Age-related changes in the human outflow apparatus

Tissue from 53 human eyes was used for qualitative and quantitative morphological study (light microscopy and electron microscopy) of age-related changes in the human outflow apparatus. The specimen source was surgical procedures. Qualitative observations showed that the general configuration of the trabecular meshwork changed gradually with age, from a long wedge shape to a shorter, more rhomboidal form. The scleral spur became more prominent, the uveal meshwork more compact, and localized canal closure increased in incidence. Intercellular cytoplasmic processes between neighboring trabecular endothelial cells were less evident and areas of trabecular denudation were frequently observed in older eyes. Quantitative light microscopic studies showed a progressive thickening of the trabeculae, and the numbers of giant vacuoles in the lining endothelium of Schlemm's canal decreasing significantly with age. Morphometric analysis of the cribriform layer (transmission electron microscopy) showed that there was a change in the character of the extracellular materials with an increase in the deposition of electron dense plaques and a decrease in the ground substances from the fifth decade onwards.     

Ultrastructural alterations in the aqueous outflow pathway of adult buphthalmic rabbits

The aqueous outflow pathway of adult rabbit eyes with congenital glaucoma (buphthalmos) was examined by light microscopy and by scanning and transmission electron microscopy. The morphology of the buphthalmic rabbit aqueous outflow pathway was markedly abnormal when examined at 6 months, 1 yr, and 2 yr displaying apparent loss and/or compression of the iris pillars, dilation of the intertrabecular spaces, loss of endothelial cell-to-cell association and disorganization of trabecular lamellae, and posterior displacement of the aqueous plexus. In addition, the trabecular meshwork lamellae were observed only adjacent to the sclera and the inner portion of the trabecular meshwork was limited to swirls of collagen with scattered cells. These morphological findings suggest that the disease process in the rabbit principally involves an alteration in the differentiation and maintenance of the structural integrity of the trabecular meshwork. The loss of structural support of the buphthalmic trabecular meshwork may be a factor in the wide variation in intraocular pressure and may allow for compression of the trabecular meshwork against the aqueous plexus.     

原发性开角型青光眼房水外流通路改变的研究进展

原发性开角型青光眼(POAG)是一种以视神经轴索及相关视网膜神经节细胞丢失为特征的视神经病变.眼压升高是POAG最重要的危险因素.大多数POAG患者眼压升高主要是房水外流阻力异常增高所致.小梁网是产生房水排出阻力的主要部位.目前多数研究者认为POAG患者小梁网功能不良与致炎因子表达、细胞老化、氧化应激损伤及细胞质成分减少等因素有关.小梁网细胞本身及细胞外基质的变化均可以引起房水外流阻力的改变,进而导致眼内压的升高.为了进一步开展对POAG发病机制的研究,有必要就目前有关POAG患者房水外流通路改变的研究进展予以综述,旨在为POAG的深入研究提供参考依据.     

Relationships between increased aqueous outflow facility during washout with the changes in hydrodynamic pattern and morphology in bovine aqueous outflow pathways

Previous studies suggest that the structural correlate for the increased outflow facility (C) during washout in the bovine eye is separation between the inner wall (IW) and underlying juxtacanalicular connective tissue (JCT). However, how these structural changes affect hydrodynamic patterns of outflow during washout has not been studied. We hypothesize that an increase in the outflow facility during washout is associated with an increase in the effective filtration area (EFA) of aqueous outflow, which is regulated by a loss of the connectivity between the IW and JCT. To test this hypothesis, the relationship between C and the hydrodynamic patterns of outflow as well as the morphological changes in JCT and IW during the washout were investigated. Ten bovine eyes were perfused at 15 mmHg with Dulbecco's PBS + 5.5 mM glucose (DPBS) for 30 min to establish stable baseline C. After measuring baseline C, five eyes (short-duration group) were perfused with 0.5 mL DPBS containing 0.002% microspheres (0.5 μm) to trace the hydrodynamic pattern of outflow. Five other eyes (long-duration group) were perfused for 3 h to elicit a significant washout effect followed by subsequent perfusion of the same volume (0.5 mL) of microspheres to map out the outflow pattern after washout. All eyes were then perfusion-fixed. Anterior segments were sectioned and prepared for confocal and light microscopy. Total length (TL) and filtration length (FL) of the IW were measured in ≥15 images/eye to calculate percent effective filtration length (PEFL = FL/TL) while TL and length exhibiting JCT/IW separation (SL) were measured in ≥13 images/eye to calculate percent separation length (PSL = SL/TL). In long-duration eyes, C increased 170.5 ± 21.3% (mean ± SEM, 1.55 ± 0.24 vs 4.13 ± 0.55 μl/min/mmHg, p = 0.001) above baseline. Pre-fixation C (4.13 ± 0.55 μl/min/mmHg) in long-duration was 1.6-fold greater than that (2.14 ± 0.61 μl/min/mmHg; p = 0.042) in short-duration. A more uniform tracer labeling was observed in the JCT/IW of long-duration eyes compared to short-duration. PEFL was 2.3-fold larger (52.82 ± 6.06 vs. 22.2 ± 6.0%; p = 0.007) and PSL was 2.6-fold larger (54.2 ± 6.0 vs. 20.5 ± 1.3%; p = 0.004) in long-duration eyes compared to short-duration. Data from all eyes revealed a positive correlation between PEFL and PSL (p = 0.02). Both PEFL and PSL demonstrated significant positive correlations with the relative increase in C due to washout (p ≤ 0.05). An additional experiment was performed in which unequal volumes of tracer (0.5 and 1.0 mL) were perfused in paired eyes for both short- and long-duration (N = 2 for each condition) to examine the affect on PEFL. No significant change in PEFL was found in eyes perfused with 0.5 and 1.0 mL within the same group. These data support our hypothesis that separations between the IW and JCT result in an increase in the EFA that then influences C. Altogether, these data suggest that outflow hydrodynamics and the tissue structure work together to regulate outflow resistance.     

Histopathological changes in iridocorneal angle of inherited glaucoma in rabbits

· Background: We examined morphologically the angular region of eyes affected by inherited glaucoma in rabbits genetically developed by crossbreeding in order to investigate the etiologic changes in the iridocorneal angle and to establish whether this strain of rabbit is a suitable animal model of goniodysgenetic glaucoma in humans. · Methods: The angular regions of both normal and glaucomatous eyes from four rabbits having unilateral inherited glaucoma were observed with light and electron microscopy. · Results: In the glaucomatous eyes angular region, the aqueous plexus corresponding to Schlemm’s canal in humans was open and located far peripherally to the peripheral margin of the anterior chamber angle, although the plexus of one glaucomatous eye was poorly developed with a small lumen. In the angular meshwork, which corresponds to the trabecular meshwork in humans, a thick abnormal tissue with round cells embedded in the extracellular matrix was located just beneath the plexus. A large amount of extracellular matrix of basal lamina-like material was observed in the thick tissue. In the normal eyes, the angular region consisted of well-developed trabecular sheets with neither a thick tissue nor accumulations of extracellular matrix in the angular meshwork. · Conclusion: The findings observed in the glaucomatous eyes are much the same as those observed in goniodysgenetic glaucoma in humans, suggesting that this strain of inherited glaucoma rabbits is a suitable animal model of goniodysgenetic glaucoma in humans. The present study also supports the hypothesis that the presence of a thick subcanalicular tissue due to maldevelopment of the iridocorneal angle is one of the main causes of this type of glaucoma. Received: 1 October 1998 Revised version received: 7 December 1998 Accepted: 9 December 1998     

糖皮质激素性青光眼小梁细胞超微结构的改变

目的:制作兔糖皮质激素性青光眼动物模型,观察小梁细胞超微结构的改变,探讨激素性青光眼房水排出阻力增加的机制.方法:40只新西兰大白兔,随机分为4组,正常对照组(10只)、单独滴地塞米松组(10只)、单独注射曲安奈德组(10只)和联合用药组(10只).实验前连续3天于每日8、10和12 am用Schitoz's眼压计测量眼压后取平均值,最后取得兔基础眼压值.实验正式开始后,正常对照组用无菌生理盐水滴兔双眼,每日3次:单独滴地塞米松组用0.5%地塞米松磷酸钠溶液滴兔双眼,每日3次,持续8周;单独注射曲安奈得组每周球结膜下注射曲安耐得1次(3 mg),持续8周;联合用药组用0.5%地塞米松磷酸钠溶液滴兔双眼,每日3次,持续8周,每周球结膜下注射曲安奈得1次(3 mg).用药开始后,第4天开始每7日用Schitoz's眼压计监测一日4组眼压(分别于8、10和12 am测一次眼压后取平均值),将眼内压≥21.975 mm Hg(1 mm Hg=0.133 kPa)并持续1周者纳入诱发成功模型.8周后取四组兔双眼标本,做成电镜超薄切片用于电镜研究.结果:1.兔基础眼压为(18.082±2.398)mm Hg(n=80),联合用药组兔2～3周眼压开始升高,第3周时升高到(24.065±1.245)mm Hg,P<0.05,具有统计学意义,随后眼压逐渐升高,第6周达到峰值,眼压升高到(30.214±0.766)mm Hg,第8周兔眼压为(29.144±0.685)mm Hg,P<0.05.联合用药组兔20只眼16只眼压升高,眼压升高率为80%.正常对照组兔眼压(18.254±3.465)mm Hg无升高.其余两组兔眼压虽有所升高,但升高不稳定,持续时间小于1周,未达到高眼压模型标准.2.联合用药组兔小梁细胞核异形性增大,细胞间质微丝微管结构增多,胞浆空泡变性±粗面内质网扩张,以及细胞间无定形物质增多.结论:1.联合用药组成功地建立了兔糖皮质激素性高眼压模型,其余3组未能成功建立兔糖皮质激素性高眼压模型.2.电镜下观察到的细胞骨架所发生一系列改变,是糖皮质激素诱导眼压升高的重要环节.     

Effects of prolonged intracameral perfusion with mock aqueous humour on the morphology of the primate outflow apparatus

The eyes of six pig-tailed macaques (Macaca nemestrina) were exposed to mock aqueous humour (Barany's fluid) at pressures within the physiological range for 4 hr in vivo. The eyes were perfuse-fixed at 18 mmHg in situ. The anterior segment tissues were studied by light microscopy, transmission- and scanning electron microscopy. The outflow apparatus of these perfused eyes showed marked structural changes when compared with non-perfused eyes. These changes included the narrowing of Schlemm's canal and a loss of trabecular endothelial cell cytoplasmic processes in the trabecular meshwork. The cribriform layer showed a loss of cell-to-cell contact and a washout of extracellular materials. The incidence of 'giant vacuoles' was increased in perfused eyes and the lining endothelium was also characterized by focal ballooning which occasionally occluded the collector channels. These morphological disturbances could not be attributed to pressure and were probably due to over exposure to mock aqueous humour which may have weakened cell-to-cell adhesion.     

Influence of non-penetrating glaucoma surgery on aqueous outflow facility in isolated porcine eyes

PURPOSE: To investigate, in vitro, the influence of non-penetrating glaucoma surgery (NPGS) and the influence of tightly suturing the superficial scleral flap on the aqueous outflow facility of isolated porcine eyes.Materials and methods: The anterior chambers of 12 enucleated porcine cadaver eyes were cannulated and perfused. NPGS was performed by the same surgeon. The overall ocular aqueous outflow facilities were assessed before and after the surgical interventions of NPGS, as well as after scleral flap closure. RESULTS: The mean (SD) aqueous outflow facility, which was 0.164 (0.014) microl/min/mm Hg before surgery, increased significantly after NPGS to 1.584 (0.217) microl/min/mm Hg, p<0.001. When the superficial flap was closed, the aqueous outflow facility significantly decreased (0.754 (0.107) microl/min/mm Hg, p<0.001) but remained significantly higher than preoperatively (p<0.01). After suturing the superficial flap, the overall resistance increased to 1.625 (0.210) microl/min/mm Hg. The difference in the resistance to outflow before and after flap closure was 0.848 (0.169) microl/min/mm Hg. CONCLUSION: After NPGS suturing the scleral flap can modulate aqueous outflow resistance. The experimental set up described might provide an efficient model for the technical training of glaucoma surgeries.     

Biomechanics of echothiophate-induced anatomic changes in monkey aqueous outflow system

Cynomolgus monkeys underwent long-term topical treatment with echothiophate, echothiophate + atropine, or control solution. Echothiophate-treated eyes exhibited increased intraocular pressure, collapse and densification of the trabecular meshwork with accumulation of extracellular material in the cribriform region, alterations in the shape and orientation of Schlemm's canal and the ciliary muscle, and discontinuity between ciliary muscle bundles and trabecular beams. Atropine or ciliary muscle disinsertion with subsequent scar formation supporting the mesh posteriorly at least partially prevented these alterations. Only sometimes did discontinuing echothiophate treatment restore normal anatomy. Collectively, these findings indicate that the pathophysiology of structural alterations in the outflow apparatus induced by echothiophate (1) is mediated at least in part by an anterior segment muscarinic receptor, (2) involves mechanical factors and underperfusion of the meshwork, and (3) does not involve any direct toxic effect of echothiophate.Supported by grant no. 124/2-2 from the Deutsche Forschungsgemeinschaft and by grants EY00137, EY02698 and TW01044 from the National Institutes of Health     

糖尿病新生血管性青光眼视神经血管内皮细胞在透射电镜下的改变

目的通过对糖尿病新生血管性青光眼患者视神经的血管内皮细胞透射电镜下形态改变的观察，分析其超微结构改变的临床意义。方法6例因糖尿病新生血管性青光眼行眼球摘除术患者的眼球，术中取球后视神经2mm，经戊二醛固定后，在透射电镜下观察视神经血管内皮细胞超微结构改变。结果糖尿病新生血管性青光眼患者的视神经血管内皮细胞表现出显著的超微结构改变，主要表现血管内皮肿胀明显、核肿胀、细胞绒毛减少、内皮细胞坏死缺失、血管腔狭窄闭塞、血栓形成。结论糖尿病新生血管性青光眼患者视神经血管内皮细胞出现显著超微结构改变，并与血栓形成互为因果，可能是迅速加重视功能损害的主要病理基础之一。     

Galactose-containing glycoconjugates of the iris,the aqueous outflow passages and the cornea in capsular glaucoma

Background: The aim of the study was to compare galactose-containing glycoconjugates of the iris, the aqueous outflow pas sages and the cornea with exfoliation material in capsular glaucoma. Methods: Six formalinfixed, paraffin-embedded human eyes with capsular glaucoma and six control eyes were studied by using a panel of 11 biotinylated lectins to galactose- and N-acetylgalactosamine-containing glycoconjugates. Results: The Gal ( 3) GaINAc-reactive lectins peanut agglutinin (PNA) and Bauhinia purpurea alba agglutinin (BPA) and the Gal (14)GlcNAc-reactive lectins Ricinus communis agglutinin (RCA-I) and Phaseolus vulgaris erythroagglutinin (PHA-E) gave the strongest label with exfoliation material. Lectin binding to the iris was variable. The binding of PNA, BPA, RCA-I, Erythrina cristagalli agglutinin (ECA), PHA-E and Glycine max agglutinin (SBA) to the subendothelial region of iris blood vessels closely resembled their binding to exfoliation material. RCA-I and PHA-E bound moderately to the aqueous outflow passages. The surface of the corneal epithelium showed positive reaction with most lectins studied, but the keratocytes reacted with RCA-I and PHA-E only. Neuraminidase pretreatment generally increased the reaction intensity. Conclusions: The findings suggest that the glycoconjugate composition of exfoliation material in the classical locations along the anterior and posterior chamber closely resembles that in the subendothelial region of iris blood vessels.The authors have no financial interest in any product or process mentioned herein     

晚期青光眼的房水动力学变化

目的：观察晚期青光眼高眼压对睫状体功能的损害作用及对角膜透明性的影响。方法：应用扫描荧光光度计及Ｓｃｈｉｏｔｚ电子眼压计分别测定１５只正常眼和１５只晚期原发性青光眼眼压、房水排出率和房水流畅系数,并观察角膜的透明性。结果：晚期青光眼眼房水排出率显著下降,下降程度与眼压水平及病程成正比。房水排出率降低至０．８μｌ／ｍｉｎ。角膜出现水肿混浊,房水排出率下降愈甚,角膜透明性改变愈明显。结论：持续高眼压将     

Effect of argon laser trabeculoplasty on unrestricted outflow of aqueous humor in eyes with simple glaucoma]

In this prospective study we used the oculopressions-tonometry (OPT) for determination of the aqueous humor outflow facility (C). 53 phacic eyes with glaucoma simplex were examined pre- and postoperatively. One hour after operation C decreased from 0.15 to 0.14. In correlation to this fact the IOD increased. After 7 days C was higher already than preoperatively, 30 days and 6 months after operation C showed normal values. After 6 months the mean decrease in IOD was 5.8 mm Hg, the mean increase in C was 39%. The rate of success after 30 days was 77.4%. IOP and C showed statistically significant changes. The problems with determining C and the causes of the fluctuation of C during our follow-up are discussed.     

Acid mucopolysaccharides in the outflow apparatus.

The two major species of phenylalanine transfer RNA (tRNA) of lens cortex have been isolated using BD cellulose and reversed-phase chromatography. Specific activities of 1200 and 1500 pmol of phenylalanine accepted per A₂₆₀ of tRNA were obtained for phe-tRNA₁ and phe-tRNA₂ respectively. The fluorescence emission spectra of both phe-tRNAs were identical, with a fluorescence maximum around 420 nm. These measurements, along with chromatographic data, confirm the presence of the Y base in both tRNAs. Nucleotide analysis was carried out on the purified phe-tRNAs. The composition of phe-tRNA₂ was almost identical to the phe-tRNA of rabbit liver. Phe-tRNA₁, however, had a markedly different major base composition. Phe-tRNA₁ therefore, represents a different gene product than phe-tRNA₂. This was confirmed by the fact that phe-tRNA₁, and phe-tRNA₂ chromatograph as separate peaks on a reversed-phase column in the presence of 8·0 m-urea. Therefore the differentiation of a lens epithelial cell into a lens fiber cell is accompanied by a doubling of phe-tRNA as a result of the activation of a new phe-tRNA gene.     

The effect of levobunolol eyedrops on trabecular outflow of aqueous humor in chronic simple glaucoma

The present paper reports a double-blind, cross-over, randomized study in which 31 patients (62 eyes) suffering from open-angle glaucoma were included. These patients were treated for one year with 0.5% levobunolol and 0.5% timolol ophthalmic solutions and followed up. Tonographic examinations of outflow facility showed a statistically significant increase following topical applications of 0.5% levobunolol, while there was little change with 0.5% timolol. The difference in the effect of outflow facility due to instillations of 0.5% levobunolol and 0.5% timolol can be explained by the different pharmacokinetic profiles of the two beta-blocker solutions in topical ocular application.