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Anterior chamber depth and change in axial intraocular lens position after cataract surgery with primary posterior capsulorhexis and posterior optic buttonholing
ARTICLE
Anterior chamber depth and change in axial intraocular lens position after cataract surgery with primary posterior capsulorhexis and posterior optic buttonholing Eva Stifter, MD, Rupert Menapace, MD, Alexandra Luksch, MD, Thomas Neumayer, MD, Stefan Sacu, MD
PURPOSE: To compare axial position changes of the intraocular lens (IOL) by measuring anterior chamber depth (ACD) after small-incision cataract surgery with primary posterior continuous curvilinear capsulorhexis (PPCCC) and posterior optic buttonholing (POBH) of the IOL and after conventional cataract surgery with phacoemulsification and in-the-bag IOL implantation. SETTING: Department of Ophthalmology, Medical University of Vienna, Austria. METHODS: This prospective comparative study comprised 23 patients (46 eyes) with age-related cataract who had bilateral cataract surgery and implantation of an acrylic IOL (YA-60BB, Hoya). In randomized order, cataract surgery with PPCCC and POBH of the IOL was performed in 1 eye of each patient. In the fellow eyes, conventional phacoemulsification cataract surgery with in-the-bag IOL implantation was performed. The ACD was measured 1 to 2, 6, and 24 hours as well as 7 and 30 days postoperatively using high-resolution partial coherence laser interferometry. A baseline measurement was taken preoperatively in all patients. RESULTS: Ten patients completed 10 to 12 months of follow-up. Postoperatively, the axial IOL position was stable in eyes with PPCCC–POBH (P>.05). In contrast, a significant axial shift of the IOL in the anterior direction was observed in control eyes with in-the-bag IOL implantation (P<.001). The resulting refractive shift was significantly higher in control eyes than in eyes with PPCCC–POBH (P<.001). CONCLUSION: Combined PPCCC and POBH for cataract surgery significantly reduced postoperative anterior movement of the IOL. J Cataract Refract Surg 2008; 34:749–754 Q 2008 ASCRS and ESCRS
Posterior optic buttonholing (POBH) through a primary posterior continuous curvilinear capsulorhexis (PPCCC) is a surgical technique primarily designed to prevent posterior capsule opacification (PCO).1
Accepted for publication December 12, 2007. From the Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. No author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Rupert Menapace, MD, Department of Ophthalmology and Optometry, Medical University of Vienna, Waehringer Guertel 18-20, A–1090, Vienna, Austria. E-mail: [email protected]. Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
Moreover, cataract surgery with combined PPCCC and POBH inherently prevents anterior capsule opacification with its fibrotic complications such as capsulorhexis contraction (phimosis) or retraction, which results in anterior optic buttonholing. To determine whether PPCCC–POBH cataract surgery has the potential to become a routine alternative to standard in-the-bag implantation of intraocular lenses (IOLs) with a sharp-edged optic,1 the technique must be evaluated in a standardized clinical setting to assess the clinical safety and possible additional benefits compared with established in-the-bag IOL implantation. In addition to the benefit of preventing PCO, in-thebag IOL implantation of acrylic and silicone IOLs may result in postoperative capsule shrinkage, leading to a change in the axial IOL position with unsatisfactory 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.12.035
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refractive outcomes after uneventful biometry and cataract surgery. The change in position can also lead to IOL decentration and optic tilt. In addition to the excellent IOL centration maintained during the postoperative follow-up,2,3 combined PPCCC and POBH may keep the axial IOL position stable. This is essential for the prediction of final IOL position in the eye and could thus improve IOL power calculation. Moreover, it would allow early prescription of the final corrective glasses. Therefore, the present study was designed to evaluate the axial movement of the IOL as reflected in the changes in anterior chamber depth (ACD) after cataract surgery with combined PPCCC and POBH. PATIENTS AND METHODS This prospective comparative study comprised 23 patients (46 eyes) who had bilateral cataract surgery. The study was performed at the Department of Ophthalmology and Optometry, Medical University of Vienna, Austria, and followed the tenets of the Declaration of Helsinki. Patients provided informed consent after they received an explanation of the nature and possible consequences of the study. Inclusion criteria were age-related cataract in both eyes and good physical condition. Preoperative exclusion criteria were a history of ocular surgery, laser treatment, or trauma; glaucoma; pseudoexfoliation syndrome; uveitis; diabetes mellitus; expected postoperative visual acuity of 20/200 or worse; and other relevant ocular disease. Cataract surgery with PPCCC and POBH of the IOL (YA60BB, Hoya) was performed in 1 of the patient’s eyes,1,4 with the eye to have surgery first selected randomly. Conventional phacoemulsification cataract surgery with in-the-bag implantation of the IOL was performed in the contralateral eye. The surgical procedures and the postoperative medication were standardized in all patients. The same experienced surgeon (R.M.) performed all cataract surgery. A temporal 3.0 mm posterior limbal incision was created. Sodium hyaluronate 1% (Healon) was used as the ophthalmic viscosurgical device (OVD). Anterior continuous curvilinear capsulorhexis (ACCC), hydrodissection, and phacoemulsification of the nucleus were followed by coaxial cortical remnant aspiration and biaxial lens fiber peeling. The anterior segment was filled with a mediumviscosity OVD (Healon) to allow the remaining peripheral anterior capsule to settle on the posterior capsule and flatten the central posterior capsule. As a result, the capsule fornix collapsed and both capsules formed a common flat diaphragm. Following the outlines of the ACCC, a wellcentered 4.5 to 5.0 mm PPCCC was created. After the central capsule flap was removed from the eye, the OVD was gently injected beneath the peripheral ring of residual posterior capsule to separate it from the underlying vitreous surface. When this was completed along the entire circumference, the anterior segment was prepared for implantation of an AF-1 YA-60BB foldable IOL. The central chamber was deepened and the nasal capsular fornix extended with OVD to take up the leading IOL haptic. The tip of the leading IOL haptic was guided into the nasal capsular bag fornix, and the optic and trailing haptic were rotated into the bag. Using gentle downward pressure, the optic was enclavated in the PPCCC. The OVD was then aspirated from the anterior
chamber and capsular bag fornix using low flow and vacuum settings. As the posterior capsule was firmly pressed into the anterior optic surface, the optic–capsule diaphragm hermetically sealed the posterior segment and no OVD was allowed to access the anterior chamber from the retrolental space during the maneuver. Next, the incisions were hydrated and the globe was pressurized. The eye was left unpatched. Anterior chamber depth was measured 1 to 2, 6, and 24 hours as well as 1 week and 1 month postoperatively by high-resolution partial coherence interferometry (PCI) using the ACMaster (Carl Zeiss Meditec AG). A baseline measurement was taken preoperatively in all patients. For long-term follow-up, an additional ACD measurement was taken 10 to 12 months after surgery in a subset of 10 patients. The ACMaster is an optical biometry instrument of the anterior segment, measuring corneal thickness, ACD, and lens thickness successively in a single session; it has been described in detail.5–11 The measurements use a noncontact technique. The white-to-white distance is determined from an image of the iris and cornea before biometry is performed. The principle of the dual-beam version of PCI has been described.6–8,10,11 An external Michelson interferometer splits an infrared light beam (wavelength approximately 855 nm) of high spatial coherence but very short coherence length into 2 parts, forming a coaxial dual short beam.5 This dual light beam, containing 2 beam components with a mutual time delay of twice the interferometer arm length difference introduced by the interferometer, illuminates the eye, and both components are reflected at several intraocular interfaces that separate media of different refractive indices. If the delay of the 2 light-beam components produced by the interferometer equals an intraocular distance within the coherence length of the light source, an interference signal (called the PCI signal) is detected, similar to that of ultrasound A-scan but with a very high resolution (approximately 12 mm) and precision (0.3 to 10 mm), the latter being more than 1 order of magnitude higher than that of ultrasound biometry. With the ACMaster, ACD is defined as the distance between the anterior surface of the cornea and anterior surface of the crystalline lens or, in the case of a pseudophakic eye, the IOL. The ACMaster measurements of corneal thickness, ACD, and lens thickness were taken at least 5 times by an experienced examiner. In all eyes, the refractive shift induced by IOL movement was calculated individually based on the eye’s axial length (AL), preoperative keratometry readings by biometry (IOLMaster, Carl Zeiss Meditec AG), IOL type and power, and ACD. This method is more exact than using a rule of thumb for all eyes. To do this, ray-tracing software (Okulix, Der Leu Technische Produkte) was applied to the biometric data.12 Input variables were AL and keratometry readings from preoperative biometry (IOLMaster), IOL type and power (characteristics of anterior and posterior IOL optic curvature, optic thickness for all IOL powers, and refractive index of the optic material are included in the software), and ACD measurements. The refractive shift induced by the IOL movement was calculated for each eye and recorded in diopters (D). Descriptive data are presented as mean values and standard deviation. Repeated-measures analysis of variance was used to reveal differences between postoperative and preoperative ACD measurements. The compound symmetry covariance structure was specified, allowing the variance
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Table 1. Anterior chamber depth measurements over time. Postop Group PCCC–POBH Mean ACD (mm) 95% CL Eyes (n) Control Mean ACD (mm) 95% CL Eyes (n) P value
Preop
1–2 H
6H
24 H
1 Wk
1 Mo
10–12 Mo
2.77 G 0.44 2.59; 2.95 23
4.65 G 0.47 4.46; 4.84 23
4.67 G 0.47 4.48; 4.86 23
4.73 G 0.53 4.52; 4.95 23
4.71 G 0.55 4.48; 4.93 23
4.73 G 0.53 4.51; 4.95 23
4.77 G 0.35 4.57; 4.98 10
2.8 G 0.41 2.64; 2.97 23 .53
4.46 G 0.6 4.22; 4.71 23 .3
4.49 G 0.52 4.28; 4.70 23 .23
4.46 G 0.63 4.20; 4.72 23 .12
4.28 G 0.51 4.03; 4.47 23 .01*
3.98 G 0.66 3.71; 4.24 23 !.001*
4.02 G 0.6 3.63; 4.37 10 !.001*
Means G SD ACD Z anterior chamber depth; CL Z confidence limits (upper; lower); POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis * Statistically significant after correction for multiple testing (a Z .05, paired t test)
to be different at various time points. For paired analyses, paired 2-sided t tests were used; the tests were adjusted for multiple comparisons using the Bonferroni post hoc test. For nonparametric data, the Mann-Whitney U test was applied. Spearman correlation coefficients were calculated to analyze the relationship between preoperative biometry data and postoperative ACD measurements. A P value less than 0.05 was considered statistically significant. All calculations were performed with SPSS for Windows (release 12.0, SPSS, Inc.).
RESULTS The mean age of the 23 patients was 76 G 7.7 years; 8 (35%) were men and 15 (65%), women. There were no
Figure 1. Comparison of ACD between eyes with PPCCC and POBH and control fellow eyes with conventional in-the-bag IOL implantation cataract surgery (IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis).
intraoperative or postoperative complications or adverse effects in any eye. Table 1 shows the ACD measurements over time. The preoperative ACD measurements were statistically comparable between the control eyes and the PPCCC–POBH eyes (P Z .53). Postoperatively, the axial IOL position was stable in eyes with combined PPCCC–POBH cataract surgery (Figure 1). There was no significant difference between the ACD measurements 1 to 2 hours postoperatively and those 1 month after cataract surgery (PO.001). The mean intraindividual ACD differences were 0.08 G 0.24 mm (95% confidence limits [CL], 0.02, 0.18), indicating that the IOL position was clinically stable. In contrast, a significant axial shift of the IOL in the anterior direction was observed in the control eyes with IOL in-the-bag implantation (P!.001). In the control eyes, the mean ACD difference was 0.48 G 0.61 mm (95% CL, 0.73, 0.24), indicating that the IOL moved significantly anteriorly. The resulting refractive shift was significantly higher in the control eyes than in the PPCCC–POBH eyes (P!.001). The mean refractive shift at 4 weeks was 0.12 G 0.32 D (95% CL, 0.01, 0.24) in PPCCC– POBH eyes and 0.74 G 0.87 D (95% CL, 1.1, 0.39]) in control eyes. In addition, the 95% CLs of the ACD measurements in Table 1 indicate that interindividual variations were smaller in the PPCCC–POBH eyes than in the control eyes. Analyzing the relationship between postoperative ACD and AL, comparable correlations were found 1 to 2 hours postoperatively (Figure 2, top). However, at 4 weeks, a relevant ACD shift was observed in the control eyes, particularly in eyes with a short AL (Figure 2, bottom).
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Anterior Chamber Depth (mm)
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PCCC /POBH
IOL in-the-bag
Linear (IOL in-the-bag)
Linear (PCCC /POBH)
refractive outcomes (PO.05). The biometric data in both groups are shown in Table 2. A significant correlation was found between the ACD 1 month after cataract surgery and the preoperative ACD in the PPCCC–POBH eyes (r Z 0.74; P!.001) and control eyes (r Z 0.28; P!.001). No significant correlations were observed between postoperative ACD measurements and preoperative corneal diameter and keratometry readings (PO.05).
6,5 5,5 4,5 3,5 2,5 20
22
24
26
28
30
Anterior Chamber Depth (mm)
Axial Eye Length (mm) PPCCC /POBH
IOL in-the-bag
DISCUSSION
Linear (IOL in-the-bag)
Linear (PPCCC /POBH)
Combining PPCCC and POBH for cataract surgery can significantly reduce the postoperative anterior movement of the IOL. The axial IOL position was stable in eyes with combined PPCCC–POBH at 1 month and 10 to 12 months postoperatively (PO.05). This is attributed to the absence of capsular bag closure and shrinkage with consecutive decay of haptic angulation and anterior optic movement. Instead, the optic is firmly fixated in the buttonhole and capsule fibrosis is not induced. Because the posterior capsule is sandwiched between the optic and the anterior capsule leaf, direct contact between the anterior capsule and the optic with consecutive myofibroblastic transformation of the lens epithelial cells residing on the backside of the anterior capsule leaf is obviated. In contrast, a significant axial shift of the IOL in the anterior direction was observed in the control eyes with IOL in-the-bag implantation (P!.001). This finding agrees with those in previous studies that showed significant postoperative changes in IOL position resulting from capsular bag shrinkage.13,14 In cases of in-the-bag IOL implantation, IOL design was shown to significantly influence postoperative axial IOL movement14,15 and the amount of capsular overlap
6,5
5,5 4,5 3,5 2,5 20
22
24
26
28
30
Axial Eye Length (mm) Figure 2. Relationship between AL and ACD measurements. Top: One to 2 hours postoperatively. Bottom: One month postoperatively (IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis).
There were no statistically significant differences between postoperative ACD measurements at 4 weeks and those at 10 to 12 months in the PPCCC–POBH eyes (P Z .54) or control eyes (P Z .7). However, there was a statistically significant difference between the 2 groups 1 month postoperatively (Table 1). No significant differences between the 2 surgical procedures were found with respect to the discrepancy between the expected and final postoperative
Table 2. Preoperative biometric data. Biometric Data Keratometry (D) Group PCCC–POBH Mean G SD 95% CL Eyes (n) Control Mean G SD 95% CL Eyes (n) P value
Spherical Equivalent (D)
AL (mm)
K1
K2
IOL Power (D)
Preop
1 Mo Postop
23.7 G 1.84 22.95; 24.46 23
7.73 G 0.33 7.6; 7.87 23
7.54 G 0.3 7.41; 7.66 23
21.33 G 4.25 19.59; 23.06 23
1.05 G 3.26 2.39; 0.28 23
1.01 G 1.05 1.44; 0.58 23
23.74 G 1.94 22.94; 24.53 23 .46
7.7 G 0.37 7.55; 7.86 23 .23
7.52 G 0.32 7.39; 7.65 23 .46
20.96 G 4.56 19.09; 22.83 23 .1
1.17 G 3.55 2.62; 0.28 23 .76
1.1 G 1.15 1.57; 0.63 23 .55
ACD Z anterior chamber depth; AL Z axial length; CL Z confidence limits (upper; lower); IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis
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was shown to influence IOL shifting.16 With angulated 3-piece foldable acrylic IOLs, a significant forward shift was observed during the first postoperative week with both sharp-edged and round-edged IOL designs.17 With the sharp-edged acrylic AR40e IOL (AMO), a slight backward shift was noted after the first week that continued to 6 months of followup.17 In contrast, the round-edged acrylic AR40 IOLs continued to move forward until the first postoperative month, followed by a slight backward shift until the sixth month.17 In eyes with nonangulated silicone IOLs, a significant postoperative change in ACD was reported for both the sharp-edged and round-edged designs; there was a forward shift in the first week with no significant difference between the 2 models.15 From 1 week to 3 months, there was backward movement of the silicone IOLs, with the sharp-edged IOLs moving a significantly greater amount.15 From 3 months to 1 year, IOLs with both optic edge designs moved slightly backward.15 Sixty-six percent of angulated IOLs showed continuous but variable forward movement and 34%, backward movement.15 These variations in axial IOL position have a clinically relevant impact on the development of postoperative refraction by the resulting refractive shift and deviation from the targeted refraction. For the present study, the YA-60BB IOL was chosen to compare the 2 surgical techniques because this acrylic 3-piece IOL has a continuous junction between the optic and haptic. This allows the crossing edge of the PPCCC rim to smoothly slide along the rim of the junction while the optic is buttoned in and centered in the PPCCC opening.1 Minimizing postoperative IOL movement is of increasing clinical importance because the axial position of an IOL of a given power determines its refractive effect and postoperative emmetropia is one of the most important goals of modern cataract surgery. Neutralizing factors influencing postoperative IOL shift help improve prediction of the final IOL position and thus IOL power calculation. Primary posterior continuous curvilinear capsulorhexis and POBH cataract surgery may be a clinically interesting alternative with respect to these concerns. Moreover, our finding that axial IOL stability increased after PPCCC–POBH IOL positioning may help surgeons determine the earliest time the anterior chamber will stabilize after cataract surgery, allowing them to prescribe glasses much earlier. The observed smaller interindividual variability in ACD measurements in PPCCC–POBH eyes than in control eyes may help increase the accuracy of preoperative biometry. However, larger study populations are needed to fully clarify this important aspect.
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The present study showed that with both surgical techniques, there were no statistically significant differences in the discrepancy between the expected and final postoperative refractive outcomes (PO.05). This can be explained by the fact that optimization of biometry constants was performed previously for both techniques. Besides the advantages of axial stability, PPCCC– POBH cataract surgery has been shown to be a safe and effective surgical technique.1,7,18 In the published evaluation of the first 500 consecutive cases,1 both capsule leaves remained clear, especially after additional polishing of the haptic–optic junction area where direct contact between anterior capsule and optic persists.19 No intraocular pressure (IOP) spike or postoperative anterior chamber flare was reported.4,18 Fixation of the optic in the PPCCC opening is crucial for the mechanisms of axial stability, and it also influences the course of IOP during the first postoperative hours by creating a watertight diaphragm. Thus, retrolental OVD cannot proceed into the anterior chamber, which can result in postoperative IOP spikes as found in a study of cataract surgery with PPCCC without POBH.20 The optic perfectly centers by itself, even when the PPCCC is not ideally centered. The optic immediately obtains its final axial position without tilt or secondary rotation. These characteristics are clear advantages to the solitary performance of a PPCCC without buttonholing of the IOL. Considering the immediate and persistent positional stability of the optic and the improved predictability in ACD, and thus refraction, in the present study, cataract surgery with PPCCC–POBH can be regarded as an interesting surgical option, particularly in cases with refractive indications such as clear lens exchange, multifocal IOL implantation, or toric IOL implantation. REFERENCES 1. Menapace R. Routine posterior optic buttonholing for eradication of posterior capsule opacification in adults; report of 500 consecutive cases. J Cataract Refract Surg 2006; 32:929–943; erratum, 1410 2. Gimbel HV. Posterior capsulorhexis with optic capture in pediatric cataract and intraocular lens surgery. Ophthalmology 1996; 103:1871–1875 3. Gimbel HV. Posterior continuous curvilinear capsulorhexis and optic capture of the intraocular lens to prevent secondary opacification in pediatric cataract surgery. J Cataract Refract Surg 1997; 23:652–656 4. Stifter E, Menapace R, Luksch A, et al. Objective assessment of intraocular flare after cataract surgery with combined primary posterior capsulorhexis and posterior optic buttonholing in adults. Br J Ophthalmol 2007; 91:1481–1484 5. Drexler W, Findl O, Menapace R, et al. Partial coherence interferometry: a novel approach to biometry in cataract surgery. Am J Ophthalmol 1998; 126:524–534
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6. Fercher AF, Mengedoht K, Werner W. Eye-length measurement by interferometer with partially coherent light. Opt Lett 1988; 13:186–188 7. Fercher AF, Roth E. Ophthalmic laser interferometer. In: Mueller GJ, ed, Optical Instrumentation for Biomedical Laser Applications. Proceedings SPIE 0658. Bellingham, WA, SPIE, 1986; 48–51 8. Drexler W, Baumgartner A, Findl O, et al. Submicrometer precision biometry of the anterior segment of the human eye. Invest Ophthalmol Vis Sci 1997; 38:1304–1313. Available at: http:// www.iovs.org/cgi/reprint/38/7/1304. Accessed January 30, 2008 9. Findl O, Drexler W, Menapace R, et al. High precision biometry of pseudophakic eyes using partial coherence interferometry. J Cataract Refract Surg 1998; 24:1087–1093 10. Hitzenberger CK. Optical measurement of the axial eye length by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1991; 32:616–624. Available at: http://www.iovs.org/cgi/ reprint/32/3/616. Accessed January 30, 2008 11. Hitzenberger CK, Drexler W, Dolezal C, et al. Measurement of the axial length of cataract eyes by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1993; 34:1886–1893. Available at: http://www.iovs.org/cgi/reprint/34/6/1886. Accessed January 30, 2008 12. Preussner PR, Wahl J, Lahdo H, et al. Ray tracing for intraocular lens calculation. J Cataract Refract Surg 2002; 28:1412–1419 13. Findl O, Drexler W, Menapace R, et al. Accurate determination of effective lens position and lens-capsule distance with 4 intraocular lenses. J Cataract Refract Surg 1998; 24:1094–1098 14. Wirtitsch MG, Findl O, Menapace R, et al. Effect of haptic design on change in axial lens position after cataract surgery. J Cataract Refract Surg 2004; 30:45–51
15. Petternel V, Menapace R, Findl O, et al. Effect of optic edge design and haptic angulation on postoperative intraocular lens position change. J Cataract Refract Surg 2004; 30:52–57 16. Nanavaty MA, Raj SM, Vasavada VA, et al. Anterior capsule cover and axial movement of intraocular lens. In press, Eye 2008. 17. Koeppl C, Findl O, Kriechbaum K, et al. Postoperative change in effective lens position of a 3-piece acrylic intraocular lens. J Cataract Refract Surg 2003; 29:1974–1979 18. Stifter E, Luksch A, Menapace R. Postoperative course of intraocular pressure after cataract surgery with combined primary posterior capsulorhexis and posterior optic buttonholing in adults. J Cataract Refract Surg 2007; 33:1585–1590 19. Menapace R, Di Nardo S. Aspiration curette for anterior capsule polishing: laboratory and clinical evaluation. J Cataract Refract Surg 2006; 32:1997–2003 20. Wirtitsch M, Menapace R, Georgopoulos M, et al. Intraocular pressure rise after primary posterior continuous curvilinear capsulorhexis with a fixed dorzolamide–timolol combination; randomized safety study with intraindividual comparison using an angulated and a nonangulated intraocular lens. J Cataract Refract Surg 2007; 33:1754–1759
J CATARACT REFRACT SURG - VOL 34, MAY 2008
First author: Eva Stifter, MD Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria
Anterior chamber depth and change in axial intraocular lens position after cataract surgery with primary posterior capsulorhexis and posterior optic buttonholing Eva Stifter, MD, Rupert Menapace, MD, Alexandra Luksch, MD, Thomas Neumayer, MD, Stefan Sacu, MD
PURPOSE: To compare axial position changes of the intraocular lens (IOL) by measuring anterior chamber depth (ACD) after small-incision cataract surgery with primary posterior continuous curvilinear capsulorhexis (PPCCC) and posterior optic buttonholing (POBH) of the IOL and after conventional cataract surgery with phacoemulsification and in-the-bag IOL implantation. SETTING: Department of Ophthalmology, Medical University of Vienna, Austria. METHODS: This prospective comparative study comprised 23 patients (46 eyes) with age-related cataract who had bilateral cataract surgery and implantation of an acrylic IOL (YA-60BB, Hoya). In randomized order, cataract surgery with PPCCC and POBH of the IOL was performed in 1 eye of each patient. In the fellow eyes, conventional phacoemulsification cataract surgery with in-the-bag IOL implantation was performed. The ACD was measured 1 to 2, 6, and 24 hours as well as 7 and 30 days postoperatively using high-resolution partial coherence laser interferometry. A baseline measurement was taken preoperatively in all patients. RESULTS: Ten patients completed 10 to 12 months of follow-up. Postoperatively, the axial IOL position was stable in eyes with PPCCC–POBH (P>.05). In contrast, a significant axial shift of the IOL in the anterior direction was observed in control eyes with in-the-bag IOL implantation (P<.001). The resulting refractive shift was significantly higher in control eyes than in eyes with PPCCC–POBH (P<.001). CONCLUSION: Combined PPCCC and POBH for cataract surgery significantly reduced postoperative anterior movement of the IOL. J Cataract Refract Surg 2008; 34:749–754 Q 2008 ASCRS and ESCRS
Posterior optic buttonholing (POBH) through a primary posterior continuous curvilinear capsulorhexis (PPCCC) is a surgical technique primarily designed to prevent posterior capsule opacification (PCO).1
Accepted for publication December 12, 2007. From the Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria. No author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Rupert Menapace, MD, Department of Ophthalmology and Optometry, Medical University of Vienna, Waehringer Guertel 18-20, A–1090, Vienna, Austria. E-mail: [email protected]. Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
Moreover, cataract surgery with combined PPCCC and POBH inherently prevents anterior capsule opacification with its fibrotic complications such as capsulorhexis contraction (phimosis) or retraction, which results in anterior optic buttonholing. To determine whether PPCCC–POBH cataract surgery has the potential to become a routine alternative to standard in-the-bag implantation of intraocular lenses (IOLs) with a sharp-edged optic,1 the technique must be evaluated in a standardized clinical setting to assess the clinical safety and possible additional benefits compared with established in-the-bag IOL implantation. In addition to the benefit of preventing PCO, in-thebag IOL implantation of acrylic and silicone IOLs may result in postoperative capsule shrinkage, leading to a change in the axial IOL position with unsatisfactory 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.12.035
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refractive outcomes after uneventful biometry and cataract surgery. The change in position can also lead to IOL decentration and optic tilt. In addition to the excellent IOL centration maintained during the postoperative follow-up,2,3 combined PPCCC and POBH may keep the axial IOL position stable. This is essential for the prediction of final IOL position in the eye and could thus improve IOL power calculation. Moreover, it would allow early prescription of the final corrective glasses. Therefore, the present study was designed to evaluate the axial movement of the IOL as reflected in the changes in anterior chamber depth (ACD) after cataract surgery with combined PPCCC and POBH. PATIENTS AND METHODS This prospective comparative study comprised 23 patients (46 eyes) who had bilateral cataract surgery. The study was performed at the Department of Ophthalmology and Optometry, Medical University of Vienna, Austria, and followed the tenets of the Declaration of Helsinki. Patients provided informed consent after they received an explanation of the nature and possible consequences of the study. Inclusion criteria were age-related cataract in both eyes and good physical condition. Preoperative exclusion criteria were a history of ocular surgery, laser treatment, or trauma; glaucoma; pseudoexfoliation syndrome; uveitis; diabetes mellitus; expected postoperative visual acuity of 20/200 or worse; and other relevant ocular disease. Cataract surgery with PPCCC and POBH of the IOL (YA60BB, Hoya) was performed in 1 of the patient’s eyes,1,4 with the eye to have surgery first selected randomly. Conventional phacoemulsification cataract surgery with in-the-bag implantation of the IOL was performed in the contralateral eye. The surgical procedures and the postoperative medication were standardized in all patients. The same experienced surgeon (R.M.) performed all cataract surgery. A temporal 3.0 mm posterior limbal incision was created. Sodium hyaluronate 1% (Healon) was used as the ophthalmic viscosurgical device (OVD). Anterior continuous curvilinear capsulorhexis (ACCC), hydrodissection, and phacoemulsification of the nucleus were followed by coaxial cortical remnant aspiration and biaxial lens fiber peeling. The anterior segment was filled with a mediumviscosity OVD (Healon) to allow the remaining peripheral anterior capsule to settle on the posterior capsule and flatten the central posterior capsule. As a result, the capsule fornix collapsed and both capsules formed a common flat diaphragm. Following the outlines of the ACCC, a wellcentered 4.5 to 5.0 mm PPCCC was created. After the central capsule flap was removed from the eye, the OVD was gently injected beneath the peripheral ring of residual posterior capsule to separate it from the underlying vitreous surface. When this was completed along the entire circumference, the anterior segment was prepared for implantation of an AF-1 YA-60BB foldable IOL. The central chamber was deepened and the nasal capsular fornix extended with OVD to take up the leading IOL haptic. The tip of the leading IOL haptic was guided into the nasal capsular bag fornix, and the optic and trailing haptic were rotated into the bag. Using gentle downward pressure, the optic was enclavated in the PPCCC. The OVD was then aspirated from the anterior
chamber and capsular bag fornix using low flow and vacuum settings. As the posterior capsule was firmly pressed into the anterior optic surface, the optic–capsule diaphragm hermetically sealed the posterior segment and no OVD was allowed to access the anterior chamber from the retrolental space during the maneuver. Next, the incisions were hydrated and the globe was pressurized. The eye was left unpatched. Anterior chamber depth was measured 1 to 2, 6, and 24 hours as well as 1 week and 1 month postoperatively by high-resolution partial coherence interferometry (PCI) using the ACMaster (Carl Zeiss Meditec AG). A baseline measurement was taken preoperatively in all patients. For long-term follow-up, an additional ACD measurement was taken 10 to 12 months after surgery in a subset of 10 patients. The ACMaster is an optical biometry instrument of the anterior segment, measuring corneal thickness, ACD, and lens thickness successively in a single session; it has been described in detail.5–11 The measurements use a noncontact technique. The white-to-white distance is determined from an image of the iris and cornea before biometry is performed. The principle of the dual-beam version of PCI has been described.6–8,10,11 An external Michelson interferometer splits an infrared light beam (wavelength approximately 855 nm) of high spatial coherence but very short coherence length into 2 parts, forming a coaxial dual short beam.5 This dual light beam, containing 2 beam components with a mutual time delay of twice the interferometer arm length difference introduced by the interferometer, illuminates the eye, and both components are reflected at several intraocular interfaces that separate media of different refractive indices. If the delay of the 2 light-beam components produced by the interferometer equals an intraocular distance within the coherence length of the light source, an interference signal (called the PCI signal) is detected, similar to that of ultrasound A-scan but with a very high resolution (approximately 12 mm) and precision (0.3 to 10 mm), the latter being more than 1 order of magnitude higher than that of ultrasound biometry. With the ACMaster, ACD is defined as the distance between the anterior surface of the cornea and anterior surface of the crystalline lens or, in the case of a pseudophakic eye, the IOL. The ACMaster measurements of corneal thickness, ACD, and lens thickness were taken at least 5 times by an experienced examiner. In all eyes, the refractive shift induced by IOL movement was calculated individually based on the eye’s axial length (AL), preoperative keratometry readings by biometry (IOLMaster, Carl Zeiss Meditec AG), IOL type and power, and ACD. This method is more exact than using a rule of thumb for all eyes. To do this, ray-tracing software (Okulix, Der Leu Technische Produkte) was applied to the biometric data.12 Input variables were AL and keratometry readings from preoperative biometry (IOLMaster), IOL type and power (characteristics of anterior and posterior IOL optic curvature, optic thickness for all IOL powers, and refractive index of the optic material are included in the software), and ACD measurements. The refractive shift induced by the IOL movement was calculated for each eye and recorded in diopters (D). Descriptive data are presented as mean values and standard deviation. Repeated-measures analysis of variance was used to reveal differences between postoperative and preoperative ACD measurements. The compound symmetry covariance structure was specified, allowing the variance
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Table 1. Anterior chamber depth measurements over time. Postop Group PCCC–POBH Mean ACD (mm) 95% CL Eyes (n) Control Mean ACD (mm) 95% CL Eyes (n) P value
Preop
1–2 H
6H
24 H
1 Wk
1 Mo
10–12 Mo
2.77 G 0.44 2.59; 2.95 23
4.65 G 0.47 4.46; 4.84 23
4.67 G 0.47 4.48; 4.86 23
4.73 G 0.53 4.52; 4.95 23
4.71 G 0.55 4.48; 4.93 23
4.73 G 0.53 4.51; 4.95 23
4.77 G 0.35 4.57; 4.98 10
2.8 G 0.41 2.64; 2.97 23 .53
4.46 G 0.6 4.22; 4.71 23 .3
4.49 G 0.52 4.28; 4.70 23 .23
4.46 G 0.63 4.20; 4.72 23 .12
4.28 G 0.51 4.03; 4.47 23 .01*
3.98 G 0.66 3.71; 4.24 23 !.001*
4.02 G 0.6 3.63; 4.37 10 !.001*
Means G SD ACD Z anterior chamber depth; CL Z confidence limits (upper; lower); POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis * Statistically significant after correction for multiple testing (a Z .05, paired t test)
to be different at various time points. For paired analyses, paired 2-sided t tests were used; the tests were adjusted for multiple comparisons using the Bonferroni post hoc test. For nonparametric data, the Mann-Whitney U test was applied. Spearman correlation coefficients were calculated to analyze the relationship between preoperative biometry data and postoperative ACD measurements. A P value less than 0.05 was considered statistically significant. All calculations were performed with SPSS for Windows (release 12.0, SPSS, Inc.).
RESULTS The mean age of the 23 patients was 76 G 7.7 years; 8 (35%) were men and 15 (65%), women. There were no
Figure 1. Comparison of ACD between eyes with PPCCC and POBH and control fellow eyes with conventional in-the-bag IOL implantation cataract surgery (IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis).
intraoperative or postoperative complications or adverse effects in any eye. Table 1 shows the ACD measurements over time. The preoperative ACD measurements were statistically comparable between the control eyes and the PPCCC–POBH eyes (P Z .53). Postoperatively, the axial IOL position was stable in eyes with combined PPCCC–POBH cataract surgery (Figure 1). There was no significant difference between the ACD measurements 1 to 2 hours postoperatively and those 1 month after cataract surgery (PO.001). The mean intraindividual ACD differences were 0.08 G 0.24 mm (95% confidence limits [CL], 0.02, 0.18), indicating that the IOL position was clinically stable. In contrast, a significant axial shift of the IOL in the anterior direction was observed in the control eyes with IOL in-the-bag implantation (P!.001). In the control eyes, the mean ACD difference was 0.48 G 0.61 mm (95% CL, 0.73, 0.24), indicating that the IOL moved significantly anteriorly. The resulting refractive shift was significantly higher in the control eyes than in the PPCCC–POBH eyes (P!.001). The mean refractive shift at 4 weeks was 0.12 G 0.32 D (95% CL, 0.01, 0.24) in PPCCC– POBH eyes and 0.74 G 0.87 D (95% CL, 1.1, 0.39]) in control eyes. In addition, the 95% CLs of the ACD measurements in Table 1 indicate that interindividual variations were smaller in the PPCCC–POBH eyes than in the control eyes. Analyzing the relationship between postoperative ACD and AL, comparable correlations were found 1 to 2 hours postoperatively (Figure 2, top). However, at 4 weeks, a relevant ACD shift was observed in the control eyes, particularly in eyes with a short AL (Figure 2, bottom).
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AXIAL IOL POSITION CHANGE AFTER CATARACT SURGERY WITH PRIMARY PCCC AND POSTERIOR OPTIC BUTTONHOLING
PCCC /POBH
IOL in-the-bag
Linear (IOL in-the-bag)
Linear (PCCC /POBH)
refractive outcomes (PO.05). The biometric data in both groups are shown in Table 2. A significant correlation was found between the ACD 1 month after cataract surgery and the preoperative ACD in the PPCCC–POBH eyes (r Z 0.74; P!.001) and control eyes (r Z 0.28; P!.001). No significant correlations were observed between postoperative ACD measurements and preoperative corneal diameter and keratometry readings (PO.05).
6,5 5,5 4,5 3,5 2,5 20
22
24
26
28
30
Anterior Chamber Depth (mm)
Axial Eye Length (mm) PPCCC /POBH
IOL in-the-bag
DISCUSSION
Linear (IOL in-the-bag)
Linear (PPCCC /POBH)
Combining PPCCC and POBH for cataract surgery can significantly reduce the postoperative anterior movement of the IOL. The axial IOL position was stable in eyes with combined PPCCC–POBH at 1 month and 10 to 12 months postoperatively (PO.05). This is attributed to the absence of capsular bag closure and shrinkage with consecutive decay of haptic angulation and anterior optic movement. Instead, the optic is firmly fixated in the buttonhole and capsule fibrosis is not induced. Because the posterior capsule is sandwiched between the optic and the anterior capsule leaf, direct contact between the anterior capsule and the optic with consecutive myofibroblastic transformation of the lens epithelial cells residing on the backside of the anterior capsule leaf is obviated. In contrast, a significant axial shift of the IOL in the anterior direction was observed in the control eyes with IOL in-the-bag implantation (P!.001). This finding agrees with those in previous studies that showed significant postoperative changes in IOL position resulting from capsular bag shrinkage.13,14 In cases of in-the-bag IOL implantation, IOL design was shown to significantly influence postoperative axial IOL movement14,15 and the amount of capsular overlap
6,5
5,5 4,5 3,5 2,5 20
22
24
26
28
30
Axial Eye Length (mm) Figure 2. Relationship between AL and ACD measurements. Top: One to 2 hours postoperatively. Bottom: One month postoperatively (IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis).
There were no statistically significant differences between postoperative ACD measurements at 4 weeks and those at 10 to 12 months in the PPCCC–POBH eyes (P Z .54) or control eyes (P Z .7). However, there was a statistically significant difference between the 2 groups 1 month postoperatively (Table 1). No significant differences between the 2 surgical procedures were found with respect to the discrepancy between the expected and final postoperative
Table 2. Preoperative biometric data. Biometric Data Keratometry (D) Group PCCC–POBH Mean G SD 95% CL Eyes (n) Control Mean G SD 95% CL Eyes (n) P value
Spherical Equivalent (D)
AL (mm)
K1
K2
IOL Power (D)
Preop
1 Mo Postop
23.7 G 1.84 22.95; 24.46 23
7.73 G 0.33 7.6; 7.87 23
7.54 G 0.3 7.41; 7.66 23
21.33 G 4.25 19.59; 23.06 23
1.05 G 3.26 2.39; 0.28 23
1.01 G 1.05 1.44; 0.58 23
23.74 G 1.94 22.94; 24.53 23 .46
7.7 G 0.37 7.55; 7.86 23 .23
7.52 G 0.32 7.39; 7.65 23 .46
20.96 G 4.56 19.09; 22.83 23 .1
1.17 G 3.55 2.62; 0.28 23 .76
1.1 G 1.15 1.57; 0.63 23 .55
ACD Z anterior chamber depth; AL Z axial length; CL Z confidence limits (upper; lower); IOL Z intraocular lens; POBH Z posterior optic buttonholing; PPCCC Z primary posterior continuous curvilinear capsulorhexis
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was shown to influence IOL shifting.16 With angulated 3-piece foldable acrylic IOLs, a significant forward shift was observed during the first postoperative week with both sharp-edged and round-edged IOL designs.17 With the sharp-edged acrylic AR40e IOL (AMO), a slight backward shift was noted after the first week that continued to 6 months of followup.17 In contrast, the round-edged acrylic AR40 IOLs continued to move forward until the first postoperative month, followed by a slight backward shift until the sixth month.17 In eyes with nonangulated silicone IOLs, a significant postoperative change in ACD was reported for both the sharp-edged and round-edged designs; there was a forward shift in the first week with no significant difference between the 2 models.15 From 1 week to 3 months, there was backward movement of the silicone IOLs, with the sharp-edged IOLs moving a significantly greater amount.15 From 3 months to 1 year, IOLs with both optic edge designs moved slightly backward.15 Sixty-six percent of angulated IOLs showed continuous but variable forward movement and 34%, backward movement.15 These variations in axial IOL position have a clinically relevant impact on the development of postoperative refraction by the resulting refractive shift and deviation from the targeted refraction. For the present study, the YA-60BB IOL was chosen to compare the 2 surgical techniques because this acrylic 3-piece IOL has a continuous junction between the optic and haptic. This allows the crossing edge of the PPCCC rim to smoothly slide along the rim of the junction while the optic is buttoned in and centered in the PPCCC opening.1 Minimizing postoperative IOL movement is of increasing clinical importance because the axial position of an IOL of a given power determines its refractive effect and postoperative emmetropia is one of the most important goals of modern cataract surgery. Neutralizing factors influencing postoperative IOL shift help improve prediction of the final IOL position and thus IOL power calculation. Primary posterior continuous curvilinear capsulorhexis and POBH cataract surgery may be a clinically interesting alternative with respect to these concerns. Moreover, our finding that axial IOL stability increased after PPCCC–POBH IOL positioning may help surgeons determine the earliest time the anterior chamber will stabilize after cataract surgery, allowing them to prescribe glasses much earlier. The observed smaller interindividual variability in ACD measurements in PPCCC–POBH eyes than in control eyes may help increase the accuracy of preoperative biometry. However, larger study populations are needed to fully clarify this important aspect.
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The present study showed that with both surgical techniques, there were no statistically significant differences in the discrepancy between the expected and final postoperative refractive outcomes (PO.05). This can be explained by the fact that optimization of biometry constants was performed previously for both techniques. Besides the advantages of axial stability, PPCCC– POBH cataract surgery has been shown to be a safe and effective surgical technique.1,7,18 In the published evaluation of the first 500 consecutive cases,1 both capsule leaves remained clear, especially after additional polishing of the haptic–optic junction area where direct contact between anterior capsule and optic persists.19 No intraocular pressure (IOP) spike or postoperative anterior chamber flare was reported.4,18 Fixation of the optic in the PPCCC opening is crucial for the mechanisms of axial stability, and it also influences the course of IOP during the first postoperative hours by creating a watertight diaphragm. Thus, retrolental OVD cannot proceed into the anterior chamber, which can result in postoperative IOP spikes as found in a study of cataract surgery with PPCCC without POBH.20 The optic perfectly centers by itself, even when the PPCCC is not ideally centered. The optic immediately obtains its final axial position without tilt or secondary rotation. These characteristics are clear advantages to the solitary performance of a PPCCC without buttonholing of the IOL. Considering the immediate and persistent positional stability of the optic and the improved predictability in ACD, and thus refraction, in the present study, cataract surgery with PPCCC–POBH can be regarded as an interesting surgical option, particularly in cases with refractive indications such as clear lens exchange, multifocal IOL implantation, or toric IOL implantation. REFERENCES 1. Menapace R. Routine posterior optic buttonholing for eradication of posterior capsule opacification in adults; report of 500 consecutive cases. J Cataract Refract Surg 2006; 32:929–943; erratum, 1410 2. Gimbel HV. Posterior capsulorhexis with optic capture in pediatric cataract and intraocular lens surgery. Ophthalmology 1996; 103:1871–1875 3. Gimbel HV. Posterior continuous curvilinear capsulorhexis and optic capture of the intraocular lens to prevent secondary opacification in pediatric cataract surgery. J Cataract Refract Surg 1997; 23:652–656 4. Stifter E, Menapace R, Luksch A, et al. Objective assessment of intraocular flare after cataract surgery with combined primary posterior capsulorhexis and posterior optic buttonholing in adults. Br J Ophthalmol 2007; 91:1481–1484 5. Drexler W, Findl O, Menapace R, et al. Partial coherence interferometry: a novel approach to biometry in cataract surgery. Am J Ophthalmol 1998; 126:524–534
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6. Fercher AF, Mengedoht K, Werner W. Eye-length measurement by interferometer with partially coherent light. Opt Lett 1988; 13:186–188 7. Fercher AF, Roth E. Ophthalmic laser interferometer. In: Mueller GJ, ed, Optical Instrumentation for Biomedical Laser Applications. Proceedings SPIE 0658. Bellingham, WA, SPIE, 1986; 48–51 8. Drexler W, Baumgartner A, Findl O, et al. Submicrometer precision biometry of the anterior segment of the human eye. Invest Ophthalmol Vis Sci 1997; 38:1304–1313. Available at: http:// www.iovs.org/cgi/reprint/38/7/1304. Accessed January 30, 2008 9. Findl O, Drexler W, Menapace R, et al. High precision biometry of pseudophakic eyes using partial coherence interferometry. J Cataract Refract Surg 1998; 24:1087–1093 10. Hitzenberger CK. Optical measurement of the axial eye length by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1991; 32:616–624. Available at: http://www.iovs.org/cgi/ reprint/32/3/616. Accessed January 30, 2008 11. Hitzenberger CK, Drexler W, Dolezal C, et al. Measurement of the axial length of cataract eyes by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1993; 34:1886–1893. Available at: http://www.iovs.org/cgi/reprint/34/6/1886. Accessed January 30, 2008 12. Preussner PR, Wahl J, Lahdo H, et al. Ray tracing for intraocular lens calculation. J Cataract Refract Surg 2002; 28:1412–1419 13. Findl O, Drexler W, Menapace R, et al. Accurate determination of effective lens position and lens-capsule distance with 4 intraocular lenses. J Cataract Refract Surg 1998; 24:1094–1098 14. Wirtitsch MG, Findl O, Menapace R, et al. Effect of haptic design on change in axial lens position after cataract surgery. J Cataract Refract Surg 2004; 30:45–51
15. Petternel V, Menapace R, Findl O, et al. Effect of optic edge design and haptic angulation on postoperative intraocular lens position change. J Cataract Refract Surg 2004; 30:52–57 16. Nanavaty MA, Raj SM, Vasavada VA, et al. Anterior capsule cover and axial movement of intraocular lens. In press, Eye 2008. 17. Koeppl C, Findl O, Kriechbaum K, et al. Postoperative change in effective lens position of a 3-piece acrylic intraocular lens. J Cataract Refract Surg 2003; 29:1974–1979 18. Stifter E, Luksch A, Menapace R. Postoperative course of intraocular pressure after cataract surgery with combined primary posterior capsulorhexis and posterior optic buttonholing in adults. J Cataract Refract Surg 2007; 33:1585–1590 19. Menapace R, Di Nardo S. Aspiration curette for anterior capsule polishing: laboratory and clinical evaluation. J Cataract Refract Surg 2006; 32:1997–2003 20. Wirtitsch M, Menapace R, Georgopoulos M, et al. Intraocular pressure rise after primary posterior continuous curvilinear capsulorhexis with a fixed dorzolamide–timolol combination; randomized safety study with intraindividual comparison using an angulated and a nonangulated intraocular lens. J Cataract Refract Surg 2007; 33:1754–1759
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First author: Eva Stifter, MD Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria