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  • 1
    Electronic Resource
    Electronic Resource
    Lasers, optical systems and safety in ophthalmology: a review (1996)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 234 (1996), S. 473-487 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This is a review of optical methods related to biomicroscopy and laser treatment of the posterior segment of the eye. Contact lenses can be used to observe optical structures and couple laser radiation into the eye for a vast range of conditions and techniques. A small laser spot size is indispensable for photodisruptive work, though this requires a large beam diameter at the pupil and therefore optical systems and techniques such as scleral indentation which maximize the pupillary beam diameter are preferred. For coagulation work the choice of beam focusing optics is crucial for optimum safety. Vitreous replacement can be used to change the refractive power of the eye and permit new combinations of treatment and optical systems. This review covers many aspects of laser irradiation of the eye. It should be clear that, with the multitude of different procedures and optical systems involved, the laser surgeon is faced with a daunting task in assessing and meeting safety limits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00184855
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  • 2
    Electronic Resource
    Electronic Resource
    Rechenmaschine für Blinde und hochgradig Sehschwache mit gesprochener Datenausgabe (1974)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 191 (1974), S. 211-213 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird eine elektronische Tischrechenmaschine mit gesprochener Datenausgabe beschrieben. Wegen der hervorragenden kortikalen Assimilierbarkeit der menschlichen Sprache als Informationsträger, dürfte diese Einheit gegenüber den bekannten konventionellen Systemen seiner Klasse mit taktiler oder akustischer Datenausgabe entscheidende Vorteile besitzen.
    Notes: Summary An electronic desk calculator with spoken words as its data output is described. Because of the outstanding ability of the human cortex to assimilate human speech, the new system may have significant advantages over units of its category that use tactile or acoustic data output systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414946
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  • 3
    Electronic Resource
    Electronic Resource
    Die Verwendung von konservierter Sklera in der Augenchirurgie (1966)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 170 (1966), S. 235-256 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Preserved sclera obtained from autopsy eyes and preserved in 95% glycerin has been used as implant material for buckling and encircling procedures in retinal detachment surgery. Homologous sclera is also suitable as substitution material in a series of selected indications for lid surgery. The various operative procedures are described in detail and illustrated. Glycerin-preserved sclera is a suitable, well-tolerated implant material and has many advantages over synthetic and organic substitution materials of other origin.
    Notes: Zusammenfassung Es wird über die Erfahrungen mit konservierter Sklera als Implantationsmaterial bei der Behandlung der Netzhautablösung und in einigen anderen Indikationsgebieten der Augenchirurgie berichtet. Die Resultate sind den Ergebnissen derjenigen Verfahren, die andere Substitutionsmaterialien verwenden, ebenbürtig. Glycerinkonservierte Sklera scheint ohne Qualitätseinbu\e bei Raum-temperatur unbegrenzt haltbar zu sein. Das Material zeichnet sich durch seine große Reißfestigkeit, tektonischen Eigenschaften und seine unmittelbare Greifbarkeit aus. Die Gewebsverträglichkeit ist ausgezeichnet, sogar wenn die Sklera subretinal verlagert wird. Silikone und Sklera stören sich gegenseitig nicht und können in geeigneten Fällen mit Erfolg kombiniert werden. Infektionen oder sonstige Komplikationen wurden weder im frühen noch im späten postoperativen Verlauf beobachtet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02429459
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  • 4
    Electronic Resource
    Electronic Resource
    Induction of vascular haemostasis by Nd:YAG laser light in melanin-rich and melanin-free tissue (1992)
    Springer
    Documenta ophthalmologica 79 (1992), S. 221-239 
    Details
    ISSN: 1573-2622
    Keywords: cw-Nd: YAG laser ; haemoglobin ; haemostatic mechanism ; melanin-free ; melaninrich
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Haemostasis was effected in vessels of melanin-rich (MR: choroid) and melanin-free (MF: mesentery) rabbit tissue irradiated with a cw-Nd: YAG laser. The following parameters were employed: - pulse duration: 200 ms (MR) and 100ms (MF); focal spot diameter: 200 μm (MR) and 80 μm (MF); pulse energies: 100–250 mJ (MR) and 0.5-1J (MF); irradiances: 1.6−4.0kWcm−2 (MR) and 1−2 × 102kWcm2 (MF). In melanin-rich tissue, laser energy is absorbed principally by melanin granules contained within the stromal melanocytes. The heat generated in these structures radiates into the surrounding tissue where it is dissipated. The damage thus incurred by the endothelium of blood vessels encompassed within this field triggers the haemostatic mechanism whereby blood flow is arrested. This effect is realized by the formation of an occluding plug of platelets, which is stabilized by the deposition of fibrin, particularly in capillaries, and to a lesser degree in larger vessels of the vascular lamina. In melanin-free tissue, haemoglobin serves as the primary site of energy absorption, which is thus shifted from the stroma to the vessel lumen. Irradiation of vessels in such tissue leads to thermocoagulation of plasma proteins and consequent stasis of blood flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00158253
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  • 5
    Electronic Resource
    Electronic Resource
    Researches on adaptive high resolution programming for automatic perimeter (1980)
    Springer
    International ophthalmology 2 (1980), S. 1-9 
    Details
    ISSN: 1573-2630
    Keywords: automatic perimetry ; Octopus ; adaptive strategies ; scotoma search programs ; high resolution ; caeconometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two adaptive perimetric strategies for the search and the analysis of scotomata have been developed and tested over the normal and pathologically disturbed blind spot area. Adaptive procedures automatically concentrate their search effort upon areas of pathological disturbance and avoid time loss used for declaring normal areas as such. Provided a first scan of low spatial resolution detects only one edge of the blind spot, spatial resolution increases and analyses the blind spot, returning to low resolution as soon as the border of the blind spot is crossed and normal sensitivity is again attained. Two adaptive strategies are described. One reduces examination duration to 1/2, the other to about 1/3 when compared to a similar non adaptive high resolution strategy. Only in the latter this time reduction has to be paid by some loss of information. The accuracy of the threshold determination method described is limited whereas spatial precision is high. Hence a more accurate threshold determination technique has to be added if the postulate of great threshold accuracy is to be fulfilled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149248
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  • 6
    Electronic Resource
    Electronic Resource
    Clinical studies on the efficiency of high power laser radiation upon some structures of the anterior segment of the eye (1981)
    Springer
    International ophthalmology 3 (1981), S. 129-139 
    Details
    ISSN: 1573-2630
    Keywords: Q-switched laser ; optical breakdown ; pathology of anterior segment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A series of pathological conditions such as pupillary block glaucoma, angle block glaucoma, acoria, pupillary membranes and goniosynechias of various origins have been treated successfully by means of pulses emitted from a Nd: YAG Q-switched laser above optical breakdown threshold. Since linear absorption is not required, non-pigmented or entirely transparent structures are easily dissected by this method. We have also opened the supraciliary and suprachoroidal space in a series of cases of wide angle glaucomas. In all cases however, the clefts closed by secondary wound reactions. This method may be applied to extracapsular cataract surgery for opening the anterior capsule before lens extraction and to the hydrophthalmic eye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00130696
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  • 7
    Electronic Resource
    Electronic Resource
    Advantages and limitations of the spatially adaptive program SAPRO in clinical perimetry (1986)
    Springer
    International ophthalmology 9 (1986), S. 179-189 
    Details
    ISSN: 1573-2630
    Keywords: perimetry ; automation ; spatially-adaptive program ; clinical applications ; SAPRO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The SAPRO* program, devised for the OCTOPUS 201 automated perimeter, consists of a number of program components. It is designed to be used on the Octopus 201 computer. In its measurement mode, it employs an algorithm which achieves high speed and efficiency. This is made possible by a threshold bracketing strategy which is simpler than the normal OCTOPUS bracketing. Moreover, three grids with test location distributions of increasing resolution are superimposed in succession on the whole or on part of the visual field to be analyzed. Out of the distribution of test locations, only those which fulfill a number of criteria are actually utilized. These criteria must be given and are adaptable to any given clinical problem. As a result, despite the high spatial resolution achieved, only a fraction of the test locations are utilized using SAPRO as compared with a program using a fixed pattern of test locations. The algorithm is thus able to imitate human intelligence, which tends to concentrate stimuli at places which appear to be relevant for the solution of a problem. The results of program SAPRO are disturbed by short-and long-term fluctuations. Their validity is limited, in a manner similar to that encountered in any other threshold determination procedure. A number of printout modes is available which are oriented towards an optimal understanding of the information contained in various examinations. These principles will be illustrated by one case of inactive disseminated chorioretinitis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159847
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of timolol on visual-field mean retinal sensitivity in normal subjects (1992)
    Springer
    International ophthalmology 16 (1992), S. 325-329 
    Details
    ISSN: 1573-2630
    Keywords: automated perimetry ; maleate timolol ; mean sensitivity ; visual field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This single-blind, randomized study investigated the effects of unilateral instillation of 0.5% maleate timolol twice a day for 7 days on visual-field parameters of both eyes. Twelve normal, young subjects (30.6±4.2 years) participated in this study. Using program Gl of the Octopus 500 automated perimeter, the visual fields were measured one week and one day before therapy and a third time one week after beginning therapy. The paired T-test was used for statistical analysis, where a P-value⩽0.05 indicated significance. Whereas nothing statistically significant was found in the treated eyes, the contralateral, untreated eyes showed a statistically significant decrease of mean sensitivity between the first visual fields and the third ones (P〈 0.01) This diminution of mean sensitivity in the untreated contralateral eyes may be due to statistically significant lowering of blood pressure (P〈0.01) and slowing of cardiac frequency, which were not compensated by a local decrease of intraocular pressure. If confirmed, these findings could be of clinical importance in the management of glaucoma patients, since some authors have, in some cases, recommended a unilateral therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00917985
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  • 9
    Electronic Resource
    Electronic Resource
    On the effects of different laser energy sources upon the iris of the pigmented and the albino rabbit (1978)
    Springer
    International ophthalmology 1 (1978), S. 39-48 
    Details
    ISSN: 1573-2630
    Keywords: Photocoagulation ; Iris ; Argon ; Nd: YAG ; Ruby Q-switched laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The irides of pigmented and albino rabbits have been irradiated by a) a CW argon laser beam (exposure duration up to 1 s), b) a 1 ms pulses Nd:YAG laser and c) a 30 ns pulses Q-switched ruby laser. The immediate and long-term pathologies were analysed by scanning and transmission electron microscopy over a period of 13 months. At both the gross and ultrastructural levels, damage configuration may differ considerably, depending on the three modes of irradiation. For each source there are both thermal and mechanical damage components and the significance of mechanical effects increases with decreasing pulse duration for a constant pulse energy. In the argon experiments, tissue destruction is predominantly a consequence of heat, resulting from conduction and convection. The subsequent regeneration of tissue after such heat-induced trauma is fast. The effects of the Nd:YAG laser, at the irradiance levels used in the present study, are again predominantly of a thermal nature and are caused by heating and local evaporation. The pigmented and the nonpigmented iris epithelium are destroyed and widespread decay of the stroma occurs over some months. Such damage never results in full repair. The most prominent feature of Q-switched ruby laser irradiations is their independence of the iris pigment content. In contrast, at the energy levels studied, the argon laser is entirely ineffective, whilst the effect of the Nd:YAG laser is much reduced in the absence of pigment. The consequences of these findings for the clinical applications of such lasers are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00133276
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  • 10
    Electronic Resource
    Electronic Resource
    Morphological studies about the efficiency of laser beams upon the structures of the angle of the anterior chamber (1979)
    Springer
    International ophthalmology 1 (1979), S. 109-122 
    Details
    ISSN: 1573-2630
    Keywords: Photocoagulation ; Non-linear effects ; Physics ; Morphology ; Nd glass Q-switched laser ; Scanning electron microscopy ; Chamber angle ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Working at a power density above optical breakdown threshold, irradiation effects upon the angle of the anterior chamber of the Macaca speciosa monkey by a Nd glass Q-switched laser, have been analysed with scanning electron microscopy. Two different damage effects can be identified: openings of Schlemm's canal and the creation of a cyclodialysis, that is opening the uveoscleral outflow routes; the latter may be a more effective one than the former. Also a third mechanism, namely a structural alteration of the trabecular meshwork, at the molecular level by laser action, has been inferred. The physical effects leading to optically induced mechanical damage are discussed. Applicability of such effects upon the morphological findings described here, is limited and to a greater part speculative. A better definition of the physical parameters, required for optimal therapeutical damage effects in the treatment of the wide angle glaucoma may be obtained by trial and error methods, which are guided by the results of electron microscopical analyses of samples obtained from in vivo and in vitro experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154198
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