Age-dependent changes in the basal retinovitreous adhesion

PURPOSE: To determine the width of the posterior vitreous base in human eyes of different ages and to clarify the nature of the postoral retinovitreous adhesion that underlies the development of juxtabasal retinal tears and retinal detachment after posterior vitreous detachment (PVD). METHODS: The posterior limit of the vitreous base was delineated with indocyanine green after mechanical peeling of the postbasal vitreous cortex from the retina in 58 pairs of donor eyes. The area of residual retinovitreous adhesion was measured by image analysis. Scanning electron microscopy was performed on the undersurface (or retinal aspect) of the inner limiting lamina (ILL) after trypsin digestion of the peripheral retina. RESULTS: An age-dependent increase in the anteroposterior dimension of the posterior vitreous base was revealed that became progressively wider in eyes of male donors than in those of female donors and in the nasal half compared with the temporal half of the globe. Ultrastructural studies showed progressive invasion of the innermost peripheral retina by bundles of collagen fibrils, initially in the form of characteristic braids splaying out beneath the ILL and eventually as a dense sublaminar mat in the elderly. The collagen fibrils penetrated the ILL through localized defects and intertwined with those in the basal gel. CONCLUSIONS: With aging, the posterior border of the vitreous base migrates posteriorly so that an annular band of firm adhesion eventually straddles the ora serrata eccentrically. Intraretinal synthesis of collagen fibrils, their penetration of the ILL, and their splicing with cortical vitreous fibrils, underlie the slowly evolving retinovitreous adhesion.     

Age-related changes on the surface of vitreous collagen fibrils

PURPOSE: To determine whether aging vitreous collagen fibrils undergo ultrastructural changes that might underlie vitreous liquefaction and posterior vitreous detachment. METHODS: Vitreous collagen fibrils from 21 human subjects (age range, 3-89 years) and from bovine eyes were isolated on electron microscopy grids. Cupromeronic blue labeling in the presence of 0.3 M MgCl(2) and immunogold labeling for collagen types II and IX were analyzed by transmission electron microscopy. RESULTS: Aging was associated with marked changes on the surface of human vitreous collagen fibrils, including an exponential loss of type IX collagen along with its chondroitin sulfate side-chains (half-life, 11 years) and a fourfold increase in the exposure of type II collagen. CONCLUSIONS: Despite being a minor component of vitreous collagen fibrils, type IX collagen, probably by virtue of its chondroitin sulfate side-chains, shields type II collagen from exposure on the fibril surface. With aging, this shielding diminishes, resulting in the surface exposure of "sticky" type II collagen and thus predisposing the vitreous collagen fibrils to fusion. These changes could underlie vitreous liquefaction and weakening of vitreoretinal adhesion.     

Posterior attachment of ciliary muscle in young, accommodating old, presbyopic monkeys

The authors studied the posterior attachment of the ciliary muscle in seven young (3-10 yr) and five old (26-34 yr) rhesus monkeys by light microscopy and electron microscopy. Posterior attachment of the muscle bundles consisted of elastic tendons, exclusively. The elastic tendons were continuous with the elastic lamina of Bruch's membrane and were also connected by smaller elastic fibers to an elastic meshwork that surrounds the pars plana vessels. In some areas, the tendons formed focal contacts with the endothelial cells. The authors found that in old eyes, the tendons and the elastic fibers of the posterior ciliary body showed pronounced structural changes. The tendons appeared thickened, showed increased amounts of associated microfibrils, and were surrounded by dense layers of thick collagen fibrils. An increased amount of collagen fibrils was also seen between the elastic layer of Bruch's membrane and the pigmented epithelium. A mechanical link between those collagen fibrils and the elastic fibers is suggested by the presence of osmiophilic points of contact. The age-related increase in elastic fibrillar material could cause decreased compliance of the posterior insertion of ciliary muscle and could be an essential factor for presbyopia in rhesus monkeys.     

Ultrastructure of internal limiting membrane removed during plasmin-assisted vitrectomy from eyes with diabetic macular edema

PURPOSE: To study the effect of autologous plasmin enzyme (APE) on the adhesion of the vitreous cortex to the internal limiting membrane (ILM) in eyes with diabetic macular edema. DESIGN: Nonrandomized, comparative, interventional case series. PARTICIPANTS: Ten eyes of 10 patients with diabetic macular edema without a posterior vitreous detachment (PVD), which were treated with APE as an adjunct to conventional pars plana vitrectomy, and 10 eyes of 9 patients without a PVD, which underwent pars plana vitrectomy without APE, were studied. METHODS: In the APE group, 0.4 IU of APE was injected into the midvitreous cavity in 9 eyes, and 0.8 IU of APE in 1 eye. Thirty minutes after plasmin injection, the eyes underwent pars plana vitrectomy with ILM peeling. All eyes in the control group had conventional vitreous surgery with ILM peeling. The removed ILMs were investigated for the presence of vitreous and for ultrastructural differences by transmission and scanning electron microscopy. MAIN OUTCOME MEASURES: The status of the vitreous and induction of a PVD during surgery, and the presence of vitreous and ultrastructural differences of the removed ILM by transmission and scanning electron microscopy. RESULTS: In APE-treated eyes, the degree of liquefaction of the vitreous was graded as high in 4 eyes. Spontaneous PVD occurred in 2 eyes, whereas core vitrectomy with a maximum vacuum of 100 mmHg induced a PVD in 2 additional eyes. In the control group, 8 eyes required suction with a maximum of 200 mmHg to induce the PVD. Scanning electron micrography of the removed ILM in the APE-treated eyes showed a smooth surface on the vitreous side in 8 eyes and only sparse collagen fibers in 2 eyes. Conversely, in the control group, dense vitreous fibers were found in 4 eyes, sparse collagen fibrils in 3 eyes, and a smooth retinal surface in 3 eyes. CONCLUSIONS: These findings indicate that APE helps separate the vitreous hyaloid from the ILM surface and may be a useful adjunct to conventional vitreous surgery for diabetic macular edema.     

高度近视眼黄斑孔玻璃体视网膜界面的超微结构研究

目的 探讨高度近视眼并发的黄斑孔源性视网膜脱离患者的玻璃体视网膜界面特征。方法 12例高度近视眼黄斑孔视网膜脱离患者，玻璃体切割术中剥离黄斑区内界膜及黏附的玻璃体组织。其中8例标本应用透射电镜观察，4例采用免疫胶体金技术进行层粘连蛋白、纤维连接蛋白标记。2例正常尸体眼作对照。结果 透射电镜显示除l例玻璃体皮质和内界膜部分脱离外，7例标本均发现有成片的玻璃体后皮质粘附于内界膜表面。6例标本发现有上皮样细胞，其胞浆中含色素颗粒，表面有较多足突。免疫电镜显示其界面的层粘连蛋白、纤维连接蛋白数量明显多于正常人（P〈0．001）。结论 高度近视眼并发的黄斑孔源性视网膜脱离患者，黄斑区形成玻璃体劈裂。其视网膜表面膜组织中，以上皮样细胞为主介导胶原纤维的收缩。纤维连接蛋白和层粘连蛋白参与了膜收缩。     

Age-related liquefaction of the human vitreous body: LM and TEM evaluation of the role of proteoglycans and collagen

PURPOSE: To evaluate morphologic aspects of age-related liquefaction of the human vitreous body by light and electron microscopy to provide a basis from which future studies directed at the pathogenesis of this phenomenon can be undertaken. The study focuses on changes in fibrillar collagen and proteoglycans (PGs). METHODS: Morphologic aspects of intravitreal liquefied spaces and matrix areas surrounding them were examined in 13 adult human donor eyes (aged 21-80 years) by light (LM) and transmission electron microscopy (TEM). Collagen fibrils were visualized by using standard contrasting methods. PGs were specifically stained by cupromeronic blue (CB). RESULTS: Eyes from older donors contained larger spaces than eyes from younger ones. Transitions between matrix and spaces were abrupt or gradual. In transition areas of all specimens, a gradual decrease in the number of collagen fibers, and to a lesser extent of PGs was observed. In addition, a fragmentation of collagen fibers and an aggregation of PG-molecules around these fragments were found. Neither cells nor their fragments were observed in these areas. CONCLUSIONS: This is the first study to evaluate vitreous liquefaction at the light and electron microscopic level. A breakdown of collagen fibrils into smaller fragments seems to be crucial to the pathogenesis of age-related liquefaction of the human vitreous body. The mechanism inducing fragmentation of vitreous fibrils has yet to be elucidated. From the absence of cells and cellular remnants in all specimens, it is tentatively concluded that an extracellular process is involved.     

基质金属蛋白酶-3在玻璃体切割术中的辅助作用研究

目的探讨玻璃体腔内注射基质金属蛋白酶-3(matrix metalloproteinase-3,MMP-3)对玻璃体切割术的辅助作用.方法将20只灰兔随机分成2组,右眼为实验眼,A组10眼玻璃体腔内注射平衡盐溶液(BSS)0.1mL,B组10眼注射MMP-3 0.1mL(10ng),注射后30min行玻璃体切割术;左眼为对照眼,玻璃体腔内注射等量BSS但不行玻璃体切割术.术毕摘除眼球行光镜、透射电镜及扫描电镜检查.结果A组兔眼后极部及赤道部内界膜均有多少不等的胶原纤维残留,且部分兔眼可见视网膜内界膜和感光细胞的损伤.B组兔眼内界膜面光滑平整、无任何物质残留.所有兔眼基底部视网膜面均见浓密的胶原纤维黏附.结论玻璃体腔内注射MMP-3可明显减少兔眼玻璃体切割术后玻璃体后皮质的残留,使手术更安全易行,可作为玻璃体切割术的辅助剂.     

Collagen fibrillar network in the optic nerve head of normal monkey eyes and monkey eyes with laser-induced glaucoma--a scanning electron microscopic study

PURPOSE: To examine the three-dimensional organization of collagen fibrils in the lamina cribrosa of normal monkey eyes and monkey eyes with laser-induced glaucoma. METHODS: Intraocular pressure elevation and glaucomatous optic discs were obtained in one eye of three adult monkeys by repeated applications of argon laser to the chamber angle. The monkey eyes were enucleated, and the collagen fibrillar network was investigated by scanning electron microscopy after cell maceration with 10% sodium hydroxide and conductive staining. RESULTS: In normal monkey eyes, round to oval shaped regular laminar pores through which axon bundles exited were observed in the lamina cribrosa. The straight, column-like pores or openings were formed by multilayered laminar plates that aligned vertically in parallel with the optic nerves. The surface of the laminar plates was covered by delicate, loosely arranged collagen fibrils. The inner surface of the pores was smooth, made up of well-packed collagen fibers. In glaucomatous eyes, the laminar pores were clogged by tightened collagen fibrils. The inner surface of the pores was irregular, and the pores were narrowed or distorted. CONCLUSIONS: Alterations in the three-dimensional organization of collagen fibrils were demonstrated in the optic nerve head of glaucomatous monkey eyes. The architectural changes may affect the flexibility and resilience required of the lamina cribrosa in supporting optic nerve fibers.     

Safety of in vivo pharmacologic vitreolysis with recombinant microplasmin in rabbit eyes

PURPOSE: To investigate the safety of intravitreal microplasmin in rabbits and to confirm previous findings of posterior vitreous detachment (PVD). METHODS: Different doses of microplasmin, from 12.5 microg to 250 microg, in 0.1 mL balanced salt solution (BSS) were injected into the vitreous cavity of rabbit eyes to induce PVD. Fellow eyes were injected with the same volume of BSS. Slit-lamp biomicroscopy, ophthalmoscopic fundus examinations, A- and B-mode ultrasonography, and electroretinography were performed to assess the retina. Electroretinograms (ERGs) were recorded up to 90 days after injection. Morphologic alterations were assessed by light microscopy, scanning electron microscopy (SEM), and transmission (TEM) electron microscopy. RESULTS: A slight aqueous flare and cells were observed in the anterior chamber after microplasmin and BSS injection. A slight inflammatory reaction was also observed transiently in the vitreous cavity. In control eyes, B-mode ultrasonography and SEM examination demonstrated that PVD did not develop after BSS injection. Intravitreal injections of 125 microg or greater of microplasmin induced complete PVD with an internal limiting membrane (ILM) devoid of vitreous collagen fibrils. Eyes injected with 12.5 microg microplasmin had partial PVD, and SEM showed residual fibrils covering the ILM. In all eyes, there was a transient reduction in the a- and b-waves of the ERG on days 2 through 7. The ERGs showed less effect with < 250 microg microplasmin. CONCLUSIONS: Intravitreal injection of recombinant microplasmin in the rabbit induces no ERG or retinal ultrastructural abnormalities. Pharmacologic vitreolysis with this agent may be a useful adjunct to vitreous surgery and could be used to induce PVD without vitreous surgery.     

High-voltage electron microscopy of normal human cornea

Conventional transmission electron microscopy (CTEM) was compared with high-voltage electron microscopy (HVEM) on 11 normal human corneas (age range, 30 weeks of gestation to 92 yr). Epithelial anchoring fibrils were noted between the basal epithelial cells and Bowman's layer (BL) as previously reported. Parallel pairs of fibers, 27.5 nm in diameter, were observed crossing into the anterior stromal lamellae from BL; their termination sites, however, were not identified. The lateral termination of BL was marked by the presence of a keratocyte lying directly below the end of the multilaminar basal lamina. In this region, BL tapered and became interwoven with the scleral collagen fibrils in the substantia propria. The HVEM accentuated the orthogonal relationship of collagen bundles apparently emerging from the stromal keratocytes. The posterior corneal stroma appeared to be attached to the anterior surface of Descemet's membrane (DM) by fibers 22.3 nm in diameter that were associated frequently with a dense amorphous material. In the periphery, DM tapered to a thin strand, 0.5 microns in thickness, containing cable-like strands of banded collagen. The posterior nonbanded portion continued laterally and anteriorly in a series of folds between the fibrous collagen sheets of the anterior trabecular meshwork. In addition, HVEM enhanced the visibility of extracellular matrix interactions in the lateral terminations of BL and DM, attachment fibers from BL to the stroma and from the stroma to DM, and keratocyte and collagen fiber orientations not seen easily by CTEM.     

Ultrastructure of the vitreoretinal interface following plasmin assisted vitrectomy

AIMS: To investigate the ultrastructure of the vitreoretinal interface following plasmin induced posterior vitreous detachment. METHODS: Plasmin (1 or 2 U/0.1 ml) was injected into the vitreous cavity of 24 eyes of freshly slaughtered pigs. The 24 fellow eyes received calcium-free and magnesium-free PBS and served as a control. After incubation at 37 degrees C for 30 and 60 minutes, the globes were placed in fixative and hemisected. Specimens for light, scanning, and transmission electron microscopy were obtained from the posterior pole, the equator, and the vitreous base using a corneal trephine. RESULTS: All plasmin treated eyes showed posterior vitreous detachment. However, the inner limiting membrane (ILM) was covered by remnants of cortical vitreous at the posterior pole and at the equator. There was a direct correlation between the concentration and exposure times of plasmin and the degree of vitreoretinal separation. Eyes exposed to 1 U plasmin for 30 minutes had a dense network of residual collagen fibrils while those exposed to 1 U plasmin for 60 minutes had only sparse collagen fibrils covering the ILM. Eyes treated with 2 U plasmin for 60 minutes had a smooth retinal surface, consistent with a bare ILM. At the vitreous base there was no vitreoretinal separation. In all control eyes the vitreous cortex was completely attached to the retina. There was no evidence of retinal damage in any plasmin treated eye. CONCLUSION: Plasmin induces a cleavage between the vitreous cortex and the ILM without morphological changes to the retina. In contrast with previous reports, plasmin produces a smooth retinal surface and additional surgery is not required in this experimental setting. The degree of vitreoretinal separation depends on the concentration and length of exposure to plasmin.     

Histopathology of tissue removed during vitrectomy for impending idiopathic macular holes

Vitrectomy may prevent the progression of an impending macular hole by removing the layer of cortical vitreous from the posterior retina. To determine the nature of the cortical vitreous tissue, we identified and removed from the surface of the posterior retina a thin sheet of what appeared to be posterior cortical vitreous in 29 patients undergoing vitrectomy for an impending macular hole. In seven patients, the tissue was isolated for transmission electron microscopic study. Millipore filter specimens of the vitreous aspirates from all of the patients were studied by light microscopy. Vitreous condensates were present in all 29 specimens, fibrocellular membrane fragments were present in three, and fragments of internal limiting membrane were present in four. A collagen matrix was present in each of the seven specimens studied by electron microscopy, and in every specimen, the collagen's diameter was consistent with indigenous vitreous collagen. These findings confirm the presence of an acellular tissue layer on the posterior retina in eyes with an impending macular hole and indicate that it is usually indigenous vitreous collagen.     

蛇毒纤溶酶诱导兔眼玻璃体后脱离的实验研究

目的观察蛇毒纤溶酶是否可以诱导兔眼玻璃体后脱离（PVD）,并评价其对视网膜的毒性作用。方法根据随机数字表法将24只新西兰白兔分为A、B、C、D组,每组6只。左眼玻璃体腔注射0.1mL生理盐水作为对照。右眼玻璃体腔分别注入1000U/mL（商品单位）的蛇毒纤溶酶0.04、0.05、0.08、0.1mL,术后1、3、7d通过裂隙灯、间接检眼镜检查,观察眼前后节的变化。术后7d通过组织病理学检查,观察药物注入后是否诱发PVD,并评价其对视网膜结构的影响。结果术后7d对照眼无PVD形成,光学显微镜下见各实验组均有不同程度的部分性PVD形成。A、B、C组的视网膜结构与对照组比较无明显改变;D组可见局限性视网膜内界膜溶解破坏,局部视网膜隆起变薄及脉络膜下渗出的毒性改变。A组和D组的扫描电镜结果与光学显微镜一致。随着玻璃体腔蛇毒纤溶酶注射剂量的增加,玻璃体液化程度加大,PVD的范围也加大。结论兔眼玻璃体腔注射适当剂量的蛇毒纤溶酶,在术后7d可以诱导部分性PVD的形成,且视网膜形态无明显改变。大剂量应用时可见视网膜结构的毒性改变。     

Ultrastructural pathology of anterior persistent hyperplastic primary vitreous

Using transmission electron microscopy, the fine structure of anterior persistent hyperplastic primary vitreous (PHPV) removed from the eyes of four infants was studied. The tissue mass was composed of vessels derived from or representing the tunica vasculosa lentis posterior and the vasa hyaloidea propria. They were embedded in a loose connective-tissue matrix containing many fibroblasts and mature collagen fibrils. Toward the posterior surface, the fibroblasts became more numerous, elongated and densely packed. At the point of its entry into the posterior pole of the mass, the hyaloid artery was found to be surrounded by glial cells, probably representing an extension of the wall cells of the hyaloid canal. Venous drainage of the PHPV nodules seemed to occur via the ciliary body to which they were connected by tiny vessels bridging the distance from the PHPV lump to elongated ciliary processes. The anterior surface of the tissue lump was covered with lens fragments. These remnants showed signs of very early disturbance of lens development, with a failure to form posterior lens fibers. Based on these findings, the authors sugget that PHPV may be secondary to a primary defect in lens development.     

Vitreoretinal morphology of plasmin-treated human eyes.

PURPOSE: To investigate the ultrastructure of the vitreoretinal interface following an intravitreal injection of plasmin. METHODS: Plasmin (2 U/0.1 ml) was injected into the vitreous cavity of five postmortem human eyes. The five fellow eyes received phosphate-buffered saline and served as controls. After incubation at 37 degrees C for 30 minutes, the globes were placed in fixative and hemisected. Specimens for scanning and transmission electron microscopy were obtained using a corneal trephine. RESULTS: All plasmin-treated eyes showed complete vitreoretinal separation with sparse collagen fibrils covering the inner limiting membrane. All control eyes showed an attached cortical vitreous. At the vitreous base, there was no cleaving effect. The retinal morphology of plasmin-treated eyes was unchanged. CONCLUSIONS: Plasmin induces a cleavage between the vitreous cortex and the inner limiting membrane without morphologic alteration of the retina.     

Electron microscopic observations of Descemet's membrane of peripheral cornea

The posterior portion of the Descemet's membrane was studied by scanning and transmission electron microscopy; the materials comprised 87 human peripheral corneas with ages from 2 to 98 years, 5 monkey corneas and 4 rabbit corneas. In some specimens, the endothelium was removed by ultrasonication. After removal of the endothelium, "curly structures" were recognized on the surface of the Descemet's membrane, where the membrane showed a gradual thinning. These structures appeared along the whole circumference of the cornea with variable width in the human specimens, but in monkey and rabbit corneas, the extent of these structures was less than in the human cornea. The "curly structures" were not encountered in young subjects, and they increased with age. There was a positive correlation (r = 0.60, P less than 0.001) between the age and the extent of these structures. Other aging products of the Descemet's membrane, ie, Hassall-Henle bodies, were partly surrounded by the "curly structures". The human "curly structures" consisted of collagen fibrils, halo structures in the collagen bundles, wide-spacing fibers, microfibrils, ground substances containing minute filaments and a structure resembling the Descemet's membrane. Components of "curly structures" of the monkey and rabbit were almost the same as those of the human except for the Descemet's membrane-like structure.     

Electron microscopic observation on the developing rabbit and human vitreous collagen fibrils by negative staining

The vitreous fibrils of developing eyes of 3-day-old rabbits and 24th week human fetuses were examined by the negative staining method (phosphotungstic acid) electron microscopically. Fibrils about 10 nm in diameter and with no periodic striated pattern as well as adult ones were observed. Peculiar fibers were observed in both vitreous samples preserved at low temperature. Particularly, dimeric segment-long-spacing (SLS) aggregates and fibrous-long-spacing (FLS)-like aggregates were observed in 3-day-old rabbit vitreous. FLS-like aggregates showed a 125-nm light band and 50-nm dark band periodic pattern and seemed to be formed with 300-nm overlapping of dimeric SLS aggregates. The present results indicate that the developing vitreous could possibly form various types of collagen fiber under native conditions.     

Three-dimensional arrangement of collagen fibrils in human ciliary body.

The purpose of this study is to visualize the three-dimensional arrangement of collagen fibrils in aged human ciliary body and discuss their significance. The ciliary bodies obtained from two human eyes were treated with a NaOH cell-maceration method for 7 days, then prepared conventionally for light and scanning electron microscopy. The general morphology of the collagen tissue in the ciliary body appeared almost the same as that normally observed. Cellular elements were completely removed, but collagen fibrils were well preserved. In the stroma of the ciliary body, collagen fibrils were arranged irregularly. In the areas of the radial and circular ciliary muscles, considerable numbers of collagen fiber bundles were observed running in a circular direction. A honeycomb structure was seen in the pars plana, the walls and base of which were formed by interweaving collagen fibrils. The results suggested that collagen fibrils in the aged human ciliary body may be largely involved in the presbyopia.     

Long-term effect of plasmin on the vitreolysis in rabbit eyes

The aim was to investigate the proteolytic activity of plasmin and its long-term complications. Plasmin was injected into the vitreous cavity of rabbits' eyes. Slit lamp biomicroscopy and electroretinography were performed. Rabbits were serially sacrificed at four months, and globes fixated and prepared for light and transmission electron microscopy. In both the plasmin-injected and control eyes, electroretinography showed a transient decrease in the amplitude, but this recovered to the baseline level in a week. Under the light microscope, the plasmin-treated eyes had a smooth retinal surface, implying separation of the vitreous cortex from the retina. In the control eyes, the collagen fibers remained on the retinal surface. By transmission electron microscopy, the plasmin-treated eyes showed a vitreous-free retinal surface, but no vitreoretinal separation was observed in the control eyes. Plasmin induces a cleavage between the vitreous and the internal limiting membrane, with no long-term complications, so may be a useful pharmacologic adjunct to vitrectomy.     

Histogenesis of the intravitreal membrane and secondary vitreous in the mouse

PURPOSE: The intravitreal membrane (IVM) is a membranous structure between the primary and secondary vitreous bodies in developing mammalian eyes. In this study, for the first time the histogenesis of the IVM and the relationship between the hyaloid vasculature and the IVM was characterized in newborn mice. METHODS: Eyes of mice less than 12 days old were fixed and embedded. From these, serial paraffin-embedded sections were made for lectin histochemistry, immunohistochemistry, and picrosirius red (PSR) staining, and ultrathin sections were made for transmission electron microscopy (TEM). Eight biotinylated lectins and antibodies for laminin and type IV collagen were used. RESULTS: Among the eight lectins tested, concanavalin A (Con A) agglutinin, Ricinus communis agglutinin I, and wheat germ agglutinin demonstrated strong positive staining in the IVM and vitreous fibrils of the primary and secondary vitreous bodies. They also bound to the internal limiting membrane (ILM) of the retina. At postgestational day 4, the secondary vitreous first appeared between the ILM and the vasa hyaloidea propria (VHP). Immunohistochemical staining revealed that the IVM consists of extracellular matrix components including laminin and type IV collagen, whereas PSR staining and TEM showed that collagen fibrils in the IVM are bundled and continuous with the basement membrane of hyaloid capillaries or the VHP. CONCLUSIONS: Lectin histochemistry and immunohistochemistry provided good methods for visualizing the structures of the IVM and vitreous fibrils. These results suggest that the IVM is separated from the basement membrane of the retinal ILM along with the vascular network of the VHP when the secondary vitreous begins to form.