Showing papers in "Graefes Archive for Clinical and Experimental Ophthalmology in 1974"

Vitreoretinal juncture —Simple epiretinal membranes

Abstract: Simple epiretinal membranes are delicate cellular membranes occurring at the vitreoretinal juncture. They produce no symptoms or macroscopically detectable change, but are a common microscopic finding in enucleated eyes. The ultrastructural features of these membranes were studies in eight eyes surgically enucleated for unrelated ocular conditions or for orbital lesions. Simple epiretinal membranes are composed exclusively of glial cells. Evidence is presented that these cells derive from accessory glia of the superficial retina which react to a variety of stimuli and migrate through breaks in the retinal surface (which may later heal). This pathogenic sequence is discussed in light of present knowledge of retinal accessory glia and their role in retinal disease.

Tear volume in normal eyes and keratoconjunctivitis sicca.

Abstract: Tear volume measurements were made in normal individuals and in patients with keratoconjunctivitis sicca using a fluorescein dilution method The mean tear volume in normals was found to be 65±03μl (SEM) with a range of 34 to 107 μl In sixteen eyes with keratoconjunctivitis sicca most of the values were moderately decreased with a mean of 48±04μl and a range of 29 to 80μl This decrease seems to manifest itself primarily as a reduction of the tear meniscus Among the keratoconjunctivitis sicca patients there was no correlation between the values of volume and the results of the Schirmer test or the degree of Rose bengal staining On the basis of average Schirmer test values for unstimulated tear secretion (“basic secretion”), the tear secretion rate was estimated to range from 06 to 11μl/min in normals, and from virtually zero to 02μl/min in the patients with keratoconjunctivitis sicca

The fine structure of the pig's retina.

Abstract: Retinas from 3 groups of pigs were examined; three farm pigs of 2 months, nine miniature pigs of 4 to 5 months and nine slaughter house pigs of about 12 months. No ultrastructural differences were observed between these 3 groups. With the major exception that the pig's retina does not have a fovea, it was found to closely resemble that of man. The inner layers of the pig's retina tended to thicken somewhat towards the peripapillary region. The more distinctive points of the pig's retina are the following: 1. The relatively even distribution of cones throughout the retina with their large, polymorphous ellipsoidal mitochondria showing transversally oriented cristae. 2. The presence of a microtubular structure in the rod from retinas fixed with glutaraldehyde. 3. The impressive size of the horizontal cells with their large cytoplasmic processes. 4. The prominant RER and mitochondria with a granular content and scarce cristae present in the Muller cells at the inner nuclear layer level. 5. The presence of numerous astrocytes in the more inner layers. 6. The presence of capillaries in the thicker nerve fiber layer in the peripapillary region.

Submacular choroidal vascular pattern. Experimental fluorescein fundus angiographic studies.

Abstract: The submacular choroidal vascular pattern was investigated by experimental occlusion of either one of the temporal short posterior ciliary arteries (SPCAs) or 1, 2, 3 or all of the vortex veins in 87 rhesus monkey eyes and evaluation of their filling defects and anastomoses by fluorescein fundus angiography (FFA). No special artery supplying the submacular choroid was seen. All the temporal SPCAs entered the eyeball in the macular region and each artery supplied a segment of the choroid, with no anastomoses between the adjacent segments. Most of the segments of the choroid supplied by the temporal SPCAs and their watershed zones met in the macular region. Similarly the four quadrants of the uveal tract drained by the four vortex veins and their watershed zones met in the macular region. Since an area where numerous watershed zones meet is most vulnerable to ischaemic disorders, the macular region is likely to show special vulnerability to any generalized chronic ischaemic disorder of the choroid. This, however, would not hold good in occlusion of a single SPCA, because the latter supplies only a small segment of the macular region. It is postulated that senile macular degeneration, senile disciform macular degeneration and allied macular disorders are most probably due to this unusual pattern of the submacular choroid and its special vulnerability to suffer in generalized chronic choroidal ischaemia as compared to the rest of the choroid.

On the question of the origin of macrophages in the retina and the vitreous following photocoagulation (autoradiographic investigations by means of 3H-thymidine)

Abstract: The question of the origin of the macrophages in the retina and in the vitreous following photocoagulation was investigated in fourteen albino rabbits by means of 3H-thymidine A group of seven animals were photocoagulated, the others served as controls Prior to photocoagulation all fourteen rabbits received intravenous injections of 3H-thymidine three times at intervals of twelve hours to label all hematogenous macrophages then being formed in the bone marrow Cells of the pigment epithelium and of the neurosensory retina on the other hand, normally being in the Go-phase, remain unlabeled The animals were sacrificed at one hour, 24 hours and thereafter at daily intervals till the sixth day following photocoagulation Five hours before death they received colchicine In this way one was able to determine, wether previously labeled cells of the bone marrow undergo further mitosis following release into the tissues Twentysix hours following photocoagulation one finds in photocoagulated animals numerous labeled cells in the area of the lesion at the walls of choroidal vessels, further immediately inside Bruch's membrane in between the photoreceptors, later even in the inner retinal layers and the adjoining vitreous, contrasting with the findings in the controls In the ciliary region in both groups labeled cells occur in the stroma, between the epithelial cells and in the vitreous These labeled cells in the coagulated animals increase with time more than in the controls Numerous such labeled cells are arrested in metaphase by the colchicine Our experiments show that at least the greater part of the macrophages appearing in and about retinal lesions following photocoagulation are of hematogenous origin Continual immigration of hematogenous macrophages through the ciliary region, which is increased following photocoagulation, also seems most likely to take place, though this is not completely proven by this study

The long posterior ciliary arteries : An experimental study

Abstract: In vivo studies on the temporal LPCA in rhesus monkeys have revealed the following: 1. The LPCA invariably supplies a sector of the choroid posterior to the equator, starting almost immediately from the point where it joins the choroid after having pierced the sciera, and extending forward. 2. Occlusion of one or both LPCAs produces no ischaemic damage to the anterior segment of the eye. 3. Occlusion of one or both LPCAs seems to have no significant effect on the IOP. The ocular hypotony seen in such cases is in all probability primarily due to damage to the accompanying ciliary nerves. This subject however, requires further exploration.

Junctions between the cells of the trabecular meshwork.

Abstract: In an electron-microscopic study of cell-to-cell attachments in the trabecular meshwork of three primate species and the rabbit, two types of junctions were identified. These junctions were common to all four species. One was classified as a macula adhaerens while the other, after uranyl acetate “en bloc” treatment of the tissue, was thought to be a macular gap junction. These junctions were common to all regions of apposition in the meshwork although their incidence in isolated sections was low; their possible role as an adhesive mechanism was discussed.

The innervation of the conjunctiva in monkeys. An electron microscopic and nerve degeneration study.

Abstract: The ultrastructure of conjunctival nerve fibres was studied in control material from two species of monkey. Nerve fibres reached the conjunctiva either in small nerves or in the adventitia of arterioles. A few myelinated nerve fibres were found within the nerves but the great majority of their fibres were unmyelinated. Bundles of unmyelinated nerve fibres were found in the interstices of the lamina propria up to the epithelial basement membrane and nerve fibres were traced into the epithelium. Other unmyelinated nerve fibre bundles lay adjacent to the walls of capillaries. Nerve fibre terminals exhibited varicosities and three types of terminals were recognised; those having varicosities packed with mitochondria, those having varicosities containing vesicles without any small granules and those having varicosities with vesicles, some with small granules. Following experimental nerve lesions induced changes were observed in the nerve fibres, and from these changes it was determined that nerve fibres from three sources were present in the conjunctiva. Nerves and interstitial nerve fibre bundles contained ophthalmic and pterygopalatine nerve fibres, from which the epithelium was supplied. Arteriolar nerve fibre bundles contained superior cervical and pterygopalatine nerve fibres which were joined by ophthalmic nerve fibres in capillary nerve fibre bundles. The combined results of electron-microscopy of control and experimental material suggested that nerve fibres from different sources innervating the conjunctiva had ultrastructurally distinct terminals.

Introduction to freeze-fracture method in retinal research

Abstract: The freeze-fracture method employs platinum-carbon replicas prepared from the exposed faces of fractured, deep-frozen material. Preparation technique, advantages and disadvantages of this method are described and briefly discussed. The applicability of the method is demonstrated on replicas of freeze-fractured human retinas: Pigment epithelial cells with their peculiar organelles are illustrated. At the level of Verhoeff's membrane, intercellular junctions composed of zonulae occludentes and gap junctions are identified. The so-called outer limiting membrane is confirmed to be composed of zonulae adhaerentes. Bidimensionally arranged particles, characteristic for astroglial cells in the central nervous system, are shown on the exposed faces of the plasma membrane of Muller cells.

A long term study on the ocular lesions in streptozotocin diabetic rats

Abstract: Diabetic retinopathy induced in 2 months old rats by injection of 35 mg/kg of streptozotocin was studied after a period of 6 to 12 months. None of the animals received any antidiabetic treatment, however the severity of the disease varied to a large extent. The study of the retinal vascular network done by trypsin digestion and with the electron microscope showed a focalised microangiopathy. This is characterised by an irregularity in the capillary's diameter, a cell loss mostly that of the pericytes, fusiform dilatation and occasional sacciform microanevrisms. This deterioration appears to increase with the duration of diabetes; however it is difficult to establish a correlation with the severity of the disease. The ultrastructural changes found are the following: A comparison was attempted with experimental microangiopathy provoked by a lathyrogenic agent (IDPN). Certain morphology similarities exist (presence of collagen fibres in the BM, proliferation between glial cells), however the differences were also very important: more diffuse lesions, a swelling of the endothelial cells, faster development and different metabolic conditions.

Scanning electron microscopy of the zonule of Zinn

Abstract: The zonule fibers are composed of numerous fibrils measuring 1–2 μ in diameter. Owing to their course, two different groups of about equal size can be distinguished: The fibers originating from the pars plana go to the anterior aspect of the lens, whereas those coming from the ciliary valleys and the sides of the ciliary processes insert on the posterior aspect of the lens. The number of zonule elements is markedly reduced in the old eye. Fibers inserting on the equator of the lens are found exclusively in the young eye. Polymorphous particles, some of which probably represent free or local cells, are scattered over the entire zonule.

Use of tobramycin in eradicating experimental bacterial endophthalmitis.

Abstract: A study of intravitreal injection of tobramycin sulfate in the treatment of experimental Pseudomonas aeruginosa endophthalmitis in rabbits resulted in the following findings: (1) A dose of 750 μg per 0.1 ml was nontoxic to ocular structures. (2) 500 μg of tobramycin sulfate remained bactericidal in both aqueous and vitreous humors for at least 96 hours. (3) Eyes cleared if treated with intravitreal injection of 500 μg tobramycin sulfate seven hours after bacterial inoculation, while only 2 of 5 eyes treated ten hours after inoculation showed complete clearing. (4) Systemic and subconjunctival administration of antibiotic failed to eradicate infection in 10 eyes.

Lincomycin by direct intravitreal injection in the treatment of experimental bacterial endophthalmitis.

Abstract: Injection of solutions directly into the vitreous can be a safe and easily performed procedure. Our study demonstrated that a 1.5 mg dose of lincomycin into the rabbit vitreous was nontoxic to intraocular structures and produced high and significant concentrations of the drug that persisted for longer than two days. Intravitreal injection of lincomycin was highly efficacious in checking experimentally induced staphylococcal endophthalmitis. The response depended not only upon the amount of drug injected, but also, and much more crucial, upon its administration early in the course of the clinical infection. In endophthalmitis, the rate of progression of the destructive process increases in direct proportion to the delay in delivering antibiotics to the infected area. Our studies suggest that intravitreal injection of an appropriate antibiotic is the most prompt, most definitive therapy available for the preservation of vision.

Microcirculation of ocular fundus in viscose rayon workers exposed to carbon disulfide.

Abstract: A neuro-ophthalmological examination, including fluorescein angiography, has been made of 100 male viscose rayon workers occupationally exposed to carbon disulfide (CS2), and 97 control males (paper-mill workers). Corrected visual acuity, visual field, eye motility, pupillary reactions and biomicroscopy, were found to be normal in all the eyes examined. Fluorescein angiography revealed the filling of retinal vasculature before choroid in 76% of the exposed subjects, and in 70% of the controls. Delayed peripapillary filling, either circumferential or segmental, or both, occurred in 68 exposed and 38 nonexposed; the difference was highly significant (p<0.01). This phenomenon was not correlated with ageing, smoking habits, serum cholesterol level, or glucose tolerance. The intraocular pressures in these eyes were normal. General narrowing and irregularity of vessel calibre were almost equally common findings in both groups. The mean widths of eight arterioles and the narrowest vein were significantly wider in the exposed group (p<0.01, and p<0.05, respectively). No evidence was found for retinopathy attributable to carbon disulfide exposure.

A comparison of retinal argon laser lesions in man and in cynomolgus monkey.

Abstract: Suprathreshold argon laser lesions produced under comparable experimental conditions in man and in cynomolgus monkey showed the same degree of retinal destruction and approximately the same width of retinal damage Four times the power necessary to produce an ophthalmoscopic threshold lesion was insufficient to inflict damage to the inner retinal half In therapeutic argon laser photocoagulations, for instance in the treatment of diabetic microaneurysms, this power level should, therefore, be exceeded

Management of retinal detachments due to giant tears

Abstract: A relatively simple method for the surgical treatment of retinal detachments due to equatorial giant tears is described. The technique consists of (1) a modified silicone cerclage, (2) injection of Ringer's solution or hyaluronic acid and (3) photocoagulation. The results are reported and indications and contraindications are elaborated.

[Relations between metabolic acidosis and intraocular pressure after inhibition of carboanhydrase with acetazolamide (author's transl)].

Abstract: An 7 unoperierten, an einem Glaucoma simplex leidenden Augen von Patienten mit einem ungestorten Saure-Basenhaushalt wurden nach intravenoser Injektion von 500 mg Azetazolamid (Diamox) gleichzeitig Bestimmungen der arteriellen Blutgaswerte und Messungen des intraocularen Druckes (AT) vorgenommen. In einer weiteren Versuchsreihe, die 11 nach den gleichen Kriterien ausgewahlte Augen umfaste, wurde die durch Diamox induzierte metabolische Acidose mittels Na-Bicarbonat-Infusionen abgepuffert. Ohne Pufferung bewirkte Diamox eine maximale Senkung des intraocularen Druckes von 38,9% und eine Hemmung der Kammerwasserproduktion um 56%, nach Pufferung eine maximale Drucksenkung von 37,8% und eine Hemmung der Kammerwasserproduktion um 55 %. Diese Ergebnisse beweisen, das einer metabolischen Acidose keine ins Gewicht fallende Bedeutung fur den drucksenkenden Effekt von Acetazolamid zukommt. Aus der Sicht des Klinikers ist ein Ausgleich der oft betrachtlichen und nicht unbedenklichen Verschiebung des Saure-Basenhaushaltes durch eine entsprechende Zufuhr basischer Valenzen zu fordern.