ARTICLE
Randomized intraindividual comparison of posterior capsule opacification between a microincision intraocular lens and a conventional intraocular lens Georgia Cleary, MRCOphth, David J. Spalton, FRCOphth, Joanne Hancox, MRCOphth, James Boyce, PhD, John Marshall, PhD
PURPOSE: To evaluate the differences in posterior capsule opacification (PCO) and visual and optical performance between a microincision intraocular lens (IOL) and a conventional IOL. SETTING: Ophthalmology Department, St. Thomas’ Hospital, London, United Kingdom. METHODS: Patients with bilateral cataract were prospectively randomized to receive a HumanOptics MC611MI microincision IOL (microlens group) or an Alcon AcrySof MA60AC 3-piece IOL (control group) in either eye and were followed for 24 months. Best corrected visual acuity (BCVA) (logMAR) was measured; PCO was quantified by POCO software analysis of retroillumination images. Aberrations and modulation transfer function (MTF) were measured at the 24-month visit. RESULTS: The study enrolled 32 patients. The mean percentage area PCO was greater in the microlens group than in the control group from 3 months onward and was statistically significant from 12 months onward. The greatest difference in PCO between groups was at 24 months: mean 25.45% G 34.51% (SD) in the microlens group versus 7.82% G 13.35% in the control group (P Z .029). The BCVA in the control group was slightly better at all time points; the difference between groups was statistically significant at 3, 6, and 12 months. No significant difference in aberrations was detected. The MTF curves were comparable for both IOLs. CONCLUSIONS: Both IOLs provided good visual performance. There was no evidence of distortion of the microincision IOL in the capsular bag. The microincision IOL had poorer PCO performance, which was visually significant and was caused by migration of lens epithelial cells through its broad optic–haptic junctions. J Cataract Refract Surg 2009; 35:265–272 Q 2009 ASCRS and ESCRS
Cataract surgery continues to undergo refinements that increase the safety and efficacy of the procedure. Recent years have seen a trend toward microincision cataract surgery (MICS), defined as cataract surgery performed though an incision smaller than 2.0 mm in diameter. The benefits of a smaller surgical wound include quicker visual rehabilitation postoperatively, reduced surgically induced astigmatism and aberrations, and a theoretical reduction in the risk for postoperative endophthalmitis.1,2 As MICS gains popularity, there is increasing demand for intraocular lenses (IOLs) that can tolerate injection into the eye through ever-smaller incisions. To confer maximum benefit to patients, MICS IOLs must deliver the same high standard of optical and visual Q 2009 ASCRS and ESCRS Published by Elsevier Inc.
quality as established IOLs used in standard small-incision cataract surgery. Microincision cataract surgery IOLs must remain stable within the capsular bag and maintain good posterior capsule opacification (PCO) performance. These IOLs are thinner and more flexible than conventional IOLs and must be able to withstand the decentering and distorting effects of capsular bag fibrosis and shrinkage postoperatively. Three-piece AcrySof IOLs have a long track record of good visual outcomes and excellent PCO performance.3–5 The aim of this study was to evaluate the PCO and optical and visual performance of the MC611MI microincision IOL (HumanOptics) and the AcrySof MA60AC IOL (Alcon Laboratories) in a prospective randomized fellow-eye controlled study. 0886-3350/09/$dsee front matter doi:10.1016/j.jcrs.2008.10.048
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Figure 1. A: HumanOptics MC611MI IOL. B: Alcon AcrySof MA60AC IOL.
PATIENTS AND METHODS Participants were recruited from the outpatient clinic in the Ophthalmology Department, St. Thomas’ Hospital, London, United Kingdom. Ethics approval was obtained from the St. Thomas’ Hospital Research Ethics Committee, and the study conformed to the tenets of the Declaration of Helsinki. Patients gave written informed consent. Patients with bilateral cataract and otherwise healthy eyes were candidates for inclusion in the study. Exclusion criteria were coexisting ocular pathology, ocular medication
Submitted: July 28, 2008. Final revision submitted: October 30, 2008. Accepted: October 30, 2008. From the Department of Ophthalmology (Cleary, Spalton, Hancox) and Vision Research (Boyce, Marshall), Rayne Institute, St. Thomas’ Hospital, London, United Kingdom, and Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia (Cleary). Drs. Spalton and Boyce are consultants to Alcon Laboratories. No author has a financial or proprietary interest in any material or method mentioned. Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Chicago, Illinois, USA, April 2008. Funded by an unrestricted research grant from Alcon Laboratories, Fort Worth, Texas, USA. Corresponding author: David J. Spalton, FRCOphth, Department of Ophthalmology, St. Thomas’ Hospital, London SE1 7EH, United Kingdom. E-mail:
[email protected].
apart from topical lubricants, a history of ocular trauma, systemic steroid or immunosuppressive therapy, surgical complications, or inability to cooperate or return for follow-up appointments. Patients were prospectively recruited to the study between February 2005 and February 2006. A random allocation sequence was generated using a computerized randomization program in a single block with a 1:1 allocation ratio. Participants were added to this nonconcealed randomized sequence list as they were recruited; this was performed by an ophthalmic resident (J.H.). The first eye was randomized to receive an MC611MI microincision IOL (microlens group) or an AcrySof MA60AC IOL (control group). Second-eye surgery was performed with the alternative IOL within 4 weeks. The MC611MI is a 1-piece hydrophilic acrylic IOL with a 26% water content. It has an optic diameter of 6.0 mm and an overall length of 11.0 mm (Figure 1, A). It has a complex haptic configuration with 2 closed-loop haptics, each of which has 2 broad attachments to the optic and can be injected into the eye through an incision of 1.8 mm or larger. The AcrySof MA60AC is a 3-piece IOL with a hydrophobic acrylic optic and poly(methyl methacrylate) haptics (Figure 1, B). Its optic diameter is 6.0 mm and its overall diameter, 13.0 mm. Biometry was performed using the IOLMaster (Zeiss). Optical A-constants of 118.6 and 118.9 were used in the microlens group and the control group, respectively, aiming for a plano to –0.50 diopter (D) postoperative refraction. Surgery was performed using a standardized procedure by the same surgeon (D.J.S.) under topical anesthesia. A 2.75 mm temporal clear corneal incision was made, and nonpreserved lidocaine hydrochloride was injected into the anterior chamber. The anterior chamber was filled with an ophthalmic viscosurgical device (OVD), and a central 5.0 mm capsulorhexis was fashioned such that the capsulorhexis would cover the peripheral anterior IOL optic surface
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with the IOL inserted. Phacoemulsification was performed using a stop-and-chop technique and was followed by aspiration of residual soft lens matter using balanced salt solution (BSS). The anterior chamber and capsular bag were refilled with OVD. In the control group, the wound was enlarged to 3.25 mm and the IOL was folded and inserted with a forceps. In the microlens group, the IOL was injected through the 2.75 mm incision using a Naviglide cartridge (Medicel). All OVD was removed from the anterior chamber, taking care to achieve complete removal from behind the IOL. The anterior chamber was refilled and the corneal wound hydrated with BSS. Patients were reviewed 1 day and 1, 3, 6, 12, and 24 months postoperatively. The observers (J.H., G.C.) were not masked to the IOL allocation between eyes. From 1 month onward, the best corrected visual acuity (BCVA) (logMAR, Early Treatment Diabetic Retinopathy Study [ETDRS] chart) was measured at 4.0 m. After pupil dilation, digital retroillumination photographs were taken and the percentage area PCO within the anterior capsulorhexis was calculated using POCO software.6 The pattern of growth of lens epithelial cells (LECs) onto the posterior capsule was evaluated subjectively in both groups. At the 24-month visit, aberrations and modulation transfer function (MTF) were measured with the Tracey Visual Function Analyzer (Tracey Technologies Corp.) with a 5.0 mm artificial pupil. Five measurements of each eye were captured, and results were averaged to give a single value for each parameter. Root-mean-square (RMS) terms for total aberrations, total lower-order aberrations (LOAs), and total higher-order aberrations (HOAs) were evaluated in addition to individual measurements of Z(4,0) (spherical aberration), Z(3,–1), Z(3,C1) (primary coma aberrations), and Z(3,–3), Z(3,C3) (primary trefoil aberrations). The MTF was derived from the point-spread function at spatial frequencies of 5, 10, 15, 20, 25, and 30 cycles per degree (cpd). The MTF curves attributable to total aberrations and HOAs were evaluated. The primary outcome measure was the difference in percentage area PCO between the 2 IOL groups. This measure was used for sample-size calculation. Secondary outcome measures were differences in BCVA, area within the anterior capsulorhexis, aberrations, and MTF. The sample-size calculation was based on unpublished data from a prospective PCO study performed by the same research group. In this study, the standard deviation for percentage area PCO for a hydrophobic acrylic AcrySof IOL was 5.76% at 2 years of follow-up. To detect a target difference of 5% area PCO between the 2 IOL groups at the 5% a level with 90% power, a sample size of 27 was calculated. To allow for a dropout rate of approximately 10% per year, 32 patients were recruited. Continuous variables were described in terms of means and standard deviations. Paired observations were compared by calculating differences between means and corresponding 95% confidence intervals, and significance was calculated using paired t tests. The significance level was set at P Z .05. Prism 3.0 software was used.
RESULTS Of the 32 patients recruited to the study, 1 withdrew before surgery, 1 declined surgery in the second eye, and 1 requested follow-up at his local hospital. One patient had a central retinal vein occlusion in the first
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Figure 2. Percentage area PCO. Mean and standard deviation shown. Only significant P values are shown (m Z months).
postoperative week. One patient died 6 months after surgery, another died shortly after the 1-year visit, and 2 suffered strokes, causing significant disability at 3 months and 18 months, respectively. Twentyfour patients completed 24 months of follow-up. The mean age of patients was 73.5 G 6.5 years; 46% were men and 54% were women. Fifty-seven percent of the microincision IOLs were implanted in right eyes and 43% in left eyes. The mean postoperative spherical equivalent refractive error was C0.12 D in the microlens group and –0.02 D in the control group (P Z .212). The percentage area PCO, the primary endpoint of the study, was greater in the microlens group than in the control group from 3 months onward, and the difference was statistically significant at 12 and 24 months (Figure 2, Table 1). There was a steady increase in PCO in the microlens group over the 24 months of follow-up. Five eyes in the control group had incomplete overlap of the capsulorhexis on the optic. In 3 of these eyes, the incomplete overlap was due to oversizing of the capsulorhexis. In the other 2 eyes at 1 month, the capsulorhexis lay partially along the optic rim, probably indicating minor buttonholing. A further PCO subanalysis was performed, evaluating only patients in whom the capsulorhexis in each eye lay completely over the IOL optic; the subanalysis showed the same results. The area within the anterior capsulorhexis was not significantly different between the 2 IOL groups at any time point. In the microlens group, there were no cases of clinically significant IOL decentration. One patient in the microlens group required a neodymium:YAG (Nd:YAG) laser capsulotomy, which was performed at 24 months. No eye in the control group required a capsulotomy. The BCVA was better in the control group at all time points. The difference in BCVA between the 2 IOL groups was statistically significant at 3, 6, and 12
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Table 1. Results for PCO and BCVA. Mean G SD Endpoint Primary Percentage area PCO 1 mo 3 mo 6 mo 12 mo 24 mo Secondary BCVA (logMAR) 1 mo 3 mo 6 mo 12 mo 24 mo
Microlens Group
Control Group
Difference in Means (95% CI)
P Value
3.628 G 6.838 5.164 G 8.609 9.233 G 14.260 17.03 G 24.150 25.45 G 34.510
4.504 G 8.595 3.224 G 3.094 4.417 G 5.758 5.104 G 9.286 7.821 G 13.350
0.876 (–5.307 to 3.555) 1.940 (–1.694 to 5.574) 4.816 (–1.904 to 11.54) 11.926 (1.183 to 22.67) 17.629 (1.947 to 33.32)
.6869 .2815 .1517 .0309* .0292*
0.026 G 0.087 0.040 G 0.088 0.031 G 0.091 0.040 G 0.094 0.023 G 0.107
0.020 G 0.084 0.010 G 0.089 0.004 G 0.092 0.005 G 0.110 0.009 G 0.093
0.006 (–0.017 to 0.030) 0.030 (0.004 to 0.057) 0.027 (0.002 to 0.052) 0.035 (0.003 to 0.067) 0.032 (–0.008 to 0.073)
.5763 .026* .034* .0324* .1088
CI Z confidence interval *Statistically significant differences (P!.05)
months (Figure 3, Table 1), although the differences were small. In 55% of eyes in the microlens group, LECs were observed to grow across the posterior capsule in a sheet, originating from the sides of the optic from which the haptics arose (through-haptic pattern of LEC migration) (Figure 4, A). Twenty-two percent had a fine membrane, the origin of which was uncertain. Some membranes regressed, leaving residual islands of LECs. Eleven percent of posterior capsules remained clear at 2 years of follow-up. The remaining eyes had scattered stable islands or in 1 case, a small posterior capsule plaque. One haptic was bent inward toward the IOL optic in 15% of eyes in the microlens group; however, this did not have an obvious influence on PCO.
Figure 3. Best corrected ETDRS logMAR visual acuity. Mean and standard deviation shown. Only significant P values are shown (m Z months).
Forty-four percent of eyes in the control group had a very thin membrane of LECs across the posterior capsule; 54% of the membranes regressed, leaving small islands of LECs. Twenty-six percent of eyes had small islands of LECs with no evidence of an early membrane to account for their origin. Fifteen percent of posterior capsules were clear throughout. Seven percent of eyes had a through-haptic pattern of PCO, and 7% had frank PCO as a result of the capsulorhexis being off the anterior IOL surface. No significant difference in any RMS terms or individual aberration evaluated was detected between the 2 IOL groups. In the microlens group versus the control group, the mean RMS for total aberrations was 1.010 mm versus 0.978 mm (P Z .752); for total LOAs, 0.895 mm versus 0.836 mm (P Z .584); and for total HOAs, 0.431 mm versus 0.468 mm (P Z .235). The mean spherical aberration was 0.192 mm versus 0.182 mm (P Z .586); vertical coma Z(3,–1), –0.006 mm versus –0.034 mm (P Z .420); and horizontal coma Z(3,C1), 0.049 mm versus 0.047 mm (P Z .968). The mean primary trefoil aberration Z(3,–3) was –0.139 mm versus –0.184 mm (P Z .291) and the mean primary trefoil aberration Z(3,C3), –0.031 mm versus –0.074 mm (P Z .480). When MTF due to all aberrations was evaluated, there was no significant difference between the 2 IOL groups at any spatial frequency (Figure 5, A). When MTF due to HOAs was evaluated, modulation was significantly higher in the control group at 20 cpd (P Z .040); however, there were no statistically significant differences at any other spatial frequency (Figure 5, B).
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Figure 4. Retroillumination images of paired eyes at 2 years of follow-up. A: Lens epithelial cell growth onto the posterior capsule arises from the optic– haptic junction in a through-haptic pattern in an eye in the microlens group. B: This fellow-eye image (control group) shows buttonholing of the optic.
DISCUSSION With increasing use of microincision phacoemulsification techniques among cataract surgeons, there is a parallel need for IOLs that can be inserted through the unenlarged incision and that deliver the same high standard of optical and visual performance as conventional IOLs used in standard coaxial surgery. Ideally, an MICS IOL would be implantable without wound enlargement or creation of an additional corneal wound as such steps defeat the primary aim of the MICS technique. The use of MICS has risen considerably in Europe, where a range of spherical and aspheric MICS IOLs are commercially available.
Microincision cataract surgery can be performed using a bimanual or microcoaxial approach, and the relative merits of each of these techniques and their advantages over conventional surgery remain a matter of discussion. Bimanual phacoemulsification has been compared with standard coaxial phacoemulsification in several prospective randomized clinical trials; such studies have to be interpreted in the light of the technology available and surgical experience. Both are undergoing rapid development. Alio´ et al.7 found a lower effective phacoemulsification time and total phacoemulsification power using a 1.5 mm bimanual technique; these results are corroborated by the findings
Figure 5. Modulation transfer function curves. Data were captured by the Tracey Visual Function Analyzer. A: The MTF generated from total aberrations. B: The MTF generated from HOAs only. Only significant P values are shown. J CATARACT REFRACT SURG - VOL 35, FEBRUARY 2009
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of Kurz et al.8 and Kahraman et al.9 using 1.5 mm and 1.4 mm bimanual MICS techniques, respectively. However, other authors10,11 found no significant differences in effective phacoemulsification time, and Crema et al.12 found lower total ultrasound times using 2.8 mm coaxial phacoemulsification than using a 1.2 mm MICS technique. One study11 found that lower total surgical times and BSS volumes were used with 1.4 mm bimanual MICS, while 2 other studies9,13 found lower total surgical times with standard coaxial phacoemulsification and no difference in BSS volumes. Several of the studies also evaluated postoperative corneal endothelial cell counts following bimanual and standard coaxial phacoemulsification. No significant difference in endothelial cell count was detected between the 2 techniques; however, Crema et al.12 detected significantly more endothelial cell loss in the MICS group.8–10 The smallest incisions require bimanual techniques; however, the trade-off between incision size, complexity of surgical technique, incision quality, and the size for IOL insertion is undecided. Incision sizes for coaxial phacoemulsification have decreased, allowing cataract surgeons to continue using a coaxial technique and insert standard IOLs though smaller incisions. For example, the widely used 1-piece AcrySof IOLs may be implanted through a 2.2 mm incision.14 Most studies have concentrated on the surgical aspects of bimanual surgery compared with conventional coaxial phacoemulsification; few comparative studies have evaluated MICS IOLs specifically. The intraoperative problems associated with MICS IOLs include stretching and distortion of the corneal wound and IOL damage during insertion.11,15 In the subsequent postoperative period, IOL decentration or folding may occur as the capsular bag fibroses, and there have been reports of very thin MICS IOLs tilting and decentering as the capsule fibroses after surgery.16,17 In our study, the haptic of the MC611MI IOL could be seen to fold toward or under the optic, although this did not appear to have an effect on vision or subsequent PCO. Posterior capsule opacification remains the most common complication of cataract surgery, and the contribution of IOL design to the development of PCO is well established.18 The most critical IOL factor in preventing PCO is a square profile to the posterior optic edge.3,18,19 Other IOL factors include optic diameter, biomaterial, and haptic design.20–22 Our intraindividual study specifically compared the MC611MI IOL and the AcrySof MA60AC, which have very different designs. An identical coaxial phacoemulsification and a similar wound were used in both groups; thus, the only variable was the 2 different IOLs. Three-piece
AcrySof IOLs have a long history of excellent PCO performance.3–5 Although both IOLs have good PCO performance overall, our results show that the PCO performance of the MC611MI IOL (microlens group) was not as good as that of the AcrySof MA60AC IOL (control group). The percentage area PCO increased steadily in the microlens group and was greater than in the control group from 3 months of follow-up onward, with statistically significant differences between groups at 12 months and 24 months. The difference in PCO performance between these IOLs is likely to reflect their differences in biomaterial and design. The MC611MI IOL has a square-edged design; however, the haptics of the IOL are each joined to the optic by 2 broad-based attachments. The gap in the square-edged barrier at the optic–haptic junction of an IOL has been described as the Achilles heel in PCO prevention as it provides a point of migration for LECs from the equatorial region of the capsule onto the central posterior capsule.22 A through-haptic pattern of PCO was observed in 55% of eyes with the microincision IOL and is the most likely cause of greater PCO in this group. The BCVA in the control group improved continuously throughout the 2 years of follow-up from 0.020 logMAR at 1 month to –0.009 logMAR at 24 months, corresponding to an improvement of 1.5 logMAR letters. The gradual improvement in BCVA observed in the control group may be related to regression of PCO membranes from the central posterior capsule, and thus the visual axis, observed when retroillumination images were assessed subjectively. The BCVA in the microlens group showed a small amount of variation over the 24 months of followup. Although visual acuity was statistically significantly worse in the microlens group than in the control group at 3, 6, and 12 months, no significant difference could be demonstrated at 24 months (P Z.1088). This is because acuity improved in the microlens group at the final visit and may also be related to the regression of LECs observed in some eyes. At the final visit, the percentage area PCO was significantly higher in the microlens group, yet no statistically significant difference in visual acuity was found between the 2 IOLs. This apparent discrepancy probably relates to the distribution of PCO in the microlens group. The through-haptic pattern of PCO, affecting 55% of eyes with the microlens, is initially peripheral in distribution. This is not reflected in the POCO score, which describes the percentage area of the posterior capsule affected by PCO, not the location of LECs. Two prospective studies report poor PCO performance with another MICS IOL, the ThinOptX UltraChoice 1.0 (ThinOptX Inc.). In a noncomparative
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study,16 64% of 50 eyes required an Nd:YAG capsulotomy for visually significant PCO after 15 months of follow-up. A comparative study17 found that the ThinOptX IOL had worse PCO performance and, consequently, visual performance than the AcrySof MA30AC 1 year postoperatively. Poor PCO performance may thus outweigh the benefits of a smaller incision with these MICS IOLs. Alio´ et al.23 evaluated in vivo MTF in eyes implanted with Acri.Smart 48S (Acri.Tec), ThinOptX UltraChoice 1.0, and AcrySof MA60BM IOLs. Bimanual 1.5 mm phacoemulsification was performed, 10 IOLs of each type were implanted, and MTF was evaluated 3 months postoperatively. No significant difference in 0.1 MTF and 0.5 MTF was found between the 3 groups. In our study, aberrometry did not show appreciable differences between the 2 IOL groups. The microincision IOL was inserted through a larger incision than is necessary, and it is conceivable that with a smaller incision, aberrations might be less with this IOL. However, if folding or buckling of the microincision IOL occurred, it would manifest as a detectable increase in HOAs, particularly coma, between the 2 IOLs. From these data, we conclude that the optic of the microincision IOL remained stable within the eye with no evidence of folding or distortion during capsular bag wound healing. In summary, this study showed that both IOLs give excellent visual results and the MC611MI microincision IOL remains stable in the eye 2 years postoperatively. The advantages of a smaller incision, however, come at the expense of poorer PCO performance. This difference is most likely due to the design of the microincision IOL, which has broad optic–haptic junctions, allowing ingrowth of LECs from the equatorial lens capsule. Microincision cataract surgery is likely to experience more widespread use when its technical and fluidic compromises are resolved and when MICS IOLs are proven to perform as well as their conventional coaxial counterparts. REFERENCES 1. Alio´ J, Rodriguez-Prats JL, Galal A. Advances in microincision cataract surgery intraocular lenses. Curr Opin Ophthalmol 2006; 17:80–93 2. Yao K, Tang X, Ye P. Corneal astigmatism, high order aberrations, and optical quality after cataract surgery: microincision versus small incision. J Refract Surg 2006; 22:S1079– S1082 3. Findl O, Menapace R, Sacu S, Buehl W, Rainer G. Effect of optic material on posterior capsule opacification in intraocular lenses with sharp-edge optics; randomized clinical trial. Ophthalmology 2005; 112:67–72 4. Davison JA. Neodymium:YAG laser posterior capsulotomy after implantation of AcrySof intraocular lenses. J Cataract Refract Surg 2004; 30:1492–1500
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5. Leydolt C, Davidovic S, Sacu S, Menapace R, Neumayer T, Prinz A, Buehl W, Findl O. Long-term effect of 1-piece and 3-piece hydrophobic acrylic intraocular lens on posterior capsule opacification; a randomized trial. Ophthalmology 2007; 114:1663–1669 6. Barman SA, Hollick EJ, Boyce JF, Spalton DJ, Uyyanonvara B, Sanguinetti G, Meacock W. Quantification of posterior capsule opacification in digital images after cataract surgery. Invest Ophthalmol and Vis Sci 2000; 41:3882–3892. Available at: http:// www.iovs.org/cgi/reprint/41/12/3882. Accessed November 6, 2008. 7. Alio´ J, Rodrı´guez-Prats JL, Galal A, Ramzy M. Outcomes of microincision cataract surgery versus coaxial phacoemulsification. Ophthalmology 2005; 112:1997–2003 8. Kurz S, Krummenauer F, Gabriel P, Pfeiffer N, Dick HB. Biaxial microincision versus coaxial small-incision clear cornea cataract surgery. Ophthalmology 2006; 113:1818–1826 9. Kahraman G, Amon M, Franz C, Prinz A, AbelaFormanek C. Intraindividual comparison of surgical trauma after bimanual microincision and conventional small-incision coaxial phacoemulsification. J Cataract Refract Surg 2007; 33:618–622 10. Mencucci R, Ponchietti C, Virgili G, Giansanti F, Menchini U. Corneal endothelial damage after cataract surgery: microincision versus standard technique. J Cataract Refract Surg 2006; 32:1351–1354 11. Cavallini GM, Campi L, Masini C, Pelloni S, Pupino A. Bimanual microphacoemulsification versus coaxial miniphacoemulsification: prospective study. J Cataract Refract Surg 2007; 33:387–392 12. Crema AS, Walsh A, Yamane Y, Nose´ W. Comparative study of coaxial phacoemulsification and microincision cataract surgery; one-year follow-up. J Cataract Refract Surg 2007; 33:1014–1018 13. Dosso AA, Cottet L, Burgener ND, Di Nardo S. Outcomes of coaxial microincision cataract surgery versus conventional coaxial cataract surgery. J Cataract Refract Surg 2008; 34:284–288 14. Osher RH. Microcoaxial phacoemulsification. Part 2: clinical study. J Cataract Refract Surg 2007; 33:408–412 15. Berdahl JP, DeStafeno JJ, Kim T. Corneal wound architecture and integrity after phacoemulsification; evaluation of coaxial, microincision coaxial, and microincision bimanual techniques. J Cataract Refract Surg 2007; 33:510–515 16. Prakash P, Kasaby HE, Aggarwal RK, Humfrey S. Microincision bimanual phacoemulsification and ThinoptxÒ implantation through a 1.70 mm incision. Eye 2007; 21:177–182 ¨ zturker ZK, O ¨ zturker C, Yasxar O ¨ , Sivrikaya H, 17. Kaya V, O ¨ F. ThinOptX vs AcrySof: comparison of viAgca A, Yilmaz O sual and refractive results, contrast sensitivity, and the incidence of posterior capsule opacification. Eur J Ophthalmol 2007; 17:307–314 18. Findl O, Buehl W, Bauer P, Sycha T. Interventions for preventing posterior capsule opacification. Cochrane Database Syst Rev 2007; CD003738 19. Hancox J, Spalton D, Cleary G, Boyce J, Nanavaty MA, Thyagarajan S, Marshall J. Fellow-eye comparison of posterior capsule opacification with the AcrySof SN60AT and the Hoya AF-1 YA-60BB blue blocking intraocular lenses. J Cataract Refract Surgery 2008; 34:1489–1494 20. Nishi O, Nishi K. Effect of the optic size of a single-piece acrylic intraocular lens on posterior capsule opacification. J Cataract Refract Surg 2003; 29:348–353 21. Heatley CJ, Spalton DJ, Kumar A, Jose R, Boyce JF, Bender LE. Comparison of posterior capsule opacification rates between
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hydrophilic and hydrophobic single-piece acrylic intraocular lenses. J Cataract Refract Surg 2005; 31:718–724 22. Nixon DR, Apple DJ. Evaluation of lens epithelial cell migration in vivo at the haptic-optic junction of a one-piece hydrophobic acrylic intraocular lens. Am J Ophthalmol 2006; 142:557–562 23. Alio´ JL, Schimchak P, Monte´s-Mico´ R, Galal A. Retinal image quality after microincision intraocular lens implantation. J Cataract Refract Surg 2005; 31:1557–1560
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First author: Georgia Cleary, MRCOphth Department of Ophthalmology, St. Thomas’ Hospital, London, United Kingdom
