance corrected acuity were 0.17 (0.11 0.23) and 0.16 (0.11 0.21), respectively. They were comparable with those reported by Chiam et al 3 (0.72, 0.77, Snellen acuity, respectively). But they were lower than those from other reports (Alfonso et al, 1 0.015, 0.014, respectively; de Vries et al, 5 0.02, 0.034, respectively; Blaylock et al, 2 0.12, 0.07, respectively; Souza et al, 4 0.16, 0.14, respectively). With respect to intermediate vision, the monocular uncorrected acuity and distance corrected acuity were 0.40 (0.30 0.60) at 50 cm, 0.32 (0.22 0.52) at 60 cm, and 0.26 (0.16 0.46) at 70 cm. They were comparable with those reported by Petermeier et al, 17 but lower than those of Alfonso et al, 1 and de Vries et al. 5 The probable explanation was that they analyzed binocular vision while we only analyzed monocular vision. The intermediate vision was worst at 50 cm, but had a better trend with the distance vision. It was different from that reported by Alfonso et al 1 where they found the mean visual acuity being 0.101 at 40 cm, and 0.352 at 70 cm. There were several reasons that the near and intermediate visual acuities were worse than those reported in some literatures. Firstly, the last line in the visual acuity chart we used was 20/20. Therefore the best near visual acuity measured at the best distance chosen by the patient was 20/20 measured distance/40. Secondly, it was influenced by the illumination conditions. The near and intermediate vision was measured with a visual acuity chart fixed onto a phoropter. The illumination was only 12 20 cd/m 2 checked by a light meter. Thirdly, pupil size was slightly larger under low illumination conditions. As a result near visual acuity was compromised. Alfonso et al 18 found the best distance-corrected near visual acuity was worse with large pupil diameters. With any multifocal IOL, the division of incoming light energy from the object into 2 or more focal points may physically result in a decrease in image quality. Alfonso and co-workers 1 reported that photopic contrast sensitivity was close to the standard contrast sensitivity function after the implantation of the ReSTOR IOLs at a 6-month follow-up, whereas the mesopic contrast sensitivity was lower, particularly at higher spatial frequencies. Blaylock et al 19 reported photopic contrast sensitivity function decreased significantly at moderate and high spatial frequencies compared to that before implantation. However, no statistically significant changes were noted in mesopic contrast sensitivity and
Chinese Medical Journal 2009;122(22):2705-2710 2709 mesopic with glare at 3- and 6-month follow-up in patients after bilateral refractive lens exchange. The inconsistency in the literatures may be due to the use of different instruments and conditions used to assess contrast sensitivity. In the present study, the contrast sensitivity results were consistent with those reported by de Vries et al 5 at 6 months post implantation, using the same testing instrument. We found that contrast sensitivity with ReSTOR IOLs was within normal range except for that at 12 cpd under non-glare conditions. This finding was different from that reported by Rekas and Zelichowska. 20 They found that CS was lower at 12 cpd and 18 cpd at 6-month postoperative visits. The possible explanation was that the brain selective adaptation improves the contrast sensitivity function over time. 9 A recent prospective study by Kaymak et al 6 also showed that visual function training could improve visual quality. There was no difference in contrast sensitivity under non-glare and glare conditions. It suggests that glare would not influence visual quality for the eyes with Acrsof ReSTOR Lens. To our knowledge, there were few studies comparing eyes bilaterally and unilaterally implanted with Acrsof ReSTOR lens, although many studies reported visual performance of eyes with bilateral implants. In our study, visual parameters between bilaterally and monocularly implanted eyes were analyzed. UCDVA and BCDVA were better in bilaterally implanted eyes than those in monocularly implanted eyes. No significant difference was found in other parameters. There were very few reports about the effect of posterior capsular opacification on eyes with AcrySof ReSTOR multifocal lens. In a study by de Vries et al, 5 there were 4 out of 44 eyes requiring Nd:YAG capsulotomy for PCO. But the impact of PCO on visual performance was not analyzed by any study. In the present study, 5 out of 54 eyes were diagnosed as having mild PCO. There was a decrease in visual performance at the first examination. Re-examination after capsulotomy showed remarkable improvement in visual acuity and contrast sensitivity. It suggests that even mild PCO could significantly influence visual quality and need early treatment. The possible mechanism was that scattered opacities on the posterior capsule blocked off the incoming light and might produce diffraction, thus interfered with the multi-focus formation. In conclusion, ReSTOR lens provides good long-term distance and near vision and contrast sensitivity. Refractive errors result in a decrease in uncorrected visual quality, particularly in distance vision. Eyes with bilateral ReSTOR lens implantation have better distance vision than eyes with monocular implantation. Mild PCO significantly influences visual performance and needs early intervention. REFERENCES 1. 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