Four year follow-up of the MemoryLens DetlefK. Potzsch, MD, Christel M. Losch-Potzsch, MD ABSTRACT Purpose: To determine whether the long-term results of implantation of thermoelastic MemoryLens intraocular lenses (IOLs) are comparable to those of conventional poly(methyl methacrylate) (PMMA) IOLs. Setting: St. Elisabeth Hospital, Oillingen, Germany. Methods: This retrospective study compared visual acuity, astigmatism, lens decen- tration, biocompatibility, and posterior capsule opacification in 36 eyes with a MemoryLens with those in 36 eyes with a conventional PMMA IOL over 4 years. The MemoryLenses were implanted in 1991 after cataract extraction by phaco- emulsification. Results: Four years postoperatively, best corrected visual acuity was 20/20 to 20/25 in 63.9% of the MemoryLens group and 55.6% of the PMMA group. Mean astigmatism was 0.84 diopters (0) in the MemoryLens group and 1.20 0 in the PMMA group. No cellular precipitates, as evaluated by biomicroscopy, or lens decentration greater than 0.5 mm were found in either group. Posterior capsule opacification, which developed in 22.2% in the MemoryLens group and 38.9% in the PMMA group, was treated with a neodymium:YAG laser capsulotomy. Conclusion: The MemoryLens allows small incision cataract surgery and long-term results that compare favorably with those of PMMA IOLs. J Cataract Refract Surg 1996; 22:1336-1341 ,\VJith Kelman's concept of phacoemulsification, it W became possible to extract cataracts through a 3.0 mm incision. This created a demand for intraocular lenses (IOLs) that could be inserted through a small incision. ' plant Fits 3 mm Incision, Enhances Phakoemulsifica- tion," Ophthalmology Times International, November 15, 1985, page 6). However, this lens was not successful. The introduction of capsulorhexis, combined with secure capsular bag fixation, led to the design of several PMMA lenses with smaller optics. lO-12 Small incisions resulted, but the phacoemulsification incision had to be enlarged before implanting these rigid lenses. In addi- tion, the smaller optic led to such complications as in- creased glare and difficulty examining the peripheral fundus. 13-15 Smaller 10Ls of flexible materials (e.g., silicone, polyHEMA) were developed. In 1984 Mazzocco did the first implantation of a flexible silicone 10L. 2-8 In 1985, Kelman introduced the Phako-fit poly(methyl methac- rylate) (PMMA) 10L, which could be implanted through a 3.2 mm incision (CD. Kelman, MD, "Im- From the Ophthalmic Department, St. Elisabeth Hospital, Dillingen, Germany. Presented in part at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, June 1996 Reprint requests to D. Potzsch, MD, Dillingerstrasse 44,89415 Lauin- gen, Germany. The development of flexible lenses with a 6.0 mm optic determined the future. In addition to silicone and polyHEMA, thermoelastic acrylate materials were de- veloped. The MemoryLens (Optical Radiation Corp.) [ORC] is a flexible 10L made of this thermoelastic material. 16-19 1336 J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 21996 FOLLOW-UP OF THE MEMORYLENS Materials and Methods We implanted 36 MemoryLenses, 30 model U780A and 6 model U940A, between May and Decem- ber 1991. Both models have the same design but differ in size. The U780A has a 7.0 mm optic diameter and a 14.0 mm overall diameter and the U940A, a 6.0 mm optic diameter and 13.0 mm overall diameter. Both three-piece 10Ls have 4-0 polypropylene (Prolene®) modified C-Ioops. The optic of the MemoryLens is of a thermoelastic co-polymer of methyl methacrylate, 2-hydroxyethyl methacrylate, and 4-methacryloxy 2-hydroxy-benzo- phenone. These ultraviolet-absorbing materials block more than 90% of such radiation at 380 nm. These three primary components are combined with ethylene gly- col dimethylacrylate, which is used as cross-linking material. The MemoryLens co-polymer has a high refractive index (1.47), is hydrophilic (20% water content), and has a glass transition temperature of 25°C. This material is easily deformable above body temperature but inflex- ible below 25°C. At body temperature, the lens returns slowly to its original flat form without distortion. At the time of this study, the MemoryLens had to be rolled before implantation. First, the lens was fixed in a rolling device. The surgeon had to maintain exact posi- tioning of the lens within the roller. The lens and roller were then heated in the Thermal Exchange Unit (ORC) (Figure 1). Next, the lens was rolled and cooled by plac- ing it while in the roller into another chamber of the Thermal Exchange Unit. After insertion in the eye, the lens slowly returned to its original shape (Figure 2). Figure 1. (Potzsch) The Thermal Exchange Unit and IOL roller. Figure 2. (Potzsch) A MemoryLens a few seconds after implan- tation but before insertion of the distal haptic. All 10Ls were implanted in the capsular bag after phacoemulsification and continuous curvilinear capsu- lorhexis by the same surgeon. All eyes had an intact lens capsule. The diameter of the capsulorhexis was 6.0 to 6.5 mm for the U780A lens and 5.0 to 5.5 mm for the U940A, allowing the anterior capsule to circularly cover the lens optic. The U780A lenses were implanted through a 3.5 to 4.0 mm wide, 3.0 mm long scleral tunnel incision and the U940A lenses, through a 3.0 to 3.3 mm scleral tunnel incision. In 14 eyes the incision was sutured; in 22, the no-stitch technique was used. The posterior capsule was polished with a Kratz cannula. Postoperative results in the MemoryLens group were compared with those in a control group of 36 eyes with a three-piece PMMA 10L (ORC, UV381K2). This 10L has a 7.0 mm optic diameter, a Prolene haptic with modified C-Ioops, and a 14.0 mm total diameter. The lenses were implanted through a 7.0 mm wide, 3 mm long scleral tunnel incision that was closed with a single radial suture. The sex distribution was similar in both groups: MemoryLens, 23 women and 13 men; PMMA, 21 women and 15 men. Mean patient age in the Memo- ryLens group was 63.7 years (range 49 to 89 years) and in the PMMA group, 69.2 years (range 52 to 86 years). The groups were not matched in age or in eye pathology. One patient in the MemoryLens group and two in the PMMA group had senile maculopathy. Both groups had two patients with diabetic maculopathy. Postoperatively, best corrected visual acuity was measured using optotypes and astigmatism was mea- sured with the T opcon refractometer. Anterior chamber J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 21996 1337 FOLLOW-UP OF THE MEMORYLENS inflammation and the IOL surface were evaluated at the slitlamp.20 Biomicroscopy on dilated eyes was used to assess IOL centration20 and posterior capsule opacifica- tion (PCO). If best corrected visual acuity had dropped two lines and no pathology other than PCO was found, a neodymium:YAG (Nd:YAG) capsulotomy was performed. Results There were no significant between-group differ- ences in postoperative best corrected visual acuity (Ta- ble 1). Two patients in the MemoryLens group with a reduced visual acuity of20/50 had diabetic maculopathy and one with a visual acuity of20/200 had senile macu- lopathy. In the PMMA group, reduced visual acuity to 20/50 was the result of senile (n = 2) or diabetic macu- lopathy (n = 2). The between-group difference in postoperative astigmatism was statistically significant (P = .025, Wil- coxon rank sums test). Mean preoperative astigmatism was 0.89 diopters (0) ± 0.24 (SO) in the MemoryLens group and 0.93 ± 0.29 0 in the PMMA group. Over 4 years, the smaller incision in the MemoryLens group induced less astigmatism (mean 0.84 ± 0.15 0) than the larger incision in the PMMA IOL group (mean 1.20 ± 0.460). Mean surgically induced astigmatism, calculated by vector analysis (Holladay-Cravy-Koch method21 ), was 0.490 in the MemoryLens group and 0.740 in the PMMA group. No patient in the MemoryLens group had a fibrin- oid reaction. One patient in the PMMA group with diabetes mellitus developed a minor fibrinoid reaction on the first postoperative day that resolved with cortico- steroid treatment. One patient in the MemoryLens group and two in the PMMA group had diabetes mellitus. Table 1. Best corrected visual acuity 4 years postoperatively. Visual Acuity 20/20-20/25 20/30-20/40 20/50 20/200 Percentage of Patients Memory Group 63.9 27.8 5.5 2.8 PMMA Group 55.6 33.3 11.1 No patient in either group had cell deposits on the IOL. The whitish deposits at the capsular edge described by Skorpik et al.22 were not found in any of our cases. One eye in the MemoryLens group had scratches on the IOL surface 1 day postoperatively (Figure 3). These scratches, which did not interfere with vision, were caused by a defective rolling device and were not ob- served after the device was changed. Another eye in the MemoryLens group had a tear in the lens optic that was discovered postoperatively (Fig- ure 4). The retrospective video analysis of this case showed that the lens edge was crushed during rolling. The IOL did not change shape or size during the 4 year follow-up. There were no IOL decentrations of more than 0.5 mm in any eye. Fourteen eyes in the PMMA group and eight eyes in the MemoryLens group required an Nd:YAG laser cap- sulotomy for PCO. There were fewer cases of fibrotic PCO in the MemoryLens (n = 1) than in the PMMA group (n = 3) but more Elschnig pearls (11 versus 3). No MemoryLens eye required an Nd:YAG laser capsu- lotomy until 2 years postoperatively. Three eyes with fibrotic PCO in the PMMA group had an Nd:YAG capsulotomy 1 year postoperatively; the other 11 pa- tients developed pearl-type PCO and were treated be- tween 2 and 4 years postoperatively. Discussion Our study showed that the MemoryLens performed as well as the conventional PMMA lens. The visual out- Figure 3. (Potzsch) Scratches on the surface of a MemoryLens 1 month postoperatively. 1338 J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 2 1996 FOLLOW-UP OF THE MEMORYLENS Figure 4. (Potzsch) A tear in the optic of a MemoryLens 2 years postoperatively. come was similar, with reduced visual acuity a result of macular diseases, not the IOLs. The induced astigma~ tism was less in the MemoryLens group because of the smaller incision. During the 4 year follow~up, the spher~ ical equivalent remained constant, and visual resolution was equal to that of PMMA. 18,22 Biocompatibility of the MemoryLens material also seemed similar to that of PMMA. 18,22 The tear in one MemoryLens optic (Figure 4) and the damaged surface (Figure 3) of another MemoryLens were the result of the complicated rolling process (Fig~ ure 1). A prerolled lens design is now available, and we have not seen any scratched anterior surfaces as de~ scribed by Faschinger and coauthors23 since we began using the new design. Posterior capsule opacification is the most frequent complication of modern cataract surgery. In 1991, we polished the posterior capsule with a Kratz cannula be~ fore IOL implantation. Today, we also thoroughly pol~ ish the anterior capsule.24 We do not know the reason for the lower peo rate in the MemoryLens group. Per~ haps it is the result of the hydrophilic surface of the lens material, as has been shown with other hydrophilic materials?5 The MemoryLens material and silicone seem to have a different degree of biocompatibility and migra~ . f fib .. 26-32 A L 4 tion 0 1 rotte tissue. ruter years, we were sur- prised by the small amount of anterior lens capsule fibrosis (Figure 5). Furthermore, we did not find any visually impairing posterior capsule fibrosis. Fibrosis of the type seen with silicone lenses did not occur. The pearl-type peo seems to occur later than with PMMA lenses; however, further prospective, ran- domized studies are necessary to quantifY this effect. Although there was no difference in Nd:YAG laser capsulotomy rates between groups in our study, the MemoryLens material has a greater YAG resistance and less tendency to pit than PMMA and silicone.33,34 The MemoryLens design has changed since our study. The new lenses must be kept in a refrigerator at B°C. In addition, the lens is prerolled and requires a larger incision than the previous design, which could be rolled so that the edges overlapped. A 3.3 mm incision is now recommended for 10 Ls up to 21.00 0 and 3.5 mm incision for those up to 26.00 O. The prerolled lens slowly unfolds intraoperatively, taking about 10 to 15 minutes. Thus, the macula is protected from the bright surgical microscope light and protective shields are unnecessary. The folds of the pre- Figure 5. (Potzsch) MemoryLens in situ 1 day postoperatively (left). Slitiamp photograph of the same eye 4 years later shows discrete opacification of the anterior capsule with a clear posterior capsule (right). J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 21996 1339 FOLLOW-UP OF THE MEMORYLENS rolled lens diminish postoperatively under the influence of body temperature; 1 day after surgery, all folds are gone (Figure 5). The prerolled design allows safe, easy, and quick lens handling, which is important for sterile implanta- tion. As the IOL requires some time to warm up and unroll, the implantation is stressless and controlled. The lens slowly returns to its functional shape within the eye. The Prolene hap tics of the prerolled IOL reach their current position in the capsular bag immediately after implantation; only the optic of the IOL lies U-shaped in the capsular bag. Since April 1995, we have implanted about 1000 MemoryLenses without severe dislocation occurring. Nevertheless, the Prolene haptic is not the most current IOL standard and should be changed.3s- 37 In conclusion, the MemoryLens is suitable as a small incision lens and causes low surgically induced astigma- tism.1t has the advantages of a PMMA IOL such as high intraocular compatibility, excellent centration, and high Nd:YAG laser resistance. In addition, in our study, PCO formation was less in eyes with the MemoryLens. The MemoryLens surface is less sticky than that of other acrylic IOLs. Compared with silicone IOLs, its insertion is much smoother and it does not spring open. If the manufacturer would change the haptic mate- rial, abolish the cooling requirement, and improve the prerolled optic shape, the lens would be an important contribution to small incision cataract surgery. References 1. Kelman CD. Phaco-emulsification and aspiration; a new technique of cataract removal. A preliminary report. Am J Ophthalmoll967; 64:23-35 2. Chen IT. Clinical experience with soft intraocular lens implantation. J Cataract Refract Surg 1987; 13:50-53 3. Mehta KR, Sathe SN, Karyekar SO. The new soft in- traocular lens implant. Am Intra-Ocular Implant Soc J 1978; 4:200-205 4. Packard RBS, Garner A, Arnott EJ. Poly-HEMA as a material for intraocular lens implantation: a preliminary report. Br J Ophthalmol1981; 65:585-587 5. Barrett G, Constable 1]. Corneal endothelial loss with new intraocular lenses. Am J Ophthalmol1984; 98: 157- 165 6. Barrett GO, Constable IJ, Stewart AD. Clinical results of hydrogel lens implantation. J Cataract Refract Surg 1986; 12:623-631 7. Epstein E. Insertion techniques and clinical experience with HEMA lenses. In: Mazzocco TR, Rajacich GM, Epstein E, eds, Soft implant lenses in cataract surgery. Thorofare, NJ, Slack Inc, 1986; 143-150 8. Schlegel HJ. Sieben Jahre Implantation von Silikonlin- sen. In: LangGK, Ruprecht KW,JacobiKW, etal, eds, 2. Kongress der Deutschen Gesellschaft fur Intraokularlin- sen Implantation, 4. bis 5. Marz 1988, Erlangen. Stutt- gart, Enke-Verlag 1989; 164-168 9. Neuhann T. Theorie und Operationstechnik der Kapsu- lorhexis. Klin Monatsbl Augenheilkd 1987; 190:542- 545 10. AuranJD, Koester CJ, DonnA. In vivo measurement of posterior chamber intraocular lens decentration and tilt. Arch Ophthalmol1990; 108:75-79 11. Duncker G, Wetzel W. Linsenposition nach geplanter Kapselsackfixierung: Ergebnisse von 200 konsekutiv operierten Phakoemulsifikationen. Fortschr Ophthalmol 1990; 87:140-143 12. McDonnell PJ, Spalton OJ, Falcon MG. Decentration of the posterior chamber lens implant: the effect of optic size on the incidence of visual aberrations. Eye 1990; 4: 132- 137 13. Jaffe NS. Sulcus versus capsular bag fixation of posterior chamber lenses. EurJ Implant Refract Surg 1989; 1: 157- 162 14. Jorgensen JS, MUller-Bergh JA. Erste Ergebnisse nach Kapselsackimplantation einer 5-mm-one-piece-PMMA- Hinterkammerlinse (Phacobag). In: Schott K, Jacobi KW, Freyler H, eds, 4. Kongress der Deutschen Gesell- schaft fUr Intraokularlinsen Implantation, 6. bis 7. April 1990, Essen. Berlin, Springer-Verlag 1991; 32-37 15. Koch H -R, Fromberg G , Weber F, et al. Klinische Ergeb- nisse nach Implantation von FV-II-Silikon-Intraokular- linsen in die Hinterkammer. In: Freyler H, Skorpik C, Grasl M, eds, 3. KongreB der Deutschen Gesellschaft fur Intraokularlinsen Implantation, 2. bis 4. Marz 1989, Wien. Wien, Springer-Verlag 1990; 148-156 16. Kammann JP, Greite JH, Dornbach G, Harde J. Ergeb- nisse der kIinischen PrUfung mit einer neuen Silikondis- kIinse. In: Schott K, Jacobi KW, Freyler H, eds, 4. Kongress der Deutschen Gesellschaft fur Intraokularlin- sen Implantation, 6. bis 7. April 1990, Essen. Berlin, Springer-Verlag, 1991; 13-19 17. Menapace R, Skorpik C, Wedrich A. Evaluation of 150 consecutive cases of poly HEMA posterior chamber lenses implanted in the bag using a small-incision tech- nique. J Cataract Refract Surg 1990; 16:567-577; cor- rection 1991; 17: 111 18. Neuhann T, Neuhann T. Erste Erfahrungen mit Mem- ory Lens-Eine thermoplastische Intraocularlinse zur Implantation durch kIeine Inzisionen. In: Wenzel M, Reim M, Freyler H, Hartmann C, eds, 5. KongreB der Deutschsprachigen Gesellschaft fUr Intraokularlinsen 1340 J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 21996 FOLLOW-UP OF THE MEMORYLENS Implantation, 8. bis 9. Marz 1991, Aachen. Berlin, Springer-Verlag 1991; 371-374 19. Wenzel M, Reim M, Heinze M, Bocking A. Cellular invasion on the surface of intraocular lenses. In vivo cy- tological observations following lens implantation. GraefesArch Clin Exp Ophthalmol1988; 226:449-454 20. Riemann S, Frohn A, Weidle EG, Lisch W. Subjektive und objektive Ermittlung der Linsenzentrierung. In: Schott K, Jacobi KW, Freyler H, eds, 4. KongreG der Deutschen Gesellschaft flir Intraokularlinsen Implanta- tion, 6. bis 7. April 1990, Essen. Berlin, Springer-Verlag 1991; 120-125 21. Holladay JT, Cravy TV, Koch DD. Calculating the in- duced refractive change following ocular surgery. J Cata- ract Refract Surg 1992; 18:429-443 22. Skorpik C, Freyler H, Scholz U, et al. Ein J ahr Erfahrung mit der "Memory-Lens", einer thermoplastischen Linse rur Kleinschnittimplantation. In: Neuhann T, Hart- mann C, Rochels R, eds, 6. KongreG der Deuschsprachi- gen Gesellschaft flir Intraokularlinsen Implantation, 6. bis 7. Marz 1992, Mlinchen. Berlin, Springer-Verlag 1993; 96-102 23. Faschinger C, Haller EM, Reich M. Oberflachenbescha- digung der MemoryLens bei der Implantation. Klin Monatsbl Augenheilkd 1996; 209:37-39 24. Rentsch FJ, Bauer W. Langzeitergebnisse nach Entfer- nung des Linsenepithels bei der extrakapsularen Katara- ktextraktion mit Phakoemulsifikation In: Rochels R, Dunker G, Hartmann C, eds, 9. KongreG der Deutschs- prachigen Gesellschaft flir Intraokularlinsen Implanta- tion, 17. bis 18. Marz 1995, Kiel. Berlin, Springer-Verlag 1995; 399-407 25. Mehdorn E, Hunold W. Acrysof-Drei Jahre Erfahrung mit einer faltbaren Akryllinse. In: Rochels R, Dunker G, Hartmann C, eds, 9. KongreG der Deutschsprachigen Gesellschaft rur Intraokularlinsen Implantation, 17. bis 18. Marz 1995, Kiel. Berlin, Springer-Verlag 1995; 254- 260 26. Greite JH, Kreiner CF. Development of a flexible disc- shaped lens for capsular fixation. Eur J Implant Refract Surg 1989; 1:131-134 27. Percival P. Capsular bag implantation of the hydrogel lens. J Cataract Refract Surg 1987; 13:627-629 28. Oshika T, Suzuki Y, Kizaki H, Yaguchi S. Two year clinical study of a soft acrylic intraocular lens. J Cataract Refract Surg 1996; 22:104-109 29. Oshika T, Yoshimura K, Miyata N. Postsurgical inflam- mation after phacoemulsification and extracapsular ex- traction with soft or conventional intraocular lens implantation. J Cataract Refract Surg 1992; 18:356- 361 30. Anderson C, Koch DD, Green G, et al. Alcon AcrySofTM acrylic intraocular lens. In: Martin RG, Gills JP, Sanders DR, eds, Foldable Intraocular Lenses. Thorofare, NJ, Slack, 1993; 161-177 31. Keates RH, Erdey RA, Ringel DM, Schild HS. Sevenry- six consecutive cases ofIOGEL intraocular lens implants. J Cataract Refract Surg 1990; 16:47-50 32. Moisseiev J, Bartov E, Schochat A, Blumenthal M. Long- term study of the prevalence of capsular opacification following extracapsular cataract extraction. J Cataract Re- fract Surg 1989; 15:531-533 33. Johnson SH, Henderson C. Neodymium:YAG laser damage to UV-absorbing poly(methyl methacrylate) and UV-absorbing MMA-HEMA-EGDMA polymer in- traocular lens materials. J Cataract Refract Surg 1991; 17:604-607 34. Bath PE, Boerner CF, Dang Y. Pathology and physics of YAG-Iaser intraocular lens damage. J Cataract Refract Surg 1987; 13:47-49; correction p 217 35. Apple DJ, Richards Sc, ParkSB, et al. Posterior chamber intraocular lenses in a series of 75 autopsy eyes. Part I: loop location. J Cataract Refract Surg 1986; 12:358- 362 36. Draeger J, GuthoffR, Abramo F. Zur Biomechanik der Intraokularlinsen-Haptik: Vergleichende Messungen von Elastizitats- und Rlickstellkraft in Abhangigkeit von Materialeigenschaften und Konstruktion. In: Lang GK, Ruprecht KW, Jacobi KW, et al, eds, 2. Kongress der Deutschen Gesellschaft flir Intraokularlinsen Implanta- tion, 4. bis 5. Marz 1988, Erlangen. Stuttgart, Enke- Verlag 1989; 42-44 37. Drews RC, Kreiner C. Comparative study of the elastic- iry and memory of intraocular lens loops. J Cataract Re- fract Surg 1987; 13:525-530 J CATARACT REFRACT SURG-VOL 22, SUPPLEMENT 21996 1341