Purpose
To compare the intensity of posterior capsule opacification (PCO) 3 years after implantation of 2 different 1-piece foldable hydrophobic acrylic intraocular lenses (IOLs).
Design
Randomized, prospective, patient- and examiner-masked clinical trial with intraindividual comparison.
Methods
One hundred patients with bilateral age-related cataract (200 eyes) had standard cataract surgery with implantation of an iMics1 NY-60 IOL (Hoya Corp) in one eye and an AcrySof SN60WF IOL (Alcon Laboratories) in the other eye. Follow-up examinations were performed at 1 week and 3 years. Digital retroillumination images were obtained of each eye. The main outcome measure was PCO score (scale, 0 to 10) assessed subjectively at the slit lamp and objectively using automated image analysis software (Automated Quantification of After-Cataract) 3 years after surgery.
Results
The objective PCO score (mean ± standard deviation) was 3.0 ± 2.0 for the iMics1 NY-60 IOL and 1.9 ± 1.4 for the AcrySof SN60WF IOL ( P < .001). Three years after surgery, 35.6% of patients underwent a neodymium:yttrium–aluminum–garnet capsulotomy in the iMics1 NY-60 eye and 13.7% underwent a capsulotomy in the AcrySof SN60WF eye ( P = .001). There was no statistically significant difference in best-corrected visual acuity, rhexis–IOL overlap, capsular folds, or anterior capsule opacification. Glistening formations were found in no iMics1 NY-60 IOLs, but in 97% of the AcrySof SN60WF IOLs.
Conclusions
Comparison of 2 sharp-edged single-piece IOLs of similar design and hydrophobic acrylic material indicated a statistically significant difference in PCO and neodymium:yttrium–aluminum–garnet capsulotomy rate 3 years after surgery.
Changes in cataract surgery in recent years have culminated in today’s small-incision phacoemulsification surgery, a safe technique with a short rehabilitation time beneficial for patients. However, posterior capsule opacification (PCO), which leads to unsatisfactory decreased visual function, remains a common complication, despite the reduction in its incidence brought about by refinements in surgical techniques and modifications in intraocular lens (IOL) design and material. Treatment of PCO by neodymium:yttrium–aluminum–garnet (Nd:YAG) laser capsulotomy is effective, but it is not always available and can lead to further complications associated with tremendous costs. The potential complications include an increase in intraocular pressure, ocular inflammation, cystoid macular edema, and retinal detachment. Therefore, a great deal of effort has gone into developing new ways to prevent the formation of PCO. These efforts comprise modifications in lens design, lens material, surgical technique, and other approaches.
A sharp posterior optic edge, which inhibits migration of lens epithelial cells (LECs) behind the IOL optic, has been shown to lower the incidence of PCO. Earlier IOL designs, known as multipiece devices, have open-loop haptics that are connected to the optic toward the end of the production process. IOLs with open-loop haptics from 1 block of material, known as single-piece designs, have been developed. These are easier to use with injector systems, can be produced with higher efficiency, have better reproducibility of haptic angulation and shape, and are more resilient to deformation during implantation. The haptics tend to be much thicker with single-piece IOLs than with multipiece IOLs. A drawback of single-piece IOLs is an incomplete fusion of the capsules at and around the thick haptic–optic junction, resulting in a lack of bending of the posterior capsule around the posterior optic edge at this site. These locations may serve as a point of entry scaffold for LECs to migrate behind the IOL optic, resulting in PCO. Nowadays a multitude of different single-piece IOLs are available, sometimes with only small discrepancies in IOL design or chemical composition of the material. The present prospective, randomized, controlled study compared the development of PCO between 2 hydrophobic acrylic single-piece, sharp-edged IOLs within a follow-up period of 3 years.
Methods
Patient Recruitment, Randomization, Intraocular Lens Assignment, and Surgical Technique
The study was approved by the local ethics committee of the Medical University of Vienna, Austria (EK 1444/2012). All the research and measurements followed the tenets of the Helsinki agreement and informed consent was obtained from all patients in this study for the treatment and participation in the research. The study is registered at ClinicalTrials.gov with identification number NCT01732484 . One hundred patients (200 eyes) were included in this prospective, randomized clinical trial for intraindividual comparison. The study was performed at the Department of Ophthalmology at the Vienna General Hospital, Medical University of Vienna, Vienna, Austria. The patients were recruited in a continuous cohort. Inclusion criteria were bilateral age-related cataract and good overall physical constitution. Exclusion criteria were a history of ocular disease or intraocular surgery, laser treatment, diabetes requiring medical control, glaucoma, and severe retinal pathologic features that would make a postoperative visual acuity of 20/40 (decimal equivalent, 0.5) or better unlikely.
All surgeries were performed between August 2009 and May 2010. Each patient received an iMics1 NY-60 IOL (Hoya Corp, Tokyo, Japan) in one eye and an AcrySof SN60WF IOL (Alcon Laboratories, Fort Worth, Texas, USA) in the contralateral eye to allow for intraindividual comparison. Before the start of the study, a randomization list was generated with the DataInf RandList version 2.0 software (DataInf GmbH, Tuebingen, Germany) for a simple randomization procedure. An investigator with no clinical involvement in the trial used the list to prepare directions assigning one of the IOLs (iMics1 NY-60 IOL or AcrySof SN60WF IOL) for placement into the patient’s right eye, the first eye to be operated. The directions for each operation were placed in sequentially numbered and sealed envelopes. The surgeon opened the envelopes in sequence on the day of surgery after hydrodissection and phacoemulsification and implanted the randomly assigned IOL specified into the patient’s first eye. The second eye was implanted with the other IOL 1 week later. Patients and investigators remained masked to which IOL had been implanted into which eye. After data entry, this information was unmasked, together with the randomization list for statistical analysis.
The iMics1 NY-60 is a single-piece IOL of blue-filtering hydrophobic acrylic material with an aspheric superior pad polished optic surface with an optimized sharp edge. It has an optic diameter of 6.0 mm, an overall length of 12.5 mm, and haptics of the same acrylic material as the optic with polymethyl methacrylate haptic tips with an angulation of 5 degrees. The AcrySof SN60WF is a single-piece IOL of blue-filtering hydrophobic acrylate and methacrylate copolymer with an anterior asymmetric biconvex sharp-edged optic. It has an optic diameter of 6.0 mm, an overall length of 13.0 mm, and supporting haptics of the same acrylic material as the optic with no haptic angulation (angulation of 0 degrees).
Surgery was performed by one surgeon (R.M.) using a standardized, small-incision phacoemulsification technique. After topical anesthesia, a posterior-limbal self-sealing incision (iMics1 NY-60, 2.0 mm; AcrySof SN60WF, 2.2 mm) was made. The anterior chamber was filled with an ophthalmic viscoelastic device, and a continuous curvilinear capsulorrhexis (slightly smaller than the IOL optic diameter) was created to attain a symmetrical 360-degree rhexis–IOL overlap. The folded IOLs were implanted in the bag with an injector. After IOL implantation, the ophthalmic viscoelastic device was removed carefully from the anterior chamber and the capsular bag by coaxial irrigation and aspiration. Care was taken to aspirate all ophthalmic viscoelastic devices from the bag by slightly tilting the IOL and positioning the irrigation-and-aspiration tip behind the IOL optic. There were no surgical complications that would have led to patient exclusion. Postoperative treatment consisted of prednisolone acetate 1% (Ultracortinol; Ciba Vision, Atlanta, Georgia, USA) and diclofenac (Voltaren Ophtha; Ciba Vision) eye drops 4 times daily for 1 month.
Follow-up Examinations and Image Acquisition
Follow-up examinations were performed 1 week and 3 years after surgery. On each occasion, patients received phenylephrine 2.5% and tropicamide 0.5% at least a half an hour before they were examined at the slit lamp. The following aspects were assessed subjectively using a standardized evaluation form: Snellen visual acuity (best-corrected visual acuity); IOL position and centration; rhexis–IOL overlap; presence of glistening, that is, white sparkling areas over all the IOL optics; amount and type of anterior capsule opacification (ACO; score, 0 to 3); and the amount and type of regeneratory PCO (score, 0 to 10). Patients also were asked about any disturbing visual symptoms such as edge glare, photophobia, or halos. Intraocular pressure measurements were obtained, followed by a retinal examination. Finally, the need for an Nd:YAG laser capsulotomy was noted.
On each occasion, digital retroillumination images of the posterior capsule were made. For this purpose, we used a digital camera (Nikon/Kodak NC2000e, Nikon Corp., Tokyo, Japan) mounted on a modified Zeiss 30 slit lamp (Carl Zeiss AG, Jena, Germany) with an external light and flash-light source, which provides coaxial illumination from the flash pack through a fiber optic cable to the camera. This system is similar to that used by Spalton and associates. It produces even illumination over the entire image with relatively small flash artifacts and shows high reproducibility. It is used for documentation of regeneratory PCO. All digital images were transferred to a personal computer and stored on hard disc for later evaluation.
Data Evaluation and Image Analysis
The data from the evaluation forms (subjective slit-lamp examination) were entered in a Microsoft Excel worksheet (Microsoft, Redmond, Washington, USA). All further evaluation was carried out on the personal computer using standard software (MS Excel and SPSS [SPSS, Inc, Chicago, Illinois, USA]). The results were separated into 2 groups according to the IOL type (iMics1 NY-60 and AcrySof SN60WF IOL), and the mean values were calculated for the attributes mentioned above. A subjective score of 0 to 3 was used for fibrotic ACO and PCO, and a score of 0 to 10 was used for regeneratory PCO, where 0 stands for a clear capsule and 3 (and 10, respectively) stands for severe fibrotic (regeneratory, respectively) ACO and PCO.
Because the amount of PCO was of major interest for this study, we also used automated image analysis software for objective PCO evaluation. This computer program (Automated Quantification of After-Cataract [AQUA]) was developed at our institution in cooperation with the Technical University of Graz (H. Siegl, A. Pinz). The 3-year retroillumination images (right and left eye) from each patient were imported into the program, and the region within the capsulorrhexis was evaluated. The rhexis edge is detected by the program in a semiautomatic (computer-aided) way. The AQUA software calculates the entropy (grade of disorder) of a bitmap. This value is converted into a score between 0 and 10 (where 0 is a clear capsule and 10 is exceptionally severe PCO). The system has been shown to correlate well with subjective scoring of PCO and has perfect reproducibility. Compared with other PCO grading systems, it is fully automated and there is no subjective aspect to the evaluation process. Many randomized controlled trials with intraindividual comparison have shown that the AQUA system is an excellent tool for assessing the effectiveness of surgical techniques and IOL design and material in preventing PCO. Mean objective PCO scores were calculated with this software for the iMics1 NY-60 and AcrySof SN60WF IOL group using the 3-year retroillumination images.
Statistical Analysis
The results from the iMics1 NY-60 and AcrySof SN60WF IOL groups were compared, and the differences between the 2 groups were calculated. Statistical significance was calculated using t tests and χ 2 tests. A P value of .05 or less was considered significant. Data are presented as mean ± standard deviation.
Results
The mean age of the study patients was 72.3 ± 9.8 years. Twenty-six patients were unavailable for the 3-year follow-up examination. Seven patients died before the 3-year follow-up, 5 patients were unavailable because of chronic illness. Fourteen patients could not be contacted; that is, mail was returned because of a change of address or possibly death, or they could not be reached via telephone. Therefore, whether these patients died or moved to a nursing home is unknown. Accordingly, 74 of the 100 patients included in the study could be examined after 3 years ( Supplemental Figure 1 , available at AJO.com ). No adverse event occurred during this study.
PCO in digital retroillumination images was evaluated objectively with the AQUA software. At 3 years, a mean objective PCO score (scale, 0 to 10) of 3.0 ± 2.0 was found for the iMics1 NY-60 group and a mean score of 1.9 ± 1.4 was found for the AcrySof SN60WF group ( Figure 1 ). The difference between the 2 groups was statistically significant ( P < .001). One (2%) of 56 patients showed the same amount of regeneratory PCO in both eyes, whereas 46 (82%) showed more regeneratory PCO in the iMics1 NY-60 eye and 9 (16%) showed more regeneratory PCO in the AcrySof SN60WF eye ( Figure 2 ). No regeneratory PCO at 3 years was seen in 3 eyes in the iMics1 NY-60 group or in 5 eyes in the AcrySof SN60WF group. Figure 3 shows 3 representative cases of our data set.
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