clinical assessment of long-term safety and efficacy of a widely implanted polyacrylic intraocular...

Clinical Assessment of Long-term Safety andEfficacy of a Widely Implanted Polyacrylic

Intraocular Lens Material

HIROSHI KOBAYASHI, MD, PHD, HIROMI IKEDA, MD, SADAHIRO IMAMURA, MD,KAORU KOBAYASHI, MD, YUMIKO MITSUMA, MD, MASAHIRO MINAMI, MD,OSAMU ISHIDA, MD, MIO HIROSE, MD, AND KAORI KOBAYASHI, MD, PHD

● PURPOSE: To evaluate the long-term safety andefficacy, in a large series of patients, of polyacrylicintraocular lens implants 1 and 3 years after surgery,compared with polymethylmethacrylate intraocularlens implants.● METHODS: This was a randomized, prospective studyof 1,514 eyes of 1,202 patients that were examined fora 1-year follow-up study and 1,264 eyes of 990patients that were examined for a 3-year follow-upstudy. All the patients were prospectively randomizedto receive a polyacrylic or polymethylmethacrylateintraocular lens implant. A standardized surgical pro-tocol was performed using a phacoemulsification tech-nique and capsulorhexis. Any surgical complicationswere excluded, and all patients had standard postoper-ative medication and follow-up. Postoperative mea-surements included spectacle-corrected visual acuity,occurrence of postoperative sight-threatening or lens-related complications, and adverse reactions. Resultswere compared between the polyacrylic intraocularlens and polymethylmethacrylate intraocular lensgroups. Results were also compared with standards forpolymethylmethacrylate intraocular lens that were estab-lished by the US Food and Drug Administration and aprevious study for silicone lens.● RESULTS: The overall complete follow-up rates were79.9% for 1-year follow-up and 69.5% for 3-yearfollow-up. At 1 year, the mean logarithm of theminimum angle of resolution (logMAR) of visualacuity was 0.037 6 0.150 and 0.042 6 0.154 in best

case patients of the polyacrylic intraocular lens groupand polymethylmethacrylate intraocular lens group,respectively. At 3 years, the mean logMAR visualacuity was 0.038 6 0.155 and 0.054 6 0.181 in bestcase patients in the polyacrylic intraocular lens groupand polymethylmethacrylate intraocular lens group.There was no significant difference between groups at1 and 3 years. At 1 year, 96.8% of best case patientsin the polyacrylic intraocular lens group and 95.8% ofthose in the polymethylmethacrylate intraocular lensgroup achieved corrected visual acuity of 0.5 or better.At 3 years, 96.4% of best case patients in the poly-acrylic intraocular lens group and 94.9% of those inthe polymethylmethacrylate group achieved a cor-rected visual acuity of 0.5 or better; no significantdifference was found at 1 and 3 years. The rate ofsight-threatening complications was 1.2% for the poly-acrylic intraocular lens group of all patients and 1.5%for the polymethylmethacrylate intraocular lens groupat 1 year, and 1.6% for the polyacrylic intraocular lensgroup and 1.4% for the polymethylmethacrylate in-traocular lens group at 3 years. No significant differ-ence was found between the groups. The cumulativerate of Nd:YAG capsulotomy for the polyacrylic in-traocular lens group (7.1%) was significantly lowerthan that for the polymethylmethacrylate intraocularlens group (38.1%) through 3 years (P < .0001).● CONCLUSIONS: Polyacrylic intraocular lenses demon-strated safe and effective performance through long-termfollow-up at a level equal to or better than polymethyl-methacrylate intraocular lenses. Patients undergoingpolyacrylic intraocular lens implantation achieved excel-lent postoperative visual acuity and experienced a lowrate of postoperative complications, adverse reactions,and Nd:YAG capsulotomy. These long-term clinicalresults are an important outcome database for the ongo-ing use of this foldable optic material. (Am J Ophthal-mol 2000;130:310–321. © 2000 by Elsevier ScienceInc. All rights reserved.)

Accepted for publication Mar 7, 2000.From the Department of Ophthalmology, Amagasaki Hospital (Drs H.

Kobayashi, Ikeda, Imamura, K. Kobayashi, Mitsuma, Minami, Ishida, andHirose), Amagasaki, Hyogo; Department of Ophthalmology and VisionScience, Kyoto University, Graduate School of Medicine (Dr H. Koba-yashi), Kyoto; and Department of Ophthalmology, Osaka Red CrossHospital (Dr K. Kobayashi), Osaka, Japan.

Correspondence to Hiroshi Kobayashi, MD, PhD, Department ofOphthalmology, Amagasaki Hospital, 1-1-1 Higashi-daimotsu-cho, Ama-gasaki, Hyogo, 660-0828, Japan; fax: 181-6-6482-7430; e-mail: [email protected]

© 2000 BY ELSEVIER SCIENCE INC. ALL RIGHTS RESERVED.310 0002-9394/00/$20.00PII S0002-9394(00)00490-6

P OLYACRYLIC FOLDABLE INTRAOCULAR LENSES HAVE

been used in cataract and implant surgery since1992.1 The structure of the AcrySof (Alcon, Fort

Worth, Texas) lens material is a random copolymer ofphenylethyl acrylate and phenylethyl methacrylate that iscrosslinked with butanediol diacrylate.1 Characteristics ofthis polyacrylic intraocular lens that differ from the com-monly used foldable silicone lens include improved vis-coelastic properties, slow and controlled unfolding, and ahigh refractive index resulting in a thinner lens thatfacilitates folding and insertion through a smaller inci-sion.1–4 Other benefits resulting from the combination ofsmall-incision surgery and foldable intraocular lenses includedecreased postoperative inflammation, less postoperativeastigmatism, reduced damage to corneal endothelium, re-duced endothelial cell loss, and faster visual rehabilitation.Optics damage, including stress fracture after folding andglistenings, pupillary block, and condensation on the intraoc-ular lens surface during vitrectomy have been reported.5–12

The AcrySof, one of the models made from polyacrylicmaterial, is currently in widespread clinical use, with morethan 4 million implants worldwide. Actual clinical datafrom large patient series are highly valuable in the consid-eration of long-term performance and establishment ofoutcomes. This study is a randomized prospective trial toinvestigate the long-term efficacy, biocompatibility, andstability of the polyacrylic intraocular lens compared withthe polymethylmethacrylate intraocular lens through theanalysis of results of a total 1514 eyes followed up for atleast 1 year and 1264 eyes followed up for 3 years aftersurgery.

PATIENTS AND METHODS

PATIENTS WERE RECRUITED IN A CONTINUOUS COHORT

after approval from the hospital ethics committee. Con-sidering the association between age and the incidence ofposterior capsule opacification,13 we enrolled patients 55years of age or older with significant cataract. Patients wereinformed of the purpose of our study and provided theirsigned consent to participate. All patients were prospec-tively randomized to implantation of polyacrylic intraocu-lar lens or polymethylmethacrylate intraocular lens.Within 24 hours after enrollment, the patients wererandomized using computer-generated numbers; for exam-ple, 0 is to receive a polyacrylic intraocular lens implant,and 1 is to receive a polymethylmethacrylate intraocularlens implant.

The primary measure of effectiveness was visual out-come. Safety was evaluated by determining the incidenceof postoperative persistent complications and postopera-tive adverse reactions. Persistent complications refer tocomplications identified by the US Food and Drug Admin-istration as sight threatening.14 Adverse reactions weredefined as hypopyon, intraocular infection, acute corneal

decompensation, or any condition requiring secondarysurgical intervention. A format similar to that of a previousstudy for silicone lens15 was used to compare with stan-dards for polymethylmethacrylate intraocular lens thatwere established by the Food and Drug Administration andthose for silicone lens. Additional outcome measurementsincluded the incidence of posterior capsular opacificationand the rate of Nd:YAG laser capsulotomy.

All recruited patients underwent a complete ophthal-mologic examination, including measurement of correctedvisual acuity, near-vision, slit-lamp biomicroscopy, specu-lar microscopy, and indirect ophthalmoscopy. Fully cor-rected distance visual acuity was measured on a visualacuity chart at 5 meters. The logarithm of the minimumangle of resolution (logMAR) was calculated and used forall statistical analyses. Preoperative nuclear sclerosis wasassessed, as described by Emery and associates.16 Postoper-atively, posterior capsule opacification was scored by eval-uating retroillumination photographs according to Tetzand associates17 and graded from 0 to 3 (none, mild,moderate, and severe opacification). Pitting of intraocularlenses from Nd:YAG laser capsulotomy was graded accord-ing to Steinert and associates15 as follows: slight pitting(damage not resulting in impairment of vision); moderatepitting (damage that might affect final achieved visualacuity); severe pitting (damage resulting in significantvisual impairment or requiring intraocular lens ex-change).15 Glistenings of the polyacrylic intraocular lenswere graded based on photographs representing trace, 11(mild), 21 (moderate), and 31 (severe), according toDhaliwal and associates.9

All surgery was performed between January 1995 andMay 1998. A standard phacoemulsification technique wasused. The pupil was dilated, a 4-mm superior cornealsection for a polyacrylic intraocular lens implantation or a6-mm section for a polymethylmethacrylate intraocularlens implantation was made, and the anterior chamberformed with viscoelastic (Heallon; Pharmacia, Uppsala,Sweden). A 5.0-mm to 5.5-mm continuous curvilinearcapsulorhexis was performed The nucleus was phacoemul-sified using a standard “divide and conquer” technique orthe “phacochop” technique and the remaining cortex wasaspirated.18,19 The capsular bag was re-formed with vis-coelastic, the intraocular lens was inserted in the bag, andthe corneal wound was not sutured. No attempt was madeto polish epithelial cells off the anterior capsule in anycase. Any surgical complication, such as continuous cur-vilinear capsulorhexis rim tear, zonular dehiscence, failureto place the intraocular lens in the bag, posterior capsularrupture, vitreous loss, or nuclear drop led to patientexclusion. No subconjunctival antibiotics or steroid wasgiven. The intraocular lenses had 6-mm bioconvex diskoptics of either polymethylmethacrylate (AlconMC60BM; Alcon, Fort Worth, Texas) or polyacrylic(AcrySof; Alcon MA60BM); both had polymethyl-methacrylate haptics and a 10-degree flexion of the hap-

CLINICAL ASSESSMENT OF POLYACRYLIC INTRAOCULAR LENSVOL. 130, NO. 3 311

TABLE 1. Demographics of Patient Groups

1-Year Follow-up 3-Year Follow-up

Polyacrylic IOL

Group PMMA IOL Group

Polyacrylic IOL


All patients

Total no. of subjects enrolled 595 607 493 497

No. of eyes 761 753 635 629

Total no. of subjects with

complete follow-up

470 490 350 338

Men 175 (37.2%) 190 (38.8%) 126 (36.0%) 137 (40.5%)

Women 295 (62.8%) 300 (61.2%) 224 (64.0%) 201 (59.5%)

Age (years)

55–64 132 (28.1%) 133 (27.1%) 99 (28.3%) 99 (29.3%)

65–74 184 (39.1%) 192 (39.2%) 138 (39.4%) 149 (44.1%)

75–84 124 (26.4%) 115 (23.5%) 93 (26.6%) 72 (21.3%)

$85 30 (6.4%) 50 (10.2%) 20 (5.7%) 18 (5.3%)

Mean 6 SD 71.826 6 9.584 71.316 6 8.979 70.063 6 9.392 69.139 6 9.891

No. of eyes 605 604 451 428

RE 323 (53.4%) 325 (53.8%) 234 (51.9%) 222 (51.9%)

LE 282 (46.6%) 279 (46.2%) 217 (48.1%) 206 (48.1%)

Preoperative visual acuity

0.5 or better 127 (21.0%) 109 (18.0%) 102 (22.6%) 93 (21.7%)

0.1–0.4 346 (57.2%) 376 (62.3%) 259 (57.4%) 235 (54.9%)

0.05–0.09 39 (6.4%) 40 (6.6%) 34 (7.5%) 38 (8.9%)

0.01–0.04 66 (10.9%) 51 (8.4%) 32 (7.1%) 39 (9.1%)

,0.01 27 (4.4%) 28 (4.6%) 24 (5.3%) 23 (5.4%)

Mean 6 SD (logMAR) 0.723 6 0.453 0.716 6 0.468 0.700 6 0.455 0.704 6 0.465

Nuclear sclerosis

Grade 1 121 (20.0%) 134 (22.2%) 87 (19.3%) 92 (21.5%)

Grade 2 283 (46.8%) 274 (45.4%) 211 (46.8%) 188 (43.9%)

Grade 3 160 (26.4%) 143 (23.7%) 123 (27.3%) 117 (27.3%)

Grade 4 34 (5.6%) 38 (6.3%) 25 (5.5%) 23 (5.4%)

Grade 5 7 (1.1%) 15 (2.5%) 5 (1.1%) 8 (1.9%)

Mean 6 SD 2.209 6 0.869 2.258 6 0.910 2.202 6 0.829 2.222 6 0.955

Best case patients

Total no. of subjects enrolled 368 396 270 264

No. of eyes 479 496 358 325

Total no. of subjects with

complete follow-up

285 305 209 203

Men 100 (35.1%) 121 (39.7%) 74 (35.4%) 84 (41.4%)

Women 185 (64.9%) 184 (60.3%) 135 (64.6%) 119 (58.6%)

Age (years)

55–64 75 (26.3%) 72 (23.6%) 58 (27.8%) 52 (25.6%)

65–74 114 (40.0%) 109 (35.7%) 82 (39.2%) 87 (42.9%)

75–84 76 (26.7%) 81 (26.6%) 56 (26.8%) 50 (24.6%)

$85 20 (7.0%) 43 (14.1%) 13 (6.2%) 14 (6.9%)

Mean 6 SD 70.919 6 9.293 71.141 6 9.123 70.545 6 9.262 70.698 6 9.281

No. of eyes 373 384 279 251

RE 194 (52.0%) 208 (54.2%) 147 (52.7%) 139 (55.4%)

LE 179 (48.0%) 176 (45.8%) 132 (47.3%) 112 (44.6%)

Preoperative visual acuity

0.5 or better 79 (21.2%) 85 (22.1%) 65 (23.3%) 52 (20.7%)

0.1–0.4 214 (57.4%) 225 (58.6%) 158 (56.6%) 156 (62.2%)

0.05–0.09 33 (8.8%) 34 (8.9%) 22 (7.9%) 13 (5.2%)

0.01–0.04 36 (9.7%) 28 (7.3%) 23 (8.2%) 20 (8.0%)

,0.01 11 (2.9%) 12 (3.1%) 11 (3.9%) 10 (4.0%)

Continued on next page

AMERICAN JOURNAL OF OPHTHALMOLOGY312 SEPTEMBER 2000

tics. For the polyacrylic intraocular lenses, Wagon Wheelpackaging was used to reduce postoperative glistenings.10

The polyacrylic intraocular lenses were folded on the 6 to12 o’clock axis and the haptics inserted one right after tothe other to avoid complications.10 After surgery, allpatients used ofloxacin and diclofenac drops three times aday for 1 month.

Nd:YAG capsulotomy was performed if clinically indicatedby a decrease in visual acuity of 2 lines since the lastappointment, in the presence of a clinically opaque capsule.

All data included in this report were expressed asmean 6 standard deviation or frequencies. This methodwas chosen as an appropriate way to express the incidenceof particular outcomes for broad categories of patients. Forall 2 3 2 comparisons, the Fisher exact test was used.Other comparisons of frequency distributions were per-formed using the chi-square test for independence. Unlessotherwise specified, data were analyzed by paired t tests. Alevel of P , .05 was accepted as statistically significant. Inmultiple comparisons, the Bonferroni procedure was usedin selecting the P value, which was considered the thresh-old for significance.

For the pairing of both groups, age, gender, visual acuity,and nuclear sclerosis at baseline were used for matching.We studied a correlation between the paired observations.If these observations correlated, the F test was used tostudy two population variances.

A comparison of visual acuity data was performedbetween best case patients (“best case” refers to patientswith no known preoperative ocular pathological condi-tions affecting vision other than cataract or postoperativemacular degeneration) in the polyacrylic intraocular lensgroup and polymethylmethacrylate intraocular lensgroup.14,15 These data were also compared with best casepatients with polymethylmethacrylate intraocular lenses,based on data from a study by Stark and associates14 andwith silicone intraocular lenses, based on a study bySteinert and associates.15

RESULTS

BASELINE DATA ARE SUMMARIZED IN TABLE 1. FOR THE

1-year follow-up study, 761 eyes of 595 patients and 753eyes of 607 patients were enrolled in the polyacrylicintraocular lens group and polymethylmethacrylate in-traocular lens group, respectively. For the 3-year follow-upstudy, 635 eyes of 493 patients and 629 eyes of 497 patientswere enrolled in the polyacrylic intraocular lens group andpolymethylmethacrylate intraocular lens group. There wasno statistically significant difference in age and genderbetween those in the polyacrylic intraocular lens group andpolymethylmethacrylate intraocular lens group in bothfollow-up studies.

The overall complete follow-up rate was 79.9% (1,209of 1,514) in the 1-year follow-up and 69.5% (879 of 1,264)in the 3-year follow-up (Table 1). There was no significantdifference between groups in the 1-year and 3-year follow-up; in the 1-year follow-up study, the complete follow-uprate was 79.5% (605 of 761) and 80.2% (604 of 753) in thepolyacrylic intraocular lens group and polymethylmethac-rylate intraocular lens group, respectively. In the 3-yearfollow-up study, the complete follow-up rate was 71.0%(451 of 635) and 68.0% (428 of 629) in the polyacrylicintraocular lens group and polymethylmethacrylate in-traocular lens group.

There was no significant difference in mean of age,visual acuity, and nuclear sclerosis score between thepolyacrylic intraocular lens group and polymethylmethac-rylate intraocular lens group in the 1-year and 3-yearfollow-up. No significant difference was found in thedistribution of age, gender, visual acuity, and nuclearsclerosis score between the groups.

Corrected visual acuity data from all patients are sum-marized in Table 2. At 1 year, mean logMAR visual acuitywas 0.130 6 0.322 and 0.144 6 0.382 in the polyacrylicintraocular lens and polymethylmethacrylate intraocularlens groups, respectively. At 3 years, mean logMAR visual

TABLE 1. (Continued) Demographics of Patient Groups


Polyacrylic IOL


Polyacrylic IOL


Mean 6 SD (logMAR) 0.704 6 0.456 0.707 6 0.480 0.688 6 0.455 0.701 6 0.478

Nuclear sclerosis

Grade 1 72 (19.3%) 92 (24.0%) 59 (21.1%) 62 (24.7%)

Grade 2 169 (45.3%) 170 (44.3%) 124 (44.4%) 109 (43.4%)

Grade 3 107 (28.7%) 93 (24.2%) 81 (29.0%) 63 (25.1%)

Grade 4 20 (5.4%) 20 (5.2%) 11 (3.9%) 12 (4.8%)

Grade 5 5 (1.3%) 9 (2.3%) 4 (1.4%) 5 (2.0%)

Mean 6 SD 2.228 6 0.867 2.188 6 0.936 2.196 6 0.858 2.159 6 0.920

IOL 5 intraocular lens; logMAR 5 logarithm of the minimum angle of resolution of visual acuity; PMMA 5 polymethylmethacrylate.


acuity was 0.126 6 0.302 and 0.148 6 0.398 in thepolyacrylic intraocular lens and polymethylmethacrylateintraocular lens groups. No significant difference was foundbetween groups at 1 and 3 years. At 1 year, 52.6% (318 of605) of all patients in the polyacrylic intraocular lensgroup and 51.7% (312 of 604) of those in the polymeth-ylmethacrylate group achieved visual acuity of 1.0 orbetter, and 86.6% (524 of 605) of the polyacrylic intraoc-ular lens group and 84.4% (510 of 604) of the polymeth-ylmethacrylate group achieved 0.5 or better; there was nosignificant difference in the percentage achieving either1.0 or 0.5 or better. At 3 years, 88.5% (399 of 451) of thepolyacrylic intraocular lens group and 85.0% (364 of 428)of the polymethylmethacrylate group achieved correctedvisual acuity of 0.5 or better; there was no significantdifference between groups.

Corrected visual acuity data on best case patients aresummarized in Table 2. At 1 year, mean logMAR visualacuity was 0.037 6 0.150 and 0.042 6 0.154 in thepolyacrylic intraocular lens group and polymethylmethac-rylate intraocular lens group, respectively. At 3 years,mean logMAR visual acuity was 0.038 6 0.155 and0.054 6 0.181 in the polyacrylic intraocular lens group andpolymethylmethacrylate intraocular lens group. Visualacuity in the polyacrylic intraocular lens was slightly betterin the polyacrylic intraocular lens group compared withthe polymethylmethacrylate intraocular lens group, butthis difference was not statistically significant at 1 and 3

years. At 1 year, 64.9% (242 of 373) of the polyacrylicintraocular lens group and 60.7% (233 of 384) of thepolymethylmethacrylate intraocular lens group achievedvisual acuity of 1.0 or better, and 96.8% (361 of 373) of thepolyacrylic intraocular lens group and 95.8% (368 of 384)of the polymethylmethacrylate intraocular lens groupachieved corrected visual acuity of 0.5 or better. At 3years, 96.4% (269 of 279) of the polyacrylic intraocularlens group and 94.9% (238 of 251) of the polymethyl-methacrylate group achieved corrected visual acuity of 0.5or better; there was no significant difference betweengroups.

Table 3 summarizes reports of persistent complications.The total rate of complications was 1.2% (seven of 605)for the polyacrylic intraocular lens group and 1.5% (nineof 604) for the polymethylmethacrylate intraocular lensgroup at 1 year, and 1.6% (seven of 451) for the polyacrylicintraocular lens group and 1.4% (six of 428) for thepolymethylmethacrylate intraocular lens group at 3 years.

Adverse reactions are summarized in Table 4 for the1-year follow-up study. None of the polyacrylic intraocularlens group and two patients (0.3%) in the polymethyl-methacrylate intraocular lens group had adverse reactions;there was no significant difference. In the polymethyl-methacrylate intraocular lens group, one patient had en-dophthalmitis requiring extensive antibiotic therapywithout vitrectomy. The other patient underwent intraoc-ular lens removal and replacement because of an incorrect

TABLE 2. Corrected Visual Acuity, Best Case Patients and All Patients


Polyacrylic IOL


Polyacrylic IOL


All patients

No. of eyes 605 604 451 428

1.0 or better 318 (52.6%) 312 (51.7%) 241 (53.4%) 217 (50.7%)

0.5–0.9 206 (34.0%) 198 (32.8%) 158 (35.0%) 147 (34.3%)

0.5 or better 524 (86.6%) 510 (84.4%) 399 (88.5%) 364 (85.0%)

0.1–0.4 59 (9.8%) 66 (10.9%) 37 (8.2%) 50 (11.7%)

0.05–0.09 9 (1.5%) 19 (3.1%) 5 (1.1%) 8 (1.9%)

0.01–0.04 11 (1.8%) 9 (1.5%) 8 (1.8%) 6 (1.4%)

,0.01 2 (0.3%) 0 (0%) 2 (0.4%) 0 (0%)

Mean 6 SD (logMAR) 0.130 6 0.322 0.144 6 0.382 0.126 6 0.302 0.148 6 0.398

Best case patients

No. of eyes 373 384 279 251

1.0 or better 242 (64.9%) 233 (60.7%) 176 (63.1%) 154 (61.4%)

0.5–0.9 119 (31.9%) 135 (35.2%) 93 (33.3%) 84 (33.5%)

0.5 or better 361 (96.8%) 368 (95.8%) 269 (96.4%) 238 (94.9%)

0.1–0.4 12 (3.2%) 16 (4.2%) 10 (3.6%) 13 (5.2%)

0.05–0.09 0 (0%) 0 (0%) 0 (0%) 0 (0%)

0.01–0.04 0 (0%) 0 (0%) 0 (0%) 0 (0%)

,0.01 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Mean 6 SD (logMAR) 0.037 6 0.150 0.042 6 0.154 0.038 6 0.155 0.054 6 0.181

Abbreviations as in Table 1.


TABLE 3. Incidence of FDA Grid Sight-threatening Complications

Category of FDA Grid Complications

All Patients Best-case Patients

Silicone

IOL15

FDA

Grid14

Polyacrylic

IOL Group

PMMA

IOL Group

Polyacrylic

IOL Group

PMMA

IOL Group

1-year follow-up

Number of eyes 605 604 373 384 1432 2465

Number of patients 470 490 285 305

Total incidence of (eyes) 7 (1.2%) 9 (1.5%) 2 (0.5%) 1 (0.3%) 1.3% NA

FDA complication (patients) 6 (1.3%) 7 (1.4%) 2 (0.7%) 1 (0.3%)

Corneal edema

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0.1% 0.6%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Iritis

Eyes 2 (0.3%) 1 (0.2%) 1 (0.3%) 0 (0%) 0% 1.0%

Patients 2 (0.4%) 1 (0.2%) 1 (0.4%) 0 (0%)

Hyphema

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0.1% 0.3%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Macular edema

Eyes 3 (0.5%) 4 (0.7%) 0 (0%) 1 (0.3%) 0.6% 0.8%

Patients 2 (0.4%) 3 (0.6%) 0 (0%) 1 (0.3%)

Pupillary block

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0% NA

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Secondary glaucoma

Eyes 2 (0.3%) 4 (0.7%) 1 (0.3%) 0 (0%) 0.1% 0.5%

Patients 2 (0.4%) 3 (0.6%) 1 (0.4%) 0 (0%)

Cyclitic membrane

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0% 0%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Vitreitis

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0.1% 0.1%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Endophthalmitis

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0% NA

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Retinal detachment

Eyes 1 (0.2%) 2 (0.3%) 1 (0.3%) 1 (0.3%) 0.1% NA

Patients 1 (0.2%) 2 (0.4%) 1 (0.4%) 1 (0.3%)

Intraocular lens dislocation/malposition

Eyes 0 (0%) 2 (0.3%) 0 (0%) 1 (0.3%) 0.1% NA

Patients 0 (0%) 2 (0.4%) 0 (0%) 0 (0%)

3-year follow-up

Number of eyes 451 428 279 251 501

Number of patients 350 338 209 203

Total incidence of (eyes) 7 (1.6%) 6 (1.4%) 1 (0.4%) 1 (0.4%) 2.0%

FDA complication (patients) 6 (1.7%) 6 (1.7%) 1 (0.5%) 1 (0.5%)

Corneal edema

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0.2%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Iritis

Eyes 2 (0.4%) 2 (0.4%) 0 (0%) 0 (0%) 0.2%

Patients 2 (0.6%) 2 (0.6%) 0 (0%) 0 (0%)

Hyphema

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0.2%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Continued on next page


preoperative power calculation and implantation of thewrong power intraocular lens.

No eye showed discoloration in the polyacrylic intraoc-ular lenses. At 1 year, 337 (55.7%), 131 (21.7%), 84(13.9%), and 53 (8.8%) of 605 eyes showed trace, mild,moderate, and severe glistenings in the polyacrylic intraoc-ular lenses, respectively (Table 5). At 3 years, 286(63.4%), 92 (20.4%), 45 (10.0%), and 28 (6.2%) of 451eyes showed trace, mild, moderate, and severe glisteningsin the polyacrylic intraocular lenses (Table 5). Withineach group, there was no significant difference in thepercentage of eyes that achieved corrected visual acuity of0.5 or better. In the best case patient group, mean logMARof visual acuity decreased with the increase in the degree ofglistenings of intraocular lenses, but there was no statisti-cally significant correlation.

The cumulative incidence of Nd:YAG laser posteriorcapsulotomies 1 year after operation was 1.5% (nine of605) of all patients in the polyacrylic intraocular lensgroup and 15.4% (93 of 604) of those in the polymethyl-methacrylate intraocular lens group (Table 6). The cumu-lative incidence 3 years after operation was 7.1% (32 of451) of all patients in the polyacrylic intraocular lens

group and 38.1% (163 of 428) of those in the polymeth-ylmethacrylate intraocular lens group. There was a signif-icant difference at 1 and 3 years (P , .0001; P , .0001).At 3 years, 17.3% (78 of 451) of the polyacrylic intraocularlens group and 63.1% (270 of 428) of the polymethyl-methacrylate intraocular lens group showed posterior cap-sule opacification, including those who underwent Nd:YAG laser posterior capsulotomy, for a statisticallysignificant difference (P , .0001; Table 6).

No moderate or severe pitting was found in the poly-acrylic intraocular lens group and polymethylmethacrylateintraocular lens group in both follow-up studies. In the1-year follow-up study, slight pitting of intraocular lensesfrom Nd:YAG laser procedures was observed in 22.2%(two of nine) of all patients in the polyacrylic intraocularlens group and 19.4% (18 of 93) of those in the poly-methylmethacrylate intraocular lens group (Table 7). Inthe 3-year follow-up study, slight pitting of intraocularlenses from Nd:YAG laser procedures was observed in18.8% (six of 32) of all patients in the polyacrylicintraocular lens group and 17.8% (29 of 163) of those inthe polymethylmethacrylate intraocular lens group (Table

TABLE 3. (Continued) Incidence of FDA Grid Sight-threatening Complications

Category of FDA Grid Complications


Silicone

IOL15

FDA

Grid14

Polyacrylic

IOL Group

PMMA

IOL Group

Polyacrylic

IOL Group

PMMA

IOL Group

Macular edema

Eyes 3 (0.7%) 2 (0.5%) 0 (0%) 1 (0.4%) 0.4%

Patients 2 (0.6%) 2 (0.6%) 0 (0%) 0 (0%)

Pupillary block

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Secondary glaucoma

Eyes 2 (0.4%) 2 (0.5%) 1 (0.4%) 0 (0%) 0.8%

Patients 2 (0.6%) 2 (0.6%) 0 (0%) 0 (0%)

Cyclitic membrane

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Vitreitis

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Endophthalmitis

Eyes 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Retinal detachment

Eyes 1 (0.2%) 2 (0.5%) 1 (0.4%) 2 (0.8%) 0%

Patients 1 (0.3%) 2 (0.6%) 1 (0.5%) 2 (1.0%)

Intraocular lens dislocation/malposition

Eyes 0 (0%) 1 (0.2%) 0 (0%) 1 (0.4%) 0.2%

Patients 0 (0%) 0 (0%) 0 (0%) 0 (0%)

FDA 5 Food and Drug Administration. Other abbreviations as in Table 1.


7). At 1 and 3 years, all patients who experienced slightpitting of intraocular lenses from Nd:YAG laser proceduresachieved corrected visual acuity of 0.5 or better afterNd:YAG. Within each group, there was no significantdifference in the percentage of eyes that achieved visualacuity of 0.5 or better after Nd:YAG between eyes withslight pitting and those with no pitting. In the best casepatient group, mean logMAR of visual acuity of eyes withno pitting was slightly better than that of eyes with slightpitting in the polyacrylic intraocular lens group and thepolymethylmethacrylate intraocular lens group 1 and 3years postoperative, but no significant difference wasfound.

DISCUSSION

THIS STUDY EVALUATED LONG-TERM EFFICACY AND

safety of polyacrylic intraocular lens compared with poly-methylmethacrylate intraocular lens. Postoperative visualoutcome was excellent. Polyacrylic intraocular lenses dem-onstrated safe and effective performance through long-term follow-up at a level equal to or better thanpolymethylmethacrylate intraocular lenses. No significantdifference was found between the polyacrylic intraocularlens group and polymethylmethacrylate intraocular lensgroup in mean corrected visual acuity at 1 and 3 years.There was no significant difference in the percentage ofeyes achieving either 1.0 or 0.5 or better.

Although strenuous efforts were made to follow uppatients, 20.1% (242 of 1202) of patients in the 1-yearfollow-up and 30.5% (302 of 990) in the 3-year follow-upwere lost to follow-up. Two eyes were not independentvariables. Analysis should be performed using one eye that

is randomly selected from patients with two eyes. However,the analysis with one eye did not change the statisticalresults in this study.

In the 1-year study, 96.8% of the polyacrylic intraocularlens group and 95.8% of the polymethylmethacrylateintraocular lens group achieved corrected visual acuity of0.5 or better; this was significantly higher compared withthe Food and Drug Administration grid (94%; P 5 .001)and similar to previous report for silicone lens (96%).14,15

In the 3-year follow-up study, the polyacrylic intraocularlens group showed a significantly higher percentage of eyesachieving 0.5 or better at 1 year compared with the Foodand Drug Administration grid (84%; P , .001) andsimilar to the previous study of silicone lens (86%).14,15

The overall rate of complications in the polyacrylicintraocular lens group was low and showed no statisticaldifference in the polymethylmethacrylate intraocular lensgroup. Within each category, the rate of complications wasnot significantly different from rates reported in the Foodand Drug Administration grid and previous study forsilicone lens. Other studies of long-term data, includingthe Food and Drug Administration grid, have reportedsimilar results.14,19

The incidence of posterior capsular opacification neces-sitating Nd:YAG capsulotomy for the polyacrylic intraoc-ular lens group was significantly lower. Our results at 3years after operation are similar to previous studies of thepolyacrylic intraocular lens with a small number of cas-es.20–22 The Nd:YAG capsulotomy rates with the siliconeintraocular lens vary considerably among the publisheddata.15,22–26 Steinert and associates15 and Hayashi andassociates22 attributed the recent reduction in theNd:YAG capsulotomy rate of the silicone lens to improve-ment of the intraocular lens fixation technique.15,22 How-

TABLE 4. Adverse Reactions in 1-Year Follow-up Study

Polyacrylic

IOL Group

PMMA IOL

Group Silicone IOL15 FDA Grid14

Number of eyes 605 604 1432 2465

Number of patients 470 490

Hypopyon

Eyes 0 (0%) 0 (0%) 0.1% 0.4%

Patients 0 (0%) 0 (0%)

Intraocular infection

Eyes 0 (0%) 1 (0.2%) 0.2% 0.1%

Patients 0 (0%) 1 (0.2%)

Acute corneal decompensation

Eyes 0 (0%) 0 (0%) 0.2% 0.2%

Patients 0 (0%) 0 (0%)

Secondary surgical intervention

Eyes 0 (0%) 1 (0.2%) 0.6% 2.0%

Patients 0 (0%) 1 (0.2%)

Abbreviations as in Tables 1 and 3.


ever, the Nd:YAG capsulotomy rate of the polyacrylicintraocular lens in this study was significantly lower thanany previous data for the silicone intraocular lens.

Posterior capsular opacification depends on intraocularlens design and its material.27 Nagamoto and Eguchi28

reported that the convex plano optic inhibited migrationof lens epithelial cells more strongly than the biconvexoptic and that the convex plano allowed firm contactbetween the intraocular lens and posterior capsule.28 Thepolyacrylic intraocular lens has a more defined and squareredge profile, which creates higher pressure on the posteriorcapsule and acts as a mechanical barrier to lens epithelialcell migration. Nagata and associates29 found strongeradhesiveness of polyacrylic lens to a collagen film, abiomaterial possessing properties similar to the lens capsu-lar surface, than the polymethylmethacrylate intraocularlens.29 Ursell and associates30 and Sickenberg and associ-ates31 reported that the polyacrylic intraocular lens pro-duced significantly less anterior capsule movement thanpolymethylmethacrylate or silicone lenses and that theanterior capsule over the intraocular lens’s bioactive sur-face bonds to the intraocular lens.30,31 Linnola32 postulated“the sandwich theory” to explain the low incidence ofposterior capsule opacification. The 90-degree edge of thepolyacrylic intraocular lens optic against the posteriorcapsule directs the proliferating lens epithelial cells to forma monolayer between the intraocular lens and posterior

capsule.28 Another bioactive bond is formed when amonolayered lens epithelial cell has the posterior capsuleon one side and the bioactive intraocular lens on theother. The cell-posterior capsule and cell bioactive in-traocular lens surface junctions prevent more cells frommigrating behind the intraocular lens. Some of the mono-layer cells die over time, and direct contact between theintraocular lens and the posterior capsule occurs in thisarea.32 Hollick and associates33 studied postoperative mi-gration of lens epithelial cells during a 2-year period andfound that lens epithelial cell regression occurred in 83%of polyacrylic intraocular lenses, compared with 15% ofpolymethylmethacrylate intraocular lenses.

Previous studies have shown the incidence of intraocularlens pitting to vary widely, ranging from 4% to 81%.34,35 Inthis study, slight pitting of intraocular lens from Nd:YAGlaser procedures was observed in 22.2% of the polyacrylicintraocular lens group and 19.4% of the polymethylmethac-rylate group in the 1-year follow-up study and 18.8% of thepolyacrylic intraocular lens group and 17.8% of the poly-methylmethacrylate group in the 3-year follow-up study;there was no significant difference between both groups. Findland associates36 measured effective lens position using partialcoherence interferometry and showed that the lens-capsuledistance was approximately the same with polyacrylic lens,silicone intraocular lens, and polymethylmethacrylate in-traocular lens. Koch indicated that Nd:YAG laser–induced

TABLE 5. Incidence of Discoloration and Glistening of Polyacrylic Intraocular Lens and Corrected Visual Acuity of EyesWith Glistenings


1-Year (N 5 605) 3-Year (N 5 451) 1-Year (N 5 373) 3-Year (N 5 279)

Incidence of discoloration and glistenings

Discoloration 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Glistenings

None 0 (0%) 0 (0%) 0 (0%) 0 (0%)

Trace 337 (55.7%) 286 (63.4%) 208 (55.8%) 159 (57.0%)

Mild 131 (21.7%) 92 (20.4%) 89 (23.9%) 64 (22.9%)

Moderate 84 (13.9%) 45 (10.0%) 51 (13.7%) 38 (13.6%)

Severe 53 (8.8%) 28 (6.2%) 25 (6.7%) 18 (6.5%)

Incidence of eyes with 0.5 or better visual acuity

Glistenings

Trace 291/337 (87.1%) 255/286 (89.2%) 203/208 (97.6%) 154/159 (96.9%)

Mild 114/131 (87.0%) 81/92 (88.0%) 85/89 (95.5%) 62/64 (96.9%)

Moderate 72/84 (85.7%) 39/45 (86.7%) 49/51 (96.1%) 36/38 (94.7%)

Severe 47/53 (88.7%) 24/28 (85.7%) 24/25 (96.0%) 17/18 (94.4%)

Mean logMAR of visual acuity

Glistenings

Trace 0.130 6 0.325 0.117 6 0.318 0.032 6 0.147 0.029 6 0.138

Mild 0.132 6 0.326 0.141 6 0.229 0.038 6 0.155 0.038 6 0.128

Moderate 0.129 6 0.272 0.121 6 0.304 0.038 6 0.158 0.038 6 0.224

Severe 0.129 6 0.261 0.175 6 0.312 0.059 6 0.135 0.079 6 0.163

logMAR 5 logarithm of the minimum angle of resolution.


damage to the polyacrylic intraocular lens was equivalent toor less than that to the polymethylmethacrylate intraocularlens when subjected to the same conditions using scanning

electron microscopy.1 This clinical study showed no signifi-cant difference in Nd:YAG performance between the poly-acrylic and polymethylmethacrylate intraocular lenses.

TABLE 6. Incidence of Nd:YAG Laser Posterior Capsulotomy and Posterior Capsule Opacification Through3 Years Postoperatively

All Patients Best Case PatientsSilicone IOL

(Steinert and

associates15)

Polyacrylic IOL

Group PMMA IOL Group P Value

Polyacrylic IOL

Group PMMA IOL Group P Value

Incidence of Nd:YAG

laser posterior

capsulotomy

1 year 9/605 (1.5%) 93/604 (15.4%) ,.0001 8/373 (2.1%) 80/384 (20.8%) ,.0001 13.4%

3 years 32/451 (7.1%) 163/428 (38.1%) ,.0001 26/279 (9.3%) 88/251 (35.1%) ,.0001 27.5%

Incidence of posterior

capsule opacification

at 3 years

No. of eyes 451 428 279 251 501

Mild 37 (8.2%) 82 (19.2%) ,.0001 24 (8.6%) 47 (18.7%) ,.0001 NA

Moderate 8 (1.8%) 25 (5.8%) .0022 5 (1.8%) 13 (5.2%) — NA

Severe 1 (0.2%) 0 (0%) — 1 (0.4%) 0 (0%) — NA

Nd:YAG laser

capsulotomy

32 (7.1%) 163 (38.1%) ,.0001 26 (9.3%) 88 (35.1%) ,.0001 27.5%

Total 78 (17.3%) 270 (63.1%) ,.0001 56 (20.1%) 148 (59.0%) ,.0001 NA

Total incidence of posterior capsule opacification includes the incidence of mild, moderate, and severe opacification and the incidence of

Nd:YAG laser posterior capsulotomy.

TABLE 7. Incidence of Pitting of Intraocular Lens from Nd:YAG Procedures and Best-corrected Visual Acuity for Patients AfterCapsulotomy Procedures (With and Without Lens Pitting)

All Patients Best Case Patients

Silicone

IOL15

Polyacrylic IOL


Polyacrylic IOL


1-Year follow-up

Incidence of capsulotomy 9/605 (1.5%) 93/604 (15.4%) 8/373 (2.1%) 80/384 (20.8%) 13.4%

Incidence of slight

Nd:YAG pitting

2/9 (22.2%) 18/93 (19.4%) 2/8 (25.0%) 16/80 (20.0%) 6.2%

Eyes with pitting 0.5 or

better visual acuity

2/2 (100.0%) 17/18 (94.4%) 2/2 (100.0%) 16/17 (94.1%) 100.0%

Mean 6 SD (logMAR) 0.048 6 0.069 0.083 6 0.203 0.048 6 0.069 0.094 6 0.214 —

Eyes without pitting 0.5

or better visual acuity

7/7 (100.0%) 70/75 (93.3%) 6/6 (100.0%) 59/63 (93.7%) 86.1%

Mean 6 SD (logMAR) 0.032 6 0.113 0.041 6 0.179 0.023 6 0.127 0.025 6 0.148 —

3-Year follow-up

Incidence of capsulotomy 32/451 (7.1%) 163/428 (38.1%) 26/279 (9.3%) 88/251 (35.1%) 27.5%

Incidence of slight

Nd:YAG pitting

6/32 (18.8%) 29/163 (17.8%) 5/26 (19.2%) 18/88 (20.5%) 12.3%

Eyes with pitting 0.5 or

better visual acuity

6/6 (100.0%) 26/29 (89.7%) 5/5 (100.0%) 18/18 (100.0%) 94.1%

Mean 6 SD (logMAR) 0.087 6 0.089 0.164 6 0.355 0.073 6 0.092 0.040 6 0.088 —

Eyes without pitting 0.5

or better visual acuity

23/26 (88.5%) 116/134 (86.6%) 21/21 (100.0%) 67/70 (95.7%) 86.0%

Mean 6 SD (logMAR) 0.142 6 0.412 0.147 6 0.301 0.015 6 0.102 0.034 6 0.153 —

Abbreviations as in Table 1.


In this study, there was no significant difference in meanvisual acuity between eyes with Nd:YAG-induced damageto the intraocular lens and eyes without damage in thepolyacrylic intraocular lens and polymethylmethacrylateintraocular lens groups. No significant difference was foundin the percentage of eyes achieving 20/40 or better visualacuity between eyes with and without an Nd:YAG–damaged intraocular lens. Previous studies with polymeth-ylmethacrylate and silicone intraocular lenses havereported that slight pitting did not affect corrected visualacuity and that the majority of patients with Nd:YAG–damaged intraocular lenses achieved corrected visual acu-ity of 20/40 or better.15,23,37,38 Because only extensivedisruption of the optical quality of intraocular lens fromNd:YAG is likely to decrease visual acuity significant-ly,39,40 slight damage to the polyacrylic intraocular lenscauses no reduction in visual acuity as well as otherintraocular lenses.

All polyacrylic intraocular lenses showed some degree ofglistenings, ranging from trace to severe. Mean logMAR ofvisual acuity decreased with the increase of the degree ofglistenings, but there was no significant correlation. Dhali-wal and associates9 reported that there was a significantdecrease in contrast sensitivity in eyes with glistenings inpolyacrylic intraocular lenses compared with that of felloweyes with silicone intraocular lenses and that no significantdifference was found in the visual acuity and glare testingbetween eyes. The glistenings are probably caused by watervacuoles that form within the intraocular lenses afterhydration in the eyes. The glistenings have been reportedto decrease over time in some patients.9 Because thelong-term change in the polyacrylic intraocular lens is yetunknown, further follow-up study is needed to clarify thisproblem.

In this clinical evaluation, lenses made of polyacrylicmaterial demonstrated safe and effective performancethrough long-term follow-up at a level equal to or betterthan polymethylmethacrylate lenses. Patients undergoingpolyacrylic intraocular lens implantation achieved excel-lent postoperative visual acuity, had a low rate of postop-erative complications and adverse reactions, and hadNd:YAG capsulotomy rates similar to those reported incontemporaneous clinical studies. These long-term clinicalresults are an important outcome database for the ongoinguse of this foldable optic material.

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