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Observation of whitening by cryo-focused ion beam scanning electron microscopy
788
CORRESPONDENCE
DISCUSSION Our results indicate that ECCE conversion can achieve good results. Converting to ECCE because of a dense nucleus or the inability to achieve a continuous curvilinear capsulorhexis seems reasonable, given that in these situations one may be able to perform an ECCE similar to the way it would have been performed had it been planned. However, if vitreous loss is present, the ECCE may result in vitreous traction. It is now generally accepted that anything that could result in vitreous traction during complicated cataract surgery should be avoided. Procedures such as cellulose sponge vitrectomy and wound sweeping with a spatula are no longer considered acceptable because of the inherent traction they produce.2 Delivery of the nucleus during ECCE can be achieved by “pulling” manually or by “pushing” externally or internally (using balanced salt solution or an ophthalmic viscosurgical device). In the presence of vitreous loss, all these techniques may result in vitreoretinal traction (unless fragments anterior to the posterior capsule are manually removed after a thorough anterior vitrectomy). Many trainees now receive little ECCE training,3 making the chance of a successful conversion less likely. If ECCE is unsuccessful, subsequent vitreoretinal surgery may be hampered by an enlarged wound and a cornea that may take longer to recover than if ECCE had not been attempted. In light of the above, we currently recommend that conversion to ECCE at our unit be considered only by surgeons who are trained in ECCE surgery and vitreous loss is neither present nor likely. We hope that future studies will elucidate the role of ECCE conversion and allow surgeons to make more informed decisions. REFERENCES 1. Ho LY, Doft BH, Wang L, Bunker CH. Clinical predictors and outcomes of pars plana vitrectomy for retained lens material after cataract extraction. Am J Ophthalmol 2009; 147:587–594 2. Arbisser LB, Charles S, Howcroft M, Werner L. Management of vitreous loss and dropped nucleus during cataract surgery. Ophthalmol Clin North Am 2006; 19(4):495–506 3. Chen CK, Tseng VL, Wu W-C, Greenberg PB. A survey of the current role of manual extracapsular cataract extraction. J Cataract Refract Surg 2010; 36:692–693
Observation of whitening by cryo-focused ion beam scanning electron microscopy Hiroyuki Matsushima, MD, PhD, Yoko Katsuki, Koichiro Mukai, PhD, Mayumi Nagata, MD, PhD, Tadashi Senoo, MD, PhD Recent reports indicate that light scattering on the surface of the AcrySof intraocular lens (IOL) optic
(Alcon Laboratories, Inc.) increases over time postoperatively.1–3 This scattering as “whitening” was first reported in 2002 by Yaguchi et al.4 We have suggested that the main cause of this phenomenon is phase separation of trace amounts of water impregnated in the IOL optic material as well as glistening.5 When we observe glistening under a light microscope, the water phase has a bright-spot-like appearance and the phase diameter is 5 to 20 mm.6,7 In contrast, when we observe whitening by light microscopy, the water phase appears as misty opacification and the diameter cannot be measured because the size of the water phase is very small. Moreover, whitening cannot be observed by electron microscopy because water within the material evaporates because of the reduced pressure in the sample chamber. In this report, we used cryofocused ion beam scanning electron microscopy (SEM) to observe the appearance of water phase separation in IOL material in which whitening developed and to confirm the size and form of the water phase separation. CASE REPORT The patient was a 77-year-old Japanese woman. In 2001, an MA60BM IOL (Alcon Laboratories) was implanted during cataract surgery with simultaneous vitreoretinal surgery for a macular hole in the right eye. The surgery was performed at another hospital. In May 2008, the patient complained of decreased visual acuity and was evaluated at a hospital associated with Dokkyo Medical University. In April 2009, with the patient’s informed consent, the IOL was removed and a new IOL was implanted. To avoid the development of glistenings from the temperature change, the extracted IOL was immediately placed in physiologic saline at 33 C. Examination of the extracted IOL showed light scattering localized on the surface layer of the IOL optic; whitening subsequently developed (Figure 1). To ensure stable phase separation of water, the extracted IOL was cooled rapidly using liquid nitrogen and the extracted IOL was then placed in the sample chamber ( 130 C, 1 10 4 Pa) of a cryo-focused ion beam SEM (Helios NanoLab 600 [FEI Co.]). A cross-section of the extracted IOL anterior to the IOL surface was created using a focused ion beam and examined by SEM. Serial SEM images (99 photographs) at 25 nm intervals were processed using image reconstruction software (Mercury Computer Systems, Inc. Amera) to obtain a three-dimensional (3-D) reconstructed image. As a control, an unopened MA60AC IOL (Alcon Laboratories, Inc.) was examined. The control was kept in physiologic saline at room temperature for at least 1 week and then examined. Figure 2 shows the cross-section (2-dimensional) and 3-D reconstructed images. In the extracted IOL (with whitening), many heterogeneous domains, not seen in the control, were distributed more toward the near surface and less toward the interior of the IOL. At a constant pressure, when the sample chamber temperature was increased to 85 C, the domain was sublimated and cavities appeared (data not shown). From the water phase diagram, this behavior corresponded to changes in the water state; thus, we confirmed that the domains were water. The mean size of the domain was 94 nm
J CATARACT REFRACT SURG - VOL 37, APRIL 2011
CORRESPONDENCE
789
Figure 1. The extracted IOL shows marked light scattering near the optic surface.
Figure 2. In contrast to homogeneity of the control, many heterogeneous domains were distributed within the extracted IOL (with whitening). Experimentally, the domains were identified as water. The 3-D image confirms the water phase separation distribution (water shown as red).
(maximum 190 nm, minimum 33 nm), and the shape was spherical.
REFERENCES 1. Miyata K, Otani S, Nejima R, Miyai T, Samejima T, Honbo M, Minami K, Amano S. Comparison of postoperative surface light scattering of different intraocular lenses. Br J Ophthalmol 2009; 93:684–687 2. Nishihara H, Yaguchi S, Onishi T, Chida M, Ayaki M. Surface scattering in implanted hydrophobic intraocular lenses. J Cataract Refract Surg 2003; 29:1385–1388 3. Yaguchi S, Nishihara H, Kambhiranond W, Stanley MS, Apple DL. Light scatter on the surface of AcrySofÒ intraocular lenses: part I. Analysis of lenses retrieved from pseudophakic postmortem human eyes. Ophthalmic Surg. Lasers Imaging 2008; 39:209–213
4. Yaguchi S, Chida M, Nishihara H, Ohnishi T, Ayaki M. [Light scattering observed on the surface of acrylic intraocular lenses ten years after implantation]. [Jananese] Nippon Ganka Gakkai Zasshi 2002; 106:109–111 5. Matsushima H, Mukai k, Nagata M, Gotoh N, Matsui E, Senoo T. Analysis of surface whitening of extracted extracted hydrophobic acrylic intraocular lenses. J Cataract Refract Surg 2009; 35:1927–1934 6. Gregori NZ, Spencer TS, Mamalis N, Olson RJ. In vitro comparison of glistening formation among hydrophobic acrylic intraocular lenses. J Cataract Refract Surg 2002; 28:1262–1268 7. Kato K, Nishida M, Yamane H, Nakamae K, Tagami Y, Tetsumoto K. Glistening formation in an Acrysof lens initiated by spinodal decomposition of the polymer network by temperature change. J Cataract Refract Surg 2001; 27: 1493–1498
J CATARACT REFRACT SURG - VOL 37, APRIL 2011
CORRESPONDENCE
DISCUSSION Our results indicate that ECCE conversion can achieve good results. Converting to ECCE because of a dense nucleus or the inability to achieve a continuous curvilinear capsulorhexis seems reasonable, given that in these situations one may be able to perform an ECCE similar to the way it would have been performed had it been planned. However, if vitreous loss is present, the ECCE may result in vitreous traction. It is now generally accepted that anything that could result in vitreous traction during complicated cataract surgery should be avoided. Procedures such as cellulose sponge vitrectomy and wound sweeping with a spatula are no longer considered acceptable because of the inherent traction they produce.2 Delivery of the nucleus during ECCE can be achieved by “pulling” manually or by “pushing” externally or internally (using balanced salt solution or an ophthalmic viscosurgical device). In the presence of vitreous loss, all these techniques may result in vitreoretinal traction (unless fragments anterior to the posterior capsule are manually removed after a thorough anterior vitrectomy). Many trainees now receive little ECCE training,3 making the chance of a successful conversion less likely. If ECCE is unsuccessful, subsequent vitreoretinal surgery may be hampered by an enlarged wound and a cornea that may take longer to recover than if ECCE had not been attempted. In light of the above, we currently recommend that conversion to ECCE at our unit be considered only by surgeons who are trained in ECCE surgery and vitreous loss is neither present nor likely. We hope that future studies will elucidate the role of ECCE conversion and allow surgeons to make more informed decisions. REFERENCES 1. Ho LY, Doft BH, Wang L, Bunker CH. Clinical predictors and outcomes of pars plana vitrectomy for retained lens material after cataract extraction. Am J Ophthalmol 2009; 147:587–594 2. Arbisser LB, Charles S, Howcroft M, Werner L. Management of vitreous loss and dropped nucleus during cataract surgery. Ophthalmol Clin North Am 2006; 19(4):495–506 3. Chen CK, Tseng VL, Wu W-C, Greenberg PB. A survey of the current role of manual extracapsular cataract extraction. J Cataract Refract Surg 2010; 36:692–693
Observation of whitening by cryo-focused ion beam scanning electron microscopy Hiroyuki Matsushima, MD, PhD, Yoko Katsuki, Koichiro Mukai, PhD, Mayumi Nagata, MD, PhD, Tadashi Senoo, MD, PhD Recent reports indicate that light scattering on the surface of the AcrySof intraocular lens (IOL) optic
(Alcon Laboratories, Inc.) increases over time postoperatively.1–3 This scattering as “whitening” was first reported in 2002 by Yaguchi et al.4 We have suggested that the main cause of this phenomenon is phase separation of trace amounts of water impregnated in the IOL optic material as well as glistening.5 When we observe glistening under a light microscope, the water phase has a bright-spot-like appearance and the phase diameter is 5 to 20 mm.6,7 In contrast, when we observe whitening by light microscopy, the water phase appears as misty opacification and the diameter cannot be measured because the size of the water phase is very small. Moreover, whitening cannot be observed by electron microscopy because water within the material evaporates because of the reduced pressure in the sample chamber. In this report, we used cryofocused ion beam scanning electron microscopy (SEM) to observe the appearance of water phase separation in IOL material in which whitening developed and to confirm the size and form of the water phase separation. CASE REPORT The patient was a 77-year-old Japanese woman. In 2001, an MA60BM IOL (Alcon Laboratories) was implanted during cataract surgery with simultaneous vitreoretinal surgery for a macular hole in the right eye. The surgery was performed at another hospital. In May 2008, the patient complained of decreased visual acuity and was evaluated at a hospital associated with Dokkyo Medical University. In April 2009, with the patient’s informed consent, the IOL was removed and a new IOL was implanted. To avoid the development of glistenings from the temperature change, the extracted IOL was immediately placed in physiologic saline at 33 C. Examination of the extracted IOL showed light scattering localized on the surface layer of the IOL optic; whitening subsequently developed (Figure 1). To ensure stable phase separation of water, the extracted IOL was cooled rapidly using liquid nitrogen and the extracted IOL was then placed in the sample chamber ( 130 C, 1 10 4 Pa) of a cryo-focused ion beam SEM (Helios NanoLab 600 [FEI Co.]). A cross-section of the extracted IOL anterior to the IOL surface was created using a focused ion beam and examined by SEM. Serial SEM images (99 photographs) at 25 nm intervals were processed using image reconstruction software (Mercury Computer Systems, Inc. Amera) to obtain a three-dimensional (3-D) reconstructed image. As a control, an unopened MA60AC IOL (Alcon Laboratories, Inc.) was examined. The control was kept in physiologic saline at room temperature for at least 1 week and then examined. Figure 2 shows the cross-section (2-dimensional) and 3-D reconstructed images. In the extracted IOL (with whitening), many heterogeneous domains, not seen in the control, were distributed more toward the near surface and less toward the interior of the IOL. At a constant pressure, when the sample chamber temperature was increased to 85 C, the domain was sublimated and cavities appeared (data not shown). From the water phase diagram, this behavior corresponded to changes in the water state; thus, we confirmed that the domains were water. The mean size of the domain was 94 nm
J CATARACT REFRACT SURG - VOL 37, APRIL 2011
CORRESPONDENCE
789
Figure 1. The extracted IOL shows marked light scattering near the optic surface.
Figure 2. In contrast to homogeneity of the control, many heterogeneous domains were distributed within the extracted IOL (with whitening). Experimentally, the domains were identified as water. The 3-D image confirms the water phase separation distribution (water shown as red).
(maximum 190 nm, minimum 33 nm), and the shape was spherical.
REFERENCES 1. Miyata K, Otani S, Nejima R, Miyai T, Samejima T, Honbo M, Minami K, Amano S. Comparison of postoperative surface light scattering of different intraocular lenses. Br J Ophthalmol 2009; 93:684–687 2. Nishihara H, Yaguchi S, Onishi T, Chida M, Ayaki M. Surface scattering in implanted hydrophobic intraocular lenses. J Cataract Refract Surg 2003; 29:1385–1388 3. Yaguchi S, Nishihara H, Kambhiranond W, Stanley MS, Apple DL. Light scatter on the surface of AcrySofÒ intraocular lenses: part I. Analysis of lenses retrieved from pseudophakic postmortem human eyes. Ophthalmic Surg. Lasers Imaging 2008; 39:209–213
4. Yaguchi S, Chida M, Nishihara H, Ohnishi T, Ayaki M. [Light scattering observed on the surface of acrylic intraocular lenses ten years after implantation]. [Jananese] Nippon Ganka Gakkai Zasshi 2002; 106:109–111 5. Matsushima H, Mukai k, Nagata M, Gotoh N, Matsui E, Senoo T. Analysis of surface whitening of extracted extracted hydrophobic acrylic intraocular lenses. J Cataract Refract Surg 2009; 35:1927–1934 6. Gregori NZ, Spencer TS, Mamalis N, Olson RJ. In vitro comparison of glistening formation among hydrophobic acrylic intraocular lenses. J Cataract Refract Surg 2002; 28:1262–1268 7. Kato K, Nishida M, Yamane H, Nakamae K, Tagami Y, Tetsumoto K. Glistening formation in an Acrysof lens initiated by spinodal decomposition of the polymer network by temperature change. J Cataract Refract Surg 2001; 27: 1493–1498
J CATARACT REFRACT SURG - VOL 37, APRIL 2011