- Email: [email protected]
Vaulting of Myopic and Toric Implantable Collamer Lenses during Accommodation Measured with Visante Optical Coherence Tomography
Vaulting of Myopic and Toric Implantable Collamer Lenses during Accommodation Measured with Visante Optical Coherence Tomography Are Lindland, MD,1 Hilde Heger, MD,1 Maria Kugelberg, MD, PhD,2 Charlotta Zetterström, MD, PhD1 Purpose: To study changes in vaulting of myopic and toric Implantable Collamer Lenses (ICLs) version 4 during accommodation with Visante optical coherence tomography (OCT), and analyze the relationship between vaulting and anterior subcapsular opacification. Design: Cross-sectional study. Participants: Seventy-seven eyes of 77 myopic patients were examined after implantation with an ICL (48 myopic, 29 toric). The median follow-up time was 63 months (range, 10 – 84). Methods: The distance between the posterior ICL surface and the anterior surface of the crystalline lens was measured in the nonaccommodative state and during accommodation with Visante OCT. The lenses were examined for opacification using slit-lamp microscopy. Main Outcome Measures: The distance between the ICL and the anterior surface of the crystalline lens. Results: At baseline, the mean distance between the ICL and the crystalline lens was 0.31⫾0.19 mm and during accommodation 0.31⫾0.26 mm; the difference did not reach significance (P ⫽ 0.77). The distance at baseline was significantly (P ⫽ 0.01) less in older patients and significantly (P ⫽ 0.04) greater in patients with a toric ICL. Contact was observed at baseline or during accommodation in 12 eyes; there was a significantly lower incidence of contact in eyes implanted with a toric ICL (P ⫽ 0.03). Anterior subcapsular opacification developed in 10 eyes, in 5 of these the ICL touched the crystalline lens. Conclusions: Anterior subcapsular opacification developed in 13.0% of eyes. We found no difference in vaulting of the ICL at baseline and during accommodation. There was contact between the ICL and the crystalline lens in 15.6% of the eyes. The association between anterior subcapsular opacification and contact was significant (P ⫽ 0.004). Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article. Ophthalmology 2010;117:1245–1250 © 2010 by the American Academy of Ophthalmology.
Implantation of a posterior chamber phakic intraocular lens (PC PIOL) is an alternative way to correct high refractive errors in patients who are not candidates for corneal laser surgery.1 The Implantable Collamer Lens (ICL; Staar Surgical Co., Monrovia, CA) is a PC PIOL approved for correcting myopia or hyperopia. A toric ICL is awaiting approval by the US Food and Drug Administration (FDA). The main concern with the ICL is the development of lens opacification.2-5 Contact between the ICL and the crystalline lens is considered a potential cause of opacification,6,7 and the current model, version 4, was designed with a higher vault. With increasing patient age, there is increasing protrusion of the anterior pole of the crystalline lens,8 a possible reason for the shorter distance to the ICL. However, there is forward movement of the anterior pole of the crystalline lens during accommodation,8,9 and increased zonular tension also develops with accommodation;10 accommodative trauma might be a cause of cataract in patients with PC PIOLs.11 © 2010 by the American Academy of Ophthalmology Published by Elsevier Inc.
Earlier studies have evaluated the distance between the ICL and the crystalline lens using ultrasound biomicroscopy12 or Scheimpflug photography.6 New anterior chamber optical coherence tomography (OCT) provides high-resolution, crosssectional images of the anterior segment.13 It is possible to obtain scans in the nonaccommodative state and during accommodation by defocusing an optical target with stepwise introduction of negative lenses to the scanned eye. The current study determines the incidence of contact between myopic and toric ICLs and the crystalline lens in the nonaccommodative and accommodative states using Visante OCT (Carl Zeiss Meditec, Dublin, CA). The relationship between contact and anterior subcapsular opacification also was analyzed.
Patients and Methods Study Design Seventy-seven eyes of 77 patients (46 women, 31 men) implanted with the ICL (model version 4) for myopia were included in this ISSN 0161-6420/10/$–see front matter doi:10.1016/j.ophtha.2009.10.033
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Table 1. Patient Data Parameter
Myopic ICL
Toric ICL
Software calculates the distance between 2 points, angles, and radius of curvature (Fig 1). P Value
No. of patients 48 29 Gender Female 30 (62%) 16 (55%) Male 18 (38%) 13 (45%) Age (yrs) Mean 36.0 34.6 0.47 Range 19.0–52.0 25.0–48.0 Mean power Spherical ⫺9.1 (⫺24.3 to ⫺4.3) ⫺8.5 (⫺17.5 to ⫺3.5) 0.45 Cylindrical ⫺0.6 (⫺1.5 to 0.0) ⫺2.5 (⫺4.8 to ⫺1.0) ⬍0.01 Median follow-up 65 (11–84) 60 (10–76) 0.01 time, mos (range) ICL ⫽ Implantable Collamer lens.
study; 48 eyes were implanted with the myopic ICL and 29 with the toric ICL. The mean patient age at the time of surgery was 35.5 years. The mean preoperative spherical equivalent was ⫺9.5⫾3.4 (range, ⫺24.9 to ⫺4.5) diopters (D). A summary of the toric and the myopic ICL data is shown in Table 1. All implantations were performed from February 2001 to May 2007 at the Department of Ophthalmology, Rikshospitalet, and the Department of Ophthalmology, Ullevål University Hospital, both in Oslo, Norway. One eye of each patient was examined using Visante OCT. The changes in distance between the ICL and the adjacent intraocular structures were measured in the nonaccommodative (baseline) and accommodative states. The lenses were examined for opacification using slit-lamp microscopy. In this cross-sectional study, the examinations were done only once, with a follow-up time of 63 months (range, 10 – 84), 65 months (range, 11– 84) for myopic ICLs and 60 months (range, 10 –76) for the toric ICLs. The local ethics committee approved the study protocol. The study followed the tenets of the Declaration of Helsinki. The participants provided written informed consent.
Operative Procedure Two neodymium:YAG laser iridotomies at the 10 and 2 o’clock positions were created 2 weeks before surgery. The surgery was done under cycloplegia using topical anesthesia or combined with a periocular injection. An ophthalmic viscosurgical device (Amvisc, sodium hyaluronate 1.6% [Bausch & Lomb] or VisThesia light sodium hyaluronate 1.0%/lidocaine 1.0% [Hyaltech Ltd., Edinburgh, Scotland]) was instilled into the anterior chamber, and the ICL was inserted with an injector (Staar Surgical Co.) through a 3.2-mm clear corneal incision. The haptics were placed behind the iris using a lens manipulator. After verification of the correct ICL position, acetylcholine chloride (Miochol, Novartis Pharma Stein AG, Stein, Switzerland) was injected. After gentle irrigation with balanced salt solution, 1 mg of cefuroxime sodium (Zinacef, Baxter Healthcare Corporation, Deerfield, IL) was injected into the anterior chamber.14 The wound was closed by stromal hydration. Postoperatively, topical dexamethasone (Spersadex, Novartis) was applied 5 times daily for 1 week then 3 times daily for 2 weeks.
Outcome Measures The preoperative best-corrected visual acuity (BCVA) was assessed using a Snellen acuity chart. Postoperatively, the uncorrected visual acuity and BCVA were measured using the Early Treatment in Diabetic Retinopathy Study chart. The focus of the optical target internal to Visante OCT was adjusted with positive or negative lenses to achieve emmetropia before scanning. The target then was defocused with negative lenses in increments of 0.25 D to induce physiologic accommodation during scanning. The eye was defined as fully accommodated when the target no longer could be focused clearly. The subjective amplitude of accommodation was noted. The lens was examined for lens opacification by slit-lamp microscopy 30 minutes after application of topical tropicamide.
Statistical Analysis Implantable Collamer Lenses The 1-piece ICL is a PC PIOL made of Collamer, a hydrophilic material composed of collagen and a poly-hydroxyethyl methacrylate-based copolymer. The lens, which is 6.5 mm wide and 11.5 to 13.0 mm long, is available in powers ranging from –3.0 to ⫺23.0 D for myopic patients. A toric lens that is awaiting approval by the FDA is available in Europe in spherical powers ranging from –3.0 to –23.0 D and astigmatic correction of 1 to 6 D. The lens size was calculated by the manufacturer according to the horizontal white-to-white measurement obtained with corneal topography (Orbscan II, Bausch & Lomb, Rochester, NY).
Snellen visual acuity was converted to logarithm of the minimum angle of resolution (logMAR) values for statistical analysis. Linear regression analysis, logistic regression, Student’s t test, or matched pairs t test was conducted after verifying the normal distribution of data. The Mann-Whitney U test was used for not normally distributed data. The Fischer exact test was used for categorical data. P⬍0.05 was considered significant.
Results Visual Acuity
Visante Optical Coherence Tomography Anterior chamber OCT is a noninvasive, noncontact optical technique based on low-coherence interferometry. It uses 1310-nm wavelength infrared light to provide high-resolution, cross-sectional images of the anterior segment.13 With the Visante OCT, the anterior segment can be visualized in horizontal, vertical, or oblique scans. The location of the PC PIOL in relation to the crystalline lens can be visualized.11 Patients focus on a fixation target internal to the Visante OCT while scanning. This target can be defocused with negative or positive lenses to obtain scans in the nonaccommodative and accommodative states.
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The mean uncorrected visual acuity was 0.19⫾0.31 logMAR postoperatively. The mean BCVA was 0.06⫾0.20 logMAR preoperatively and ⫺0.04⫾0.18 logMAR postoperatively. The difference between the preoperative and postoperative BCVA values was significant (P⬍0.00001).
Vaulting of the Implantable Collamer Lens at Baseline and during Accommodation During accommodation, the distance between the posterior corneal surface and the anterior ICL surface decreased with 0.17⫾0.15
Lindland et al 䡠 ICL and Visante OCT
Figure 1. Visante optical coherence tomography shows the changes in vaulting during different stages of accommodation (Acc) in an eye implanted with an Implantable Collamer Lens. There is decreased vaulting during accommodation from baseline to 3 diopters (D) of accommodation. There is an increased central vaulting from 3 to 6 D.
mm, and anterior chamber depth (ACD) with 0.17⫾0.11 mm. At baseline, the mean distance between the posterior ICL surface and the anterior surface of the crystalline lens was 0.31⫾0.19 mm. During accommodation, the mean distance was 0.31⫾0.26 mm. There was no significant difference in the distance at baseline and during accommodation (P ⫽ 0.77). During accommodation, the distance increased in 33 patients (43%), decreased in 37 patients (48%), and was unchanged in 7 patients (9%). We found no obvious decentration or tilt of the ICL in the nonaccommodative state, but in accommodation, minor tilts were observed in 2 patients. Contact between the ICL and the crystalline lens was observed in 12 eyes (15.6%); in these 12 eyes, there was contact only during accommodation in seven eyes (9.1%), both at baseline and during accommodation in 4 eyes (5.2%), and only at baseline in 1 eye (1.3%). Contact was found centrally, except in 1 eye where it was paracentrally found. We observed a higher vault at baseline with toric ICLs (0.36⫾0.18 mm) than with myopic ICLs (0.27⫾0.19); the difference reached significance (P ⫽ 0.04). The vault of the toric ICLs also was higher during full accommodation (P ⫽ 0.03; Table 2).
There was no significant difference in the vault at baseline or during accommodation in either the toric (P ⫽ 0.78) or the myopic group (P ⫽ 0.20; Fig 2). Contact was seen in 1 eye (3.4%) with a toric ICL, and in 11 eyes (22.9%) with a myopic ICL; the difference between the 2 lenses reached significance (P ⫽ 0.03).
Correlation between Patient Age and Vaulting The mean patient age at surgery was 35.5⫾7.9. Figure 3 shows the relationship of the distance between the ICL and the crystalline Table 2. Difference (mm) in Vaulting between Myopic and Toric Implantable Collamer Lens (ICL) ICL Myopic Toric P value
No. Patients
Distance Baseline
Distance Accommodation
48 29
0.27 ⫾ 0.19 0.36 ⫾ 0.18 0.04
0.26 ⫾ 0.25 0.39 ⫾ 0.25 0.03
P Value 0.78 0.20
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Figure 2. Box-whisker plot of the distance between the myopic Implantable Collamer Lens (ICL) and the toric ICL with the anterior lens surface (ALS) in the nonaccommodative state (baseline) and fully accommodated state (accommodation).
lens at baseline and patient age. This distance was significantly lower in older patients (P ⫽ 0.01). We found no significant correlation between anterior subcapsular opacification and age (P ⫽ 0.99) or between anterior subcapsular opacification and ACD (P ⫽ 0.49).
Change in Pupil Diameter during Accommodation In eyes with myopic ICLs, the horizontal diameter of the pupil was 5.2⫾0.9 at baseline and 3.9⫾1.1 in accommodation. In eyes with toric ICLs, the pupil diameter was 4.9⫾1.1 at baseline and 3.9⫾1.1 in accommodation. The difference in pupil size between myopic and toric ICLs did not reach significance, either at baseline (P ⫽ 0.12) or in accommodation (P ⫽ 0.9). The pupil size decreased in all eyes during accommodation.
Anterior Subcapsular Opacification and Relation with Vaulting of the Implantable Collamer Lens In 1 patient, anterior subcapsular opacification was seen on the first postoperative day. At the time of our examination, we found anterior subcapsular opacification in another 9 eyes (Fig 4), 3 of which were implanted with a toric ICL. There was no significant
Figure 3. A scatterplot shows the distance between the Implantable Collamer Lens (ICL) and the anterior lens surface (ALS) relative to age.
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difference in the incidence of opacification between the toric and the myopic ICLs (P ⫽ 1.00). There was no decrease in BCVA compared with the preoperative BCVA. Of the 9 patients with opacification, the ICL touched the crystalline lens in 5 eyes (3 at baseline, 2 during accommodation). The association between contact between the crystalline lens and the ICL and cataract formation was significant (P ⫽ 0.004; Table 3).
Discussion In the current study, there was no difference in the distance between the posterior ICL surface and the anterior surface of the crystalline lens at baseline and during accommodation. This is in contrast with a recent study which reported preserved vaulting with the phakic refractive lens (PRL; Medennium Inc., Irvine, CA) 100 model during accommodation,15 which might be explained by the fact that the PRL rests on the zonules and floats on the crystalline lens,
Figure 4. Anterior subcapsular opacification in an eye implanted with an Implantable Collamer Lens.
Lindland et al 䡠 ICL and Visante OCT Table 3. Correlation between Opacification and Contact between the Implantable Collamer Lens and the Crystalline Lens*
Opacification Absence of opacification Total
Contact
No Contact
Total
5 7 12
4 61 65
9 68 77
*P ⫽ 0.004.
whereas the ICL haptics are supposed to rest in the ciliary sulcus.16 However, both the PRL 101 and the PRL 200 had decreased vaulting during accommodation, which probably results from the increased weight and the larger size.15 In a previous study of 16 patients implanted with the PRL, both haptics were on the zonules in only 6 eyes; in the other 10 eyes, the haptics were in the ciliary sulcus, the ciliary body, or in mixed positions. That study postulated that a PRL that is too large probably will be placed in the sulcus and will not float.17 An OCT study of accommodation in an albino patient found that the horizontal diameter of the ciliary sulcus decreased by about 900 m for 10 D of accommodation.18 The PRL is made of a relatively inflexible material silicone, and it is likely that a PRL in the ciliary sulcus will vault less during accommodation compared to a ICL, which is made of the more adaptive material Collamer. In the current study, we observed anterior subcapsular opacification on the first postoperative day in 1 eye (1.3%). The United States FDA Clinical Trial of the ICL found presumably surgically induced anterior subcapsular opacities in 2.7% of cases.19 The only case of surgically induced opacification in the current study did not change during follow-up, and there was no contact between the ICL and the crystalline lens 6 years later. Intraoperative difficulties developed in 3 of the current patients; however, there was no opacification in those eyes. No other operative complications developed. In addition to the previously described lens change in 1 eye, we identified 9 eyes with anterior subcapsular opacification; the ICLs in 5 eyes were in contact with the crystalline lens. These eyes had been followed for ⱖ3 months postoperatively without such changes. A previous study of 76 eyes of 46 patients found no correlation between ICL vaulting and lens opacification. However, the distance between the ICL and the crystalline lens was evaluated using an optical depth-measuring device (Jaeger II, Haag-Streit, Bern, Switzerland), and the examination was not performed during accommodation.4 We found that 4 eyes had opacification without contact between the lenses and the crystalline lens. We assume that surgical trauma did not induce these lens changes because no changes were seen during ⱖ3 months of follow-up. Despite the fact that the mean central vaulting at baseline and during full accommodation was not particularly low, it is possible that opacification developed because of contact under other circumstances. Petternel et al20 found significantly reduced vaulting under photopic conditions in 13 eyes implanted with the ICL version 3 or 4. The current Visante OCT examinations were conducted in dim light, and we would
probably have found lower mean vaulting if the examination had been conducted in bright light with smaller pupils. The causes of lens changes other than intraoperative trauma and central contact have been postulated to include subclinical inflammation12 and changes in aqueous humor circulation.21 In 2 of the eyes in which the ICL was touching the crystalline lens at baseline, no lens changes developed. This finding is difficult to explain. It is possible that the contact between the ICL and the crystalline lens occurred recently. In this cross-sectional study, we found a positive correlation between contact and opacification. In a prospective study with statistical power of 80%, and equal number of patients in each group, a total of 38 patients (n1 ⫽ 19 with opacification, n2 ⫽ 19 without opacification) would be necessary to find a similar correlation. There are 2 commercially available PC PIOLs, the ICL and the PRL. A lower incidence of induced opacification is reported with the latter.16,22 Reduced incidence of contact with the crystalline lens owing to floating of the PRL could be an explanation for this. However, there has been some concern with the PRL after some reports of luxation of the PRL into the vitreous cavity.23 We found a correlation between age and vaulting at baseline, with lower vaulting in older patients. Similar findings have previously been reported with both PRLs and ICLs,15,24 probably owing to the thicker crystalline lens in older patients. With aging, there is decreased ACD and protrusion of the anterior pole of the crystalline lens.8,9 Low vaulting of the ICL may be a major risk factor for anterior subcapsular opacification,6,7 and studies also have reported an increased incident of opacification in older patients implanted with an ICL.4,6,25 However, we found no correlation between anterior subcapsular opacification and age or between anterior subcapsular opacification and the ACD. We expect that a greater number of included patients maybe could have revealed such a correlation. We found higher vaulting at baseline and a lower incidence of contact between the crystalline lens and the ICL in eyes implanted with a toric ICL compared with eyes implanted with a myopic ICL. The sizing of the 2 lenses was calculated in the same way, and there were no differences in spherical power or patient age. The haptic design was similar in both ICLs,26 but the addition of cylinder to the optical zone of the toric ICLs may have contributed to the difference in the initial vaulting in the current study. One study found that myopic ICLs behave differently than toric ICLs during accommodation, and the authors postulated that toric ICLs are less flexible.24 However, we found that the change in vaulting during accommodation did not differ between the 2 lenses. We expected to find a lower incidence of opacification in toric lenses owing to significantly higher vaulting at baseline, and we observed that the toric ICL was in contact with the crystalline lens in only 1 eye. However, there was no difference in the incidence of opacification between the toric and the myopic ICLs. Such a difference could perhaps have been found with a higher number of included patients, which is in accordance with the US FDA Clinical Trial of the toric ICL, which found anterior subcapsular opacification in 2.9% 1 year postoperatively26 compared with 2.7% in the US FDA Clinical Trial of the myopic ICL.27 In conclusion, the distance between the ICL and the crystalline lens at baseline was significantly lower in older
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patients. We found no difference in vaulting of the ICL at baseline and during accommodation. Toric ICLs had significantly higher vaulting at baseline. We found anterior subcapsular opacification in 10 eyes (13.0%), and in 5 of these the ICL was in contact with the crystalline lens. Contact was seen at baseline or during accommodation in 12 eyes (15.6%). The association between anterior subcapsular opacification and contact is significant.
13. 14.
15.
References 1. Koivula A, Petrelius A, Zetterstrom C. Clinical outcomes of phakic refractive lens in myopic and hyperopic eyes: 1-year results. J Cataract Refract Surg 2005;31:1145–52. 2. Assetto V, Benedetti S, Pesando P. Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg 1996;22:551– 6. 3. Gonvers M, Othenin-Girard P, Bornet C, Sickenberg M. Implantable contact lens for moderate to high myopia: short-term follow-up of 2 models. J Cataract Refract Surg 2001;27:380–8. 4. Lackner B, Pieh S, Schmidinger G, et al. Long-term results of implantation of phakic posterior chamber intraocular lenses. J Cataract Refract Surg 2004;30:2269 –76. 5. Menezo JL, Peris-Martinez C, Cisneros A, Martinez-Costa R. Posterior chamber phakic intraocular lenses to correct high myopia: a comparative study between Staar and Adatomed models. J Refract Surg 2001;17:32– 42. 6. Gonvers M, Bornet C, Othenin-Girard P. Implantable contact lens for moderate to high myopia: relationship of vaulting to cataract formation. J Cataract Refract Surg 2003;29:918 –24. 7. Zaldivar R, Oscherow S, Ricur G. The STAAR posterior chamber phakic intraocular lens. Int Ophthalmol Clin 2000; 40:237– 44. 8. Baikoff G, Lutun E, Ferraz C, Wei J. Static and dynamic analysis of the anterior segment with optical coherence tomography. J Cataract Refract Surg 2004;30:1843–50. 9. Koretz JF, Cook CA, Kaufman PL. Accommodation and presbyopia in the human eye: changes in the anterior segment and crystalline lens with focus. Invest Ophthalmol Vis Sci 1997;38:569 –78. 10. Schachar RA, Koivula A. The stress on the anterior lens surface during human in vivo accommodation. Br J Ophthalmol 2008;92:348 –50. 11. Baikoff G, Lutun E, Wei J, Ferraz C. Contact between 3 phakic intraocular lens models and the crystalline lens: an anterior chamber optical coherence tomography study. J Cataract Refract Surg 2004;30:2007–12. 12. Jimenez-Alfaro I, Benitez del Castillo JM, Garcia-Feijoo J, et al. Safety of posterior chamber phakic intraocular lenses for the correction of high myopia: anterior segment changes after
16. 17.
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20. 21. 22. 23. 24.
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posterior chamber phakic intraocular lens implantation. Ophthalmology 2001;108:90 –9. Radhakrishnan S, Rollins AM, Roth JE, et al. Real-time optical coherence tomography of the anterior segment at 1310 nm. Arch Ophthalmol 2001;119:1179 – 85. Barry P, Seal DV, Gettinby G, et al, ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: preliminary report of principal results from a European multicenter study. J Cataract Refract Surg 2006;32:407–10. Koivula A, Kugelberg M. Optical coherence tomography of the anterior segment in eyes with phakic refractive lenses. Ophthalmology 2007;114:2031–7. Koivula A, Taube M, Zetterstrom C. Phakic refractive lens: two-year results. J Refract Surg 2008;24:507–15. Garcia-Feijoo J, Hernandez-Matamoros JL, Mendez-Hernandez C, et al. Ultrasound biomicroscopy of silicone posterior chamber phakic intraocular lens for myopia. J Cataract Refract Surg 2003; 29:1932–9. Baikoff G, Lutun E, Wei J, Ferraz C. Anterior chamber optical coherence tomography study of human natural accommodation in a 19-year-old albino. J Cataract Refract Surg 2004;30:696–701. ICL in Treatment of Myopia (ITM) Study Group. United States Food and Drug Administration clinical trial of the Implantable Collamer Lens (ICL) for moderate to high myopia: three-year followup. Ophthalmology 2004;111:1683–92. Petternel V, Koppl CM, Dejaco-Ruhswurm I, et al. Effect of accommodation and pupil size on the movement of a posterior chamber lens in the phakic eye. Ophthalmology 2004;111:325–31. Shiratani T, Shimizu K, Fujisawa K, et al. Crystalline lens changes in porcine eyes with implanted phakic IOL (ICL) with a central hole. Graefes Arch Clin Exp Ophthalmol 2008;246:719–28. Pallikaris IG, Kalyvianaki MI, Kymionis GD, Panagopoulou SI. Phakic refractive lens implantation in high myopic patients: one-year results. J Cataract Refract Surg 2004;30:1190–7. Eleftheriadis H, Amoros S, Bilbao R, Teijeiro MA. Spontaneous dislocation of a phakic refractive lens into the vitreous cavity. J Cataract Refract Surg 2004;30:2013– 6. Lege BA, Haigis W, Neuhann TF, Bauer MH. Age-related behavior of posterior chamber lenses in myopic phakic eyes during accommodation measured by anterior segment partial coherence interferometry. J Cataract Refract Surg 2006;32:999–1006. Sarikkola AU, Sen HN, Uusitalo RJ, Laatikainen L. Traumatic cataract and other adverse events with the implantable contact lens. J Cataract Refract Surg 2005;31:511–24. Sanders DR, Schneider D, Martin R, et al. Toric Implantable Collamer Lens for moderate to high myopic astigmatism. Ophthalmology 2007;114:54 – 61. Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. U.S. Food and Drug Administration clinical trial of the Implantable Contact Lens for moderate to high myopia. Ophthalmology 2003;110:255– 66.
Footnotes and Financial Disclosures Originally received: April 19, 2009. Final revision: September 8, 2009. Accepted: October 14, 2009. Available online: February 16, 2010.
and Refractive Surgeons, September 2008, Berlin, Germany; and the American Society of Cataract and Refractive Surgery annual meeting, April 2009, San Francisco, California. Manuscript no. 2009-541.
2
Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
Presented at: XXXVIII Nordic Congress of Ophthalmology, June 2008, Tromsø, Norway; the XXVI Congress of the European Society of Cataract
Correspondence: Are Lindland, MD, Department of Ophthalmology, University of Oslo, 0407 Oslo, Norway. E-mail: [email protected].
1
Department of Ophthalmology, University of Oslo, Norway.
St. Erik’s Eye Hospital, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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Implantation of a posterior chamber phakic intraocular lens (PC PIOL) is an alternative way to correct high refractive errors in patients who are not candidates for corneal laser surgery.1 The Implantable Collamer Lens (ICL; Staar Surgical Co., Monrovia, CA) is a PC PIOL approved for correcting myopia or hyperopia. A toric ICL is awaiting approval by the US Food and Drug Administration (FDA). The main concern with the ICL is the development of lens opacification.2-5 Contact between the ICL and the crystalline lens is considered a potential cause of opacification,6,7 and the current model, version 4, was designed with a higher vault. With increasing patient age, there is increasing protrusion of the anterior pole of the crystalline lens,8 a possible reason for the shorter distance to the ICL. However, there is forward movement of the anterior pole of the crystalline lens during accommodation,8,9 and increased zonular tension also develops with accommodation;10 accommodative trauma might be a cause of cataract in patients with PC PIOLs.11 © 2010 by the American Academy of Ophthalmology Published by Elsevier Inc.
Earlier studies have evaluated the distance between the ICL and the crystalline lens using ultrasound biomicroscopy12 or Scheimpflug photography.6 New anterior chamber optical coherence tomography (OCT) provides high-resolution, crosssectional images of the anterior segment.13 It is possible to obtain scans in the nonaccommodative state and during accommodation by defocusing an optical target with stepwise introduction of negative lenses to the scanned eye. The current study determines the incidence of contact between myopic and toric ICLs and the crystalline lens in the nonaccommodative and accommodative states using Visante OCT (Carl Zeiss Meditec, Dublin, CA). The relationship between contact and anterior subcapsular opacification also was analyzed.
Patients and Methods Study Design Seventy-seven eyes of 77 patients (46 women, 31 men) implanted with the ICL (model version 4) for myopia were included in this ISSN 0161-6420/10/$–see front matter doi:10.1016/j.ophtha.2009.10.033
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Table 1. Patient Data Parameter
Myopic ICL
Toric ICL
Software calculates the distance between 2 points, angles, and radius of curvature (Fig 1). P Value
No. of patients 48 29 Gender Female 30 (62%) 16 (55%) Male 18 (38%) 13 (45%) Age (yrs) Mean 36.0 34.6 0.47 Range 19.0–52.0 25.0–48.0 Mean power Spherical ⫺9.1 (⫺24.3 to ⫺4.3) ⫺8.5 (⫺17.5 to ⫺3.5) 0.45 Cylindrical ⫺0.6 (⫺1.5 to 0.0) ⫺2.5 (⫺4.8 to ⫺1.0) ⬍0.01 Median follow-up 65 (11–84) 60 (10–76) 0.01 time, mos (range) ICL ⫽ Implantable Collamer lens.
study; 48 eyes were implanted with the myopic ICL and 29 with the toric ICL. The mean patient age at the time of surgery was 35.5 years. The mean preoperative spherical equivalent was ⫺9.5⫾3.4 (range, ⫺24.9 to ⫺4.5) diopters (D). A summary of the toric and the myopic ICL data is shown in Table 1. All implantations were performed from February 2001 to May 2007 at the Department of Ophthalmology, Rikshospitalet, and the Department of Ophthalmology, Ullevål University Hospital, both in Oslo, Norway. One eye of each patient was examined using Visante OCT. The changes in distance between the ICL and the adjacent intraocular structures were measured in the nonaccommodative (baseline) and accommodative states. The lenses were examined for opacification using slit-lamp microscopy. In this cross-sectional study, the examinations were done only once, with a follow-up time of 63 months (range, 10 – 84), 65 months (range, 11– 84) for myopic ICLs and 60 months (range, 10 –76) for the toric ICLs. The local ethics committee approved the study protocol. The study followed the tenets of the Declaration of Helsinki. The participants provided written informed consent.
Operative Procedure Two neodymium:YAG laser iridotomies at the 10 and 2 o’clock positions were created 2 weeks before surgery. The surgery was done under cycloplegia using topical anesthesia or combined with a periocular injection. An ophthalmic viscosurgical device (Amvisc, sodium hyaluronate 1.6% [Bausch & Lomb] or VisThesia light sodium hyaluronate 1.0%/lidocaine 1.0% [Hyaltech Ltd., Edinburgh, Scotland]) was instilled into the anterior chamber, and the ICL was inserted with an injector (Staar Surgical Co.) through a 3.2-mm clear corneal incision. The haptics were placed behind the iris using a lens manipulator. After verification of the correct ICL position, acetylcholine chloride (Miochol, Novartis Pharma Stein AG, Stein, Switzerland) was injected. After gentle irrigation with balanced salt solution, 1 mg of cefuroxime sodium (Zinacef, Baxter Healthcare Corporation, Deerfield, IL) was injected into the anterior chamber.14 The wound was closed by stromal hydration. Postoperatively, topical dexamethasone (Spersadex, Novartis) was applied 5 times daily for 1 week then 3 times daily for 2 weeks.
Outcome Measures The preoperative best-corrected visual acuity (BCVA) was assessed using a Snellen acuity chart. Postoperatively, the uncorrected visual acuity and BCVA were measured using the Early Treatment in Diabetic Retinopathy Study chart. The focus of the optical target internal to Visante OCT was adjusted with positive or negative lenses to achieve emmetropia before scanning. The target then was defocused with negative lenses in increments of 0.25 D to induce physiologic accommodation during scanning. The eye was defined as fully accommodated when the target no longer could be focused clearly. The subjective amplitude of accommodation was noted. The lens was examined for lens opacification by slit-lamp microscopy 30 minutes after application of topical tropicamide.
Statistical Analysis Implantable Collamer Lenses The 1-piece ICL is a PC PIOL made of Collamer, a hydrophilic material composed of collagen and a poly-hydroxyethyl methacrylate-based copolymer. The lens, which is 6.5 mm wide and 11.5 to 13.0 mm long, is available in powers ranging from –3.0 to ⫺23.0 D for myopic patients. A toric lens that is awaiting approval by the FDA is available in Europe in spherical powers ranging from –3.0 to –23.0 D and astigmatic correction of 1 to 6 D. The lens size was calculated by the manufacturer according to the horizontal white-to-white measurement obtained with corneal topography (Orbscan II, Bausch & Lomb, Rochester, NY).
Snellen visual acuity was converted to logarithm of the minimum angle of resolution (logMAR) values for statistical analysis. Linear regression analysis, logistic regression, Student’s t test, or matched pairs t test was conducted after verifying the normal distribution of data. The Mann-Whitney U test was used for not normally distributed data. The Fischer exact test was used for categorical data. P⬍0.05 was considered significant.
Results Visual Acuity
Visante Optical Coherence Tomography Anterior chamber OCT is a noninvasive, noncontact optical technique based on low-coherence interferometry. It uses 1310-nm wavelength infrared light to provide high-resolution, cross-sectional images of the anterior segment.13 With the Visante OCT, the anterior segment can be visualized in horizontal, vertical, or oblique scans. The location of the PC PIOL in relation to the crystalline lens can be visualized.11 Patients focus on a fixation target internal to the Visante OCT while scanning. This target can be defocused with negative or positive lenses to obtain scans in the nonaccommodative and accommodative states.
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The mean uncorrected visual acuity was 0.19⫾0.31 logMAR postoperatively. The mean BCVA was 0.06⫾0.20 logMAR preoperatively and ⫺0.04⫾0.18 logMAR postoperatively. The difference between the preoperative and postoperative BCVA values was significant (P⬍0.00001).
Vaulting of the Implantable Collamer Lens at Baseline and during Accommodation During accommodation, the distance between the posterior corneal surface and the anterior ICL surface decreased with 0.17⫾0.15
Lindland et al 䡠 ICL and Visante OCT
Figure 1. Visante optical coherence tomography shows the changes in vaulting during different stages of accommodation (Acc) in an eye implanted with an Implantable Collamer Lens. There is decreased vaulting during accommodation from baseline to 3 diopters (D) of accommodation. There is an increased central vaulting from 3 to 6 D.
mm, and anterior chamber depth (ACD) with 0.17⫾0.11 mm. At baseline, the mean distance between the posterior ICL surface and the anterior surface of the crystalline lens was 0.31⫾0.19 mm. During accommodation, the mean distance was 0.31⫾0.26 mm. There was no significant difference in the distance at baseline and during accommodation (P ⫽ 0.77). During accommodation, the distance increased in 33 patients (43%), decreased in 37 patients (48%), and was unchanged in 7 patients (9%). We found no obvious decentration or tilt of the ICL in the nonaccommodative state, but in accommodation, minor tilts were observed in 2 patients. Contact between the ICL and the crystalline lens was observed in 12 eyes (15.6%); in these 12 eyes, there was contact only during accommodation in seven eyes (9.1%), both at baseline and during accommodation in 4 eyes (5.2%), and only at baseline in 1 eye (1.3%). Contact was found centrally, except in 1 eye where it was paracentrally found. We observed a higher vault at baseline with toric ICLs (0.36⫾0.18 mm) than with myopic ICLs (0.27⫾0.19); the difference reached significance (P ⫽ 0.04). The vault of the toric ICLs also was higher during full accommodation (P ⫽ 0.03; Table 2).
There was no significant difference in the vault at baseline or during accommodation in either the toric (P ⫽ 0.78) or the myopic group (P ⫽ 0.20; Fig 2). Contact was seen in 1 eye (3.4%) with a toric ICL, and in 11 eyes (22.9%) with a myopic ICL; the difference between the 2 lenses reached significance (P ⫽ 0.03).
Correlation between Patient Age and Vaulting The mean patient age at surgery was 35.5⫾7.9. Figure 3 shows the relationship of the distance between the ICL and the crystalline Table 2. Difference (mm) in Vaulting between Myopic and Toric Implantable Collamer Lens (ICL) ICL Myopic Toric P value
No. Patients
Distance Baseline
Distance Accommodation
48 29
0.27 ⫾ 0.19 0.36 ⫾ 0.18 0.04
0.26 ⫾ 0.25 0.39 ⫾ 0.25 0.03
P Value 0.78 0.20
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Figure 2. Box-whisker plot of the distance between the myopic Implantable Collamer Lens (ICL) and the toric ICL with the anterior lens surface (ALS) in the nonaccommodative state (baseline) and fully accommodated state (accommodation).
lens at baseline and patient age. This distance was significantly lower in older patients (P ⫽ 0.01). We found no significant correlation between anterior subcapsular opacification and age (P ⫽ 0.99) or between anterior subcapsular opacification and ACD (P ⫽ 0.49).
Change in Pupil Diameter during Accommodation In eyes with myopic ICLs, the horizontal diameter of the pupil was 5.2⫾0.9 at baseline and 3.9⫾1.1 in accommodation. In eyes with toric ICLs, the pupil diameter was 4.9⫾1.1 at baseline and 3.9⫾1.1 in accommodation. The difference in pupil size between myopic and toric ICLs did not reach significance, either at baseline (P ⫽ 0.12) or in accommodation (P ⫽ 0.9). The pupil size decreased in all eyes during accommodation.
Anterior Subcapsular Opacification and Relation with Vaulting of the Implantable Collamer Lens In 1 patient, anterior subcapsular opacification was seen on the first postoperative day. At the time of our examination, we found anterior subcapsular opacification in another 9 eyes (Fig 4), 3 of which were implanted with a toric ICL. There was no significant
Figure 3. A scatterplot shows the distance between the Implantable Collamer Lens (ICL) and the anterior lens surface (ALS) relative to age.
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difference in the incidence of opacification between the toric and the myopic ICLs (P ⫽ 1.00). There was no decrease in BCVA compared with the preoperative BCVA. Of the 9 patients with opacification, the ICL touched the crystalline lens in 5 eyes (3 at baseline, 2 during accommodation). The association between contact between the crystalline lens and the ICL and cataract formation was significant (P ⫽ 0.004; Table 3).
Discussion In the current study, there was no difference in the distance between the posterior ICL surface and the anterior surface of the crystalline lens at baseline and during accommodation. This is in contrast with a recent study which reported preserved vaulting with the phakic refractive lens (PRL; Medennium Inc., Irvine, CA) 100 model during accommodation,15 which might be explained by the fact that the PRL rests on the zonules and floats on the crystalline lens,
Figure 4. Anterior subcapsular opacification in an eye implanted with an Implantable Collamer Lens.
Lindland et al 䡠 ICL and Visante OCT Table 3. Correlation between Opacification and Contact between the Implantable Collamer Lens and the Crystalline Lens*
Opacification Absence of opacification Total
Contact
No Contact
Total
5 7 12
4 61 65
9 68 77
*P ⫽ 0.004.
whereas the ICL haptics are supposed to rest in the ciliary sulcus.16 However, both the PRL 101 and the PRL 200 had decreased vaulting during accommodation, which probably results from the increased weight and the larger size.15 In a previous study of 16 patients implanted with the PRL, both haptics were on the zonules in only 6 eyes; in the other 10 eyes, the haptics were in the ciliary sulcus, the ciliary body, or in mixed positions. That study postulated that a PRL that is too large probably will be placed in the sulcus and will not float.17 An OCT study of accommodation in an albino patient found that the horizontal diameter of the ciliary sulcus decreased by about 900 m for 10 D of accommodation.18 The PRL is made of a relatively inflexible material silicone, and it is likely that a PRL in the ciliary sulcus will vault less during accommodation compared to a ICL, which is made of the more adaptive material Collamer. In the current study, we observed anterior subcapsular opacification on the first postoperative day in 1 eye (1.3%). The United States FDA Clinical Trial of the ICL found presumably surgically induced anterior subcapsular opacities in 2.7% of cases.19 The only case of surgically induced opacification in the current study did not change during follow-up, and there was no contact between the ICL and the crystalline lens 6 years later. Intraoperative difficulties developed in 3 of the current patients; however, there was no opacification in those eyes. No other operative complications developed. In addition to the previously described lens change in 1 eye, we identified 9 eyes with anterior subcapsular opacification; the ICLs in 5 eyes were in contact with the crystalline lens. These eyes had been followed for ⱖ3 months postoperatively without such changes. A previous study of 76 eyes of 46 patients found no correlation between ICL vaulting and lens opacification. However, the distance between the ICL and the crystalline lens was evaluated using an optical depth-measuring device (Jaeger II, Haag-Streit, Bern, Switzerland), and the examination was not performed during accommodation.4 We found that 4 eyes had opacification without contact between the lenses and the crystalline lens. We assume that surgical trauma did not induce these lens changes because no changes were seen during ⱖ3 months of follow-up. Despite the fact that the mean central vaulting at baseline and during full accommodation was not particularly low, it is possible that opacification developed because of contact under other circumstances. Petternel et al20 found significantly reduced vaulting under photopic conditions in 13 eyes implanted with the ICL version 3 or 4. The current Visante OCT examinations were conducted in dim light, and we would
probably have found lower mean vaulting if the examination had been conducted in bright light with smaller pupils. The causes of lens changes other than intraoperative trauma and central contact have been postulated to include subclinical inflammation12 and changes in aqueous humor circulation.21 In 2 of the eyes in which the ICL was touching the crystalline lens at baseline, no lens changes developed. This finding is difficult to explain. It is possible that the contact between the ICL and the crystalline lens occurred recently. In this cross-sectional study, we found a positive correlation between contact and opacification. In a prospective study with statistical power of 80%, and equal number of patients in each group, a total of 38 patients (n1 ⫽ 19 with opacification, n2 ⫽ 19 without opacification) would be necessary to find a similar correlation. There are 2 commercially available PC PIOLs, the ICL and the PRL. A lower incidence of induced opacification is reported with the latter.16,22 Reduced incidence of contact with the crystalline lens owing to floating of the PRL could be an explanation for this. However, there has been some concern with the PRL after some reports of luxation of the PRL into the vitreous cavity.23 We found a correlation between age and vaulting at baseline, with lower vaulting in older patients. Similar findings have previously been reported with both PRLs and ICLs,15,24 probably owing to the thicker crystalline lens in older patients. With aging, there is decreased ACD and protrusion of the anterior pole of the crystalline lens.8,9 Low vaulting of the ICL may be a major risk factor for anterior subcapsular opacification,6,7 and studies also have reported an increased incident of opacification in older patients implanted with an ICL.4,6,25 However, we found no correlation between anterior subcapsular opacification and age or between anterior subcapsular opacification and the ACD. We expect that a greater number of included patients maybe could have revealed such a correlation. We found higher vaulting at baseline and a lower incidence of contact between the crystalline lens and the ICL in eyes implanted with a toric ICL compared with eyes implanted with a myopic ICL. The sizing of the 2 lenses was calculated in the same way, and there were no differences in spherical power or patient age. The haptic design was similar in both ICLs,26 but the addition of cylinder to the optical zone of the toric ICLs may have contributed to the difference in the initial vaulting in the current study. One study found that myopic ICLs behave differently than toric ICLs during accommodation, and the authors postulated that toric ICLs are less flexible.24 However, we found that the change in vaulting during accommodation did not differ between the 2 lenses. We expected to find a lower incidence of opacification in toric lenses owing to significantly higher vaulting at baseline, and we observed that the toric ICL was in contact with the crystalline lens in only 1 eye. However, there was no difference in the incidence of opacification between the toric and the myopic ICLs. Such a difference could perhaps have been found with a higher number of included patients, which is in accordance with the US FDA Clinical Trial of the toric ICL, which found anterior subcapsular opacification in 2.9% 1 year postoperatively26 compared with 2.7% in the US FDA Clinical Trial of the myopic ICL.27 In conclusion, the distance between the ICL and the crystalline lens at baseline was significantly lower in older
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patients. We found no difference in vaulting of the ICL at baseline and during accommodation. Toric ICLs had significantly higher vaulting at baseline. We found anterior subcapsular opacification in 10 eyes (13.0%), and in 5 of these the ICL was in contact with the crystalline lens. Contact was seen at baseline or during accommodation in 12 eyes (15.6%). The association between anterior subcapsular opacification and contact is significant.
13. 14.
15.
References 1. Koivula A, Petrelius A, Zetterstrom C. Clinical outcomes of phakic refractive lens in myopic and hyperopic eyes: 1-year results. J Cataract Refract Surg 2005;31:1145–52. 2. Assetto V, Benedetti S, Pesando P. Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg 1996;22:551– 6. 3. Gonvers M, Othenin-Girard P, Bornet C, Sickenberg M. Implantable contact lens for moderate to high myopia: short-term follow-up of 2 models. J Cataract Refract Surg 2001;27:380–8. 4. Lackner B, Pieh S, Schmidinger G, et al. Long-term results of implantation of phakic posterior chamber intraocular lenses. J Cataract Refract Surg 2004;30:2269 –76. 5. Menezo JL, Peris-Martinez C, Cisneros A, Martinez-Costa R. Posterior chamber phakic intraocular lenses to correct high myopia: a comparative study between Staar and Adatomed models. J Refract Surg 2001;17:32– 42. 6. Gonvers M, Bornet C, Othenin-Girard P. Implantable contact lens for moderate to high myopia: relationship of vaulting to cataract formation. J Cataract Refract Surg 2003;29:918 –24. 7. Zaldivar R, Oscherow S, Ricur G. The STAAR posterior chamber phakic intraocular lens. Int Ophthalmol Clin 2000; 40:237– 44. 8. Baikoff G, Lutun E, Ferraz C, Wei J. Static and dynamic analysis of the anterior segment with optical coherence tomography. J Cataract Refract Surg 2004;30:1843–50. 9. Koretz JF, Cook CA, Kaufman PL. Accommodation and presbyopia in the human eye: changes in the anterior segment and crystalline lens with focus. Invest Ophthalmol Vis Sci 1997;38:569 –78. 10. Schachar RA, Koivula A. The stress on the anterior lens surface during human in vivo accommodation. Br J Ophthalmol 2008;92:348 –50. 11. Baikoff G, Lutun E, Wei J, Ferraz C. Contact between 3 phakic intraocular lens models and the crystalline lens: an anterior chamber optical coherence tomography study. J Cataract Refract Surg 2004;30:2007–12. 12. Jimenez-Alfaro I, Benitez del Castillo JM, Garcia-Feijoo J, et al. Safety of posterior chamber phakic intraocular lenses for the correction of high myopia: anterior segment changes after
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posterior chamber phakic intraocular lens implantation. Ophthalmology 2001;108:90 –9. Radhakrishnan S, Rollins AM, Roth JE, et al. Real-time optical coherence tomography of the anterior segment at 1310 nm. Arch Ophthalmol 2001;119:1179 – 85. Barry P, Seal DV, Gettinby G, et al, ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: preliminary report of principal results from a European multicenter study. J Cataract Refract Surg 2006;32:407–10. Koivula A, Kugelberg M. Optical coherence tomography of the anterior segment in eyes with phakic refractive lenses. Ophthalmology 2007;114:2031–7. Koivula A, Taube M, Zetterstrom C. Phakic refractive lens: two-year results. J Refract Surg 2008;24:507–15. Garcia-Feijoo J, Hernandez-Matamoros JL, Mendez-Hernandez C, et al. Ultrasound biomicroscopy of silicone posterior chamber phakic intraocular lens for myopia. J Cataract Refract Surg 2003; 29:1932–9. Baikoff G, Lutun E, Wei J, Ferraz C. Anterior chamber optical coherence tomography study of human natural accommodation in a 19-year-old albino. J Cataract Refract Surg 2004;30:696–701. ICL in Treatment of Myopia (ITM) Study Group. United States Food and Drug Administration clinical trial of the Implantable Collamer Lens (ICL) for moderate to high myopia: three-year followup. Ophthalmology 2004;111:1683–92. Petternel V, Koppl CM, Dejaco-Ruhswurm I, et al. Effect of accommodation and pupil size on the movement of a posterior chamber lens in the phakic eye. Ophthalmology 2004;111:325–31. Shiratani T, Shimizu K, Fujisawa K, et al. Crystalline lens changes in porcine eyes with implanted phakic IOL (ICL) with a central hole. Graefes Arch Clin Exp Ophthalmol 2008;246:719–28. Pallikaris IG, Kalyvianaki MI, Kymionis GD, Panagopoulou SI. Phakic refractive lens implantation in high myopic patients: one-year results. J Cataract Refract Surg 2004;30:1190–7. Eleftheriadis H, Amoros S, Bilbao R, Teijeiro MA. Spontaneous dislocation of a phakic refractive lens into the vitreous cavity. J Cataract Refract Surg 2004;30:2013– 6. Lege BA, Haigis W, Neuhann TF, Bauer MH. Age-related behavior of posterior chamber lenses in myopic phakic eyes during accommodation measured by anterior segment partial coherence interferometry. J Cataract Refract Surg 2006;32:999–1006. Sarikkola AU, Sen HN, Uusitalo RJ, Laatikainen L. Traumatic cataract and other adverse events with the implantable contact lens. J Cataract Refract Surg 2005;31:511–24. Sanders DR, Schneider D, Martin R, et al. Toric Implantable Collamer Lens for moderate to high myopic astigmatism. Ophthalmology 2007;114:54 – 61. Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. U.S. Food and Drug Administration clinical trial of the Implantable Contact Lens for moderate to high myopia. Ophthalmology 2003;110:255– 66.
Footnotes and Financial Disclosures Originally received: April 19, 2009. Final revision: September 8, 2009. Accepted: October 14, 2009. Available online: February 16, 2010.
and Refractive Surgeons, September 2008, Berlin, Germany; and the American Society of Cataract and Refractive Surgery annual meeting, April 2009, San Francisco, California. Manuscript no. 2009-541.
2
Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
Presented at: XXXVIII Nordic Congress of Ophthalmology, June 2008, Tromsø, Norway; the XXVI Congress of the European Society of Cataract
Correspondence: Are Lindland, MD, Department of Ophthalmology, University of Oslo, 0407 Oslo, Norway. E-mail: [email protected].
1
Department of Ophthalmology, University of Oslo, Norway.
St. Erik’s Eye Hospital, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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