Jrs0811kranitz.indd

Femtosecond Laser Capsulotomy and Manual Continuous Curvilinear Capsulorrhexis Parameters and Their Effects on Intraocular Lens Centration Kinga Kránitz, MD; Agnes Takacs, MD; Kata Miháltz, MD; Illés Kovács, MD, PhD; Michael C. Knorz, MD; Zoltán Z. Nagy, MD, DSC C reation of a precise anterior capsulorrhexis is one of the most important steps of cataract surgery. In recent years, the most commonly used technique during PURPOSE: To measure and compare sizing and position-ing parameters of femtosecond laser capsulotomy with phacoemulsifi cation is continuous curvilinear capsulorrhexis manual continuous curvilinear capsulorrhexis (CCC).
(CCC). Popularized by Gimbel and Neuhann,1-3 CCC has sev-eral surgical and postoperative advantages but its completion METHODS: Femtosecond capsulotomies (Alcon-LenSx takes special attention and surgical expertise. Obtaining a pre- Lasers Inc) and CCC were carried out in 20 eyes of 20 cise capsulorrhexis is essential to reach demanding refractive patients, respectively. Intraocular lens (IOL) decentra- results because a properly sized and well-centered capsulor- tion, circularity, vertical and horizontal diameters of capsulotomies, and capsule overlap were measured rhexis with a 360° overlapping capsular edge prevents optic with Adobe Photoshop (Adobe Systems Inc) 1 week, 1 decentration, tilt, myopic shift, posterior and anterior capsular month, and 1 year after surgery. Between-group differ- opacifi cation due to symmetric contractile forces of the cap- ences of parameters and predictors of IOL decentration sular bag, and shrink wrap effect.4-10 However, an eccentric or were determined with repeated measures analysis of vari- irregularly shaped capsulorrhexis with a diameter extending ance, chi-square test, and logistic regression analyses. beyond the optic edge may lose these advantages. RESULTS: Vertical diameter of CCC was statistically Until now, capsulorrhexis has been a manual procedure. signifi cantly higher in the fi rst week and month. Signifi - With the advent of femtosecond lasers in ophthalmic sur- cantly higher values of capsule overlap over 1 year and gery, a predictably sized and centered anterior capsulotomy circularity in the fi rst week showed more regular femto- became possible through a laser–tissue interaction known as second capsulotomies. Horizontal IOL decentration was photodisruption.11 Femtosecond lasers were initially devel- statistically signifi cantly higher in the CCC group over 1 year. A signifi cant difference was noted between the two oped for LASIK fl ap creation during corneal refractive sur- groups in dichotomized horizontal decentration values gery. Recently introduced laser technology enables surgeons at 0.4 mm with chi-square test after 1 week and 1 year to achieve effi cient lens fragmentation or liquefaction and (P=.035 and P=.016, respectively). In univariable gen- precise and reproducible creation of capsulotomies and cor- eral estimating equation models, type of capsulorrhexis neal incisions during refractive cataract surgery.11-14 (PϽ.01) and capsule overlap (P=.002) were signifi cant predictors of horizontal decentration. Vertical diameter The purpose of this study was to measure and compare sizing showed signifi cant correlation to the overlap in the CCC and positioning parameters of the femtosecond laser capsulotomy group (1 week: r=Ϫ0.91; 1 month: r=Ϫ0.76, PϽ.01; with manual CCC during 1-year follow-up. We also studied the 1 year: r=Ϫ0.62, PϽ.01), whereas no signifi cant cor- effects of these differences on IOL centration. To our knowledge, relation was noted in the femtosecond group (PϾ.05). no such comparisons have been performed previously.
CONCLUSIONS: More precise capsulotomy sizing and centering can be achieved with femtosecond laser. Prop- From Semmelweis University Budapest, Faculty of Medicine, Department of erly sized, shaped, and centered femtosecond laser cap- Ophthalmology, Hungary (Kránitz, Takacs, Miháltz, Kovács, Nagy); and Medical sulotomies resulted in better overlap parameters that help Faculty Mannheim, University of Heidelberg, Mannheim, Germany (Knorz). maintain proper positioning of the IOL. [J Refract Surg. 2011;27(8):558-563.] Drs Knorz and Nagy are consultants to Alcon-LenSx Lasers Inc. The remaining authors have no financial interest in the materials presented herein. Correspondence: Kinga Kránitz, MD, Semmelweiss University Budapest, Dept of Ophthalmology, Mária u. 39, 1085 Budapest, Hungary. Tel: 36 20 825 8503; Fax: 36 1 317 9061; E-mail: kranitzkinga@gmail.com Received: October 14, 2010; Accepted: June 3, 2011 Posted online: June 30, 2011
IOL Centration in Femtosecond Laser and Manual Capsulorrhexis/Kránitz et al chamber and capsular bag by irrigation/aspiration. Femtosecond capsulotomies were carried out in 20 eyes No stromal hydration was needed. All incisions were of 20 patients and manual CCC was performed in 20 eyes left sutureless. No intra- or postoperative complica- of 20 patients undergoing cataract surgery with IOL im- tions occurred. Within the fi rst 10 days, all patients plantation. Each patient underwent a complete ophthal- received a combination of antibiotic and steroid eye mologic evaluation. Patients with previous ocular surgery, trauma, active ocular disease, poorly dilated pupils, or known zonular weakness were excluded from the study.
The study was conducted in compliance with the To document capsulotomies, digital retroillumina- Declaration of Helsinki, as well as with applicable tion photographs were taken 1 week, 1 month, and country and local requirements regarding ethics com- 1 year after surgery. Photographs were imported into mittee/institutional review boards and other statutes Adobe Photoshop (Adobe Systems Inc, San Jose, Cali- or regulations regarding protection of the rights and fornia) for measuring IOL decentration and the follow- welfare of human subjects participating in biomedi- ing capsulotomy parameters: vertical and horizontal cal research. A written informed consent was obtained diameter, circularity, and the shortest and longest distance between the edge of capsulorrhexis and the IOL optic edge (distance min, distance max) along an elongated radius of capsulorrhexis. The diameter of The surgical technique was standardized in each the implanted IOL was used as a scale to eliminate the patient, except for the method of capsulorrhexis. All magnifi cation effect of the cornea (Fig 1). surgeries were performed by the same surgeon (Z.Z.N.). Intraocular lens decentration was evaluated accord- After pupillary dilation (1 drop of tropicamide 0.5% ing to Becker et al.15 The previously described method every 15 minutes ϫ 3) and instillation of topical anes- was altered by changing the reference point to the cen- thetics (proparacaine HCl 0.5%), the femtosecond laser ter of the pupil, because both the femtosecond cap- (Alcon-LenSx Lasers Inc, Aliso Viejo, California) was sulotomies and the manual procedures were aligned docked to the eye using a curved contact lens to applanate at the pupil center (Fig 2). To eliminate the effect of the cornea. The location of the crystalline lens surface mydriatic drops on changing the position of the pupil was determined with an integrated optical coherence to- center, the same amount and type of mydriatic drops mography imaging system. A 4.5-mm diameter capsulot- were used to dilate patients’ pupils before surgery and omy procedure was performed by scanning a cylindrical pattern starting at least 100 µm below the anterior cap- Adobe Photoshop gives a vector (determined by its sule and ending at least 100 µm above the capsule. Pro- length and angle to the horizontal plane) between the prietary energy and spot separation parameters, which pupil center and center of the IOL. The length of the had been optimized in previous studies, were used for vector shows the total IOL decentration. Horizontal and vertical decentration were calculated using trigonome- Following the laser capsulotomy procedure, a 2.8-mm try analysis. To determine the magnitude of horizontal clear corneal incision was created with the laser. The and vertical decentration without reference to nasal/ cut capsule was removed with capsule forceps under a temporal or up/down orientation, the absolute values standard ophthalmic operating microscope. A 4.5-mm of the above-mentioned parameters were counted. capsulorrhexis was attempted in the CCC group and Circularity is a parameter used for determining the was performed with the aid of a cystotome and capsu- regularity of capsulotomy shape according to the fol- lorrhexis forceps. After hydrodissection, phacoemul- lowing formula: circularity = 4⌸ (area/perimeter2). The sifi cation of the nucleus and aspiration of the residual quotient of the shortest and longest distance between cortex were performed using the Accurus phacoemul- the edge of the capsulorrhexis and the edge of the IOL sifi cation machine (Alcon Laboratories Inc, Ft Worth, optic was calculated to determine capsule–IOL over- Texas). All IOLs were folded and implanted in the cap- lap (overlap=distance min/distance max). Circularity sular bag with the aid of an injection cartridge through and overlap values of 1.0 indicate a perfect circle and the corneal wound. All IOLs were three-piece or one- an absolute regularly overlapping anterior capsule on piece spherical lenses of hydrophobic acrylic material. the optic of the implanted IOL, respectively.
The haptics of the IOL were situated in the same posi- Shifting of the visual axis from the pupil center tion (at 3 and 9 o’clock). The IOL power was calculated was determined with a Lenstar biometer (Haag-Streit, using the SRK/T formula. After IOL implantation, the Koeniz, Switzerland) in all eyes before and 1 year after viscoelastic material was removed from the anterior Journal of Refractive Surgery • Vol. 27, No. 8, 2011 IOL Centration in Femtosecond Laser and Manual Capsulorrhexis/Kránitz et al Figure 1. Parameters characteristic to the capsulorrhexis measured by Figure 2. Decentration of the IOL from the pupil center.
Statistical analyses were performed with SPSS No statistically signifi cant differences were noted 16.0 (SPSS Inc, Chicago, Illinois). Departure from between the femtosecond (FS) and CCC groups in re- normal distribution assumption was tested by the gards to age and gender distribution, refractive status, Shapiro-Wilks W test. Due to normality of data, de- scriptive statistics show mean and standard devia- Table 2 shows mean and standard deviation values of parameters characteristic to capsulotomies and IOL de- Differences between the two groups of capsulor- centrations in the two study groups measured by Adobe rhexis parameters were analyzed using repeated mea- Photoshop. Although capsulotomies were not perfectly sures analysis of variance (ANOVA) test with Newman- round in the postoperative follow-up period in either the CCC or FS group, statistically signifi cant differences To determine predictors of IOL decentration, logis- were noted between the two groups at the given time tic regression analyses were performed via univari- point analyzed by repeated measures ANOVA. Vertical able general estimating equation (GEE) models treat- diameter was signifi cantly higher 1 week and 1 month ing data from eyes of patients in statistical analysis as after surgery in the CCC group. Statistically signifi cant repeated measures. This technique took into account differences were observed in the shortest and longest the correlated nature of data from patients who con- distance between the edge of the IOL optic and the edge tributed two eyes to the repeated measurements. We of the capsulorrhexis 1 week and 1 month after surgery dichotomized decentration parameters at the level and in circularity 1 week after surgery. Signifi cantly of 0.4 mm, as previous results showed that Ͻ0.4-mm higher values of overlap and circularity showed more decentration provides the best optical performance regular capsulotomies in the FS group. Horizontal de- whereas Ͼ0.4 mm can worsen the visual outcome of centration of the IOL was also signifi cantly higher in the aspheric and wavefront-corrected IOLs.17 Chi-square test of homogeneity was applied to The type of capsulorrhexis was found to be a sig- compare the distribution of dichotomized horizontal nifi cant predictor of horizontal decentration in the decentration values at 0.4 mm between the two study univariable GEE model (odds ratio [OR]: 5.95, 95% confi dence limit [CL]: 1.58-22.22, PϽ.01). When pre- Correlations between vertical diameter and overlap dictors of horizontal IOL decentration were explored, parameters were analyzed with Spearman rank corre- only capsulorrhexis overlap showed a signifi cant ef- fect (P=.002) among all capsulorrhexis parameters. The signifi cance level was set at PϽ.05 in all statisti- Decentration was not infl uenced by type of implanted IOL according to a GEE model (PϾ.05). No statistically IOL Centration in Femtosecond Laser and Manual Capsulorrhexis/Kránitz et al signifi cant differences in total decentration or decen-tration in horizontal or vertical direction were noted between one-piece and three-piece IOLs according to repeated measurements ANOVA test with Newman- The ratios of Ͻ0.4 mm and Ͼ0.4 mm horizontal de- centration values were 4/16, 3/17, and 5/15 eyes in the CCC group 1 week, 1 month, and 1 year after surgery, respectively. Horizontal decentration did not exceed 0.4 mm in any eye in the FS group (0/20 at all time points) (Table 3). Chi-square test of homogeneity was applied to compare the distribution of dichotomized horizontal decentration values at 0.4 mm between the two study groups. A statistically signifi cant difference was found between groups at 1 week and 1 year post- operatively (P=.035 and .016, respectively). No statisti- CCC = continuous curvilinear capsulorrhexis, MRSE = manifest refraction cally signifi cant difference was noted between the FS spherical equivalentNote. Values presented as meanϮstandard deviation (range). and CCC group 1 month after surgery (PϾ.05).
According to Figures 3-5, vertical diameter demon- strated a statistically signifi cant correlation to the over-lap in the CCC group at all three time points (1 week: ued development since the introduction of phacoemul- r=Ϫ0.91, PϽ.01; 1 month: r=Ϫ0.76, PϽ.01; and 1 year: sifi cation. However, with the advent of premium IOLs, r=Ϫ0.62, PϽ.01), whereas no signifi cant correlation an increasing need appeared for methods that ensure was noted between the two parameters in the FS group higher precision and predictability in cataract surgery. This is the fi rst study to describe the better centration No statistically signifi cant difference was observed of IOLs 1 year after cataract surgery when capsulor- in shifting of the visual axis from the pupil center in rhexis was performed with a femtosecond laser.
either absolute value or in horizontal or vertical direc- A properly sized CCC provides several surgical ad- tion 1 year postoperatively between groups (PϾ.05).
vantages, and initial results with femtosecond laser showed higher precision of capsulorrhexis compared Cataract surgery techniques have undergone contin- Corresponding to previous results where we com- Parameters of Capsulotomies and Intraocular Decentrations in Eyes That Underwent Continuous Curvilinear Capsulorrhexis or Femtosecond Laser Capsulotomy CCC = continuous curvilinear capsulorrhexis*PϽ.05 between groups at the given time point using repeated measures analysis of variance.
Values presented as meanϮstandard deviation. Journal of Refractive Surgery • Vol. 27, No. 8, 2011 IOL Centration in Femtosecond Laser and Manual Capsulorrhexis/Kránitz et al FS = femtosecond laser, CCC = continuous curvilinear capsulorrhexis*PϽ.05 between groups using Chi-square test. Figure 3. Correlation of vertical diameter to overlap 1 week after sur-gery. A statistically significant correlation was noted between the two parameters in the manual capsulorrhexis group (r=Ϫ0.91, PϪ.01), but no correlation was found between these parameters in the femtosecond capsulotomy group (r=0.05, PϾ.05).
Figure 4. Correlation of vertical diameter to overlap 1 month after sur- Figure 5. Correlation of vertical diameter to overlap 1 year after sur- gery. A statistically significant correlation was noted between the two gery. A statistically significant correlation was noted between the two parameters in the manual capsulorrhexis group (r=Ϫ0.76, PϽ.01), but parameters in the manual capsulorrhexis group (r=Ϫ0.62, PϪ.01), no correlation was found between these parameters in the femtosecond but no correlation was found in the femtosecond capsulotomy group capsulotomy group (r=Ϫ0.11, PϾ.05).
pared circularity of femtosecond capsulotomies and group. Figures 3-5 demonstrate how higher values of this manually performed capsulorrhexis at 1 week, we ob- parameter are able to lead to irregular anterior capsule served more regular shape in the FS group.18 Differ- overlap. A 360° overlapping capsular edge is thought to ence in circularity between the two study groups can be an important factor for standardizing refractive re- be explained by disproportion of vertical and horizon- sults by keeping the IOL in the desired center position. tal diameter values in the CCC group. Properly sized, The overlap sets not only the horizontal–vertical but shaped, and centered femtosecond capsulotomies also the anteroposterior positioning of the IOL.19 resulted in better overlap parameters during the fi rst In our study, we examined decentration of implanted year. Worsening irregularity of manual capsulorrhexis IOLs according to a previous report from Becker et al.15 through asymmetric contractile and vector forces ag- Decentration Ͼ0.4 mm can deteriorate optical outcomes gravated the IOL centration over time. In our study, the of accommodating and multifocal IOLs.17 Our results length of vertical diameter correlated with the overlap show statistically higher horizontal decentration in the of the anterior capsule in the manual capsulorrhexis CCC group 1 week and 1 year after IOL implantation IOL Centration in Femtosecond Laser and Manual Capsulorrhexis/Kránitz et al and a statistically signifi cant difference in the distribu- 3. Gimbel HV, Neuhann T. Continuous curvilinear capsulorhexis. J Cataract Refract Surg. 1991;17(1):110-111.
tion of dichotomized horizontal decentration values at 0.4 mm between the two study groups 1 week and 1 4. Ravalico G, Tognetto D, Palomba M, Busatto P, Baccara F. Cap- sulorhexis size and posterior capsule opacifi cation. J Cataract year after surgery. We found IOL decentration was six Refract Surg. 1996;22(1):98-103.
times more likely to occur when capsulorrhexis was 5. Aykan U, Bilge AH, Karadayi K. The effect of capsulorhexis performed manually. Moreover, it seems that “over- size on development of posterior capsule opacifi cation: small lap” captures all characteristics of the capsulorrhexis (4.5 to 5.0mm) versus large (6.0 to 7.0mm). Eur J Ophthalmol. 2003;13(6):541-545.
shape. Among all capsulorrhexis parameters, only 6. Hollick EJ, Spalton DJ, Meacock WR. The effect of capsu- overlap showed signifi cant effect on IOL horizontal lorhexis size on posterior capsular opacifi cation: one-year decentration, representing the importance of precise results of a randomized prospective trial. Am J Ophthalmol. sizing and centration of capsulotomy. During analysis of the centration results, we were able to statistically 7. Ram J, Pandey SK, Apple DJ, et al. Effect of in-the-bag intraocu- exclude the infl uence of implanted IOL type and larger lar lens fi xation on the prevention of posterior capsule opacifi -cation. J Cataract Refract Surg. 2001;27(7):367-370.
capsular bag on IOL decentration because no statisti- 8. Chang DF, Dewey S, Tipperman R, Wallace RB. Pearls for siz- cally signifi cant differences were found between the ing the capsulorrhexis. Cataract & Refractive Surgery Today two study groups in preoperative refractive status or axial length. No differences in magnitude or direction 9. Hayashi K, Hayashi H, Nakao F, Hayashi F. Anterior capsule of visual axis shifting from the pupil center were found contraction and intraocular lens decentration and tilt after hy-drogel lens implantation. Br J Ophthalmol. 2001;85(11):1294-1297.
between the two study groups that could infl uence the visual outcome of cataract surgery in relation to IOL 10. Hayashi H, Hayashi K, Nakao F, Hayashi F. Anterior capsule contraction and intraocular lens dislocation in eyes with pseudo- exfoliation syndrome. Br J Ophthalmol. 1998;82(12):1429-1432.
The limitation of our study is that we did not evalu- 11. Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evalu- ate the anteroposterior position of the IOL. It would ation of an intraocular femtosecond laser in cataract surgery. be interesting and important to examine whether the J Refract Surg. 2009;25(12):1053-1060.
above described effect of regular femtosecond capsu- 12. Ratkay-Traub I, Ferincz IE, Juhasz T, Kurtz RM, Krueger RR. First clinical results with the femtosecond neodymium-glass lotomies infl uences anteroposterior positioning and laser in refractive surgery. J Refract Surg. 2003;19(2):94-103.
13. Nordan LT, Slade SG, Baker RN, Suarez C, Juhasz T, Kurtz R. According to the results of our study, potential clini- Femtosecond laser fl ap creation for laser in situ keratomileusis: cal advantages can be achieved during refractive cata- six month follow-up of initial U.S. clinical series. J Refract Surg. ract surgery through effective prevention of optic de- centration with precisely controlled shape, size, and 14. Tran DB, Sarayba MA, Bor Z, et al. Randomized prospective clinical study comparing induced aberrations with IntraLase centration of capsulotomy with femtosecond laser. and Hansatome fl ap creation in fellow eyes: potential impact However, to present clinical relevance of more predict- on wavefront-guided laser in situ keratomileusis. J Cataract able postoperative IOL positioning, additional analyses Refract Surg. 2005;31(1):97-105.
15. Becker KA, Auffarth GU, Völcker HE. Measurement method for the determination of rotation and decentration of intraocular lenses [German]. Ophthalmologe. 2004;101(6):600-603.
16. Yang Y, Thompson K, Burns SA. Pupil location under meso- Study concept and design (K.K., K.M., Z.Z.N.); data collection pic, photopic, and pharmacologically dilated conditions. Invest (K.K., A.T., I.K.); analysis and interpretation of data (K.K., I.K., Ophthalmol Vis Sci. 2002;43(7):2508-2512.
M.C.K., Z.Z.N.); drafting of the manuscript (K.K., I.K.); critical revi- 17. Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby sion of the manuscript (A.T., K.M., I.K., M.C.K., Z.Z.N.); statistical NE. A new intraocular lens design to reduce spherical aberra-tion of pseudophakic eyes. J Refract Surg. 2002;18(6):683-691.
expertise (K.K., K.M.); administrative, technical, or material support 18. Nagy ZZ, Kránitz K, Takacs AI, Miháltz K, Kovacs I, Knorz MC. Comparison of IOL decentration parameters after femtosecond and manual capsulotomies. J Refract Surg. 2011;27(8):564-569.
19. Cekiç O, Batman C. The relationship between capsulorhexis 1. Neuhann T. Theory and surgical technic of capsulorhexis size and anterior chamber depth relation. Ophthalmic Surg Lasers. [German]. Klin Monatsbl Augenheilkd. 1987;190(6):542-545.
1999;30(3):185-190. Erratum in Ophthalmic Surg Lasers. 2. Gimbel HV, Neuhann T. Development, advantages, and methods of the continuous circular capsulorhexis technique. J Cataract Refract Surg. 1990;16(1):31-37.
Journal of Refractive Surgery • Vol. 27, No. 8, 2011

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