Theoretical and practical aspects relating to the photothermal therapy of tumors of the retina and choroid: A review.

Photothermal treatment of tumors of the retina and choroid such as retinoblastomas, malignant melanomas, benign tumors as well as of vascular malformations can be performed by using laser radiation. A number of basic physical laws have to be taken into account in this procedure. Of particular importance thereby are: Arrhenius' law to approximate the kinetics of protein denaturation and photocoagulation, furthermore the electromagnetic radiation field, the distribution of both radiant and thermal energy induced in tumors and vascular structures, the influence of the wavelength and laser pulse duration (exposure time), as well as of the optical properties of the tissue. Strict confinement of the extent of the photothermal damage is critical since such pathological entities are frequently located close to the macula or optic nerve head.The conditions for tumor destruction 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 the Nd: YAG (1064 nm) laser, because of the good optical penetration properties of these radiations in tissue. Short wavelength sources of radiation, such as the argon ion (488, 514 nm) or the freqeuency-doubled Nd: YAG (532 nm) laser are less well suited for the irradiation of large vascular structures due to their poor penetration depths. However, for vascular formations with a small thickness (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 positive contact lenses is furthermore of importance. Strong positive lenses may lead to severe constrictions of the laser beam within the anterior segment, that leads to high irradiance increasing the probability for structures to be damaged; with negative contact lenses, such as the -64 D Goldmann type lens, this danger is largely absent.

[Hydrodynamics of aqueous humor in chronic simple glaucoma : Mechanisms of pressure normalization by an artificial outflow system]. / Fluiddynamik des Kammerwassers beim chronischen einfachen Glaukom : Mechanismen der Drucknormalisierung durch ein künstliches Abflusssystem.

To help elucidate the interplay of physical forces, in particular pressure and flow, controlling the distribution and absorption of aqueous humor in subconjunctival tissue, a recently published computational model was considered where the fluid production in the eye, its removal via the trabecular/uveoscleral pathways and a surgical pathway are taken into account. The target quantity is the intraocular pressure. The surgical outflow pathway is linked to a fluid bleb that is positioned below the subconjunctival tissue and is modeled as a porous medium. The computational study was conducted on the basis of the geometry and relevant parameters characterizing fluid production, the surgically formed fluid pathway as well as absorption by the subconjunctival vessels, the hydraulic and geometrical characteristics of the bleb and the outflow facility. Clinical observations can be physically interpreted on the basis of parametric studies.

Nonlinear refractive index of porcine cornea studied by z-scan and self-focusing during femtosecond laser processing.

We have investigated the nonlinear refractive index of ex-vivo pig cornea by a combined approach using the standard z-scan technique on extracted corneas or corneal slices, as well as studying the deviations caused by self-focusing during femtosecond laser processing of the pig eyes. The experiments yield consistently an upper limit of 1.2 MW for the critical power of self-focusing in porcine cornea, and a value of 2 x 10(-19) m(2)/W for its nonlinear refractive index. We also demonstrate that due to this nonlinear refraction the cutting depth of typical fs-laser surgery processing in cornea may depend considerably, albeit in a well controllable way, on the laser parameters.

[Application of static and dynamic light scattering--a review]. / Anwendung der statischen und dynamischen Lichtstreuung--Eine Abersicht.

Dynamic light scattering (DLS) measures the oscillations of macromolecules (MM) (Brownian motion). Small MM move fast, large MM slowly. DLS allows one to measure the relaxation of the movements of these MM, together with their sizes and their hydrodynamic diffusion coefficients. By DLS not only the pathogenesis of a large number of eye diseases but also those of general diseases may be determined. The origin of this class of diseases is the condensation (agglutination) of MM. Medicaments, such as Panthetine, have been shown to be effective in animal experiments by acting on the ionic strength of disturbed MM. They may have a fair chance to be effective also in humans. Static light scattering (tyndallometry, nephelometry) (SLS) is able to determine the weight of MM, but however their shape, as DLS can.

Cortical mechanisms of normal and abnormal processing in the visual system, Part 1. Spatial vision, amblyopia, hyperacuity, modal assumptions: a review.

Vernier thresholds rise much more rapidly in the periphery than do grating thresholds. A similar dissociation between acuity and hyperacuity has been shown to be present in strabismic but not in anisometropic amblyopia, thus leading to the suggestion that the strabismic fovea is similar to the normal periphery. Here it is shown that a quantitative model for spatial pattern discrimination, which accounts for foveal hyperacuity data, can be extended to encompass both the periphery and amblyopia if appropriate alterations are made. For the periphery it is necessary to increase the size of model receptive fields and to introduce both spatial undersampling and position irregularity (i.e. irregularity in the location of cortical filters). The strabismic fovea also requires spatial undersampling and position irregularity but no change in receptive field size. Defects in the good eye of strabismus can be explained by spatial irregularity. Finally, the anisometropic fovea requires a reduction in mechanism sensitivity but neither spatial untersampling nor position irregularity.

Competitive and seasonal oxidative stress in elite alpine ski racers.

We investigated competitive- and long-term oxidative stress during a competition season in eight top-ranked members of the Austrian Men's Alpine Ski Team. Serum total peroxides, antibody titers against oxidized LDL (oLAb) and lag time of the degradation of the fluorophore 1-palmitoyl-2-((2-(4-(6-phenyl-trans-1,3,5-hexatrienyl)phenyl)ethyl)-carbonyl)-sn-glycero-3-phosphocholine were measured, along with plasma concentrations of ascorbate, alpha- and gamma-tocopherol, beta-carotene, uric acid and the lipid status. Competitive stress was indicated through an increased post-race uric acid level (286 +/- 50 microM pre-race vs 456 +/- 77 microM post-race, P<0.001) in December. Long-term effects were already apparent in November, with the highest concentrations of total peroxides (680 +/- 458 microM H(2)O(2) equivalents vs December 47 +/- 58 microM H(2)O(2) equivalents and January 15 +/- 28 microM H(2)O(2) equivalents, P<0.001) and a concomitant decrease in oLAb titers with an antibody trough in December (439 +/- 150 mU/mL vs baseline 1036 +/- 328 mU/mL; P=0.003). In January, after recovery, they attained nearly pre-season levels of oxidative stress biomarkers. This study indicates midseason oxidative stress in top-level skiers, which was associated with the performance in these athletes.

[A new high-power biconcave contact lens for observation and coagulation tasks of the posterior segment]. / Ein neues, bikonkaves Weitwinkel-Kontaktglas (CGR4) für Beobachtung und Photokoagulation am hinteren Augensegment.

BACKGROUND: At the present time, positive, wide-angle contact (and preset) lenses, having a large field of view, are widely used for inspecting and irradiating the fundus. They provide a real, inverted image of the fundus, but illuminate only the slit projected. The wide-field they provide (125 degrees ) is considered to be an advantage, but their image inversion and the lack of illumination of the whole field is disadvantageous. Contact lenses of the Goldmann type have a comparably restricted field of view (standard Goldmann: 46 degrees, CGR 3: 53 degrees). They illuminate the whole field inspected, but it is necessary to use internal mirrors when looking at the periphery. MATERIAL: The new contact lens has a lateral magnification of 0.44 and a field of view of 64 degrees. Owing to the prismatics of its biconcave structure, the field of view may be shifted by tilting the lens and/or by induced eye movements, beyond the ora serrata. CONCLUSIONS: The new contact lens CGR4 has an upright field of view of 64 degrees and tilting enables one to reach the equator with very little optical image degradation. The new lens has a negative power of - 139 dioptres. Safety during laser irradiation tasks is increased as compared to positive lenses because the irradiance at the crystalline part is significantly reduced. The lens is made of laser-resistant glass with a refractive index of 1,516 BK 7 (Schott).

Some aspects of wave aberrations of the human eye and supervision: a review.

Supervision is defined by a visual acuity of 20/10 or 20/8 and may be attained by custom-correcting the aberrations of higher order of the human eye. Higher order aberrations are those aberrations which are left in the eye after having corrected lower order aberrations, i.e., defocus (myopia, hypermetropia) regular astigmatism, and which can be corrected by ordinary spectacle lenses or contact lenses. Higher order aberrations are found to a higher or lesser degree in normal or pathological human eyes and in eyes having undergone conventional corneal surgery. According to custom keratorefractive surgery limits, given by the neural visual apparatus and the receptor mosaic, supervision (i.e., 20/10 or even 20/8) may be attained. A number of dedicated sensors have been developed in recent years that are able to detect and measure aberrations of the wave front which is a sensitive procedure for the determination and surgical control of the optical quality of the eye. Not every custom keratorefractive procedure results in supervision, however. This is because not every "normal" eye is able to reach such limits because of its basic design (anatomy or function) and also because keratorefractive procedures neglect the plastic behaviour of the cornea. The plasticity of the central neural system may furthermore interact with corrected or non-corrected visual function.

[Supernormal sight and high-resolution retinal imaging: a review]. / Supernormales Sehen und hochauflösende retinale Bildgebung -- Eine Ubersicht.

BACKGROUND: An analysis of the wavefront in human eyes has yielded new findings with respect to the cones and other elements of the retina. But the correction of higher-order wavefront aberrations in photorefractive processes is still associated with basic difficulties. MATERIALS AND METHODS: The world literature relating to wavefront corrections in experimental research and the correction of photorefractive aberrations in the human eye is surveyed. RESULTS AND CONCLUSIONS: The correction of higher-order aberrations has permitted a vast improvement in the resolution of the cone-pattern picture existing in vivo. As a consequence, new findings with regard to colour physiology have been forthcoming. On the other hand, the application of wavefront corrections in photorefractive procedures has been only partially successful.

[AS Eddington: Prokrustes and the fisherman--the ambiguous meaning of the word significance in biological and medical research]. / AS Eddington: Prokrustes und der Fischer -- Uber die unterschiedliche Bedeutung des Wortes Signifikanz in der biologischen und klinischen Forschung.

BACKGROUND: Statistical significance and biological/medical significance are not equivalent and should be distinguished from one another. MATERIALS AND METHODS: Pertinent data gleaned from the world literature have been analyzed and appraised. RESULTS: A semi-schematic display of the available data facilitates an overview of the relevant statistical quantities. CONCLUSIONS: The significance level of experimental findings should be gauged in accordance with the clinical requirements.

Lipid peroxidation and antioxidant status in professional American football players during competition.

BACKGROUND: Oxidative stress occurs during strenuous physical exercise, perhaps as a result of increased consumption of oxygen. MATERIALS AND METHODS: In this study, different markers of oxidative stress were determined in eight national league American football players. Before (March) and at three time-points during the competition season (May, June, July) serum total peroxide concentrations, auto-antibody titres against oxidized low-density lipoprotein (oLab), and lag time of reactive oxygen species-induced degradation of the fluorophore 1-palmitoyl-2-((2-(4-(6-phenyl-trans-1,3,5-hexatrienyl)phenyl)ethyl)- carbonyl)-sn-glycero-3-phosphocholine (DPHPC) were measured along with serum ascorbate, alpha- and gamma-tocopherol, and beta-carotene concentrations. RESULTS: Before the competition season, serum antioxidant concentrations were within the lower normal range; ascorbate concentrations increased significantly during the competition period (P < 0.05). Serum peroxide concentrations were within the normal range and increased significantly during the competition period (P < 0.05); in four of the eight subjects the increase was several times the baseline values, while four athletes did not show any increase. The oLab titres increased significantly at the mid-competition period time-point (P < 0.01), but levelled off thereafter. DISCUSSION: Given that it could not be predicted from the baseline oxidative stress and antioxidant status which subject would respond to strenuous exercise with an increase in oxidative stress status, it is concluded that oxidative stress should be monitored in all athletes.

[Ultrasound diagnosis in shoulder trauma]. / Die Sonographie beim Schultertrauma.

In cases of injuries to the shoulder region, ultrasonography is an ideal supplement to clinical and radiologic examination, including dynamic functional evaluation. The advantages of the method in children and adults are mainly the reduction of conventional radiographs and thus a minimum exposure to radiation. Despite the growing experience of clinicians and the development of high-resolution sonographic technology, primary conventional radiology cannot be dispensed with. Moreover, sonographic examination is rather time-consuming. Evaluation of the subacromial space and the glenohumeral joint itself is impossible in adults, and diagnosis of lesions to the labrum and the articular capsule requires a great deal of experience on the part of the clinician. Ultrasonography has gained increasing importance in the evaluation and follow-up of shoulder trauma in adults and children.

[Ultrasound diagnosis of the Achilles tendon]. / Sonographische Achillessehnendiagnostik.

Due to the superficial position of the Achilles tendon and the development of high-resolution probes with 7.5, 10, and more MHz, which allow the exact depiction of even very small structures, ultrasonography is the method of choice for the diagnosis of acute and chronic Achilles tendon disorders. Using sonography, both chronic achillodynia (disorders of the tendon itself, peritendinous tissue, bursa, and insertion of the tendon at the calcaneus) and ruptures of the Achilles tendon are exactly diagnosed. By sonographic examination, depiction of changes of the tendon itself (rupture, calcification, thickening) and evaluation of the peritendinous soft tissue with dynamic assessment of the gliding sheath are possible. The risk for the less experienced clinician using ultrasonographic assessment of the locomotor system is not to miss pathologic findings, but to overestimate them, due to artifacts. Sufficient knowledge of ultrasound physics as a reason for typical artifacts and the use of a standardized examination technique are necessary. However, by using high-resolution small ultrasound probes, the depiction of "problem areas" (e.g., musculotendinous junction, insertion of the tendon on the calcaneus) has become easier and more accurate.

[Cellular surgery with laser in ophthalmology. A review]. / Mikroskopgestützte Laserchirurgie - zelluläre Laserchirurgie in der Augenheilkunde. Eine Ubersicht.

This is a review of a number of laser methods, allowing to realize strongly localized, atraumatic, molecular, cellular, and subcellular microeffects. New instruments are the laser tweezers and the laser knife to be used with a microscope (microscopical surgery). Laser tweezers allow fixation, by means of the radiation pressure of molecular, cellular, and subcellular elements, of diameters as small as 1 microm. These may be irradiated atraumatically by means of short-pulsed lasers. A reversible damage of the cell membrane allows to introduce living genetic material into living cells and to reversibly modify their genetic behaviour. Micromanipulation/irradiation of living cells by means of the short-pulse laser method of living cells may be optimal in in-vivo fertilization experiments. Short-pulse laser methods have been tentatively introduced in ophthalmology and highly localized effects have been realized in the trabecular meshwork for the treatment of glaucoma and in the retina in retinal pathology.

HAGL lesion occurring after successful arthroscopic Bankart repair.

Recurrent traumatic anterior shoulder instability following surgical repair may be associated with implant failure and an array of capsulolabral pathology including separation of the labrum (Bankart lesion), humeral avulsion of the glenohumeral ligaments (HAGL lesion), and capsular rupture. We detail a previously unreported case of a HAGL lesion occurring in a shoulder with an intact arthrosopic Bankart repair following an additional traumatic event. Anatomic repair of this subsequent injury resulted in an excellent outcome. The patient returned to his high-demand ski racing activities without any shoulder limitation.

Transpupillary laser phototherapy of tumors and vascular anomalies of retina and choroid: theoretical approach and clinical implications.

BACKGROUND: Small retinal and choroidal tumors situated near the optic nerve or macula, such as retinoblastomas and malignant melanomas, as well as various other anomalies, in particular vascular malformations, may successfully be treated by photocoagulation. Model assumptions geared towards maximizing efficiency and minimizing undesirable side effects are forwarded, and the most important parameters subserving photothermal destruction, such as radiation field and thermal energy, analyzed. The influence exerted by physical traits of various tissues involved are also considered. METHODS: The model approximations presented are based on classical radiation and absorption laws, as well as on the scattering properties of the various tissues implicated, these being considered as a function of wavelength and their relevance to the photodestructive task at hand. Particular attention is paid to the rate processes and reaction kinetics of irradiated proteins. CONCLUSIONS: Radiation sources emitting in the near-infrared range of the electromagnetic spectrum, such as the diode (810 nm) and the cw Nd:YAG (1064 nm) lasers, are optimal for the treatment of tumors and large, voluminous entities (such as Hippel-Lindau angiomas), owing to the good tissue penetration properties of their light. Those emitting in the shorter wavelength range, such as the argon ion (488 and 514 nm) and first harmonic--mode Nd:YAG (532 nm) lasers, are not suitable for such tasks, but they are ideal for the destruction of fine sanguinous structures, within which their light is strongly absorbed but through which it penetrates poorly. For the treatment of large anomalous structures, a combined short/long wavelength--strategy should also be considered as a viable alternative. Such a "wavelength mixture" is emitted by the xenon high pressure lamp of the once renowned Meyer-Schwickerath light coagulator. The precision and safety of photothermal destruction methods depend, in the first approximation, upon the details of the pulse energy deposition (wavelength, pulse height and duration, pulse dynamics, mode composition, focussing), the choice of which is determined by the optical and thermal constants of the irradiated tissues. Higher pulse energies will, of course, be more effective in destroying neoplastic cells, but the risk of producing undesired collateral heat damage will also increase concomitantly. Until we can ascertain the physical properties of the pathological tissues treated with certainty, we will hardly be able to achieve more than an approximation of an ideal treatment strategy. But with increasing developments in in vivo-diagnostic techniques, we expect that this goal will be attainable in the not too distant future.

Transpupillar laser phototherapy for retinal and choroidal tumors: a rational approach.

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.

[Protein-condensation diseases--molecular basis of cataract formation]. / Protein-Kondensationskrankheiten--Molekulare Mechanismen bei der Kataraktogenese.

There are reasons to classify a number of apparently disparate diseases as "condensation" (or molecular aggregation) diseases. Examples of such condensation diseases include the late phase of diabetes mellitus, Alzheimer's disease and others. With an expanding knowledge, the list of these diseases is likely to increase. We shall describe the underlying common mechanisms, the aim being to find anticataractogenic drugs based on this insight. The common, most important denominator of various clinically differing condensation diseases derives from the interaction of the macromolecules which is in part attractive and in part repulsive. Aggregation resp. clumping of the macromolecules of the crystalline lens, the reasons for light scattering, may be prevented by introducing a number of molecules of various designs into the original macromolecular complex which reduce the tendency of aggregation. Cataract inhibitors of this category may be regarded as effective if they are able to increase the time constant of the normal aging process (i.e. the increment of scatter) by about 20%.