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Biomedical subjects

W Kulnig

Publications and source records attributed to W Kulnig.

At least 19 recordsLinked to original sources
PubMed1992

Symmetrically banded collagen fibrils: observations on a new cross striation pattern in vivo.

Collagen fibrils with a symmetric banding pattern, an as yet overlooked component of the extracellular matrix, were found in the reticular layer of the basement membrane of human sebaceous glands. In longitudinal sections this newly described banding pattern is D-periodic (D = 67 nm) resembling the period length of native type collagen fibrils. In cross sections the symmetrically banded fibrils are irregularly outlined. The period length and the symmetric banding pattern led to the assumption that collagen molecules are staggered by the distance D, similar to native type collagen fibrils, but are arranged antiparallel. This hypothesis was tested by antiparallel superposing transparent photocopies of native type fibrils. In addition, schematic drawings of the cross striation pattern of native type fibrils were superposed in reverse directions by means of computerized image-manipulation. A model of molecular alignment was evolved from these experiments, which is characterized by two features: 1) pairs of antiparallel collagen molecules are D-staggered and 2) the two molecules of a pair are slightly shifted from precise register. The proposed model is the only one correlating with the data obtained from direct measurements on symmetrically cross striated fibrils. The fibrils described in the present study represent a supramolecular aggregate of collagen previously not observed in vivo.

Basement Membrane↗
PubMed1990

Optical resolution of foldable intraocular lenses.

Recently manufactured intraocular lenses (IOLs) (STAAR AA 4203 made of silicone and IOGEL PC-12 made of polyHEMA) were tested before and after implantation simulation for axial optical resolution (model eye), for optical surface quality (photokeratoscope), and for surface microtrauma (scanning electron microscopy). At a 3 mm pupillary opening, both lens types achieved a mean axial resolution of 1.25 (range 1.0 to 1.5) on an optotype analogous resolution target. When the pupillary opening was increased to 6 mm, polymacon IOLs showed only a moderate resolution decrease (up to one line) and loss of contrast (up to 30%); silicone IOLs showed almost no decrease. Photokeratoscopic evaluation revealed that a circular optical nonhomogeneity at the peripheral optical zone of the hydrogel IOLs is the source of this impairment. Groove-like surface deformities occasionally observed by scanning electron microscopy did not detectably decrease resolution or contrast.

Humans↗
PubMed1989

Tissue reaction after silicone and poly(methyl methacrylate) intraocular lens implantation: a light and electron microscopy study in a rabbit model.

We describe the histopathologic results of extracapsular lens extraction and silicone and poly(methyl methacrylate) (PMMA) intraocular lens (IOL) implantation in 36 rabbit eyes. Phase-contrast microscopy was used to examine precipitates on IOL surfaces and posterior capsules. Semithin and ultrathin sections were taken from the central cornea, anterior uvea, capsular bag, and retina near the posterior pole. The follow-up was one to 16 weeks. Silicone IOLs did not cause significantly less precipitation than PMMA IOLs. Precipitates consisted of spindle-shaped fibroblast-like cells, various forms of inflammatory cells and multinucleated giant cells, single melanophages, and irregularly arranged birefringent collagen fibers. Corneal endothelial edema was slightly more prominent in PMMA IOL implanted eyes. Significant retinal edema in the posterior pole area was not observed with either of the two lens types. Severe precipitation in the form of large clusters of pigment cells and inflammatory reactions seemed to depend on mechanical trauma (iris capture and lens dislocation) and individual animal reactions, but not on the lens type used.

Animals↗
PubMed1988

[Sources of error in the performance of the R5 test].

A prospective study examining 48 children (age 3.5-7 years) without any ophthalmological symptoms was comparatively performed using the Rodenstock R5 screening test and free examination of visual acuity, phoria and stereopsis. Besides this retinoscopy, interpupillary distance and inclination to instrument accommodation were determined. Using stereopsis targets 121 and 122, the findings of Marquardt (3- to 4-year-old children incline to prefer certain figures, leading to wrong results) can be confirmed. If the actual interpupillary distance is apart from the instrument eyepiece distance, especially if the child's distance is smaller, esophoria can be simulated. Instrument myopia on the one hand may appear as decrease of visual acuity, on the other hand it can be misinterpreted as esophoria. Being aware of these possible errors, the rate of wrong results (mean 22%) can be reduced, leading to better agreement between both methods.

Accommodation, Ocular↗
PubMed1987

Clinicopathologic findings after in-the-bag implantation of open-loop polymethylmethacrylate and silicone lenses in the rabbit eye.

Two lens models, one all silicone with J-loop haptics, the second with PMMA optics and angled polypropylene C-loop haptics, were implanted in the capsular bag of 36 rabbit eyes following extracapsular lens extraction. Technical ease of implantation, inflammatory response, lens position, and fibrin exudation as well as precipitate formation were examined. Biomicroscopy, light and phase-contrast microscopy were used. Differences in haptic vulnerability, lens position, and fibrin clot formation were found between the two lens types. Lens-specific differences in precipitate formation could not be substantiated.

Animals↗
PubMed1987

Optical resolution of silicone and polymethylmethacrylate intraocular lenses.

The optical resolution and contrast of 18 silicone and 18 polymethylmethacrylate (PMMA) intraocular lenses were determined before implantation in and after removal from rabbit eyes. A specially designed microphotographic system that allows documentation and comparison of the image quality of different lens types was used. Silicone intraocular lenses showed a mean axial resolution of 1.25, PMMA lenses showed 1.60, of an optotype analogous resolution target (1.0 = 20/20) at a 3 mm pupil opening preoperatively. At one to 16 weeks postoperatively, both types of IOLs demonstrated nearly unchanged resolution. Contrast, however, decreased to between 60% and 85% of the preoperative 100% standard. This decrease was due to precipitates deposited on the lens surface, to posterior capsule opacification, and to lens decentration.

Animals↗
PubMed1987

[Assessing refraction in children with cerebral damage].

In children with brain damage or multiple disabilities ophthalmological care may involve a variety of problems if it extends beyond mere diagnosis. Above all, difficulties can occur if a patient does not tolerate a trial spectacle frame and/or trial glasses in front of his/her eyes, so that it is impossible to perform retinoscopy in the usual way. If refraction has to be measured as a prerequisite for further treatment (in cases of squint, anisometropia etc.), close range retinoscopy and other modified refraction methods may be useful. The potential and limitations of these methods are described on the basis of the patient collective of a special outpatient department for children with brain damage.

Anesthesia, General↗
PubMed1987

High-energy electrons used to inhibit experimental intraocular proliferation and detachment.

Irradiation of rabbit eyes with high-energy electrons was used to test the inhibition of experimental intraocular proliferation and retinal detachment, produced by intravitreal implantation of 250,000 homologous fibroblasts. After irradiation with 2,000 rad, started 5 days after implantation, 45% of eyes (9 of 20) still manifested traction detachment. When the dose was increased to 3,000 rad and radiation treatment was started 1 day after implantation, proliferation and traction detachment were observed in only 10% of eyes (2 of 20). No acute damage to retinal tissue or nerve fibers was observed. Because it is easily available, simple in application and dose adjustment, and without toxic side effects, radiation therapy should be considered as an effective alternative to drug treatment for the inhibition of intraocular proliferation and detachment. Statistically significant results of this investigation suggest its use combined with surgery in certain reproliferative cases in man.

Animals↗
PubMed1986

[Ophthalmologic after care of premature infants].

Preterm infants, owing to their relative immaturity of organs and tissues show an increased vulnerability to exogenous factors such as oxygen, which may be required as a life-saving measure. In certain cases this may lead to retinopathy of prematurity and even blindness in the most severe cases. Regular ophthalmological follow up of at-risk infants is, therefore, essential to avoid irreparable retinal damage. From 1.8. 1983 till 31.7. 1985 159 at-risk infants were investigated ophthalmologically by direct and indirect ophthalmoscopy. 14 cases (8.8%) of stage I/II and one case (0.6%) of terminal stage retinopathy of prematurity were observed. In 34 children (21.4%) other changes of lesser (dacryostenosis) or greater pathological severity (hydrophthalmus, disc abnormalities, manifest squint) were seen. Initial results in preterm infants with an improved ophthalmoscopic device für examining the temporal periphery of the fundus, the site of predilection for early retinopathic changes, are reported.

Aftercare↗
PubMed1985

[Light and electron microscopic findings in eyelid tumors after cryotherapy].

Over the past five years 112 patients underwent cryotherapy of lid tumours. Two methods of freezing, contact freezing and spray freezing, were used. Biopsy specimens for histological studies were taken before and after cryotherapy. The results of light and electron microscopy are reported. Electron microscopic examination shows that cryonecrosis exhibits the well known general characteristics of necrosis. Cryotherapy results in extensive tumour necroses and this fact explains the success rate of 90.9% in basalioma 5 years after therapy.

Adult↗
PubMed1985

[Ultrastructural findings in secondary lipoidosis of the cornea].

A patient suffering from a progressive keratopathy which could not be identified clinically underwent penetrating keratoplasty. Light microscopy showed cholesterol deposits in deep stromal regions. Further ultrastructural investigations confirmed these findings and, in addition, fibrous long spacing collagen was found in that region; this represents a new factor in the possible pathogenesis of corneal lipid degenerations.

Cholesterol↗
PubMed1985

[Vital staining of the conjunctiva for prevention of epithelial implantation cysts].

Selective vital staining with 1% toluidine blue makes short-term intraoperative differentiation of the conjunctiva from Tenon's capsule possible. It is used with advantage in operations where the anatomical situation is unclear to avoid displacement of conjunctival epithelium into deeper tissues and subsequent growth of cysts. Examples of its application are reoperations with excessive scars after squint or detachment surgery, wound dehiscence after enucleations, lacerated wounds after accidents, and as an aid for beginners in ophthalmic surgery.

Animals↗
PubMed1985

[Surface atypia following recurrent corneal lesions (light and electron microscopy findings)].

A case of recurrent herpetic keratitis was followed by therapy-resistant corneal opacities. Histological sections revealed epithelial ectopias in superficial stromal layers of the cornea; their formal pathogenesis appears to be due to defects in Bowman's membrane. Another patient developed several intraocular complications after a penetrating corneal injury, and each surgical intervention resulted in increasing corneal decompensation. Semithin and ultrathin sections of the explant revealed endothelial metaplasia with fibroblastic activity.

Cornea↗
PubMed1985

[Measurement of coaxial position in lens implants].

Intraocular lens implantation occasionally causes binocular diplopia resistant to prismatic correction. Present methods of examination cannot determine the cause of this incurable diplopia. Therefore, a new method based on keratometry has been invented to allow qualitative and quantitative analysis of biomicroscopically undetectable decentration of intraocular lens implants producing asthenopic complaints. The present study investigates the type and frequency of intraocular lens decentration relative to the visual axis.

Diplopia↗