Incidence and influence of posterior capsule striae on the development of posterior capsule opacification after 1-piece hydrophobic acrylic intraocular lens implantation

ARTICLE

Incidence and influence of posterior capsule striae on the development of posterior capsule opacification after 1-piece hydrophobic acrylic intraocular lens implantation Gauri D. Shah, MS, Abhay R. Vasavada, MS, FRCS, Mamidipudi R. Praveen, DOMS, MS, Alpesh R. Shah, MS, Rupal H. Trivedi, MD, MSCR

PURPOSE: To determine the incidence of intraoperative posterior capsule striae after implantation of a 1-piece hydrophobic acrylic intraocular lens (IOL), study the clinical impact on the patients’ vision, and assess whether the presence of posterior capsule striae increases the risk for posterior capsule opacification (PCO). SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. DESIGN: Case-control study. METHODS: Part 1 of this study evaluated consecutive adult eyes having cataract surgery performed using standardized techniques with in-the-bag 1-piece hydrophobic acrylic IOL implantation. Posterior capsule striae details were noted at the end of surgery. Part 2 was a case-control study comprising all patients with intraoperative striae and an age- and biometry-matched control group without striae, which was selected on a 1:1 ratio. RESULTS: Intraoperative posterior capsule striae were observed in 68 (13.6%) of 500 eyes. A single stria was seen in 43 eyes [63.2%], and multiple striae were seen in 25 eyes [36.7%]). There was no significant difference in logMAR corrected distance visual acuity at baseline (PZ.881) or at 3 years (PZ.191) between cases and controls. At 3 years, there was no statistically significant betweengroup difference in the median Evaluation of Posterior Capsule Opacification score or area values in the capsulorhexis margin (PZ.36 and PZ.39, respectively) or in the central 3.0 mm optic area (PZ.40 and PZ.42, respectively). CONCLUSION: The incidence of posterior capsule striae was 13.6%. Intraoperative striae did not influence visual acuity or the development of PCO at the 3-year follow-up. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2012; 38:202–207 Q 2011 ASCRS and ESCRS

Intraoperative posterior capsule striae appear as undulations or folds on the axis joining the apices of the haptics of the intraocular lens (IOL).1 Posterior capsule striae are observed after IOL implantation in the capsular bag during cataract surgery. Experimental studies2–5 have attempted to determine how IOL implantation in the capsular bag influences the development of posterior capsule striae. The posterior video–photographic technique pioneered by Miyake and Miyake6 and later modified and modernized by Apple et al.7 gave us greater insight into the possible mechanisms of the formation of folds or striae in the 202

Q 2011 ASCRS and ESCRS Published by Elsevier Inc.

posterior capsule. It has been hypothesized that the striae are the result of a disparity between the size of the IOL and the size of the capsular bag.2–4 Furthermore, there are reports of the occurrence of posterior capsule opacification (PCO) in eyes in which capsule striae develop after implantation of a 3-piece hydrophobic acrylic IOL.8 In an earlier study of 100 consecutive patients having age-related cataract surgery,9 we found a 56% incidence of posterior capsule striae after implantation of a 3-piece hydrophobic acrylic IOL. In a prospective randomized clinical trial,10 capsule folds were found 0886-3350/$ - see front matter doi:10.1016/j.jcrs.2011.07.038

POSTERIOR CAPSULE STRIAE AND PCO AFTER 1-PIECE IOL IMPLANTATION

behind the IOL optic area in eyes that had implantation of a 1-piece Acrysof IOL (Alcon Laboratories, Inc.). To date, there has been a paucity of peer-reviewed literature on the incidence and clinical course of intraoperative posterior capsule striae after implantation of a 1-piece acrylic hydrophobic IOL. We set out to determine whether the incidence of posterior capsule striae with 1-piece acrylic hydrophobic IOLs is different than that reported with 3-piece hydrophobic acrylic IOLs. We also assessed whether the presence of posterior capsule striae increases the risk for PCO. PATIENTS AND METHODS This study was performed at Iladevi Cataract and IOL Research Center between January 2005 and December 2007. Patients with uncomplicated age-related cataract who had phacoemulsification were evaluated in a prospective observational standardized manner. The eye having surgery first was selected for analysis. An institutional review board approved the study. All patients enrolled in the study provided informed consent. Following were the exclusion criteria: glaucoma, pseudoexfoliation, traumatic cataract, subluxated cataract, previous ocular surgery, allergy to dilating drops, prophylactic laser photocoagulation, cryo treatment, and intraoperative complications (eg, anterior capsule tear, posterior capsule rupture). The study was performed in 2 parts. Part 1 evaluated consecutive eyes of adults having cataract surgery using a standardized technique with in-the-bag implantation of an Acrysof SA60AT 1-piece hydrophobic acrylic IOL. Details on posterior capsule striae (presence or absence; if present, number) were noted at the end of surgery. Part 2 was a case-control study in which cases and controls were selected from the original cohort in part 1. The cohort was divided into 2 groups based on whether the patient had intraoperative posterior capsule striae after IOL implantation (cases) or no posterior capsule striae (controls).

Surgical Technique The same surgeon (A.R.V.) performed all the operations using the Infiniti Vision System (Alcon Laboratories, Inc.) and a standardized technique, which has been described.11

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The 1-piece hydrophobic acrylic IOL was implanted in the capsular bag. Subsequently, bimanual irrigation/aspiration was performed to remove the residual ophthalmic viscosurgical device. The presence of posterior capsule striae was noted at the end of the surgery. Stromal hydration was performed on the 2 paracenteses and the main incision. The eye was closed after 0.1 mL of intracameral vancomycin 0.1% was injected into the anterior chamber.

Outcome Measures and Postoperative Assessment The main outcome measures were the incidence and clinical course of posterior capsule striae, the clinical impact of posterior capsule striae on the patient’s vision, and the influence of posterior capsule striae on the development of PCO at 3 years. Based on the previously described methodology,9,12 the Maddox rod test for visual phenomenon was performed at the 1-month follow-up visit. First, the eye with striae was covered. Then, with the patient wearing corrected visual acuity glasses, a Maddox rod was placed in front of the eye without striae. The patient was asked to look at a single source of light in a dark room. Next, the eye without striae was covered and the eye with striae was tested.9,12 Postoperatively at 1 month (baseline) and at 3 years, images were acquired using a previously described methodology.13 The digital images were used to assess the morphology of posterior capsule striae. The morphology was categorized as (1) single, in which a single fold covering the entire optic area on the posterior capsule was observed; (2) multiple, in which 2 or more folds covering the entire optic area were observed; (3) in the optic area, in which the striae were confined to the optic area; (4) beyond the optic area, in which the striae extended beyond the optic area. The digital images were further evaluated for the presence of PCO using Evaluation of Posterior Capsule Opacification (EPCO) 2000 software.14 The PCO was evaluated in the entire IOL optic and in the central 3.0 mm optic zone. The boundaries of the posterior capsule and of each opaque area of the posterior capsule were drawn on the stored images. The density of opacification was clinically graded as 0 (none), 1 (minimal), 2 (mild), 3 (moderate), or 4 (severe). Individual PCO values (PCO index) were calculated for each image by multiplying the density of opacification by the fraction of the capsule area involved behind the IOL optic and the central 3.0 mm optic zone. The result was interpreted in terms of the EPCO score and the EPCO area.

Statistical Analysis

Submitted: March 8, 2011. Final revision submitted: July 20, 2011. Accepted: July 22, 2011. From Iladevi Cataract & IOL Research Center (G.D. Shah, Vasavada, Praveen, A.R. Shah), Raghudeep Eye Clinic, Memnagar, Ahmedabad, India, and the Storm Eye Institute (Trivedi), Medical University of South Carolina, Charleston, South Carolina, USA. Supported in part by an unrestricted grant to the Medical University of South Carolina-Storm Eye Institute from Research to Prevent Blindness, Inc., New York, New York, USA (Dr. Trivedi). Corresponding author: Abhay R. Vasavada, MS, FRCS, Iladevi Cataract & IOL Research Center, Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad–380052, India. E-mail: icirc@ abhayvasavada.com.

The Kolmogorov-Smirnov test was used to test for normality. However, the data were not normally distributed; thus, nonparametric tests were used. The Mann-Whitney U test was used to compare the EPCO scores and EPCO area in the capsulorhexis margin and in the central 3.0 mm margin between cases and controls.

RESULTS The study population enrolled 500 consecutive eyes of 500 patients. Of these eyes, 68 (13.6%) had intraoperative posterior capsule striae. In all 68 eyes, the IOL was geometrically centered intraoperatively and the striae were perpendicular to the optic–haptic junction. The capsulorhexis totally covered the IOL optic in 64

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Figure 1. Postoperative images of posterior capsule with (a) single striae, (b) multiple striae, (c) striae in the capsulorhexis margin, and (d) striae extending beyond the capsulorhexis margin after 1-piece hydrophobic acrylic IOL implantation in the capsular bag.

eyes with striae and partially covered the IOL optic in 4 eyes. A single stria was found in 43 eyes (63.2%), and multiple striae were found in 25 eyes (36.8%) (Figure 1, a and b). In 48 eyes (70.6%), the striae remained confined to the IOL optic, while in 20 eyes (29.4%) they extended beyond the optic margin (Figure 1, c and d). No eye had intraoperative posterior capsule plaque or residual lens fibers. None of the striae had resolved by the end of the 3-year follow-up. None of the patients with striae tested positive for Maddox rod phenomenon. There was no significant difference in logMAR corrected distance visual acuity at baseline (PZ.881) or 3 years (PZ.191) between cases and controls (Table 1). There was no significant difference in patient age (PZ.49), axial length (PZ.98), anterior chamber depth

(PZ.28), or lens thickness (PZ.99) between 68 cases with intraoperative posterior capsule striae and 68 controls without intraoperative posterior capsule striae. At the baseline (within 1 month after surgery), there was no significant difference in the median EPCO score (PZ.34) or median EPCO area (PZ.34) in the capsulorhexis margin between cases and controls (Table 2). There were also no statistically significant differences between the 2 groups at 3 years (PZ.36 and PZ.39, respectively) (Table 2 and Figure 2). Three years postoperatively, there was no statistically significant difference in the mean EPCO score or mean EPCO area values in the central 3.0 mm optic area between cases and controls (PZ.40 and PZ.42, respectively) (Table 3). No eye in any group had a neodymium:YAG laser capsulotomy.

Table 1. Comparison of logMAR CDVA between cases and controls at baseline and 3 years. LogMAR CDVA Baseline Value Mean G SD Minimum Maximum P value

At 3 Years

Cases (n Z 68)

Controls (n Z 68)

Cases (n Z 68)

Controls (n Z 68)

0.07 G 0.10 0.000 0.300

0.08 G 0.10 0.000 0.480

0.13 G 0.20 0.000 0.600

0.09 G 0.11 0.000 0.480

.881

CDVA Z corrected distance visual acuity

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.191

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Table 2. Median EPCO score and EPCO area in the capsulorhexis area at baseline and 3 years. Median Parameter EPCO score Baseline At 3 years EPCO area Baseline At 3 years

Cases

Controls

P Value

0.100 0.400

0.100 0.700

.34 .36

0.100 0.400

0.100 0.700

.34 .39

EPCO Z Evaluation of Posterior Capsule Opacification

DISCUSSION Posterior capsule striae can develop intraoperatively or postoperatively.2–5,8,9 It has been well documented in experimental studies2–5 that small IOLs have unstable fixation because of an inadequate arc of contact between the haptics and the capsular bag, while a large IOL can cause posterior capsule folds. One can determine whether an IOL is a good fit by the absence of intraoperative posterior capsule striae. The presence of posterior capsule striae means that the capsular bag is distorted.2–5 If the striae have more than 2 folds and extend outside the optic, there is a greater disparity between the IOL size and the capsular bag size.3,15 To date, few detailed experimental studies of the dimensions of anterior segment structures have been

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published.16,17 There are reports of experimental trials evaluating the influence of 1-piece hydrophobic acrylic IOLs on the development of posterior capsule striae.4,5 However, in a clinical scenario, not much attention has been given to whether 1-piece hydrophobic acrylic IOLs influence the development of posterior capsule striae or on the long-term consequences of posterior capsule striae on postoperative PCO. In the present study, the incidence of intraoperative posterior capsule striae was 13.6%. We believe that the lower incidence of posterior capsule striae than that reported for the 3-piece IOL design (56%) is likely the result of the optic–haptic design of the 1-piece IOL.9 The memory and flexibility of the hydrophobic acrylic biomaterial allows the haptics of the 1-piece design to bend back on themselves and to twist and contort to a much greater degree. Hence, these modified L-shaped bulky haptics stretch the capsular bag more evenly along the entire circumference, which is probably not the case with the 3-piece design, which has thinner haptics.18 The 1-piece Acrysof IOL has a planar design. Thus, there is no optic–haptic angulation. It has been suggested that this IOL design does not exert excessive traction on the capsular bag. It was clearly observed in a study that the 1-piece hydrophobic acrylic IOL was associated with significantly less capsulorhexis ovaling and capsular bag stretch.4 Experimental studies of pediatric human cadaver eyes and adult eyes4,5 found the capsular bag configuration was well maintained with little ovaling.

Figure 2. Comparative evaluation of postoperative images of PCO between eyes with striae (a and b) and eyes without striae (c and d) 1 month and 3 years after 1-piece hydrophobic acrylic IOL implantation in the capsular bag.

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Table 3. Median EPCO score and EPCO area in the central 3.0 mm optic area at 3 years. Median Parameter

Cases

Controls

P Value

EPCO score EPCO area

0.100 0.100

0.300 0.200

.42 .40

EPCO Z Evaluation of Posterior Capsule Opacification

Moreover, posterior capsule folds were not observed in any eye after implantation of a 1-piece hydrophobic acrylic IOL using the Miyake-Apple technique. We attribute this to the small-sized optic of the hydrophobic acrylic AcrySof SA30AL IOL implanted in the capsular bag in both studies. Furthermore, in the same studies, the authors suggest that acrylic biomaterial may play a role in reducing the extent of capsulorhexis and capsular bag distortion. In the present study, all the eyes developed striae in the meridian perpendicular to the IOL optic–haptic junction. Similar results were reported in a previous study of the 3-piece hydrophobic acrylic IOL.9 In the present study, there was no statistically significant difference in the development of PCO between cases and controls. A few studies of eyes with posterior capsule striae also did a follow-up assessment of PCO. A study of 3-piece hydrophobic acrylic IOLs8 found linear PCO along the circumference of the optic with linear posterior extension along the previous striae. The authors suggest that persistent posterior capsule striae create a gap between the IOL edge and the capsule interface, providing a channel for epithelial cells to migrate centrally beyond the block of the square optic edge, forming linear PCO.9 Furthermore, they found striae generally traversing the center of the IOL involving the central visual axis; this pattern of linear PCO may be visually significant for the patient. The importance of this observation is that it offers support for the theory that a sharp lens edge design serves as a barrier to epithelial cell migration. Conceptually, striae provide a channel around the IOL edge barrier that facilitates limited posterior linear migration of epithelial cells. Another study of 1-piece hydrophobic acrylic IOLs10 found a dynamic correlation between PCO values (in the entire IOL optic area and in the central optic zone) and capsule folds behind the IOL optic area 6 months after surgery. However, in the present study, there were no cases in which PCO developed from the posterior capsule striae. We attribute this to the IOL design. In 1-piece IOLs, the fusion of the anterior capsule and posterior capsule is more asymmetric, with the bulk of the haptics interfering with capsular

bend formation. Therefore, PCO is more likely to enter behind the optic from the optic–haptic junction and not from the striae. However, with the 3-piece design, the fusion of the anterior capsule and posterior capsule is more symmetric throughout the circumference of the bag and the haptics do not pose a significant barrier to capsular bend formation. Therefore, the formation of striae creates a channel for lens epithelial cells to travel toward the center of the optic. Furthermore, Nishi and Nishi19 found in a rabbit model that the bulky haptics of the 1-piece Acrysof IOL hampered adhesion between the anterior capsule and the posterior capsule and thus hindered capsular bend formation. A study by Vasavada and Trivedi9 found that eyes with a 3-piece hydrophobic acrylic IOL did not have posterior capsule striae 5 months postoperatively. The authors speculate that over time, the haptic configuration will remodel, resulting in a bag size that causes the posterior capsule striae to disappear. In the present study, none of the striae disappeared, even by 3 years postoperatively. We speculate that the bulky haptics of the 1-piece design may not mold easily and do not conform to the shape of the capsular bag, causing the striae to persist postoperatively. There have been reports that posterior capsule striae might induce visual symptoms, such as glare and Maddox rod phenomena.20 However, in the present study, no patient reported visual symptoms or tested positive for Maddox rod phenomenon. It has been hypothesized that the Maddox rod phenomenon occurs because the eye is not able to focus the rays that pass through the cylinder in the same planes in which they are refracted but only in a plane that is perpendicular to that plane and in which the cylinder does not have a refracting effect.21 In our previous study,9 eyes with the 3-piece hydrophobic acrylic IOL and striae did not have a positive Maddox rod phenomenon. Our current study has limitations. In contrast to our previous study, we did not compare age, AL, and lens thickness in eyes that developed posterior capsule striae versus eyes that did not develop posterior capsule striae. That is because for us to assess the impact of posterior capsule striae on PCO, it was important for patients to have comparable age, ALs, ACDs, and lens thicknesses and to use standardized surgical techniques for in-the-bag IOL fixation and postoperative medication. Thus, we cannot comment on whether age, AL, or lens thickness was associated with an increased incidence of striae. In conclusion, in this prospective observational case-control study, the incidence of posterior capsule striae was relatively low (13.6%). Furthermore, visual symptoms related to the striae were not reported and the capsule striae did not act as a channel for the

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development of PCO in adult eyes having phacoemulsification with IOL implantation. REFERENCES 1. Richter CU, Steinert RF. Neodymium:yttrium-aluminium-garnet laser posterior capsulotomy. In: Steinert RF, ed, Cataract Surgery: Technique, Complications & Management. Philadelphia, PA, WB Saunders, 1995; 378–388 2. Werner L, Hickman MS, LeBoyer RM, Mamalis N. Experimental evaluation of the Corneal Concept 360 intraocular lens with the Miyake-Apple view. J Cataract Refract Surg 2005; 31: 1231–1237 3. Assia EI, Legler UFC, Apple DJ. The capsular bag after shortand long-term fixation of intraocular lenses. Ophthalmology 1995; 102:1151–1157 4. Pandey SK, Werner L, Wilson ME Jr, Izak AM, Apple DJ. Capsulorhexis ovaling and capsular bag stretch after rigid and foldable intraocular lens implantation; experimental study in pediatric human eyes. J Cataract Refract Surg 2004; 30:2183–2191 5. Izak AM, Werner L, Pandey SK, Apple DJ. Pathological evaluation of postmortem human eyes implanted with a new single-piece hydrophobic acrylic lens. J Cataract Refract Surg 2004; 30:1537–1544 6. Miyake K, Miyake C. Intraoperative posterior chamber lens haptic fixation in the human cadaver eye. Ophthalmic Surg 1985; 16:230–236 7. Apple DJ, Lim ES, Morgan RC, Tsai JC, Gwin TD, Brown SJ, Carlson AN. Preparation and study of human eyes obtained postmortem with the Miyake posterior photographic technique. Ophthalmology 1990; 97:810–816 8. Wolken MA, Oetting TA. Linear posterior capsule opacification with the AcrySof intraocular lens. J Cataract Refract Surg 2001; 27:1889–1891 9. Vasavada AR, Trivedi RH. Posterior capsule striae. J Cataract Refract Surg 1999; 25:1527–1531 10. Zemaitiene R, Jasinskas V, Auffarth GU. Influence of three-piece and single-piece designs of two sharp-edge optic hydrophobic acrylic intraocular lenses on the prevention of posterior capsule opacification: a prospective, randomized, long-term clinical trial. Br J Ophthalmol 2007; 91:644–648. Available at: http://www. ncbi.nlm.nih.gov/pmc/articles/PMC1954737/pdf/644.pdf. Accessed August 24, 2011

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First author: Gauri D. Shah, MS Iladevi Cataract & IOL Research Center, Raghudeep Eye Clinic, Memnagar, Ahmedabad, India