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Evaluation of intraocular lens position during phacoemulsification using intraoperative spectral-domain optical coherence tomography
ARTICLE
Evaluation of intraocular lens position during phacoemulsification using intraoperative spectral-domain optical coherence tomography Lyubomyr M. Lytvynchuk, MD, PhD, Carl G. Glittenberg, MD, Christiane I. Falkner-Radler, MD, Beatrix Neumaier-Ammerer, MD, Eva Smretschnig, MD, Stefan Hagen, MD, Siamak Ansari-Shahrezaei, MD, Susanne Binder, MD
PURPOSE: To assess the position of intraocular lenses (IOLs) at the end of standard phacoemulsification with intraoperative spectral-domain optical coherence tomography (SD-OCT). SETTINGS: Department of Ophthalmology, Rudolf Foundation Hospital, Vienna, Austria. DESIGN: Prospective case series. METHODS: Standard phacoemulsification with IOL implantation was performed. The Rescan 700 SD-OCT system was used for intraoperative imaging. The anterior segment of the eye was scanned using SD-OCT at the end of the surgery. The distance from the IOL optic center and the IOL optic edge to the posterior capsule was measured postoperatively using graphic software. RESULTS: The study comprised 74 patients (101 eyes). The mean axial length was 23.97 mm (range 21.43 to 28.61 mm). The mean IOL power was 20.39 diopters (D) (range 6.5 to 27.5 D). Contact between the IOL and posterior capsule was absent in 88 cases (87.13%), and partial or full contact was present in 13 cases (12.87%). The mean distance between the IOL central optic and posterior capsule was 0.71 pixel (range 0.06 to 1.38 pixels) in 99 cases (98.02%). In 42 cases (57.53%), partial contact between the IOL edges and the posterior capsule was noticed. The mean distance between the IOL edge and posterior capsule was 0.21 pixel (range 0.04 to 0.92 pixel). CONCLUSIONS: Intraoperative SD-OCT facilitated the imaging of IOL position during standard phacoemulsification. Contact between the IOL central optic and posterior capsule at the end of the surgery occurred rarely. Improved IOL design should be considered. Financial Disclosure: Drs. Binder and Glittenberg are consultants to Carl Zeiss Meditech AG. None of the other authors has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2016; 42:694–702 Q 2016 ASCRS and ESCRS Online Video
The position of the intraocular lens (IOL) after phacoemulsification is essential to reach postoperative emmetropia and optimum visual acuity performance, especially when multifocal, aspheric, or toric IOLs are used. In the majority of cataract surgery cases, IOLs with a standard diameter are implanted regardless of the size of different anatomic structures, such as the capsular bag diameter or axial length (AL), which clearly differ in every patient.1,2,A 694
Q 2016 ASCRS and ESCRS Published by Elsevier Inc.
Posterior capsule opacification (PCO) is 1 of the most common complications of modern cataract surgery with IOL implantation.3,4 Many factors influence the formation of PCO, such as activity of postsurgical inflammation, IOL design, IOL material, technique of implantation, and concomitant ophthalmic or general diseases.5–7 Studies7,8 suggest that IOLs with a squareedged design create the most effective impediment to cell growth behind the IOL optic and prevent early http://dx.doi.org/10.1016/j.jcrs.2016.01.044 0886-3350
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formation of PCO. This concept is supported by the theory that a square edge mechanically slows the migration of lens epithelial cells (LECs) because the edge presses against the posterior capsule. The reduction in the space between the posterior surface of the IOL and the posterior capsule after surgery is considered to play a role in preventing PCO. This idea is supported by the no space, no cells concept.9,10 However, the rate of PCO after cataract surgery is still significant3,4 and it is not clear exactly when firm contact between the IOL edge and the posterior capsule is established. Intraoperative spectral-domain optical coherence tomography (SD-OCT) is a diagnostic technique that, although relatively new, has attained an important place in ophthalmic surgery of the anterior and the posterior segments of the eye.11,B The feasibility of intraoperative SD-OCT in anterior segment surgery has been shown.12–14 This study evaluated the position of the IOL relative to the posterior capsule using intraoperative SD-OCT during standard phacoemulsification by measuring the distance between the IOL and the posterior capsule at different locations. PATIENTS AND METHODS This prospective single-center study was performed at the Ophthalmology Department, Rudolf Foundation Hospital, Vienna, Austria, during a period of 5 months. All patients in the study were diagnosed with senile cataract and scheduled for phacoemulsification with IOL implantation. The
Submitted: October 27, 2015. Final revision submitted: January 4, 2016. Accepted: January 26, 2016. From the Department of Ophthalmology (Lytvynchuk, Glittenberg, Falkner-Radler, Neumaier-Ammerer, Smretschnig, Hagen, AnsariShahrezaei, Binder), Rudolf Foundation Hospital, the Karl Landsteiner Institute for Retinal Research and Imaging (Lytvynchuk, Glittenberg, Falkner-Radler, Neumaier-Ammerer, Smretschnig, Hagen, Ansari-Shahrezaei, Binder), and the Retina Center (AnsariShahrezaei, Binder), Vienna, and the Department of Ophthalmology (Ansari-Shahrezaei), Medical University of Graz, Graz, Austria; the Ophthalmology Department (Lytvynchuk), University Clinic Gießen and Marburg GmbH, Gießen, Germany; the Professor Sergienko Eye Clinic (Lytvynchuk), Vinnytsia, Ukraine. Drs. Lytvynchuk and Glittenberg contributed equally to this work. Supported by the Karl Landsteiner Institute for Retinal Research and Imaging, Vienna, Austria. Presented at the XXXIII Congress of the European Society of Cataract and Refractive Surgeons, Barcelona, Spain, September 2015. Corresponding author: Lyubomyr M. Lytvynchuk, MD, PhD, Karl Landsteiner Institute for Retinal Research and Imaging, Juchgasse 25, A-1030, Vienna, Austria. E-mail: [email protected].
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study was performed according to the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of the city of Vienna, Austria. All patients signed a written informed consent form. Exclusion criteria were pseudoexfoliation syndrome, previous ocular surgery, previous eye trauma, and intraoperative floppy-iris syndrome. Intraocular lens calculation was performed preoperatively using partial coherence interferometry (IOLMaster 500, Carl Zeiss Meditec AG).
Surgical Technique Surgery was performed using topical or general anesthesia by 1 of 5 experienced surgeons (S.B., Ch.F-R., B.N-A., E.S., S.H.). Both eyes had surgery during the same surgical session. Standard phacoemulsification procedures with 2.2 mm self-sealing clear corneolimbal incisions at 11 o’clock and 1 paracentesis at 2 o’clock were performed in all cases. The capsulorhexis was made at least 1.0 mm smaller than the IOL optic (4.5 to 5.0 mm) to cover the edge of the IOL optic (6.0 mm). After capsulorhexis, hydrodissection, phacoemulsification, and cortical material aspiration were performed, a 1-piece foldable hydrophobic IOL was implanted using an IOL delivery system in every case. Thorough removal of the ophthalmic viscoelastic device (OVD) (sodium hyaluronate [Hyalon]) from the posterior surface of the IOL and behind the IOL was performed at the end of each surgery to ensure the absence of barriers that could obstruct contact between the posterior capsule and the IOL. After complete removal of the OVD, regular filling of the anterior chamber with a balanced salt solution using a cannula was performed. During the filling, the push-back maneuver was applied to the IOL surface using the tip of the cannula. Normal intraocular pressure (IOP) values (z20 mm Hg) were maintained and measured with the method described by Hirnschall et al.14 To standardize the height of the bottle, IOP measurements were performed in 5 eyes at the beginning of the study, assuming that an IOP of 20 mm Hg is equal to 2.7 kPa, with a conversion factor of 1.36 from millimeters of mercury to centimeters of water. At the end of the surgery after all incisions were hydrated, an irrigation handpiece was inserted into the paracentesis at 2 o’clock. Then, the bottle height on the phaco machine was adjusted. With the surgeon holding the irrigation handpiece in the paracentesis, the IOP was measured with a Schiotz tonometer (Rudolf Riester GmbH) at every 5 cm increase in the bottle height. In addition, the height of the patient's eye and the bottle was measured. Therefore, it was calculated that for a normal IOP of approximately 20 mm Hg, a distance of 27.5 cm from the patient's eye to the bottle had to be maintained. Standard antibiotic and antiinflammatory therapy was prescribed in the postoperative period.
Intraocular Lenses In this study, eyes had implantation of an Acrysof IQ SN60WF IOL using the Acrysert delivery system (Alcon Laboratories, Inc.) (Group 1) or a Tecnis IOL using the iTec preloaded delivery system (Abbott Medical Optics, Inc.) (Group 2). Both IOLs are 1-piece with a 360-degree squareedge, are hydrophobic acrylic, and have an aspheric design, an optic diameter of 6.0 mm, and an overall length of 13.0 mm. The 360-degree square edge of the latter IOL is designed to provide uninterrupted contact at the haptic– optic junction.
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Intraoperative Spectral-Domain Optical Coherence Tomography Imaging For intraoperative imaging, the first commercially available intraoperative SD-OCT system, Rescan700 (Carl Zeiss Meditec AG), was used; the system is fully integrated in the surgical microscope footstand (Opmi Lumera 700). The intraoperative SD-OCT machine has the following characteristics: OCT engine Z spectral domain, wavelength 840 nm, scanning speed 27 000 A-scans per second, refresh rate (5 Hz to 50 Hz, axial resolution) 5.5 mm in tissue, scan depth 2.0 mm, scan length 6.0 or 9.0 mm, and a crosshair scan mode. Visual control of intraoperative SD-OCT imaging is facilitated through the heads-up display in the right ocular of the microscope. Adjustment and capture of the intraoperative SD-OCT images were performed by the surgeon using the footpedal of the microscope. Each eye was aligned so that the iris and the IOL were situated at a horizontal plane or close to a horizontal plane on the intraoperative SD-OCT image on the screen so that all details of the capsular bag and IOL would be visible. In each case, the following 4 intraoperative SD-OCT crosshair images with a 6.0 or 9.0 mm scan length were taken during the surgery: cornea, anterior surface of the crystalline lens, posterior surface of the crystalline lens, and IOL in
the bag. The cornea and both crystalline lens surfaces were imaged for calibration purposes. Intraoperative SD-OCT imaging of the IOL and posterior capsule was evaluated, and the distances between them were measured. The crosshair intraoperative SD-OCT mode was used to ensure intraoperative SD-OCT scanning of the central area of the IOL optic while simultaneously catching the edge of the optic. This was controlled by the surgeon via the heads-up display. The presence of mydriasis at the end of the surgery was assessed to ensure the visibility of IOL edges. Intraoperative SD-OCT scanning was performed using the video and snapshot modes, focusing on the IOL optic's center, IOL edges, and posterior capsule (Figure 1, A).
Post-Processing and Measurements The intraoperative SD-OCT images were exported and post-processed using ImageJ (version 1.48v).C The intraoperative SD-OCT images captured in cube mode (snapshot) were resized from the raw 512 pixels 1024 pixels (Figure 1, B) to 600 pixels 200 pixels or 900 pixels 200 pixels (depending on cube scan length) (Figure 1, C). This proportion corresponds to the dimensions of the real scan with a 6.0 or 9.0 mm length and 2.0 mm height, resulting in a square pixels
Figure 1. A: Real-time color snapshot taken during intraoperative SD-OCT video streaming. B: Compressed gray-scale intraoperative SD-OCT image of the capture mode. C: Resized gray-scale intraoperative SD-OCT image performed in ImageJ software (OCT Z optical coherence tomography).
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aspect ratio. Because the distances in the intraoperative SD-OCT scans are not calibrated, the measured distances are relative measurements and not absolute measurements. Therefore, all measurements are presented in pixels, not millimeters. Central distance refers to the distance between the central optic area and the posterior capsule. Edge distance refers to the distance between the IOL edge and the posterior capsule. The distances were measured using the “straight line” option in ImageJ, marking the distances with calipers between the IOL center (crosshair-scan guided) and the posterior capsule. Edge distance was derived from the distances measured at 12, 3, 6, and 9 o’clock at the edge, respective to the crosshair scan. All measurements were performed twice. In addition, the presence of contact between the IOL edges and posterior capsule was designated as absence, less than 90 degrees, less than 180 degrees, or over 180 degrees of the IOL optic edge. Contact between the IOL haptic point of origin and the posterior capsule, posterior capsule wrinkling, contact between the anterior capsule and IOL, and the presence of anterior vitreous hyperreflectivity were evaluated in all cases.
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Of the patients, 62 (77 eyes) had surgery under topical anesthesia and 12 (24 eyes) under general anesthesia. Standard phacoemulsification was performed in 88 eyes (87.1%) and combined surgery with pars plana vitrectomy (PPV) in 13 eyes (12.9%). The Acrysof IQ SN60WF IOL was implanted in 59 eyes (58.6%) (Group 1) and the Tecnis IOL in 42 eyes (41.6%) (Group 2). The mean AL was 23.97 mm (range 21.43 to 28.61 mm), and the mean IOL power was 20.39 D (range 6.5 D to 27.5 D), including 15 long eyes with (emmetropic IOL power !18.0 D), 69 normal eyes (emmetropic IOL 18.0 to 23.0 D), and 17 short eyes (emmetropic IOL O23.0 D). Mydriasis of more than 6.0 mm and good visibility of the IOL edge were detected in 73 cases (72.3%). In these cases, intraoperative SD-OCT imaging of 360 degrees of the IOL edge was possible. All surgeries were uneventful. The IOLs were well centered in all cases.
Statistical Analysis Statistical analysis was performed using descriptive statistics, frequency tables, and correlation matrices. The data were analyzed using Statistica 10 software (Statsoft, Inc.). A P value less than 0.05 was considered statistically significant.
RESULTS The total number of phacoemulsification procedures within the 5-month period was 521; 101 eyes of 74 patients met the inclusion criteria and were included in the study. The mean age of the 39 men (38.61%) and 62 women (61.39%) was 71.43 years (range 49 to 91 years).
Intraocular Lens Central Optic to Posterior Capsule Distance (Central Distance) In 99 eyes (98%), a separation between the IOL central optic and the posterior capsule was observed. In 99 cases, the mean central distance was 0.72 pixel (range 0.06 to 1.38 pixels) (Figure 2, A, B, C, D, and E). No contact between the IOL central optic and the posterior capsule was observed in 88 eyes (87.13%), partial contact between the IOL central optic was observed in 11 eyes (10.89%), and full contact was
Figure 2. Case 1. A: Compressed snapshot of the IOL and the posterior capsule. B and C: Resized snapshots of the same case. White arrows show the central distance between the IOL and the posterior capsule. C: Red arrow shows the contact between the IOL edge and the posterior capsule. Yellow arrows point to the hyperreflectivity of the anterior vitreous. Case 2. D: Compressed snapshot of the IOL and the posterior capsule. E and F: Resized snapshots of the same case. White arrows show the central distance and the edge distance between the IOL and posterior capsule. E: Red arrows show the slight upward rolling of the capsulorhexis edge. F: Yellow arrow points to the distal part of the IOL haptic (OCT Z optical coherence tomography; px Z pixels).
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Figure 3. Box-and-whisker plots. A: The mean central distance between the IOL and the posterior capsule. B: The mean edge distance between the IOL and the posterior capsule (px Z pixels).
observed in 2 eyes (1.98%) only (Figure 2) (Video 1, part 1, available at http://jcrsjournal.org). There was a significant correlation between the central distance and the AL. Thus, an increase in the AL led to an increase in the central distance, with a correlation coefficient of 0.213 (P Z .05) (Figure 4, A). In cases with no contact between the IOL central optic and the posterior capsule, the mean AL was 23.65 mm, whereas cases with full or partial contact had a mean AL of 24.00 mm. The correlation between the central distance and the IOL power was also shown to be a reciprocal dependence, meaning that an increase in the IOL power led to a decrease in the central distance, with a correlation coefficient of 0.248 (P Z .05) (Figure 4, B). Although the central distance decreased with an increase in patient age (Figure 4, C), this correlation was not statistically significant. The mean central distance in Group 1 was 0.77 pixel (range 0.06 to 1.38 pixels) and 0.64 pixel (range 0.15 to 1.32 pixels) in Group 2 (Figure 6, A). The central distance difference of 0.13 pixel between the 2 types of IOL was statistically significant (P Z .04). In 13 combined surgery cases (12.9%), 0.2 mL of OVD was injected into the anterior chamber immediately after phacoemulsification and before PPV to
prevent sudden anterior chamber shallowing during manipulation of the eye. Repeated intraoperative SDOCT imaging of the posterior chamber performed after the OVD injection showed full contact between the posterior capsule and posterior IOL surface (Figure 7, B). This resulted from simple downward depression of the IOL by the OVD. After the PPV was complete and the OVD was washed out, intraoperative SD-OCT showed restoration of the IOL position away from the posterior capsule. Intraocular Lens Edge to Posterior Capsule Distance (Edge Distance) In 73 eyes (72.3%), 360 degrees of the IOL edges were visible at the end of the surgery. The mean edge distance was 0.21 pixel (range 0.04 to 0.92 pixel) (Figures 2, C and F, and 3, B). In 31 eyes (42.47%), there was no contact between the IOL edges and the posterior capsule. In 42 eyes (57.53%), partial contact between the IOL edges and the posterior capsule was noticed (Video 1, part 2, available at http://jcrsjournal.org). Contact between the IOL edge and the posterior capsule over 180 degrees was observed in 29 eyes (69.05%), less than 180 degrees in 11 eyes (26.19%), and less than 90 degrees in 2 eyes (4.76%) (Figure 2, C).
Figure 4. Correlation between edge distance and AL (A), IOL power (B), and age (C) (Conf. Int. Z confidence interval; IOL Z intraocular lens; px Z pixels). J CATARACT REFRACT SURG - VOL 42, MAY 2016
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Figure 5. Correlation between the central distance and AL (A), IOL power (B), and age (C) (Conf. Int. Z confidence interval; IOL Z intraocular lens; px Z pixels).
Correlations between the edge distance and the AL, IOL power, and age were not statistically significant (Figure 5, A to C), and no dependence was found. The mean edge distance was 0.28 pixel (range 0.04 to 0.92 pixel) in Group 1 and 0.23 pixel (range 0.05 to 0.53 pixel) in Group 2 (Figure 6, B). The difference in the edge distance between the 2 types of IOLs was 0.04 pixel and was not statistically significant. Contact between the IOL haptic point of origin and the posterior capsule was detected in 35 eyes (34.65%). Contact was detected in 20 eyes (57.14%) in Group 1 and in 15 eyes (42.86%) in Group 2. Posterior Capsule Wrinkling, Anterior Vitreous Hyperreflectivity, Anterior Capsule to Intraocular Lens Contact Wrinkling of the posterior capsule, a marker of reduced capsular bag volume after phacoemulsification that might be correlated with supportive properties of the anterior vitreous, was observed in 63 eyes (62.38%) and absent in 38 eyes (37.62%). The location of the wrinkling was in the projection of the IOL optic center in 54 eyes (85.71%) and in the projection of the IOL optic periphery in 9 eyes (14.29%) (Figure 1, C). Intraoperative SD-OCT imaging showed linear hyperreflectivity from the anterior vitreous behind the
posterior capsule in 20 cases (19.8%) (Figures 1, B, and 2, C). The mean age of these patients was 69.8 years (range 53 to 81 years). In 81 cases (80.2%), there were no signs of hyperreflectivity from the anterior vitreous on intraoperative SD-OCT scans. The mean age of these patients was 71.8 years (range 49 to 91 years). In 66 eyes (90.4%), there was no contact between the IOL and anterior capsule with slight upward rolling of the capsulorhexis edge (Figures 1, B, and 2, E). There was contact between the anterior surface of the IOL optic and anterior capsule capsulorhexis margin in 7 (9.6%) of 73 eyes, with 360-degree visibility of the IOL edges and a mydriatic pupil larger than 6.0 mm. DISCUSSION Posterior capsule opacification is the main problem after standard phacoemulsification. The complication is strongly connected to IOL design and posterior capsule reaction. To our knowledge, this is the first study of IOL positioning relative to the capsular bag at the end of a standard phacoemulsification assessed using intraoperative SD-OCT. Our data show no contact between the IOL central optic and posterior capsule (central distance) in 87.13% of cases (88 eyes), while partial or full contact appeared in only 12.87% of cases (13 eyes). In 57.53% of cases
Figure 6. Box-and-whisker plots of the central distance (A) and edge distance (B) between the 2 IOL groups (px Z pixels).
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Figure 7. Contact between the IOL and posterior capsule during combined surgery was achieved by injection of OVD after IOL implantation to stabilize the anterior chamber during PPV.
(42 eyes), partial contact between the IOL edge and posterior capsule was noticed. Using intraoperative OCT, Hirnschall et al.14 studied the distance between the corneal endothelium and the anterior capsule before phacoemulsification and after capsular tension ring (CTR) implantation to improve the prediction of the postoperative IOL position. The authors used a CTR to tighten the lens capsule and stabilize the IOL position. They found that the intraoperative OCT measurement of the anterior lens capsule, with the presence of a CTR, served as a better predictor of postoperative IOL position than preoperative factors. Because the primary goal of our study was to analyze IOL position in uncomplicated cases in which a CTR was not used, we performed routine phacoemulsification only. Although, we saw no contact between the IOL central optic and posterior capsule in 87.13% of cases (88 eyes), we did find a significant difference in the central distance between the 2 types of IOLs. In our study, both IOLs that were implanted have a square-edged design. They have a similar design except that the Tecnis IOL has a 3-point fixation on the posterior surface. This can explain why the mean distance between the IOL central optic and posterior capsule in eyes with the Tecnis IOL was less than that in eyes with the Acrysof IQ IOL, with a difference of 0.13 pixel (P Z .04). There was a significant correlation between the central distance and the AL (P Z .05). Our results suggest that the IOL design has to be adapted to the AL and other parameters of ocular structures. The IOL haptic plays a major role in supporting the IOL's position in the capsular bag. Visualization of the IOL haptic was performed by Mostafavi et al.15 postoperatively to show the exact position of the IOL using ultrasound biomicroscopy in cases complicated by uveitis–glaucoma–hyphema syndrome. This study determined the cause of the complications and treated them using IOL repositioning or removal. In our study, intraoperative SD-OCT imaging of the
proximal part of the IOL haptic only was achievable. This necessitated proper IOL centration and a mydriatic pupil (O6.0 mm). Another important finding was the linear hyperreflectivity of the anterior vitreous in 19.8% of cases (20 eyes). This hyperreflectivity of vitreous can correspond to the margin of Berger space and the beginning of the anterior vitreous, which was probably not noticed in the remaining cases because of the insufficient intraoperative SD-OCT scan depth. The condition of the vitreous gel, especially regarding the grade of its liquefaction with age, and hydration during the surgery might also play a role in the position of the posterior capsule after phacoemulsification.16 Contact between the anterior capsule and IOL predisposes the eye to anterior subcapsular opacification with a risk for anterior capsule fibrosis and phimosis.17 In our study, 90.4% of cases (91 eyes) had no contact between the anterior capsule and the IOL at the end of phacoemulsification. The unfavorable contact between the anterior capsule and the IOL as well as favorable contact between the posterior capsule and the IOL probably appear in the postoperative period. In combined surgery cases, with the use of OVD after IOL implantation to stabilize the anterior chamber, we can achieve contact between the IOL and the posterior capsule (Video 1, part 3, available at http:// jcrsjournal.org). This contact, however, is temporary and disappears after OVD washout. In addition, the injection of OVD at the end of uneventful phacoemulsification is not a standard surgical step. Intraocular pressure at the end of phacoemulsification varies in every patient. The depth of the anterior chamber and hydration of the vitreous is dependent on the hydration technique of paracentesis and main entrance and is difficult to standardize in every case. In our study, we applied a method to gain nearly equal IOP at the end of each surgery, as described by Hirnschall et al.14 Intraoperative SD-OCT of the anterior segment with the Rescan 700 system is limited by the 2.0 mm scan
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depth. Therefore, only intraoperative SD-OCT imaging of a certain depth of the anterior and posterior segments is possible. In this study, we focused on the posterior chamber to capture the anterior capsule, the IOL, the posterior capsule, and the anterior vitreous. Another limitation of this study was that the intraoperative SD-OCT scanning beam is blocked by the iris, which is why the distal part of the IOL haptic was not seen. During post-processing and measurements performed with ImageJ,C the distances we obtained were not absolute, but relative. Distance measurements are relevant, and their expression in millimeters would be incorrect because the manufacturer has not calibrated absolute distances in the Rescan 700 system. That is why we presented the data in pixels. Resizing intraoperative SD-OCT scans from 512 pixels 1024 pixels (standard image size from Rescan 700) to 600 pixels 200 pixels or 900 pixels 200 pixels was optimum because this size corresponds to the dimensions of the real-time intraoperative SD-OCT scans, which are equal to 6.0 mm 2.0 mm or 9.0 mm 2.0 mm (6000 mm 2000 mm or 9000 mm 2000 mm). Axial length, age, and individual variations can determine the size of the capsular bag and crystalline lens.1,2 The diameter of the natural crystalline lens differs in every patient and is also dependent on the patient's age.18 Discrepancies between the size of the standard implanted IOL and variable capsular bag size can lead to a refractive error, IOL displacement, or IOL tilt in the postoperative period. The distance between the IOL and the posterior capsule could also depend on other factors, including AL, the condition of the vitreous and zonular fibers, elasticity of posterior capsule, size of the capsular bag, IOL dimensions and design, and surgical technique. Wesendahl et al.19 have shown in cadaver eyes that only IOLs with a bent-forward haptic design of more than 10 degrees can make contact with the posterior capsule and the IOL optic and that haptic diameter has limited influence. The incomplete contact between the IOL edges and the posterior capsule in our study can cause IOL instability within the capsular bag and LEC migration in the early postoperative period. This can lead to postoperative IOL decentration, IOL tilting, and PCO, with a further effect on the correlation between visual acuity and anterior chamber structures. The IOLs used in this study had the same optic dimensions and overall length. It is possible that a larger optic diameter would have facilitated better contact between the IOL edge and the posterior capsule. Future iterations of intraoperative OCT systems using new OCT engines (eg, swept source) would improve the visualization of the anterior and posterior segments of the eye.20
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In conclusion, intraoperative SD-OCT facilitated the visualization of the IOL position because it obtained substantial hyperreflectivity from the IOL, the capsular bag, and the anterior vitreous. Contact between the IOL central optic and central posterior capsule was rare, probably because the volume of the lens capsule is larger than volume of the IOL. The contact between the IOL's square edge and the posterior capsule was only partial in 57.53% of eyes. New IOL designs that support and improve intraoperative contact between the IOL and the posterior capsule have to be developed. WHAT WAS KNOWN Contact between an IOL’s square edge and the posterior capsule slows the migration of LECs because of mechanical pressing of the edge against the posterior capsule. The prevention of PCO is also supported by the no space, no cells concept. Posterior capsule opacification remains 1 of the major complications after phacoemulsification with IOL implantation. WHAT THIS PAPER ADDS Full contact between the hydrophobic IOL’s central optic and the central posterior capsule at the end of standard phacoemulsification was rare. New IOL designs to improve immediate contact between the IOL and the posterior capsule at the end of surgery should be developed.
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€tz W, Strobel J, 7. Kohnen T, Fabian E, Gerl R, Hunold W, Hu Hoyer H, Mester U. Optic edge design as long-term factor for posterior capsular opacification rates. Ophthalmology 2008; 115:1308–1314.e1–3 8. Peng Q, Visessook N, Apple DJ, Pandey SK, Werner L, Escobar-Gomez M, Schoderbek R, Solomon KD, Guindi A. Surgical prevention of posterior capsule opacification. Part 3: intraocular lens optic barrier effect as a second line of defense. J Cataract Refract Surg 2000; 26:198–213 9. Nishi O, Nishi K, Sakanishi K. Inhibition of migrating lens epithelial cels at the capsular bag bend created by rectangular optic edge of posterior chamber intraocular lens. Ophthalmic Surg Lasers 1998; 29:587–594 10. Menapace R, Findl O, Georgopoulos M, Rainer G, Vass C, Schmetterer K. The capsular tension ring: designs, applications, and techniques. J Cataract Refract Surg 2000; 26:898–912 11. Binder S, Falkner-Radler CI, Hauger C, Matz H, Glittenberg C. Feasibility of intrasurgical spectral-domain optical coherence tomography. Retina 2011; 31:1332–1336 €ttmann G, Lankenau E, 12. Heindl LM, Siebelmann S, Dietlein T, Hu Cursiefen C, Steven P. Future prospects: Assessment of intraoperative optical coherence tomography in ab interno glaucoma surgery. Curr Eye Res 2015; 40:1288–1291 13. Hirnschall N, Norrby S, Weber M, Maedel S, Amir-Asgari S, Findl O. Using continuous intraoperative optical coherence tomography measurements of the aphakic eye for intraocular lens power calculation. Br J Ophthalmol 2015; 99:7–10 14. Hirnschall N, Amir-Asgari S, Maedel S, Findl O. Predicting the postoperative intraocular lens position using continuous intraoperative optical coherence tomography measurements. Invest Ophthalmol Vis Sci 2013; 54:5196–5203. Available at: http:// iovs.arvojournals.org/article.aspx?articleidZ2127773. Accessed February 15, 2016 15. Mostafavi D, Nagel D, Danias J. Haptic-induced postoperative complications. Evaluation using ultrasound biomicroscopy. Can J Ophthalmology 2013; 48:478–481 16. Oh J-H, Chuck RS, Do JR, Park CY. Vitreous hyper-reflective dots in optical coherent tomography and cystoid macular deem after uneventful phacoemulsification surgery. PLoS One 2014; 9:e95066. Available at: http://www.ncbi.nlm.nih. gov/pmc/articles/PMC3988138/pdf/pone.0095066.pdf. Accessed February 15, 2016 17. Trivedi RH, Werner L, Apple DJ, Pandey SK, Izak AM. Post cataract-intraocular lens (IOL) surgery opacification. Eye 2002; 16:217–241. Available at: http://www.nature.com/eye/journal/ v16/n3/pdf/6700066a.pdf. Accessed February 15, 2016
18. Glasser A, Campbell MCW. Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia. Vision Res 1999; 39:1991–2015 19. Wesendahl TA, Hunold W, Auffarth GU, Apple DJ. Kontaktbereich von Kunstlinse und Hinterkapsel; systematische Untersuchung unterschiedlicher Haptikparameter [Area of contact between IOL and posterior capsule; systematic analysis of different haptic parameters]. Ophthalmologe 1994; 91:680–684 20. Grulkowski I, Liu J, Potsaid B, Jayaraman V, Lu CD, Jiang J, Cable AE, Duker JS, Fujimoto JG. Retinal, anterior segment and full eye imaging using ultrahigh speed swept source OCT with vertical-cavity surface emitting lasers. Biomed Opt Express 2012; 3:2733–2751. Available at: http://www.ncbi.nlm.nih.gov/ pmc/articles/PMC3493240/pdf/2733.pdf. Accessed February 15, 2016
OTHER CITED MATERIAL A. Sourdille P. Does one diameter IOL fit all capsular bags? Cataract & Refractive Surgery Today Europe February 2009. Available at: http://crstodayeurope.com/2009/02/0209_04.php. Accessed February 15, 2016 B. Matz H, Binder S, Glittenberg C, Scharioth G, Findl O, Hirnschall N, Hauger Ch, “Intraoperative Applications of OCT in Ophthalmic Surgery,” presented at the 46th Congress of the € r Biomedizinische Technik (BiomedDeutsche Gesellschaft fu ical Engineering [Biomedizinische Technik, BMT]), Jena, Germany, September 2012. Abstract in. Biomed Tech (Berl) 2012; 57(suppl 1). Available at: http://www.degruyter.com/ dg/viewarticle.fullcontentlink:pdfeventlink/$002fj$002fbmte.2012 .57.issue-s1-P$002fbmt-2012-4460$002fbmt-2012-4460.pdf? resultZ1&rskeyZrcH0BN&t:acZj$002fbmte.2012.57.issue-s1 -P$002fbmt-2012-4460$002fbmt-2012-4460.xml. Accessed February 15, 2016 C. Rasband W. ImageJ; Image Processing and Analysis in Java. Bethesda, Maryland, Research Services Branch, National Institutes of Health, Bethesda. Available at: http://rsb.info.nih.gov/ij/. Accessed February 15, 2016
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First author: Lyubomyr M. Lytvynchuk, MD, PhD Department of Ophthalmology, Karl Landsteiner Institute for Retinal Research and Imaging, Vienna, Austria
Evaluation of intraocular lens position during phacoemulsification using intraoperative spectral-domain optical coherence tomography Lyubomyr M. Lytvynchuk, MD, PhD, Carl G. Glittenberg, MD, Christiane I. Falkner-Radler, MD, Beatrix Neumaier-Ammerer, MD, Eva Smretschnig, MD, Stefan Hagen, MD, Siamak Ansari-Shahrezaei, MD, Susanne Binder, MD
PURPOSE: To assess the position of intraocular lenses (IOLs) at the end of standard phacoemulsification with intraoperative spectral-domain optical coherence tomography (SD-OCT). SETTINGS: Department of Ophthalmology, Rudolf Foundation Hospital, Vienna, Austria. DESIGN: Prospective case series. METHODS: Standard phacoemulsification with IOL implantation was performed. The Rescan 700 SD-OCT system was used for intraoperative imaging. The anterior segment of the eye was scanned using SD-OCT at the end of the surgery. The distance from the IOL optic center and the IOL optic edge to the posterior capsule was measured postoperatively using graphic software. RESULTS: The study comprised 74 patients (101 eyes). The mean axial length was 23.97 mm (range 21.43 to 28.61 mm). The mean IOL power was 20.39 diopters (D) (range 6.5 to 27.5 D). Contact between the IOL and posterior capsule was absent in 88 cases (87.13%), and partial or full contact was present in 13 cases (12.87%). The mean distance between the IOL central optic and posterior capsule was 0.71 pixel (range 0.06 to 1.38 pixels) in 99 cases (98.02%). In 42 cases (57.53%), partial contact between the IOL edges and the posterior capsule was noticed. The mean distance between the IOL edge and posterior capsule was 0.21 pixel (range 0.04 to 0.92 pixel). CONCLUSIONS: Intraoperative SD-OCT facilitated the imaging of IOL position during standard phacoemulsification. Contact between the IOL central optic and posterior capsule at the end of the surgery occurred rarely. Improved IOL design should be considered. Financial Disclosure: Drs. Binder and Glittenberg are consultants to Carl Zeiss Meditech AG. None of the other authors has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2016; 42:694–702 Q 2016 ASCRS and ESCRS Online Video
The position of the intraocular lens (IOL) after phacoemulsification is essential to reach postoperative emmetropia and optimum visual acuity performance, especially when multifocal, aspheric, or toric IOLs are used. In the majority of cataract surgery cases, IOLs with a standard diameter are implanted regardless of the size of different anatomic structures, such as the capsular bag diameter or axial length (AL), which clearly differ in every patient.1,2,A 694
Q 2016 ASCRS and ESCRS Published by Elsevier Inc.
Posterior capsule opacification (PCO) is 1 of the most common complications of modern cataract surgery with IOL implantation.3,4 Many factors influence the formation of PCO, such as activity of postsurgical inflammation, IOL design, IOL material, technique of implantation, and concomitant ophthalmic or general diseases.5–7 Studies7,8 suggest that IOLs with a squareedged design create the most effective impediment to cell growth behind the IOL optic and prevent early http://dx.doi.org/10.1016/j.jcrs.2016.01.044 0886-3350
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formation of PCO. This concept is supported by the theory that a square edge mechanically slows the migration of lens epithelial cells (LECs) because the edge presses against the posterior capsule. The reduction in the space between the posterior surface of the IOL and the posterior capsule after surgery is considered to play a role in preventing PCO. This idea is supported by the no space, no cells concept.9,10 However, the rate of PCO after cataract surgery is still significant3,4 and it is not clear exactly when firm contact between the IOL edge and the posterior capsule is established. Intraoperative spectral-domain optical coherence tomography (SD-OCT) is a diagnostic technique that, although relatively new, has attained an important place in ophthalmic surgery of the anterior and the posterior segments of the eye.11,B The feasibility of intraoperative SD-OCT in anterior segment surgery has been shown.12–14 This study evaluated the position of the IOL relative to the posterior capsule using intraoperative SD-OCT during standard phacoemulsification by measuring the distance between the IOL and the posterior capsule at different locations. PATIENTS AND METHODS This prospective single-center study was performed at the Ophthalmology Department, Rudolf Foundation Hospital, Vienna, Austria, during a period of 5 months. All patients in the study were diagnosed with senile cataract and scheduled for phacoemulsification with IOL implantation. The
Submitted: October 27, 2015. Final revision submitted: January 4, 2016. Accepted: January 26, 2016. From the Department of Ophthalmology (Lytvynchuk, Glittenberg, Falkner-Radler, Neumaier-Ammerer, Smretschnig, Hagen, AnsariShahrezaei, Binder), Rudolf Foundation Hospital, the Karl Landsteiner Institute for Retinal Research and Imaging (Lytvynchuk, Glittenberg, Falkner-Radler, Neumaier-Ammerer, Smretschnig, Hagen, Ansari-Shahrezaei, Binder), and the Retina Center (AnsariShahrezaei, Binder), Vienna, and the Department of Ophthalmology (Ansari-Shahrezaei), Medical University of Graz, Graz, Austria; the Ophthalmology Department (Lytvynchuk), University Clinic Gießen and Marburg GmbH, Gießen, Germany; the Professor Sergienko Eye Clinic (Lytvynchuk), Vinnytsia, Ukraine. Drs. Lytvynchuk and Glittenberg contributed equally to this work. Supported by the Karl Landsteiner Institute for Retinal Research and Imaging, Vienna, Austria. Presented at the XXXIII Congress of the European Society of Cataract and Refractive Surgeons, Barcelona, Spain, September 2015. Corresponding author: Lyubomyr M. Lytvynchuk, MD, PhD, Karl Landsteiner Institute for Retinal Research and Imaging, Juchgasse 25, A-1030, Vienna, Austria. E-mail: [email protected].
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study was performed according to the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of the city of Vienna, Austria. All patients signed a written informed consent form. Exclusion criteria were pseudoexfoliation syndrome, previous ocular surgery, previous eye trauma, and intraoperative floppy-iris syndrome. Intraocular lens calculation was performed preoperatively using partial coherence interferometry (IOLMaster 500, Carl Zeiss Meditec AG).
Surgical Technique Surgery was performed using topical or general anesthesia by 1 of 5 experienced surgeons (S.B., Ch.F-R., B.N-A., E.S., S.H.). Both eyes had surgery during the same surgical session. Standard phacoemulsification procedures with 2.2 mm self-sealing clear corneolimbal incisions at 11 o’clock and 1 paracentesis at 2 o’clock were performed in all cases. The capsulorhexis was made at least 1.0 mm smaller than the IOL optic (4.5 to 5.0 mm) to cover the edge of the IOL optic (6.0 mm). After capsulorhexis, hydrodissection, phacoemulsification, and cortical material aspiration were performed, a 1-piece foldable hydrophobic IOL was implanted using an IOL delivery system in every case. Thorough removal of the ophthalmic viscoelastic device (OVD) (sodium hyaluronate [Hyalon]) from the posterior surface of the IOL and behind the IOL was performed at the end of each surgery to ensure the absence of barriers that could obstruct contact between the posterior capsule and the IOL. After complete removal of the OVD, regular filling of the anterior chamber with a balanced salt solution using a cannula was performed. During the filling, the push-back maneuver was applied to the IOL surface using the tip of the cannula. Normal intraocular pressure (IOP) values (z20 mm Hg) were maintained and measured with the method described by Hirnschall et al.14 To standardize the height of the bottle, IOP measurements were performed in 5 eyes at the beginning of the study, assuming that an IOP of 20 mm Hg is equal to 2.7 kPa, with a conversion factor of 1.36 from millimeters of mercury to centimeters of water. At the end of the surgery after all incisions were hydrated, an irrigation handpiece was inserted into the paracentesis at 2 o’clock. Then, the bottle height on the phaco machine was adjusted. With the surgeon holding the irrigation handpiece in the paracentesis, the IOP was measured with a Schiotz tonometer (Rudolf Riester GmbH) at every 5 cm increase in the bottle height. In addition, the height of the patient's eye and the bottle was measured. Therefore, it was calculated that for a normal IOP of approximately 20 mm Hg, a distance of 27.5 cm from the patient's eye to the bottle had to be maintained. Standard antibiotic and antiinflammatory therapy was prescribed in the postoperative period.
Intraocular Lenses In this study, eyes had implantation of an Acrysof IQ SN60WF IOL using the Acrysert delivery system (Alcon Laboratories, Inc.) (Group 1) or a Tecnis IOL using the iTec preloaded delivery system (Abbott Medical Optics, Inc.) (Group 2). Both IOLs are 1-piece with a 360-degree squareedge, are hydrophobic acrylic, and have an aspheric design, an optic diameter of 6.0 mm, and an overall length of 13.0 mm. The 360-degree square edge of the latter IOL is designed to provide uninterrupted contact at the haptic– optic junction.
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Intraoperative Spectral-Domain Optical Coherence Tomography Imaging For intraoperative imaging, the first commercially available intraoperative SD-OCT system, Rescan700 (Carl Zeiss Meditec AG), was used; the system is fully integrated in the surgical microscope footstand (Opmi Lumera 700). The intraoperative SD-OCT machine has the following characteristics: OCT engine Z spectral domain, wavelength 840 nm, scanning speed 27 000 A-scans per second, refresh rate (5 Hz to 50 Hz, axial resolution) 5.5 mm in tissue, scan depth 2.0 mm, scan length 6.0 or 9.0 mm, and a crosshair scan mode. Visual control of intraoperative SD-OCT imaging is facilitated through the heads-up display in the right ocular of the microscope. Adjustment and capture of the intraoperative SD-OCT images were performed by the surgeon using the footpedal of the microscope. Each eye was aligned so that the iris and the IOL were situated at a horizontal plane or close to a horizontal plane on the intraoperative SD-OCT image on the screen so that all details of the capsular bag and IOL would be visible. In each case, the following 4 intraoperative SD-OCT crosshair images with a 6.0 or 9.0 mm scan length were taken during the surgery: cornea, anterior surface of the crystalline lens, posterior surface of the crystalline lens, and IOL in
the bag. The cornea and both crystalline lens surfaces were imaged for calibration purposes. Intraoperative SD-OCT imaging of the IOL and posterior capsule was evaluated, and the distances between them were measured. The crosshair intraoperative SD-OCT mode was used to ensure intraoperative SD-OCT scanning of the central area of the IOL optic while simultaneously catching the edge of the optic. This was controlled by the surgeon via the heads-up display. The presence of mydriasis at the end of the surgery was assessed to ensure the visibility of IOL edges. Intraoperative SD-OCT scanning was performed using the video and snapshot modes, focusing on the IOL optic's center, IOL edges, and posterior capsule (Figure 1, A).
Post-Processing and Measurements The intraoperative SD-OCT images were exported and post-processed using ImageJ (version 1.48v).C The intraoperative SD-OCT images captured in cube mode (snapshot) were resized from the raw 512 pixels 1024 pixels (Figure 1, B) to 600 pixels 200 pixels or 900 pixels 200 pixels (depending on cube scan length) (Figure 1, C). This proportion corresponds to the dimensions of the real scan with a 6.0 or 9.0 mm length and 2.0 mm height, resulting in a square pixels
Figure 1. A: Real-time color snapshot taken during intraoperative SD-OCT video streaming. B: Compressed gray-scale intraoperative SD-OCT image of the capture mode. C: Resized gray-scale intraoperative SD-OCT image performed in ImageJ software (OCT Z optical coherence tomography).
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aspect ratio. Because the distances in the intraoperative SD-OCT scans are not calibrated, the measured distances are relative measurements and not absolute measurements. Therefore, all measurements are presented in pixels, not millimeters. Central distance refers to the distance between the central optic area and the posterior capsule. Edge distance refers to the distance between the IOL edge and the posterior capsule. The distances were measured using the “straight line” option in ImageJ, marking the distances with calipers between the IOL center (crosshair-scan guided) and the posterior capsule. Edge distance was derived from the distances measured at 12, 3, 6, and 9 o’clock at the edge, respective to the crosshair scan. All measurements were performed twice. In addition, the presence of contact between the IOL edges and posterior capsule was designated as absence, less than 90 degrees, less than 180 degrees, or over 180 degrees of the IOL optic edge. Contact between the IOL haptic point of origin and the posterior capsule, posterior capsule wrinkling, contact between the anterior capsule and IOL, and the presence of anterior vitreous hyperreflectivity were evaluated in all cases.
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Of the patients, 62 (77 eyes) had surgery under topical anesthesia and 12 (24 eyes) under general anesthesia. Standard phacoemulsification was performed in 88 eyes (87.1%) and combined surgery with pars plana vitrectomy (PPV) in 13 eyes (12.9%). The Acrysof IQ SN60WF IOL was implanted in 59 eyes (58.6%) (Group 1) and the Tecnis IOL in 42 eyes (41.6%) (Group 2). The mean AL was 23.97 mm (range 21.43 to 28.61 mm), and the mean IOL power was 20.39 D (range 6.5 D to 27.5 D), including 15 long eyes with (emmetropic IOL power !18.0 D), 69 normal eyes (emmetropic IOL 18.0 to 23.0 D), and 17 short eyes (emmetropic IOL O23.0 D). Mydriasis of more than 6.0 mm and good visibility of the IOL edge were detected in 73 cases (72.3%). In these cases, intraoperative SD-OCT imaging of 360 degrees of the IOL edge was possible. All surgeries were uneventful. The IOLs were well centered in all cases.
Statistical Analysis Statistical analysis was performed using descriptive statistics, frequency tables, and correlation matrices. The data were analyzed using Statistica 10 software (Statsoft, Inc.). A P value less than 0.05 was considered statistically significant.
RESULTS The total number of phacoemulsification procedures within the 5-month period was 521; 101 eyes of 74 patients met the inclusion criteria and were included in the study. The mean age of the 39 men (38.61%) and 62 women (61.39%) was 71.43 years (range 49 to 91 years).
Intraocular Lens Central Optic to Posterior Capsule Distance (Central Distance) In 99 eyes (98%), a separation between the IOL central optic and the posterior capsule was observed. In 99 cases, the mean central distance was 0.72 pixel (range 0.06 to 1.38 pixels) (Figure 2, A, B, C, D, and E). No contact between the IOL central optic and the posterior capsule was observed in 88 eyes (87.13%), partial contact between the IOL central optic was observed in 11 eyes (10.89%), and full contact was
Figure 2. Case 1. A: Compressed snapshot of the IOL and the posterior capsule. B and C: Resized snapshots of the same case. White arrows show the central distance between the IOL and the posterior capsule. C: Red arrow shows the contact between the IOL edge and the posterior capsule. Yellow arrows point to the hyperreflectivity of the anterior vitreous. Case 2. D: Compressed snapshot of the IOL and the posterior capsule. E and F: Resized snapshots of the same case. White arrows show the central distance and the edge distance between the IOL and posterior capsule. E: Red arrows show the slight upward rolling of the capsulorhexis edge. F: Yellow arrow points to the distal part of the IOL haptic (OCT Z optical coherence tomography; px Z pixels).
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Figure 3. Box-and-whisker plots. A: The mean central distance between the IOL and the posterior capsule. B: The mean edge distance between the IOL and the posterior capsule (px Z pixels).
observed in 2 eyes (1.98%) only (Figure 2) (Video 1, part 1, available at http://jcrsjournal.org). There was a significant correlation between the central distance and the AL. Thus, an increase in the AL led to an increase in the central distance, with a correlation coefficient of 0.213 (P Z .05) (Figure 4, A). In cases with no contact between the IOL central optic and the posterior capsule, the mean AL was 23.65 mm, whereas cases with full or partial contact had a mean AL of 24.00 mm. The correlation between the central distance and the IOL power was also shown to be a reciprocal dependence, meaning that an increase in the IOL power led to a decrease in the central distance, with a correlation coefficient of 0.248 (P Z .05) (Figure 4, B). Although the central distance decreased with an increase in patient age (Figure 4, C), this correlation was not statistically significant. The mean central distance in Group 1 was 0.77 pixel (range 0.06 to 1.38 pixels) and 0.64 pixel (range 0.15 to 1.32 pixels) in Group 2 (Figure 6, A). The central distance difference of 0.13 pixel between the 2 types of IOL was statistically significant (P Z .04). In 13 combined surgery cases (12.9%), 0.2 mL of OVD was injected into the anterior chamber immediately after phacoemulsification and before PPV to
prevent sudden anterior chamber shallowing during manipulation of the eye. Repeated intraoperative SDOCT imaging of the posterior chamber performed after the OVD injection showed full contact between the posterior capsule and posterior IOL surface (Figure 7, B). This resulted from simple downward depression of the IOL by the OVD. After the PPV was complete and the OVD was washed out, intraoperative SD-OCT showed restoration of the IOL position away from the posterior capsule. Intraocular Lens Edge to Posterior Capsule Distance (Edge Distance) In 73 eyes (72.3%), 360 degrees of the IOL edges were visible at the end of the surgery. The mean edge distance was 0.21 pixel (range 0.04 to 0.92 pixel) (Figures 2, C and F, and 3, B). In 31 eyes (42.47%), there was no contact between the IOL edges and the posterior capsule. In 42 eyes (57.53%), partial contact between the IOL edges and the posterior capsule was noticed (Video 1, part 2, available at http://jcrsjournal.org). Contact between the IOL edge and the posterior capsule over 180 degrees was observed in 29 eyes (69.05%), less than 180 degrees in 11 eyes (26.19%), and less than 90 degrees in 2 eyes (4.76%) (Figure 2, C).
Figure 4. Correlation between edge distance and AL (A), IOL power (B), and age (C) (Conf. Int. Z confidence interval; IOL Z intraocular lens; px Z pixels). J CATARACT REFRACT SURG - VOL 42, MAY 2016
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Figure 5. Correlation between the central distance and AL (A), IOL power (B), and age (C) (Conf. Int. Z confidence interval; IOL Z intraocular lens; px Z pixels).
Correlations between the edge distance and the AL, IOL power, and age were not statistically significant (Figure 5, A to C), and no dependence was found. The mean edge distance was 0.28 pixel (range 0.04 to 0.92 pixel) in Group 1 and 0.23 pixel (range 0.05 to 0.53 pixel) in Group 2 (Figure 6, B). The difference in the edge distance between the 2 types of IOLs was 0.04 pixel and was not statistically significant. Contact between the IOL haptic point of origin and the posterior capsule was detected in 35 eyes (34.65%). Contact was detected in 20 eyes (57.14%) in Group 1 and in 15 eyes (42.86%) in Group 2. Posterior Capsule Wrinkling, Anterior Vitreous Hyperreflectivity, Anterior Capsule to Intraocular Lens Contact Wrinkling of the posterior capsule, a marker of reduced capsular bag volume after phacoemulsification that might be correlated with supportive properties of the anterior vitreous, was observed in 63 eyes (62.38%) and absent in 38 eyes (37.62%). The location of the wrinkling was in the projection of the IOL optic center in 54 eyes (85.71%) and in the projection of the IOL optic periphery in 9 eyes (14.29%) (Figure 1, C). Intraoperative SD-OCT imaging showed linear hyperreflectivity from the anterior vitreous behind the
posterior capsule in 20 cases (19.8%) (Figures 1, B, and 2, C). The mean age of these patients was 69.8 years (range 53 to 81 years). In 81 cases (80.2%), there were no signs of hyperreflectivity from the anterior vitreous on intraoperative SD-OCT scans. The mean age of these patients was 71.8 years (range 49 to 91 years). In 66 eyes (90.4%), there was no contact between the IOL and anterior capsule with slight upward rolling of the capsulorhexis edge (Figures 1, B, and 2, E). There was contact between the anterior surface of the IOL optic and anterior capsule capsulorhexis margin in 7 (9.6%) of 73 eyes, with 360-degree visibility of the IOL edges and a mydriatic pupil larger than 6.0 mm. DISCUSSION Posterior capsule opacification is the main problem after standard phacoemulsification. The complication is strongly connected to IOL design and posterior capsule reaction. To our knowledge, this is the first study of IOL positioning relative to the capsular bag at the end of a standard phacoemulsification assessed using intraoperative SD-OCT. Our data show no contact between the IOL central optic and posterior capsule (central distance) in 87.13% of cases (88 eyes), while partial or full contact appeared in only 12.87% of cases (13 eyes). In 57.53% of cases
Figure 6. Box-and-whisker plots of the central distance (A) and edge distance (B) between the 2 IOL groups (px Z pixels).
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Figure 7. Contact between the IOL and posterior capsule during combined surgery was achieved by injection of OVD after IOL implantation to stabilize the anterior chamber during PPV.
(42 eyes), partial contact between the IOL edge and posterior capsule was noticed. Using intraoperative OCT, Hirnschall et al.14 studied the distance between the corneal endothelium and the anterior capsule before phacoemulsification and after capsular tension ring (CTR) implantation to improve the prediction of the postoperative IOL position. The authors used a CTR to tighten the lens capsule and stabilize the IOL position. They found that the intraoperative OCT measurement of the anterior lens capsule, with the presence of a CTR, served as a better predictor of postoperative IOL position than preoperative factors. Because the primary goal of our study was to analyze IOL position in uncomplicated cases in which a CTR was not used, we performed routine phacoemulsification only. Although, we saw no contact between the IOL central optic and posterior capsule in 87.13% of cases (88 eyes), we did find a significant difference in the central distance between the 2 types of IOLs. In our study, both IOLs that were implanted have a square-edged design. They have a similar design except that the Tecnis IOL has a 3-point fixation on the posterior surface. This can explain why the mean distance between the IOL central optic and posterior capsule in eyes with the Tecnis IOL was less than that in eyes with the Acrysof IQ IOL, with a difference of 0.13 pixel (P Z .04). There was a significant correlation between the central distance and the AL (P Z .05). Our results suggest that the IOL design has to be adapted to the AL and other parameters of ocular structures. The IOL haptic plays a major role in supporting the IOL's position in the capsular bag. Visualization of the IOL haptic was performed by Mostafavi et al.15 postoperatively to show the exact position of the IOL using ultrasound biomicroscopy in cases complicated by uveitis–glaucoma–hyphema syndrome. This study determined the cause of the complications and treated them using IOL repositioning or removal. In our study, intraoperative SD-OCT imaging of the
proximal part of the IOL haptic only was achievable. This necessitated proper IOL centration and a mydriatic pupil (O6.0 mm). Another important finding was the linear hyperreflectivity of the anterior vitreous in 19.8% of cases (20 eyes). This hyperreflectivity of vitreous can correspond to the margin of Berger space and the beginning of the anterior vitreous, which was probably not noticed in the remaining cases because of the insufficient intraoperative SD-OCT scan depth. The condition of the vitreous gel, especially regarding the grade of its liquefaction with age, and hydration during the surgery might also play a role in the position of the posterior capsule after phacoemulsification.16 Contact between the anterior capsule and IOL predisposes the eye to anterior subcapsular opacification with a risk for anterior capsule fibrosis and phimosis.17 In our study, 90.4% of cases (91 eyes) had no contact between the anterior capsule and the IOL at the end of phacoemulsification. The unfavorable contact between the anterior capsule and the IOL as well as favorable contact between the posterior capsule and the IOL probably appear in the postoperative period. In combined surgery cases, with the use of OVD after IOL implantation to stabilize the anterior chamber, we can achieve contact between the IOL and the posterior capsule (Video 1, part 3, available at http:// jcrsjournal.org). This contact, however, is temporary and disappears after OVD washout. In addition, the injection of OVD at the end of uneventful phacoemulsification is not a standard surgical step. Intraocular pressure at the end of phacoemulsification varies in every patient. The depth of the anterior chamber and hydration of the vitreous is dependent on the hydration technique of paracentesis and main entrance and is difficult to standardize in every case. In our study, we applied a method to gain nearly equal IOP at the end of each surgery, as described by Hirnschall et al.14 Intraoperative SD-OCT of the anterior segment with the Rescan 700 system is limited by the 2.0 mm scan
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depth. Therefore, only intraoperative SD-OCT imaging of a certain depth of the anterior and posterior segments is possible. In this study, we focused on the posterior chamber to capture the anterior capsule, the IOL, the posterior capsule, and the anterior vitreous. Another limitation of this study was that the intraoperative SD-OCT scanning beam is blocked by the iris, which is why the distal part of the IOL haptic was not seen. During post-processing and measurements performed with ImageJ,C the distances we obtained were not absolute, but relative. Distance measurements are relevant, and their expression in millimeters would be incorrect because the manufacturer has not calibrated absolute distances in the Rescan 700 system. That is why we presented the data in pixels. Resizing intraoperative SD-OCT scans from 512 pixels 1024 pixels (standard image size from Rescan 700) to 600 pixels 200 pixels or 900 pixels 200 pixels was optimum because this size corresponds to the dimensions of the real-time intraoperative SD-OCT scans, which are equal to 6.0 mm 2.0 mm or 9.0 mm 2.0 mm (6000 mm 2000 mm or 9000 mm 2000 mm). Axial length, age, and individual variations can determine the size of the capsular bag and crystalline lens.1,2 The diameter of the natural crystalline lens differs in every patient and is also dependent on the patient's age.18 Discrepancies between the size of the standard implanted IOL and variable capsular bag size can lead to a refractive error, IOL displacement, or IOL tilt in the postoperative period. The distance between the IOL and the posterior capsule could also depend on other factors, including AL, the condition of the vitreous and zonular fibers, elasticity of posterior capsule, size of the capsular bag, IOL dimensions and design, and surgical technique. Wesendahl et al.19 have shown in cadaver eyes that only IOLs with a bent-forward haptic design of more than 10 degrees can make contact with the posterior capsule and the IOL optic and that haptic diameter has limited influence. The incomplete contact between the IOL edges and the posterior capsule in our study can cause IOL instability within the capsular bag and LEC migration in the early postoperative period. This can lead to postoperative IOL decentration, IOL tilting, and PCO, with a further effect on the correlation between visual acuity and anterior chamber structures. The IOLs used in this study had the same optic dimensions and overall length. It is possible that a larger optic diameter would have facilitated better contact between the IOL edge and the posterior capsule. Future iterations of intraoperative OCT systems using new OCT engines (eg, swept source) would improve the visualization of the anterior and posterior segments of the eye.20
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In conclusion, intraoperative SD-OCT facilitated the visualization of the IOL position because it obtained substantial hyperreflectivity from the IOL, the capsular bag, and the anterior vitreous. Contact between the IOL central optic and central posterior capsule was rare, probably because the volume of the lens capsule is larger than volume of the IOL. The contact between the IOL's square edge and the posterior capsule was only partial in 57.53% of eyes. New IOL designs that support and improve intraoperative contact between the IOL and the posterior capsule have to be developed. WHAT WAS KNOWN Contact between an IOL’s square edge and the posterior capsule slows the migration of LECs because of mechanical pressing of the edge against the posterior capsule. The prevention of PCO is also supported by the no space, no cells concept. Posterior capsule opacification remains 1 of the major complications after phacoemulsification with IOL implantation. WHAT THIS PAPER ADDS Full contact between the hydrophobic IOL’s central optic and the central posterior capsule at the end of standard phacoemulsification was rare. New IOL designs to improve immediate contact between the IOL and the posterior capsule at the end of surgery should be developed.
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First author: Lyubomyr M. Lytvynchuk, MD, PhD Department of Ophthalmology, Karl Landsteiner Institute for Retinal Research and Imaging, Vienna, Austria