Eugen van der Zypen

The phagocytic activity of the trabecularmeshwork endothelium. An electron-microscopic study of the vervet (Cercopithecus aethiops).

In living vervets, the cells bordering the anterior chamber of the eye were allowed contact for various periods of times (1–40 min) with India ink-, gold- or mercurysulfide particles before fixation. In electronmicrographs the trabecular endothelium cells showed an intense microphagocytic activity, particles were engulfed already after 2–5 min. Various types of free cells (histiocytes, wandering cells etc.) were also found within the trabecular meshwork involved in the process of microphagocytosis. These cells probably originate in the iris tissue or emigrate from the ciliary body. Having engulfed the foreign material in vacuoles of various sizes bordered by a fine membrane, the trabecular endothelial cells change their form and appearance. They often detach tehmselves from the trabecular lamellae and leave the meshwork by way of Schlemms canal. Cells were found which penetrated with muschroom-like processes through small intercellular stomata in the inner wall of Schlemms canal (Figs. 18, 19). The trabecular cells are also able to engulf red blood cells or bacteria entirely (Figs. 10, 14). The microphagocytic activity of the inner wall endothelium of Schlemms canal is low. Sometimes little vacuoles filled with the particles were seen. However in contrast to the trabecular cells no form changes occur within the inner wall endothelium. The particles seem to pass through the cells while the cells remain extended in the row lining the canal (cytopempsis).In living vervets, the cells bordering the anterior chamber of the eye were allowed contact for various periods of times (1–40 min) with India ink-, gold- or mercurysulfide particles before fixation. In electronmicrographs the trabecular endothelium cells showed an intense microphagocytic activity, particles were engulfed already after 2–5 min. Various types of free cells (histiocytes, wandering cells etc.) were also found within the trabecular meshwork involved in the process of microphagocytosis. These cells probably originate in the iris tissue or emigrate from the ciliary body. Having engulfed the foreign material in vacuoles of various sizes bordered by a fine membrane, the trabecular endothelial cells change their form and appearance. They often detach tehmselves from the trabecular lamellae and leave the meshwork by way of Schlemms canal. Cells were found which penetrated with muschroom-like processes through small intercellular stomata in the inner wall of Schlemms canal (Figs. 18, 19). The trabecular cells are also able to engulf red blood cells or bacteria entirely (Figs. 10, 14). The microphagocytic activity of the inner wall endothelium of Schlemms canal is low. Sometimes little vacuoles filled with the particles were seen. However in contrast to the trabecular cells no form changes occur within the inner wall endothelium. The particles seem to pass through the cells while the cells remain extended in the row lining the canal (cytopempsis). Bei Meerkatzen (Cercopithecus aethiops) wurde die Vorderkammer des Auges mit einer Tuscheaufschwemmung bzw. Goldsol- oder Quecksilbersulfidlösung perfundiert. Die Perfusion wurde in verschiedenen Zeitabständen (1–40 min) abgebrochen. Bei der elektronenmikroskopischen Analyse des Trabekelwerkes zeigte sich, daß die Trabekelendothelien schon nach kürzester Kontaktzeit (2–5 min) eineintensive Mikrophagocytoseaktivität entfalten. Die Zellen bilden Fortsätze und Vacuolen verschiedener Größe, die von einer dünnen Membran umgeben sind, aus. Häufig ändern sich Form und Aussehen der Zellen. Sie können sich von den Trabekellamellen ablösen und über den Schlemmschen Kanal in den Kreislauf gelangen. Gelegentlich wurden Zellen beobachtet, die sich gerade durch die Innenwand des Kanals hindurchzwängen. Sie scheinen durch kleine intercelluläre Stomata hindurchgepreßt zu werden oder hindurchzukriechen (Abb. 18

Licht- und elektronenmikroskopische Untersuchungen über die Altersveränderungen am M. ciliaris im menschlichen Auge

In children, the ciliary muscle consists of bundles of smooth fibres. Each bundle is entirely surrounded by a sheath of fibrocytes or fibroblasts. The spaces between the muscle bundles represent a sliding zone of variable width containing myelinated and non-myelinated nerves, blood vessels and scattered pigment cells. The sliding zone communicates with the intertrabecular spaces of the trabecular meshwork, permitting aqueous humour to enter the spaces between the ciliary muscle bundles. At term the ciliary muscle is still in process of formation, and only gradually attains full development. Changes due to ageing occur mainly between the 20th and 30th year of age. Initially, they are characterized by a marked increase in the amount of connective tissue in the sliding zone of the muscle. The muscle fibres are forced apart by what appears in the electron micrograph as a finely granulated amorphous mass, wherein diffuse collagen fibrils are visible in apparent disorder. Fibroblasts, containing activated organelles of the cytoplasma can be observed between the muscle bundles which are located for the most part within the interstitial granular ground substance. The inner, circular muscle layer is affected early by these changes. The process advances steadily, between the radial muscle layers until it finally affects the meridional layers. Beyond the age of 45, the augmenting connective tissue pervades even the individual muscle bundles. In this manner the typical structure of the ciliary muscle, i.e., the fasciculation of discrete bundles representing the functional units of the muscle system, becomes disintegrated. At about the age of 50 a change takes place in the fibres of the ciliary muscle itself. The deposition of lipofuscin in the muscle cells can be regarded as a consequence of the increment of connective tissue, since this swelling separates the muscle bundles more and more from the nutrient-bearing blood vessels. In addition to the brown atrophy, a lamellar degeneration of individual muscle fibres also takes place. In old age, the granular amorphous substance is replaced by coarse bundles of collagen fibres. The ciliary muscle fibres are at this stage forced far apart from one another and lie, largely damaged by lipofuscin deposits or the presence of lamellar bodies, without recognizable order in the collagen connective tissue. With advancing senility, the basement membrane of the vessels of the ciliary body becomes stretched, and degenerative changes occur in the endothelial cells. Der M. ciliaris des Jugendlichen besteht aus Bündeln glatter Muskelfasern. Zwischen den durch eine Fibrocytenscheide vollständig umschlossenen Muskelbündeln findet sich eine mehr oder weniger breite Gleitzone, in der gemischte, mit einer Fibrocytenhülle umgebene Nerven, Gefäße sowie vereinzelt Pigmentzellen gelegen sind. Die Gleitzone steht mit dem intertrabeculären Raum der Kammerwinkelregion in Verbindung, so daß Kammerwasser zwischen die Bündel des Ciliarmuskels eindringen kann. Zum Zeitpunkt der Geburt ist der Ciliarmuskel noch nicht voll ausgebildet und reift erst allmählich heran. Altersveränderungen setzen jedoch schon zwischen dem 20. und 30. Lebensjahr ein. Sie sind zunächst durch eine starke Bindegewebsvermehrung in der Muskelgleitzone charakterisiert. Eine im elektronenmikroskopischen Bild feingranuläre, amorphe Masse, in die nur vereinzelt kollagene Fibrillen scheinbar ungeordnet eingelagert sind, drängt die Muskelbündel auseinander. Fibroblasten, mit deutlich aktivierten cytoplasmatischen Differenzierungen können in gleicher Ausdehnung wie die granuläre Substanz zwischen den Muskelbündeln beobachtet werden. Die innere, zirkuläre Muskelschicht wird frühzeitig von diesen Veränderungen befallen. Der Prozeß schreitet kontinuierlich zwischen die radiären und schließlich meridionalen Muskelschichten fort. Nach dem 45. Lebensjahr dringt das Bindegewebe auch in die einzelnen Muskelbündel ein. Damit geht der typische Bau des Ciliarmuskels, die Bündelung einzelner Fasern zu funktionellen Einheiten, verloren. Um das 50. Lebensjahr findet sich auch eine Veränderung der Ciliarmuskelfaser selbst. Die Einlagerung von Lipofuscin in die Muskelzelle kann als eine Folge der Bindegewebsvermehrung angesehen werden, da das Bindegewebe die Muskelbündel immer mehr von den sie versorgenden Gefäßen abdrängt. Außer der braunen Atrophie tritt auch eine lamelläre Degeneration einzelner Muskelfasern auf. Im Greisenalter wird die granuläre, amorphe Substanz durch derbe kollagene Faserbündel ersetzt. Die Ciliarmuskelfasern liegen, größtenteils durch Einlagerungen von Lipofuscin oder durch Auftreten von Lammellenkörpern geschädigt, weit auseinandergedrängt, ohne erkennbare Ordnung im kollagenen Bindegewebe. An den Gefäßen des Ciliarkörpers finden sich mit zunehmendem Alter eine Verbreiterung der Basalmembran und eine degenerative Veränderung der Endothelzellen.

Optical Principles Related to Optimizing Sclerostomy Procedures

A simple probe, consisting of a 200-micrometer uncladded silica optical fiber, advanced from a protecting 22-gauge hypodermic needle, was used to create sclerostomy fistulas both ab interno and ab externo by means of a combined radiation/mechanical effect. Perforation was achieved by exerting gentle forward pressure on the fiber in synchrony with the delivery of radiation pulses. An irradiation protocol suitable for producing such canals in cadaver porcine eyes was delineated using Ho:YAG, Nd:YAG, and diode laser energy sources. Despite significant differences in the pulse energy required for perforation (0.25, 7, and 8 J for the Ho:YAG, diode, and Nd:YAG lasers, respectively), the extent of collateral damage was comparable for each type of laser. The physical mechanisms underlying these findings are discussed.

Diffusion barriers impeding the flow of solutes to the ciliary body epithelium during immersion fixation of rabbit eyes

Various manipulations of rabbit anterior eye segments were carried out during the initial stages of glutaraldehyde fixation in order to assess the contribution made by particular tissues in restricting the flow of solutes to the ciliary body epithelium. Ultrastructural preservation quality was monitored by inspection of mitochondrial profiles. These organelles are structurally extremely sensitive to environmental disturbances, and hence changes in their morphological appearance may be used as an early indication of such adverse conditions. The results indicate that the principal barriers to diffusion are represented by the vitreous, posteriorly, and by the cornea at the anterior face. Since the cortical vitreous is strongly attached to the inner basement membrane of the ciliary epithelium, its removal may cause damage to this layer. A simpler and equally effective means of improving flow of fixative to the ciliary epithelium is to remove the cornea.

A new instrument for controlling pressure exerted on the sclera during contact Nd:YAG laser cyclodestruction

We tested the device described by Rol et al in their article in this issue, designed to define and precisely control the pressure applied to the sclera during contact cyclodestruction with a cw-Nd:YAG laser. Since scleral transparency, and hence transmission of laser energy, depends on the pressure applied, control of this parameter represents an important advance toward the goal of standardizing the cyclodestructive procedure. In eight of nine cadaver pig eyes, pressure was exerted on the sclera using the pressure-controlling device, with a setting of 0.25 N for two of these eyes, and one of 0.4 N for the other six. In the remaining eye, pressure was controlled intuitively by an experienced surgeon. Applying forces of 0.25 or 0.4 N yielded similar success rates, although these fluctuated greatly even under constant pressure conditions (from 17% to 50% at 0.25 N; from 27% to 42% at 0.4 N). The highest success rate (55%) was achieved by the intuitively controlled pressure irradiations of the experienced surgeon. The variation in coagulation intensity that occurred despite constant pressure suggests that additional factors contribute to the results achieved. Nonetheless, this pressure-controlling probe represents an important achievement. It will permit not only the novice but even experienced operators to adhere unambiguously to a protocol of quantitative, reproducible parameters, and will also help researchers to better understand the relationship between energy delivered and intraocular pressure reduction achieved in contact cyclophotocoagulation.