Search

From a collection of 288 visual fields of glaucomatous or glaucoma suspects, 30 were selected at random and were analyzed by one expert interpreter. Visual field damage varied from nonexistent to severe. The interpreter defined clusters or scotomas subjectively according to adjacency criteria: adjacent test locations which exceeded a critical loss value were grouped as clusters or scotomas. A computer algorithm has been devised which simulates such evaluation methods. In general, a standard setting of several parameters produced a cluster display containing the same number of clusters as determined by the expert interpreter. Another display mode grouped clusters according to polygonal areas of a predetermined size (Voronoi diagram). Due to the broad selection of visual field defects, the specificity of the program with regard to various field decay patterns was small and it should thus be applicable to a broad spectrum of glaucomatous field damage.

AbstractThe program Perisim 2000 enables one to simulate the interaction of a number of visual field examination strategies with a number of stored visual fields, both normal and pathological, with several patterns of observer (patient) behavior. A considerable number of visual fields, patient behavior patterns and examination strategies, including a full bracketing strategy, Gonzalez de la Rosa’s tendency-oriented perimetry (TOP) and Weber’s dynamic program, are available. Statistical programs are also incorporated. While the examination strategies to be used in the simulations must be selected from a predefined list, new visual field and observer patterns may be defined by the user. The results may be shown as numerical tables, symbolic or gray tone, pseudocolor or profile displays. Cumulative defect curves may also be selected. The learning/teaching benefits of the program Perisim 2000 are considerable. It is easy to understand and to operate, and ample explanations are available at each step of the program.Copyright © 2005 S. Karger AG, Basel

AbstractMethods used in laser destructive procedures are detailed. While in noncontact procedures laser energy is delivered via the optics of a slitlamp, often enhanced by contact lenses, the contact method takes advantage of optical fibers for the delivery of energy. Endpieces such as hemispherical or microlens probes enhance the cyclodestructive effect and/or allow the dose of laser energy to be reduced. Laser energy may also be delivered under direct view by endoscopic systems. Advances in laser cyclodestruction are possible by studying the physical effects.Copyright © 2004 S. Karger AG, Basel

AbstractLaser cyclophotocoagulation is an accepted method of cyclodestruction, such as cyclocryothermy and the application of cyclodiathermy, microwaves and ultrasound. These procedures may be considered as ultima ratios or ‘last-resort interventions’. Also, in cases where surgery is not possible, cyclodestruction may be the initial intervention. Among other lasers, the Nd:YAG and diode lasers are the energy sources of choice. Contact and noncontact methods have about the same clinical efficiency and risk. While immediate complications are transitory, other, late complications, mentioned in the world literature, such as sympathetic ophthalmia, malignant glaucoma and retinal detachment, are more serious but are rare, and their causal relationship with the cyclodestructive procedure is doubtful. However, they still merit our attention. The ultrastructural mechanisms related to cyclocoagulation have been studied. The study of aqueous flow may improve our understanding of cyclophotocoagulation techniques. Cyclophotocoagulation is considered an important cornerstone in glaucoma therapy. The uncertainty of its effect is no greater than that of any other therapeutic measure in the treatment of glaucoma. Copyright © 2004 S. Karger AG, Basel

Abstract: Background: The physical laws are considered that need to be taken into account for optimal photothermal treatment of solid and vascular tumors, as well as other vascular anomalies of various etiology of the retina and choroid. Optimal irradiation therapy should take into account the distribution of both radiant and thermal energy in tumors, such as retinoblastomas, malignant melanomas and vascular malformations. Strict confinement of the extent of photothermal damage is critical since such pathological entities are frequently located close to the macula or optic nerve head.  Methods: A formal treatment of the optical quantities related to these requirements is presented. In this analysis we emphasize the following topics: Arrhenius’ law, the kinetics of protein denaturation, the electromagnetic radiation field, wavelength, laser pulse duration (exposure time), optical properties of tissue, photocoagulation and thermotherapy. Results: Generally, the conditions are best fulfilled when using radiation in the near-infrared range of the electromagnetic spectrum, such as that emitted from the diode (810 nm) and Nd:YAG (1064 nm) laser, because of the good optical penetration properties of this radiation in tissue. The xenon arc lamp was a very effective and particularly appropriate energy source for such purposes, and its withdrawal from the world market may have been untimely. Short wavelength sources of radiation, such as the argon ion (488, 514 nm) or the frequency-doubled Nd:YAG (532 nm) laser, are unsuitable for the irradiation of large vascular structures, as they have poor penetration depths. However, for vascular formations with a short path length (1 mm or less), short wavelength sources appear to be the most appropriate choice. Optical coupling of radiant energy to the eye by means of indirect ophthalmoscopic systems or contact lenses to the eye is crucial. Strong positive lenses may lead to severe constriction of the laser beam which leads to high irradiance within the anterior segment, increasing the chances of it being damaged; with negative contact lenses, such as the –64 D Goldmann type, this danger is reduced.  Conclusions: Photothermotherapy is not without risk unless the temperature field can be well adapted to the tumorous structure, as temperature elevations outside a small therapeutic range that affect vital structures are considered to be a risk factor.

Abstract Up to 30% of all operative procedures in orthopaedic surgery are performed arthroscopically. Because of the steadily increasing number of residents, it seems to be difficult both to maintain high standards and to guarantee an adequate training in arthroscopic surgery. However, in contrast to many other surgical techniques it is possible to learn and practice arthroscopy using artificial models and cadaver joints, provided that experienced surgeons and anatomists act as supervisors and instructors. The aim of this paper is to assess practice models and training programs which should guarantee sufficient practical experience during the training period.

The automatic Octopus perimeter has a large software development potential. An important property of the Octopus programs developed to date is their ability to distinguish between pathological and normal behaviour. At the moment, program development is concentrating upon programs in which criteria of normality are used as feed-back parameters during the examination itself, and thus guide the visual field analysis. This property permits the algorithm to undertake a precise spatial analysis of disturbed visual field areas, without wasting time on a detailed analysis of normal areas. The efficiency of a visual field examination program is thereby substantially increased (SAPRO program). Using the F-program series, individual (as opposed to fixed) stimuli configurations can be realised, which may represent a better fit to a particular problem. The principles of two other programs, SARGON and DELTA, have been described before (Fankhauser and Jenni 1981).

The new Octopus programs SARGON and DELTA are described. The SARGON program makes possible the arbitrary distribution of a maximum number of 66 test locations with a resolution of up to 0.2 ° across the 60 ° visual field. Eighty user-defined self-created programs can be permanently stored and recalled later at will from the program discette. The program DELTA evaluates perimetric examination results with the aid of a series of statistical tests and investigates whether the data base is sufficient to assume a significant deviation, or alternatively, whether a visual field defect can be explained simply by spontaneous fluctuations or if a true pathologic defect should be assumed at a particular level of significance. Furthermore, the program tests changes in the visual field as a function of time for their statistical significance.

The effects of the argon-ion laser upon the iris of the pigmented rabbit were analysed by ultrastructural methods.1.Apart from the physical parameters of the energy source, the damage strongly depends on the concentration, location, and distribution of the iris pigment.2.The irradiation of the iris results in the formation of a crater. Depending on the distance of the epicentre of the impact, various degrees of ultrastructural damage are observed.a.The region immediately adjacent to the crater lumen at a revealing distance of 25 µm consists of homogenous collagenous masses, revealing a vacuolar structure. As the only residuals of destroyed cells, melanin granules are observed within the homogenous masses.b.Destruction of the collagen fibrils and their disintegration into subfibrils with elimination of all cell compartments is found in an area ranging from 25 µm to 300 µm from the wall of the crater.c.Damage to the chromatin structure is visible up to a distance of 300 urn to 375 µm from the wall of the crater.3.Characterised by an invasion of macrophages into the damaged area, the cleaning phase starts 24 h after irradiation.4.The results of this experiment indicate that because of the great energy dose required for man with the inherent widespread tissue damage and low probability of a lasting iridectomy, the cw argon-ion laser appears to be an unsuitable energy source for clinical iridectomy.

The reparative processes of the pigmented iris of the rabbit were analysed with ultrastructural methods.1.Clearing of the damaged area by macrophages is the first step in the reparative processes. Clump cells are macrophages which are observed from the first day of the injury until the ninth week.2.Repair of the anterior surface of the iris is largely finished after 32 days.3.The repair of collagenous fibres reaches its maximum activity 32 days after irradiation.4.The pigment epithelium has only an insignificant regeneration potential.5.Irradiation of the iris by the argon-ion laser results in an atrophie, hyperpigmented scar.

In a morphological study, the long-term effects of transscleral cyclophotocoagulation on rabbits using the free-running Nd: YAG laser with either a contact or a non-contact delivery system are described. A marked atrophy of the irradiated ciliary processes may be observed. Regeneration of the ciliary epithelial layers is incomplete at least up to 8 months after treatment. The vasucular network is also astrophic, and shows a small regenerative capacity only.

The morphological effects of trabeculectomy, performed as therapy for a case of chronic simple glaucoma, are described in the two eyes of a patient ten and thirteen months after treatment. Ten months after surgery, a transscleral channel, extending from the position formerly occupied by Schlemm's canal to the conjunctiva, is found. This channel is formed from a network of extended fibroblasts and loosely-packed collagenous tissue, and a large number of vessels, including both dilated blood capillaries and lymphatic vessels, develop within it. The sclera and subconjunctiva react differently to the presence of the nylon sutures. The findings support the hypothesis that the formation of an intrascleral outflow route stimulated by surgical intervention plays an important role in lowering IOP after trabeculectomy.

The local mean and the average difference of four pairs of test locations within the 26° visual field, situated above and below the horizontal nasal meridian, were used to predict the global field indices MD and CLV of the Gl glaucoma program. Out of 539 examinations (194 eyes suspected of having glaucoma), the local indices NDIFF (describing asymmetrical behavior around the nasal horizontal meridian), ND0 (the mean defect in the nasal region), and the global indices MD and CLV were calculated. Seven hundred fifty-five examinations (446 normal eyes) served as a control group. First and second examinations of 146 glaucoma suspect eyes were used to calculate the retest reliability scores for the indices in question. When analyzing the glaucoma suspects, the local index NDIFF, together with the local mean defect, ND0, yielded highly reliable estimates of the global indices MD and CLV, with a retest correlation r = 0.86 for NDIFF, and r = 0.96 for ND0. The covariance of NDIFF with CLV was r = 0.67, while the co-variance of MD with ND0 was r = 0.95. The ranges of the local indices ND0 and NDIFF were each classified into ‘normal range’ and ‘range of suspected pathology’, in analogy to the normal and pathological ranges of the global field indices. Equivalence of the local indices with the corresponding ranges of MD and CLV was investigated and the results are shown. The establishment of local indices may prove to be a powerful tool in early detection of glaucomatous damage.

The role of intraocular stray light upon contrast threshold of two skilled human observers was studied by perimetric methods using the automatic perimeter Octopus. Stray light falsifies the contrast sensitivity profile of the blind spot when a critical test stimulus luminance, which differs for various targets, is exceeded. At still higher luminance levels, because stray light effects increase, the blind spot shrinks and finally disappears. A series of high resolution measurements of the blind spot with the automatic perimeter Octopus provide a quantitative answer concerning the commencement and amount of this disturbance as a function of target size and target luminance. The amount of stray light, when using targets varying from 0 to 5 (Goldmann standard) is related to luminous power (target luminance x target area). Using first order assumptions about the stray light emitting characteristics of the disc and empirical data, one may conclude that an increase in luminance of target 0 from 103 to 105 asb only increases the effective dynamic range by about 2 dB (= 0.2 log units 3, the standard target as compared with target) size used in Octopus perimetry, at a luminance level of 103 asb. Falsification of sensitivity gradients and underestimates of depths of scotomata due to stray light effects may be an ever present danger in perimetric determinations. The useful dynamic range in perimetry appears to be limited by photon noise and noise in the neurovisual system on the one hand and by stray light interference on the other.

Adaptive programs have been developed, which adjust the spatial resolution of automatic perimeter measurement according to the presence or absence of visual field defects. Information obtained during the examination is fed back to an adaptively interacting algorithm controlling further examination steps. Using this strategy, defective areas are examined in detail but less time is wasted on regions of normal contrast sensivity.

The main visual field indices of Flammer and the analogous ones of Heijl have been compared based on a population of 113 glaucomatous visual fields. It is shown that for the population studied, the differences between the two sets of indices are negligible for Octopus G1 program results and that they may thus be used interchangeably.

A novel laser scalpel, consisting of a clad conically-sculptured silica tip (core diameter: 600Μm; end diameter: 150Μm transmitting radiation from a 10 W CW Nd-YAG laser, was used for the excision of a dorsal wrist ganglion. The dynamic range of this instrument (17–57 kW cm−2) easily suffices for the cutting of soft tissues, which feature is combined with impressive haemostatic properties, thus obviating the need for tourniquet control. Morphological examination of the excised ganglion reveals a peripheral zone of heat-damaged collagenoius tissue containing vessel profiles which show signs of thermally-induced blood flow stasis.

The course of tissue repair evoked by Nd:YAG laser sclerostomy ab interno and the effect of mitomycin-C on same were investigated ultrastructurally in 15 rabbits. In ten of them, the dynamics of the spontaneous postoperative healing response (i.e. in the absence of medication) was analyzed at two-day intervals by light- and electron microscopy. In two, fibroblast activity was assessed autoradiographically. In the last three rabbits, the sclerostomy site was exposed transconjunctivally to mitomycin-C (0.5 mg/ml; 5 minutes) before surgery, and morphological analysis was done on postoperative days 6 and 12.Results. In the spontaneously healing group, blebs disappeared within five days of surgery. This corresponded to a massive invasion of macrophages and fibroblasts from the episclera and iris root. The sheath of coagulated tissue around the fistula appeared to act as a barrier to cell migration from the sclera itself at this stage. By days 8 to 12, the canal had become occluded by a network of cells and capillaries, and collagen fibrils in the coagulation sheath had undergone repolymerization. In the mitomycin-C group, large filtering blebs and patent, cell-free fistulas were observed over the entire period. Although applied transconjunctivally, the drug penetrated the whole scleral depth, as the iris root and ciliary body cell reaction was inhibited. Repolymerization of heat-damaged collagen was also hindered. The overall findings provide information on the sequence of repair events following laser sclerostomy. Local, non-invasive application of mitomycin-C delays the onset of this process, not only by inhibition of cell proliferation but also by suppressing the collagen recovery.

Baso-cellular carcinomas involving the medial canthal regions of both eyes were resected using a 10 W cw-Nd: YAG laser scalpel.The wound bed was repaired one side by a free, split-thickness graft and on the other by a frontal pedicle flap. Surgery was, for the most part, virtually bloodless. Since laser radiation immediately seals both capillaries and lymphatics, the incidence of postoperative hemorrhage and edema was significantly less than after cold scalpel surgery. Healing was uneventful. The advantages of laser-assisted surgery are worthy of consideration: not only is the operation time markedly curtailed, but the wound healing response is excellent, with only a minimal inflammatory reaction.

A portable binocular microscope for retinal surgery is described which combines the advantages of mobility and of stereoscopic biomicroscopy through the contact glass. By the use of a suction contact glass this instrument enables irregular deformation of the cornea, which in the free eye is often the result of atonia, to be overcome. As a consequence image quality is much enhanced. This principle can be applied to human retinal surgery as well as to experimental research on animals.

The problem of hypercoagulation and the occurrence of post-coagulative maculopathy have long been associated with xenon arc photocoagulation procedures. The virtual absence of these complications with pulsed ruby laser coagulations has led many workers to experiment with short pulse exposure techniques. We describe and compare the histo-pathology and electron microscopy of short and long term retinal scars produced by both quasi-continuous ruby laser and short pulse xenon arc exposures. Our results show, that both systems produce damage only in the outer retinal layer, and result in very similar scar formations, with no involvement of the inner plexiform or nerve fibre layers.

Using our optical attachment to the photocoagulator of Zeiss-Oberkochen, enabling to work with the Goldmann 3 mirror contact glass, an effort has been made to reduce both pulse energy and damage to the choroid and nerve fiber layer. This has been found to be possible by electronic control of exposure time in combination with measurement of radiation dose. Small, not overdosed lesions, which in most respects resemble those generated by low-power pulsed lasers, can be obtained by superposing the cathode hot spot of the xenon arc with its mirror image, using small field stops and an exposure time of, typically, 0.1 sec. No modification of the electrical equipment of the coagulator is necessary. The lesions produced in this way on rabbits are characterized by a relatively rapid resorption of edema and abundant pigment proliferation. The choroid and nerve fiber layer are not affected.

A photocoagulation method for treating retinal holes requiring relatively little energy is proposed. This consists in firing only one shot over the hole, the cathode hot-spot and its mirror image being adjusted so that they fall on functionally irrelevant tissue near the center of the lesion. The retinal area to be coagulated around the hole is then exposed only to relatively low light intensity, but heated additionally by conduction from the center. This results in strong stimulation of the cellular elements without damage to the choroid. As an example one case treated in this manner is described in detail.

A short-pulse, small-spot xenon arc coagulation technique, worked out on rabbits as described in a preceding paper, has been applied to humans with good results. The lesions can be made to resemble in most respects to those generated by weak ruby laser pulses, insofar as the choroid and the nerve fiber layer are not damaged, resorption of edema is rapid and pigment proliferation abundant. The technique consists in superposing the cathode hot-spot of the xenon arc by its mirror image, using small field stops and electronically controlled exposure times of typically 0.1 sec. The apparatus used was the photocoagulator of Zeiss-Oberkochen equipped with the optical attachement which allows of working with the Goldmann contact glass. Detailed description of some cases treated illustrates this method.

A method enabling a fully automated computer analysis of the visual field is described. Starting from the most probable assumptions about the sensitivity distribution within the visual field, this distribution is approximated in 4 steps.

The results obtained in 48 cases of diabetic retinopathy treated with the xenon are coagulator of Zeiss-Oberkochen, supplemented by the attachment for coagulation through the contact glass, on one hand, and with a argon laser coagulator devised by the authors, on the other hand, are summarised. Two representative cases are described in detail. In our experience the two methods, when applied as described, are practically equivalent in regard to the treatment of diabetic retinopathy.

The pathogenesis of diabetic retinopathy and the theoretical foundations of different methods of its phototherapy are reviewed. One aim of the treatment may be seen in the destruction of comparatively large retinal areas of small functional value, preferably in the periphery. Another aim of equal importance is the obliteration of the pathological vessels themselves. The two methods may also be combined.

A second prototype of the optical attachment to the Zeiss-Oberkochen photocoagulator allowing the use of the Goldmann contact glass is presented, showing improvements mainly on the observation system by the addition of a slit lamp and allowing for fluorescein funduscopy. Some development of the ruby-laser coagulator described in part II is also reported. A contact glass with a cover glass coated by an antireflection layer is proposed.

A contact glass combined with an adjustable indentor mechanism is described. Length and angle variations of the indentation stylus can be effected during use with the index finger of the hand holding the glass.

A new laser of high pulse repetition rate, typically 50 to 100 Hertz, for retinal photocoagulation offers significant advantages over conventional continuous or single-pulse light sources. High collimation permits one to generate very small burns. Optical aberrations of the eye media are neutralized for the most part by the application of Goldmann's mirror contact glass. In combination with a specially designed optical aiming and viewing system of high image quality, it is therefore possible to treat microlesions in the most peripheral parts of the retina with high accuracy and at low pulse energies. A foot pedal allows a very fine and continuous control of the laser output. A second observer is able to follow operations through a two-way eyepiece. The role of astigmatism caused by tilting the contact glass is discussed.

Clinical technique and results on some cases treated with a new photocoagulator using the Goldmann contact glass and a quasi-continuous ruby laser as an energy source are reported. It is shown that small burns can be positioned exactly out to the far periphery of the retina using very low pulse energies. The coagulator is mounted on a Haag-Streit table and patients can easily be treated in an upright position. A discussion of the coagulation strategy to be followed when generating multiple small welds is given. The advantages of this procedure are pointed out.

Abstract: We present the case of a 44-year-old female patient, who sustained an odontoid fracture after a minor trauma (uncomplicated fall). The radiologic evaluation revealed a skeletal tumor of the second cervical vertebra together with a fracture line at the base of the odontoid process of the axis. The patient underwent surgery, the tumor was resected and the odontoid was stabilised using an autologous cortico-cancellous bone graft and a halo fixator. Histologic examination revealed benign fibrous histiocytoma, which is reported to be a very rare skeletal tumor.