Effects on the surrounding tissues and morphological changes of components after implantation of PMMA and heparin surface modified PMMA intraocular lens in rabbit eyes

The aim of this study was to evaluate the cellular response and morphological changes of cells on the intraocular lens(IOL) implanted over a course of time and to identify the basic mechanism of IOL adaptation to tissue reaction in the implanted eye by comparing polymethylmethacrylate (PMMA) IOL with heparin surface modified PMMA IOL. ECCE using Healon was done in 36 eyes of 36 rabbits. A heparin surface modified IOL was implanted in 18 eyes (Group I), while PMMA IOL was implanted into another 18 eyes (Group II). Corneal thickness and endothelial cell density were measured for 3 months. Postoperatively, the eyes were enucleated, and a cytopathologic examination of the cells on the surface of the IOL and their ultrastructural changes were observed with light and scanning microscope at various points of time. The findings of this present study suggested that heparin surface modified PMMA IOL reduced the degree of endothelial cell damage, postoperative tissue reaction, and pigment deposits on the surface of the IOL. These were statistically significant. The most important cell was considered to be the macrophage for the adaptation of IOL in the eye which gradually changed into a fibroblast-like cell, giant cell and finally disappeared after forming an acellular membrane on the IOL.     

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part II: Morphological stages of the macrophage on the implanted lens surface

Macrophages appearing on implanted intraocular lenses (IOLs) in the rabbit eye and in the mouse peritoneal space were observed using Wolter's implant cytology staining and scanning and transmission electron microscopy. In response to the implanted IOL, macrophages in the mouse peritoneal space displayed an activated form with marked ruffles on the surface. They were attached to the IOL with a broad base (sessile macrophage). The macrophages metamorphosed gradually to the flat shape of so-called epithelioid cells with many processes. They showed a tendency to fuse together or become more flat by extending the cytoplasmic lamellipodia and finally disappeared, leaving a thin membrane or a fibrous matrix. Phagocytic activity of macrophages and related cells was also observed. However, those observed on the IOL implanted in the rabbit eye showed less surface structure and appeared to adhere weakly to the IOL.     

Immunohistochemical study of cellular response on the intraocular lens surface

This immunohistochemical study was conducted to observe the cellular proliferation on the surface of an intraocular lens (IOL) implanted in the rabbit eye. One week after extracapsular lens extraction followed by posterior chamber lens implantation, the IOL was removed and examined by an indirect immunohistochemical method using anti-macrophage antiserum. Macrophage immunoreactivities were observed on the small round cells, the middle-sized oval cells, the foreign-body giant cells and the fibroblast-like cells attached to the surface of the IOL. Most of the cellular components on the implanted IOL seemed to be macrophages.     

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part I: Cellular components observed on the implanted lens surface

Polymethylmethacrylate and silicone intraocular lenses (IOLs) were implanted in the rabbit eye and in the mouse peritoneal space to study cellular response to the implanted IOL. Animals were sacrificed at various times after implantation. The removed IOLs were properly fixed and stained using Wolter's implant cytology technique. Scanning and transmission electron microscopic studies were performed. Macrophages, lymphocytes, and fibroblast-like cells were the major components identified. Occasional formations of foreign-body giant cells were seen. The responses observed on IOLs implanted in the rabbit eye were generally milder than those observed on IOLs implanted in the mouse peritoneal space.     

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part IV: Cell adhesion, fibroblast-like cell, and lymphocytic cluster observed on the implanted lens surface

Transmission and scanning electron microscopy, Wolter's implant cytology staining, and an immunohistochemical method were used to investigate the process of cell adhesion, the origin of fibroblast-like cells, and the nature of lymphocytic clusters that were observed on intraocular lenses (IOLs) experimentally implanted in the rabbit eye and in the mouse peritoneal space. On the IOL implanted in the mouse peritoneal space, pseudopodia extended during cell adhesion showed morphological variety; on the IOL implanted in the rabbit eye, membranous extensions were seen. Many of the fibroblast-like cells exhibited positive staining for macrophagic antigen, indicating a macrophagic origin. The build-up of lymphocytic clusters, as an indicator of immunologic activity, was frequently observed on IOLs implanted in the mouse peritoneal space, particularly on silicone IOLs. However, such clusters were rarely seen on poly(methyl methacrylate) or silicone IOLs implanted in the rabbit eye, suggesting a much reduced immune response to those materials in the eye chamber.     

Experimental study of cellular response on the intraocular lens surface in terms of the presence and distribution of fibronectin

An immunohistochemical study was performed to observe cellular proliferation on the surface of implanted intraocular lenses (IOLs) in rabbit eyes. Rabbits were killed 3-28 days postoperatively. The removed IOLs were examined by an immunoperoxidase staining method using anti-fibronectin antibodies. The immunoreactivity for fibronectin was detected in macrophages and multinucleated giant cells attached to the IOL surface. Prominent stains were observed in these cells 1 week after the operation, and staining for fibronectin was less intense in the specimens 2 and 4 weeks after implantation. Fibronectin is produced by macrophages and multinucleated giant cells on the IOL surface, and might play important role in cellular adhesion and motility. Fibronectin immunoreactivity decreased with time and it may be related to cellular activity.     

Long-term pathologic follow-up of obsolete design: Choyce Mark VIII anterior chamber intraocular lens

We analyzed an enucleated eye that was blind and painful from a 66-year-old patient implanted with a Tennant modification of the Choyce Mark VIII anterior chamber intraocular lens (IOL) as a secondary procedure in 1978. The eye developed glaucoma, with implantation of an Ahmed valve in 2006. Gross and light microscopic analyses showed corneal decompensation and vascularization, peripheral anterior and posterior synechiae, iris thinning, significant changes in the iris pigmented layer, fibrous tissue on the anterior surface of the iris, and Soemmerring ring formation in the periphery of capsular bag remnants. In addition, there was severe attenuation of the nerve fiber layer and extensive cupping of the optic disc. The IOL surface was overall smooth and regular, without warping of the footplates, and was partially covered by clumps of various cell elements, including giant cells intermixed with pigment. This study represents the longest clinicopathologic correlation report on this IOL.     

Cytopathology of intraocular lens implantation

The cytopathology of intraocular lens (IOL) following implantation is reviewed. A newly placed implant attracts macrophages and these settle on its surfaces to form optically clear membranes composed of so-called fibroblast-like cells and a film of proteinaceous material. The membranes apparently become tougher and more firmly adherent with time. The fibroblast-like cells have phagocytic abilities and may form fibrous structures on the surface of implants in complicated situations. Few multinucleated giant cells may be seen in successful cases, but great numbers of giant cells are indicators of adaptation problems. The giant cells on implants include foreign-body, Touton, and Langhans' types. Giant cells on lens implants are commonly associated with nongranulomatous inflammatory cell infiltration in the iris and ciliary body. Inflammatory reactions to IOLs appear to be related to the intolerance of the eye to the IOL foreign body. I present evidence that such inflammatory reactions are a limiting factor in the success of IOL implantation.     

缝线固定人工晶状体植入术后房水细胞学实验研究

目的研究兔眼缝线固定式后房型人工晶状体植入术后早期炎症反应中房水的细胞学动态变化。方法分为缝线固定人工晶状体植入术组；晶状体囊外摘出组；正常对照组。术后1、3、7和14天抽取房水计数白细胞总数及分类。结果缝线固定人工晶状体植入术组术后房水炎症细胞数明显高于单纯晶状体囊外摘出组。结论术后早期房水白细胞总数和嗜中性粒细胞增加可能与手术所致的机械性创伤及血房水屏障破坏有关；术后房水巨噬细胞增多可能是对人工晶状体材料的一种免疫反应。     

Inhibition of lens epithelial cell migration at the intraocular lens optic edge: role of capsule bending and contact pressure

PURPOSE: To evaluate the inhibitory effect of a sharp intraocular lens (IOL) optic edge, a sharp capsule bend, and contact pressure between the optic edge and posterior capsule on lens epithelial cell (LEC) migration. SETTING: Department of Ophthalmology, Kyorin University, Tokyo, Japan. METHODS: This in vitro laboratory study evaluated a tumble-polished convex-plano IOL (CP group), an AcrySof IOL (Alcon) with a sharp edge (AS group), a new IOL with a round ridge (RR group), and a new IOL with a sharp ridge (SR group). The 2 new IOLs have high ridges and high angled loops that create firm contact between the ridge and posterior capsule. After sham cataract surgery, an IOL and a capsular tension ring (CTR) were implanted in the capsular bag of rabbit eyes. The extracted capsular bags containing the CTR and IOL were cultured. The inhibitory effect of each IOL on cell migration was analyzed. Furthermore, LEC migration on the posterior capsule was compared in culture between capsules having a sharp right angle and those with gradually curving bends. RESULTS: The inhibitory effect on cell migration was statistically greatest in the SR group followed by the RR, AS, and CP groups. A sharp capsule bend did not inhibit cell migration. CONCLUSIONS: The results suggest that inhibition of cell migration at the optic edge is regulated by the degree of contact pressure between the optic edge and posterior capsule. A sharp capsule bend might indicate strong contact but does not in itself inhibit cell migration.     

Implanting a clear intraocular lens in one eye and a yellow lens in the other eye: a case series

PURPOSE: To describe the color vision disturbance reported by patients in whom a clear intraocular lens (IOL) was implanted in one eye and a yellow-tinted (blue-light-absorbing) IOL in the other eye. DESIGN: Retrospective interventional case series. METHODS: Data recorded included demographic information, dates of surgery, IOL model and power (manufacturer is the same for all lenses), best-corrected visual acuity, and subjective visual complaints. RESULTS: Four of five patients had no spontaneous color vision complaints. When these patients were informed of the unintended mismatch, all remarked that they could perceive a color vision difference, but that it was not bothersome. One of the five patients reported "beige" vision. None of the patients wanted an IOL exchange. CONCLUSION: Many patients can tolerate the color vision imbalance that results when a clear IOL is implanted in one eye and a yellow-tinted IOL is implanted in the other eye.     

Comparison of the cellular response on intraocular lenses implanted in rabbit eyes with and without extracapsular lens extraction

Three-piece poly(methyl methacrylate) intraocular lenses (IOLs) were implanted in rabbit eyes with and without lens extraction to examine the cellular response on the IOL surface without the effects of the residual lens cortex. Each rabbit had extracapsular lens extraction (ECCE) with IOL implantation in the posterior chamber of one eye. In the second eye, the IOL was implanted in the anterior chamber without lens extraction. The lenses were removed and studied with light microscopy and scanning electron microscopy one week after surgery. Light microscopic findings revealed a similar cellular response on the surface of the IOLs in both groups. Scanning electron microscopy suggested that the cellular adhesiveness on the IOL surface in the eyes without lens extraction was weaker than in the eyes that had ECCE. Cells on the IOLs in the eyes without lens extraction were flatter and had membranous pseudopodia. It appears that the cells on the IOL surface were caused by a foreign body reaction and that their adhesiveness to the IOL was affected by residual lens cortex.     

Effects of tinted intraocular lens on contrast sensitivity

We evaluated contrast sensitivity and glare in 64 pseudophakic eyes. An ultraviolet-absorbing intraocular lens (IOL) was implanted in 32 eyes and a noncyanopsia yellow-tinted IOL was implanted in 32 eyes. The latter lens was designed to effectively absorb light below a wavelength of 500 nm. Contrast sensitivity was measured at a pupil diameter of 3 mm using an artificial pupil. The implanted yellow-tinted IOL showed improved contrast sensitivity in the middle spatial frequencies of 6 and 12 c/deg in photopic and mesopic vision. In addition, the yellow-tinted IOL decreased the effect of central glare on the contrast sensitivity.     

Tilt and decentration of the implanted posterior chamber intraocular lens

Management of surgically induced astigmatism is an important problem for surgeons implanting intraocular lenses. Besides corneal astigmatism, the fixation status of the intraocular lens (IOL) may contribute to total astigmatism. This study was undertaken to evaluate the effect of tilt and decentration of the implanted posterior chamber IOL on the total astigmatism. The tilting angle of the IOL was measured by a method using the 3rd and 4th Purkinje images, and the grade of the decentration was obtained photogrammetrically. The average tilt angle was 7.53 +/- 3.03 degrees (SD). The average decentration was 0.68 +/- 0.33 mm (SD) from the corneal center. Based on these data, the astigmatic error induced by the tilt or decentration of the implanted IOL was calculated as within 0.4 diopter. These data suggest that the fixation status of the IOL implanted in the bag does not cause a serious astigmatic error.     

Intraocular lens as a drug delivery system for dexamethasone

Purpose: To evaluate the effect of an intraocular lens (IOL) coated with dexamethasone on postoperative inflammation after cataract surgery. Methods: Clear lens extraction was performed bilaterally in eight 8‐week‐old rabbits. An uncoated silicone IOL (CeeOn; AMO, Santa Ana, CA, USA) was implanted in one randomly selected eye. In the other eye, the same silicone IOL model was implanted but was coated with dexamethasone. Aqueous humour was obtained preoperatively and on days 1, 3, 7, 14 and 28 postoperatively. Three inflammatory parameters were measured and compared between the eyes: prostaglandin E2 (PGE2), white blood cell (WBC) count and protein content. The animals were killed on day 28 postoperatively. Results: PGE2 levels measured on days 1, 3 and 7 were significantly lower in eyes with a coated IOL compared to eyes with an uncoated IOL (p < 0.01). The WBC count was significantly lower in eyes with a coated IOL on days 1 (p < 0.01) and 3 (p < 0.05). There was significantly less protein in eyes with a coated IOL on days 1 and 3 (p < 0.01). Conclusion: Coating a silicone IOL with dexamethasone significantly reduced postoperative inflammation after clear lens extraction in rabbits.     

Experimental intraocular lens implantation in the rabbit eye and in the mouse peritoneal space. Part V: Phagocytosis and nuclear patterns of giant cells observed on the implanted lens surface

The major cellular components on intraocular lenses experimentally implanted in the rabbit eye and in the mouse peritoneal space were examined. They consisted of macrophages and their metamorphosed epithelioid cells with occasional formations of foreign-body giant cells from the fusion of the macrophage-related cells. Lymphocytes, individually and in clusters, were also seen on the lenses implanted in the mouse peritoneal space but rarely on those implanted in the rabbit eye. Macrophages, epithelioid cells, and giant cells exhibited active phagocytosis on the implanted intraocular lenses. These cells phagocytized not only minor foreign particles such as artificially fed latex or carbon colloids but also living cells including erythrocytes, leukocytes, and lymphocytes. The nuclear pattern of the giant cell formation process initially assumed a centrally located nuclear distribution of a foreign-body giant cell type, and then a peripherally located Langhans type distribution when the number of nuclei reached about five in both the mouse peritoneal space and the rabbit eye chamber. Ultra-large giant cells containing a number of nuclei, however, were only observed on lenses implanted in the rabbit eye, demonstrating a difference between the two environments.     

Spontaneous fracture of an implanted posterior chamber intraocular lens

PURPOSE: Spontaneous fracture of an intraocular lens (IOL) haptic is a rare complication of cataract surgery. The authors report a case of spontaneous fracture of an implanted posterior chamber IOL. CASE: Five years ago, a 12-year-old patient underwent linear lens extraction, posterior capsulotomy, and anterior vitrectomy due to traumatic cataract and received a polymethyl methacrylate (PMMA) biconvex posterior chamber IOL implanted in ciliary sulcus. Five years later, IOL optic was found in anterior chamber with its haptics broken from the optic-haptic junction. DISCUSSION: The broken haptic was examined with scanning electron microscopy. The fracture site of the haptic was on the optic-haptic junction. The fractured surface had a regular appearance. CONCLUSIONS: To our knowledge, this is the fourth report of spontaneous fracture of an implanted posterior chamber IOL.     

Calculating the optimal rotation of a misaligned toric intraocular lens

PURPOSE: To present a formula for calculating the theoretical optimal position of a toric intraocular lens (IOL) that is rotationally misaligned. SETTING: Private practice in an academically affiliated setting. METHODS: Using equations for astigmatic decomposition, a formula to calculate the optimal rotation of an implanted toric IOL requiring only the power and axis of the IOL and the total eye astigmatism was derived. RESULTS: The optimal rotational position can be obtained from the derivation. CONCLUSION: The formula calculates the rotation an implanted toric IOL must undergo to minimize an eye's manifest astigmatism.     

PGE(2) and leucocyte levels in aqueous humor after lens extraction and intraocular lens implantation

In order to study the inflammatory response after cataract surgery and intraocular lens implantation the leukocyte (WBC) and prostaglandin E(2) (PGE(2)) levels in aqueous humor were measured in rabbit eyes at different time points (1, 3, 7, 14 and 28 days) postoperatively. In the first group lenses were implanted in the anterior chamber of the eye, without lens extraction, while in the second group the lens was removed and the IOL was placed in the capsular bag. A third group of animals was injected with 10 ng endotoxin into the vitreous in order to induce an inflammation of the uvea. In the endotoxin group high levels of WBC and PGE(2) were observed at 24 h postoperatively, followed by a decrease over time. In the intraocular lens groups WBC and PGE(2) were detected at all time points, and at higher levels compared to the endotoxin group. The WBC was high at day 1 and 3, declined over time, and then increased at day 28 postoperatively. The PGE(2) level was highest at day 3 in rabbits with anterior chamber lenses, while it peaked at day 7 in the animals with IOLs implanted in the capsular bag. In animals with the extracapsular lens extraction without an implanted IOL, the levels of WBC and PGE(2) decreased over time, and were statistically lower after one week compared with animals with an IOL placed in the capsular bag. The results demonstrate that the inflammatory response after cataract surgery persists for at least one month, probably due to surgical trauma and foreign body reactions. PGE(2) and WBC could be used to study postoperative trauma and biocompatibility of different IOL materials and designs.     

人工晶体表面细胞学反应实验研究

目的观察兔眼后房型人工晶体植人术后人工晶体表面细胞学反应的病变特征及规律，探讨术后眼内炎症反应的发生机理。方法９只青紫蓝兔分为３组。后房型人工晶体植人术后１、７、１４天摘除人工晶体，行光镜和扫描电镜检查，计数炎性细胞数，采用ＳＡＳ软件包，对统计资料做方差分析。结果术后人工晶休表面有明显的炎性细胞；描述了巨噬细胞演变为上皮样细胞、纤维母细胞样细胞和成纤维细胞的过程；首先发现纤维母细胞佯细胞、上皮样细胞与巨噬细胞胞浆内均含有吞噬颗粒，结论推测人工晶体表面的巨噬细胞、纤维母细胞样细胞和上皮详细胞具有效强的吞噬能力，人工晶体表面存在的淋巴细胞群、巨噬细胞和嗜酸性粒细胞提示对人工晶体所在抗原的兔疫反应。