Biomedical subjects

W Wiegand

Publications and source records attributed to W Wiegand.

At least 37 records · Page 2Linked to original sources

PubMed1996

[Intrastromal keratectomy in high myopia. 1 year results].

Photorefractive keratectomy (PRK) by excimer laser is now a scientifically established treatment method in low and moderate myopia. In high and very high myopia, however, the formation of severe corneal haze or scars and a considerable regression of refraction remain obstacles to the use of PRK. One approach to these two problems is to perform an intrastromal keratectomy. PATIENTS AND METHOD. Between September 1992 and September 1994 intrastromal keratectomy was carried out in 42 eyes with myopia between -8.625 and -36 D. Twenty-one eyes (spherical equivalent of pre-operative refraction between -12.12 and -36 D) were treated by keratomileusis in situ, and 21 eyes (spherical equivalent of pre-operative refraction between -8.625 and -29.25 D) by intrastromal excimer laser keratectomy. Thirty-two eyes were followed up for at least 12 months. RESULTS. The post-operative refraction (spherical equivalent) ranged between +1.375 D and -5.0 D in the keratomileusis in situ group and between +1.5 D and -3.0 D in the intrastromal excimer laser keratectomy group. Nearly all patients regained their pre-operative visual acuity quickly. In the long-term follow-up (1 year) no significant regression of refraction occurred; the pre-operative visual acuity was regained in both groups after 1 year. Significant astigmatism was not induced. CONCLUSIONS. Intrastromal keratectomy is able to correct even very high myopias quite precisely and without regression of the refractive outcome. In addition, considerable haze can be avoided. For these reasons, in high and very high myopia intrastromal keratectomy seems to be superior to conventional anterior photorefractive keratectomy (PRK) by excimer laser.

Adult↗

PubMed1996

[Light scattering study of the cornea in contact lens patients. In vivo studies using confocal slit scanning microscopy].

For the first time, we present measurements of the scattered light intensity of the human cornea to determine the functional state of the corneal endothelium. In 94 contact lens wearers endothelial alterations were measured by means of a newly developed confocal slit scanning video microscope and correlated with photometrically recorded stromal scattered light intensity. Our control group consisted of 26 persons without corneal pathology. It was shown that in persons wearing contact lenses the endothelial cell density was significantly below that of the control group and endothelial cell polymegatism (coefficient of variability of cell size) was significantly greater. Further, in contact lens wearers the level of scattered light intensity was significantly higher than in the control group, and the difference increased with the wearing time. In addition, the variation of the endothelial cell size correlated with the increased scattered light within the stroma, only a low correlation was found between the endothelial cell density and the scattered light intensity, however. From our results it can be assumed that a corneal endothelium with marked polymegatism has a reduced hydration function. Thus, decreased endothelial function can be determined very early and non-invasively by measuring the corneal scattered light intensity. In addition, the scattered light intensity gives topographical information about corneal swelling.

Adult↗

PubMed1996

[Optic nerve involvement in chronic lymphatic leukemia of the B-cell series].

BACKGROUND: Malignant Non-Hodgkin lymphomas rarely manifest with ocular symptoms. We report on a patient with a low grade malignant lymphoma of the b-cell type with optic nerve involvement. PATIENT: In 1990 a 38-year old patient presented with typical symptoms of optic neuritis in the left eye. Magnetic resonance imaging (MRI) revealed a signal enhancement in the left optic nerve. Hematologically a well differentiated Non Hodgkin's lymphoma of the b-cell type was diagnosed. Neurological signs and symptoms in the following years were regarded as manifestations of multiple sclerosis (MS). In 1994 the patient presented with an acute visual loss in the right eye. MRI this time revealed a signal enhancement in the right optic nerve and a big CNS lesion. Gradually a bilateral partial optic nerve atrophy developed. The cerebrospinal fluid contained atypical lymphocytes, matching with the cells in the peripheral blood, morphologically and in the fluorescence-activated cell sorter (FACS). These findings suggest an intracerebral manifestation of a well differentiated Non-Hodgkin's lymphoma. CONCLUSION: Low grade malignant well-differentiated Non-Hodgkin lymphomas infiltrate the optic nerve. The clinical course in our case mimicked multiple sclerosis.

Adult↗

PubMed1996

In vivo observation of corneal nerve regeneration after photorefractive keratectomy with a confocal videomicroscope.

The aim of the present study was to study corneal nerve regeneration after photorefractive keratectomy (PRK) in vivo by means of a confocal videomicroscope. A total of 25 myopic eyes of 16 patients were examined biomicroscopically and with the confocal microscope (Microphthal, Hund Company, Wetzlar, Germany) before and after PRK. The mean age of the patients was 30.4 (range 21-44) years, the mean follow-up period was 13.7 (11.0-15.1) months, the mean preoperative refraction was -5.5 (-1.75 to -9.0) D, the mean amount of attempted correction was -4.75 (-1.75 to -7.5) D, the mean ablation depth was 50 (30-75) microns, and the single central ablation zone measured 6.0 mm in diameter. The postoperative refractive and visual outcome was favorable in most eyes. The mean postoperative refraction was -0.5 (-2.75 to + 0.5) D. Among the 25 eyes, 22 (88%) had +/- 1.0 D of attempted correction at 1 year and only 2 eyes showed a loss of 2 Snellen lines. Despite increased light scattering and reflection due to haze, sufficient postoperative imaging of the corneal nerve architecture was possible in all cases. Recovery of corneal innervation started from the margin of the ablation, being directed toward the center of the cornea and the epithelium. At 5-8 months following PRK, stromal nerves and the subepithelial nerve plexus took on their definite appearance. The original nerve structure was not reestablished, abnormal branching and accessory thin nerve fibers being present without exception. Confocal slit-scanning video-microscopy is a very useful technique for in vivo investigation of corneal nerve regeneration after PRK and, presumably, other keratorefractive procedures. In comparison with histology studies in animals, reinnervation of the human cornea after PRK seems to be completed earlier but follows the same morphologic principles.

Adult↗

PubMed1995

Optical sectioning of the cornea with a new confocal in vivo slit-scanning videomicroscope.

PURPOSE: The purpose of this article is to introduce a newly developed confocal in vivo slit-scanning microscope for continuous recording and real-time imaging of the various corneal subsegments of the patient's eye with high microscopical resolution and adequate contrast. METHODS: One-dimensional confocal slit-scanning videomicroscopy of the human cornea was performed with an instrument mainly consisting of a scanning module, an image-intensifier video camera, a video monitor, and a synchronization unit for matching optical scan and video cycle with respect to frequency and phase. Light intensity or fluorescence intensity profiles through the cornea could be obtained by microphotometric recording of part of the imaging light. An immersion contact technique using an isotonic tear replacement liquid with thixotropic properties avoids any mechanical contact between the front lens of the microscope objective and the corneal surface. RESULTS: In normal human eyes, the corneal micromorphology could be made visible with satisfactory lateral and axial resolution and with good contrast. The separately focussed sections of the cornea showed the endothelial cells, the superficial, intermediary, and basal cells of the epithelium, as well as stromal keratocytes and nerves. Even in eyes with significant corneal opacities resulting from corneal edema, the endothelial pathology could be imaged with sufficient contrast. CONCLUSION: The in vivo slit-scanning videomicroscopy offers real-time noninvasive and noncontact serial imaging of corneal subsegments with resolution and imaging contrast. Thus, an important step toward using confocal scanning microscopy for corneal diagnosis seems to be done.

Cornea↗

PubMed1995

[Phototherapeutic keratectomy in recurrences of granular corneal dystrophy after keratoplasty].

BACKGROUND: Recurrences of granular corneal dystrophy (Groenouw type I dystrophy) after penetrating keratoplasty have been often reported in the literature. Up to now the therapy of these recurrences consists in performing a lamellar or penetrating re-keratoplasty. As those recurrent opacities at first are located in the area of Bowman's membrane and the superficial corneal stroma, a phototherapeutic keratectomy (PTK) with an excimer laser offers a therapeutic alternative to re-keratoplasty. PATIENTS AND METHODS: We describe three eyes of two patients with recurrent opacities on the transplant after successful keratoplasty because of granular corneal dystrophy. In all eyes we performed an excimer-laser PTK (Keratom of Schwind Company, Kleinostheim/Germany, wave length 193 nm) after abrasion of the epithelium with a hockey-knife. The depth of ablation depended on the location of the opacities and was between 7 microns and 35 microns. During the excimer-laser treatment several biomicroscopical slit-lamp controls were performed to make sure whether a sufficient depth of ablation was obtained. RESULTS: The opacities could be totally removed in all eyes by excimer-laser PTK. Postoperatively the visual acuity increased and the patient's photophobia decreased. At the same time a slight progression of hyperopia developed depending on the depth of ablation. During the follow-up period of 5 to 12 months no recurrent opacities could be found until now. CONCLUSIONS: Phototherapeutic keratectomy with the excimer laser seems to be a good alternative to re-keratoplasty in superficially located recurrences of granular corneal dystrophy in a graft after keratoplasty. A slight progression of hyperopia depending on the depth of ablation has to be accepted. The future will show whether there will develops recurrent opacities of the dystrophy after an excimer laser treatment.

Aged↗

PubMed1995

[Early vitrectomy in endogenous juvenile uveitis intermedia--a long-term study].

BACKGROUND: The intermediate uveitis is one of the most common intraocular manifestations of inflammation during infancy and adolescence. The success of intensive pharmacological treatment is rather limited and often associated with heavy side effects. PATIENTS AND METHODS: In 25 eyes with juvenile uveitis intermedia (age of the patients between 5 and 18 years, mean 13.5 years) and visual acuities between 0.02 and 0.4 (mean 0.19) an early vitrectomy was performed after failure of conservative treatment and peripheral cryocoagulation. RESULTS: Almost all patients (22 out of 25) showed an improvement of visual acuity within the first 6 months of the surgery. Among the patients with a remarkable improvement of visual acuity 7 eyes had a chronic cystoid macular oedema which showed a regression postoperatively. Additionally, the number and the course of inflammatory periods could be reduced postoperatively. An increase of preexisting lens opacities, however, has not been noticed even after a follow-up period of 10 years. CONCLUSIONS: The results show that an early vitrectomy in cases of juvenile uveitis intermedia often leads to a stabilization or an improvement of visual acuity and a regression of the inflammatory attacks (episodes). Therefore, in children and adolescents with endogenous uveitis intermedia a pars plana vitrectomy instead of a long-term systemic immunosuppression associated with heavy side-effects should be considered.

Adolescent↗

PubMed1995

Endogenous fluorescence of ocular malignant melanomas.

The endogenous fluorescence of human choroid, sclera, and retinal pigment epithelium (RPE) in normal tissue and tissue with uveal melanoma was studied in vitro by a non-invasive and non-destructive fluorescence technique which had previously been applied for the diagnostic evaluation of pigmented lesions of the skin. The fluorescence of the normal choroid is rather dark, the normal sclera exhibits blue fluorescence and the RPE bright yellow fluorescence due to deposits of lipofuscin. In choroidal melanoma, the lipofuscin granulae at the level of the retinal pigment epithelium are cleaved off above the tumour and broken up into small remnants. The fluorescence intensity emitted from the tumour is rather low which agrees with previous findings on skin melanomas. The results may become interesting for diagnostic evaluation of uveal melanomas, uveal naevi, and pigmented conjunctival tumours by endogenous fluorescence.

Choroid Neoplasms↗

PubMed1995

[Corneal changes and corneal healing after keratomileusis in situ. In vivo studies using confocal slit-scanning microscopy].

So far, no investigations of micromorphological changes in the human cornea after in situ keratomileusis have been published. In 10 eyes of five patients who had undergone in situ keratomileusis, wound healing processes were followed up with a newly developed confocal slit-scanning video-microscope. Post-operatively, alterations in the corneal endothelium and in the corneal stroma were found. Wide streaky distortions were observed within the stroma above and below the lamellar incision during the early days immediately after surgery. These distortions were probably induced by shearing stresses of the oscillating blade of the microkeratome. Small scattering centers were seen at the level of the lamellar incision, which are thought to reflect a very slight roughness of the interface. In the immediate postoperative period the corneal endothelium showed reversible inhomogeneitis similar to blebs after short-term contact lens wearing, which are thought to be due to a hypoxia during the surgery. The endothelial alterations and the streaky distortions within the stroma disappeared within 9 days after the surgery whereas the scattering centers regressed much more slowly and could still be observed 60 days after the surgery. The total amount of scattered light of the cornea, however, was not increased except in one patient. The results show that outside the level of the lamellar incision, in situ keratomileusis leads to only short-term alterations of the corneal micromorphology, and that confocal in vivo slit-scanning video-microscopy allows thorough examination of these alterations.

Adolescent↗

PubMed1995

[Keratomileusis in situ in high grade myopia. Initial results].

Besides photorefractive keratectomy (PRK) with the excimer laser, different methods of intrastromal keratectomy are now available for refractive corneal surgery in myopic patients. The first results of keratomileusis in situ in high-grade myopia are presented. Keratomileusis in situ was performed with a semiautomatic mechanical microkeratome in 15 amblyopic eyes with a refraction (spherical equivalent) between -12 and -25 D (mean -18.18 D). The principle of the method consists in a change of the anterior corneal curvature by resection of a refractive lenticulus out of the corneal stroma. The first step is the removal of a superficial corneal lamella consisting of epithelium, Bowman's layer, and superficial stroma. After this, the refractive lenticulus is resected out of the stroma, and the superficial lamella is sutured back to the cornea. The postoperative refraction (spherical equivalent) 4 weeks after the operation ranged between + 1.5 and -4.5 D (mean -1.37 D). Best corrected preoperative visual acuity was achieved again postoperatively within 4 weeks in most of the patients; in some patients the postoperative visual acuity even exceeded the preoperative values. After an uncomplicated healing process in 14 of the 15 eyes the cornea remained completely transparent in the optical zone, and the effect of treatment remained stable. Scar formation was observed in one eye only, where the lamellar cut was inadvertently performed in Bowman's layer and not in the stroma. Thus, keratomileusis in situ is a supplementary technique to conventional refractive surgery in high-grade myopia. Its advantages are quick optical rehabilitation and an almost scar-free optical zone, because the integrity of Bowman's layer is almost completely maintained with this technique.

Adolescent↗

PubMed1995

[Compiling the data of vitrectomy patients. Waiting list organization and quality assurance].

Owing to an increasing frequency of ophthalmological operations and the necessity of shortening the patient's stay in hospital surgical scheduling and data compilation in ophthalmology can only be managed by means of electronic data processing. We present a computer program that compiles a waiting list for vitrectomies and organizes the scheduling of operations. On each patient's first visit a standardized form containing the essential clinical findings if filled out. On the basis of these data the computer, using a specially designed algorithm places the patient in an appropriate position on the waiting list and eventually informs him or her of the date of the operation. In a similar manner the postoperative findings and the results of the follow-up examinations are documented. The system allows effective scheduling based on the urgency of the operation and the prognosis of the disease. Furthermore, it facilitates prospective recording of the clinical course and the treatment outcome. The use of electronic data processing does not only mean an improvement in clinical organization and, especially, in surgical planning, but also facilitates a quick evaluation of clinical studies with a large number of patients.

Algorithms↗

PubMed1995

[Traction vitreoretinal opticopathy in proliferative diabetic vitreoretinopathy].

UNLABELLED: In patients with proliferative diabetic vitreoretinopathy the authors noticed tractive vitreoretinal distortion of the optic disk to the nasal side. As a result of this distortion a reduction in visual acuity, pallor of the optic disk, and changes in the visual evoked potentials were registered. The disease in called "tractive vitreoretinal opticopathy." METHOD: We examined 15 diabetics with vitreoretinal traction and temporal pallor of the optic disk, as well as a reduction in visual acuity. Six patients were observed retrospectively and 9 patients prospectively before and after vitrectomy. Pre- and postoperative examinations included visual acuity, visual field, fluorescence angiography, and the conduction of visual evoked potentials (VEP). RESULTS: Within a postoperative follow-up of 2-8 months (mean 6.5 months) a return of optical vitality combined with an increase in visual acuity could be seen in 14 of 15 patients. In addition, some of the patients showed an improvement in the amplitudes and a reduction in the latency of the VEP. CONCLUSIONS: The authors assume that the axoplasmatic flow in the optic nerve fibers is reduced according to vitreoretinal traction. Furthermore, the traction may cause elongation of the capillaries, resulting in reduced perfusion of the optic disk. For these reasons early vitrectomy in patients with tractive vitreoretinal opticopathy is recommended.

Adult↗

PubMed1995

Panophthalmitis with acute scleral necrosis after brachytherapy of a malignant melanoma of the ciliary body.

A 52-year-old man who presented with a large ciliochoroidal malignant melanoma was treated by application of a 106Ru plaque. At 8 days after removal of the plaque, severe panophthalmitis with rapidly progressive scleral necrosis at the site of the tumor made enucleation inevitable because of impending perforation of the globe. Microscopic examination revealed an intense inflammatory response and almost complete necrosis of the tumor and overlying sclera. Possible mechanisms for the occurrence of this rare complication are discussed.

Acute Disease↗

PubMed1994

[Computer-assisted, improved evaluation of Comberg images with three-dimensional graphic reconstruction].

BACKGROUND: Small metallic foreign bodies may easily be identified by conventional x-ray. The Comberg shell is a useful tool to discriminate between extra-respectively intraocular localization of the foreign body. However, poor results are common when evaluating the x-ray films. METHODS: We have improved evaluation of the radiographs by means of a program for a personal computer, regarding the following aspects: To avoid errors of measurement the relevant points of the radiograms are read by a digitizer-tableau. The different projection failure of the lateral respectively posteroanterior x-ray is calculated separately. For the calculation of the modell the true axial length of the eye is considered. CONCLUSION: A three dimensional image from varying points of view gives an instructive impression of the foreign body and its relation to structures of the eye. Handling of the presented computer program is easy. It standardizes analysis of the Comberg radiograms.

Computer Graphics↗

PubMed1994

[Failures in primary surgery of retinal detachment with cerclage].

In a retrospective study we analysed 30 unsuccessful circumferential buckling operations being performed in the years 1990 and 1991 as primary interventions on simple retinal detachments without PVR, directing our attention to the cause of the failure. 13 eyes (43%) showed simple retinal detachments with holes located anterior (20%) or posterior (23%) to the circumferential buckle. In 12 of these eyes (40%) the retina could be reattached permanently by a re-operation with a second scleral buckling procedure. Another 15 eyes (50%) showed retinal holes not being sealed by the circumferential buckle. In addition, however, the retina in these eyes was kept from reattachment by a PVR grade C or D at the time of the re-operation. In 9 eyes (30%) of this group reattachment could be achieved after vitrectomy with endotamponade, in 6 eyes (20%) the retina could not be reattached. Only 2 eyes (7% of all patients) showed a PVR detachment without detectable retinal breaks. Thus, failures of primary circumferential buckling operations in numerous cases are caused by either inadequate surgical procedures or by a poor surgical technique.

Adolescent↗

PubMed1994

[Computer-assisted provocation and detection of optokinetic nystagmus].

A computer-controlled system for the automatic induction, registration, and analysis of optokinetic nystagmus is presented. On a high-resolution computer video monitor, a horizontally moving pattern of vertical stripes of equal size and distance is displayed. Stimulus size, velocity, and direction of movement are computer-controlled and variable. Exposure to this display induces horizontal optokinetic nystagmus in the patient. The patient's eye movements are registered by an infrared non-contact limbus-tracker system and transferred to the computer in a digitized format. With a specifically developed computer program the pursuit eye movements are detected and analyzed for amplitude, duration, and velocity and may be displayed on a second monitor. Simultaneously, the congruence of the direction of the stimulus and of the direction of the eye movement are automatically supervised and quantified by an "acceptance coefficient." The first clinical studies with healthy experimentees showed that for each stimulus size a certain stimulus velocity exists that provides maximal nystagmus provocation. Smaller stimulus sizes require slower stimulus velocities. Future developments of the system will allow applications in other fields of nystagmus research and in the accessment of objective visual acuity.

Electronystagmography↗

PubMed1993

[The laryngeal mask versus intubation in difficult intubation conditions in the Franceschetti-Zwahlen-Klein syndrome (Treacher-Collins syndrome)].

A twenty-nine-year-old man suffering from Franceschetti syndrome requiring a retinal detachment operation was successfully anaesthetised using the laryngeal mask airway. The laryngeal mask has many advantages compared to endotracheal intubation in patients suffering from craniofacial abnormalities i.e. hypoplasia of the mandibular bone and ventral position of the larynx. In these cases the laryngeal mask is easily placed. However, the facilities of fibreoptic bronchoscopy should be readily available. The physician should have gained confidence in using a laryngeal mask before employing this device in cases of difficult intubation.

Adult↗

PubMed1993

[Radical conjunctivectomy in therapy of malignant melanoma of the conjunctiva].

BACKGROUND: In tumor excision of large malignant melanomas of the conjunctiva or in the excision of widespread precancerous melanosis the development of symblepharon is a threatening complication after conjunctivectomy, especially if the conjunctival fornix is afflicted. PATIENTS: Three patients with suspected nodular melanoma and surrounding precancerous melanosis of the conjunctiva were treated by extended excision of the conjunctiva. Instead of a conjunctival graft, spontaneous epithelization under the protection of an 'Illig' contact lens was achieved. After this, two patients with histologically proven malignant melanomas were treated by beta-ray radiation with 90-Strontium. RESULTS: Within four weeks after the excision a complete epithelization of the wound occurred and the functional as well as the cosmetic results were very satisfying. During the follow-up between 12 and 22 months no recurrence of the melanomas and no formation of symblepharon was observed. CONCLUSIONS: With regard to these results extended tumor excision without conjunctival graft seems to be a reasonable therapy for large nodular melanomas and widespread melanosis, while the application of an 'Illig' contact lens avoids the formation of symblepharon.

Adult↗