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Biomedical subjects

Franz Fankhauser

Publications and source records attributed to Franz Fankhauser.

9 recordsLinked to original sources
PubMed2006

Dynamic light scattering in ophthalmology: results of in vitro and in vivo experiments.

OBJECTIVE: To calibrate new dynamic light scattering (DLS) devices in defined solutions and post mortem porcine and human eyes. To examine all segments of the eye and to become familiar with the usage of the technique in living subjects. METHODS, DESIGN: Three new DLS devices for the usage in patients were developed. Mono-disperse solutions, poly-disperse solutions, gels, post mortem porcine and human eyes as well as healthy volunteers were studied. The detected signals were inverted into autocorrelation functions. RESULTS: We constructed three DLS devices appropriate for in vitro as well as in vivo examinations. In mono disperse solution precise disintegration rates could be calculated. In poly-disperse solutions, in gel and in the vitreous the results did not correlate with movements of individual particles but we could calculate characteristics of the complete scattering system. In vivo measurements demonstrated that DLS can be used in all human eye segments. DISCUSSION: DLS is a unique technique. With DLS the molecular composition of eye segments can be studied in living subjects. This can be used to understand the molecular basis of severe eye diseases. The presented data demonstrate that DLS delivers reproducible data from all eye segments. CONCLUSIONS: It is possible to study the molecular structures of eye segments in living subjects. The developed devices were proved successfully in vitro as well as in vivo. Limitations are the low specificity of DLS and its sensitivity to background noise. Now clinical studies are necessary to demonstrate potential diagnostic benefits of DLS in specific eye diseases.

Animals↗
PubMed2005

Adjustment of guidelines for exposure of the eye to optical radiation from ocular instruments: statement from a task group of the International Commission on Non-Ionizing Radiation Protection (ICNIRP).

A variety of optical and electro-optical instruments are used for both diagnostic and therapeutic applications to the human eye. These generally expose ocular structures to either coherent or incoherent optical radiation (ultraviolet, visible, or infrared radiation) under unique conditions. We convert both laser and incoherent exposure guidelines derived for normal exposure conditions to the application of ophthalmic sources.

Eye Injuries↗
PubMed2004

Supernormal vision, high-resolution retinal imaging, multiphoton imaging and nanosurgery of the cornea--a review.

Wavelength-corrected, adaptive optics and their relevance for diagnostic procedures of the human retina are considered. First, it is shown that the compensation of errors of the dioptric apparatus of the eye allows sharp and high-contrast images of retinal elements, such as the photoreceptors, to be generated. This technology is expected to enable on the one hand an improved laser therapy by the application of laser spots of the size of single receptors as well as on the other a further understanding of the mechanisms of vision, in particular of colour vision by using colour stimuli not larger than the cones. Second, femtosecond laser pulses, emitted from lasers working in the near infrared, based on multiphoton effects allow both imaging and laser effects to be generated which are in the submicron range and which do not cause collateral damage (nanoimaging and nanosurgery). These procedures, related to experimental ophthalmology may be considered a milestone for the research of cell physiology, in particular in the subcellular range.

Biomedical Technology↗
PubMedDate not supplied

Clinical effects of the Nd:YAG laser operating in the photodisruptive and thermal modes. A review.

The clinical effects of the Nd:YAG laser operating in both the photodisruptive (Q-switched) and thermal (free-running, cw) modes are discussed, and their clinical applications investigated. Moreover, the physical background of the working modes is explored. When working in the photodisruptive and fundamental (TEM(00)) modes, it is possible to carry out delicate clinical tasks with minimally invasive effects. When the laser is being used in the multimode regime, tasks that are highly resistant to photodisruptive laser radiation can be undertaken. In the thermal mode, photocoagulation can be performed. Nd:YAG laser light (1,064 nm) has high optical tissue penetration and good hemostatic properties, particularly when it is being operated in the frequency-doubled mode (KTP laser).

Adolescent↗
PubMedDate not supplied

Cyclodestructive procedures. I. Clinical and morphological aspects: a review.

Laser 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.

Aqueous Humor↗
PubMedDate not supplied

Cyclodestructive procedures. II. Optical fibers, endoscopy, physics: a review.

Methods 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.

Animals↗
PubMedDate not supplied

Simulation in perimetry -- program Perisim 2000.

The 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.

Computer Simulation↗
PubMedDate not supplied

Anterior lamellar keratoplasty with a microkeratome: a method for managing complications after refractive surgery.

PURPOSE: To demonstrate a technique of anterior lamellar keratoplasty with standardized and automated preparation of surface-parallel cuts in both donor and recipient appropriate for addressing several problems after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: We report a noncomparative series of ten eyes with complications after LASIK and PRK. Lamellar cuts were performed in donor and recipient eyes by means of an automated microkeratome. Lamellar grafts were fixed by only four single sutures. In two eyes, a re-lift LASIK was performed after 6 months. RESULTS: Surgery was uneventful and visual acuity was improved in all eyes. Residual irregular astigmatism and refractive error were corrected in two eyes by means of excimer laser computer-assisted ablation and resulted in a further improvement of uncorrected and best spectacle-corrected visual acuity. CONCLUSIONS: Anterior lamellar keratoplasty with a microkeratome can be used for the management of certain complications of PRK and LASIK.

Adult↗