Biomedical subjects

A Holschbach

Publications and source records attributed to A Holschbach.

10 recordsLinked to original sources

PubMed1998

[High resolution functional magnetic resonance tomography with Gd-DTPA eyedrops in diagnosis of lacrimal apparatus diseases].

UNLABELLED: Both dacryocystography and dacryoscintigraphy are well established in the evaluation of stenoses of the lacrimal drainage system. They provide limited information about the ductal anatomy itself and about periductal structures. MR imaging was evaluated for its capability to directly visualize the lacrimal drainage system in detail and simultaneously provide functional characterization of dacryostenosis. SUBJECTS AND METHODS: Twenty-seven lacrimal drainage systems of 23 patients suffering from epiphora were examined in an MR unit before and after conjunctival and intravenous application of Gd-DTPA using a surface coil. RESULTS: Dacryostenosis was found in 23 of 27 lacrimal systems. Stenoses were localized to the canalicular (n = 3), saccular (n = 8), and ductal (n = 12) level, and were classified as stenosis or occlusion. CONCLUSION: MR imaging with conjunctival contrast application allows within one examination both detailed morphological and functional assessment of the lacrimal drainage system with depiction of surrounding structures. Limitations arise mainly from demands on technical and patient-related preconditions.

Contrast Media↗

PubMed1997

Combined phacoemulsification and filtering surgery with the 'no-stitch' technique.

OBJECTIVE: To determine if intentionally making a radial incision could lead to a lasting decrease in intraocular pressure and the development of filtering blebs. METHODS: Forty-three eyes treated with combined filtering surgery were compared with a control group of 42 eyes treated with cataract surgery (phacoemulsification) alone. All of the patients had advanced chronic open-angle glaucoma. During combined cataract and glaucoma surgery, the tunnel floor was transected with Vannas scissors. RESULTS: One year after surgery, the mean intraocular pressure in the study group decreased 7.6 mm Hg from a preoperative mean (+/-SD) of 25.9+/-5.3 mm Hg. The decrease in the control group was 3.7+/-4.2 mm Hg. The difference between the 2 groups was statistically significant (P<.001). In the study group, an average of 1.5+/-0.8 fewer medications were required 1 year after surgery. In the control group, 0.5+/-0.6 fewer medications were required. CONCLUSIONS: The combined surgical procedure discussed in this article led to a lasting decrease in intraocular pressure. Cataract surgery alone using the no-stitch technique and posterior chamber lens implantation also reduced intraocular pressure, although significantly less.

Aged↗

PubMed1997

[Early postoperative endothelial cell loss after corneoscleral tunnel incision and phacoemulsification in pseudoexfoliation syndrome].

INTRODUCTION: Corneal endothelial involvement can be found in pseudoexfoliation syndrome (PEX). Evaluation of possible differences in endothelial cell loss following cataract extraction was compared to normal eyes. PATIENTS AND METHODS: In a controlled clinical study we prospectively studied 20 patients with PEX and compared them with an age-matched control group with senile cataract. All patients were treated with a standardized self-sealing 7-mm corneoscleral tunnel incision, phacoemulsification and posterior intraocular lens implantation using sodium hyaluronate. In addition to a complete ophthalmological examination, quantitative and qualitative endothelial cell analysis of the central and peripheral cornea was performed preoperatively, at the first postoperative day and after 4 weeks using non-contact specular microscopy (Konan Noncon Robo-ca SP 8000, Konan, Japan). RESULTS: In eyes with PEX (2394 +/- 271 cells/mm2) endothelial cell counts were 10.5% (P < 0.05) lower than in the control group (2674 + 341 cells/mm2). Intraoperatively, ultrasound time (90 +/- 51 s) and power (38 +/- 17%) did not differ between the two groups. After 4 weeks the mean endothelial cell loss in the two groups was 10.4% and 9.8%, respectively (P < 0.001). The mean cell area increased by 55 and 48 microns2 (P < 0.001), respectively. Polymegethism increased postoperatively in both groups and stabilized at 4 weeks at preoperative values. Pleomorphism increased significantly only in the PEX group. CONCLUSIONS: In eyes with PEX no increased cell loss was found in the early postoperative period compared to normal eyes following corneoscleral tunnel incision and phacoemulsification. Due to preoperative reduced endothelial cell densities, endothelium-protecting measures are recommended in eyes with PEX.

Aged↗

PubMed1997

Photovaporization rate and profile of an erbium-chromium:YAG laser in the fundamental mode.

PURPOSE: To evaluate the ablation characteristics of an experimental erbium:YAG (Er:YAG) laser and assess whether it delivers sufficient output for performing photorefractive keratectomy. SETTING: Department of Ophthalmology, Virchow-Clinics, Humboldt University, Berlin, Germany. METHODS: An experimental Er:YAG laser, the erbium-chromium:YAG, running in fundamental mode was used to evaluate the energy profile. Measurements obtained using a joulemeter were compared to the ablation profiles of cadaver pig eyes. The pig eyes were treated with different fluences (mean 0.8 to 2.9 J/cm2) and, after histological preparation, were examined using light and scanning electron microscopy. RESULTS: Measurements with the joulemeter and in the cadaver pig eyes showed a Gaussian-curved profile of energy (ablation). In the current setting, the diameter of ablation was 3.5 mm. Histological examination showed a homogeneous profile of ablation with minor thermal damage. CONCLUSION: The Er:YAG laser running in the fundamental mode allows homogeneous ablation of corneal tissue. The Er:YAG laser is easier to handle technically than the excimer laser and has none of the potential risks of ultraviolet light.

Animals↗

PubMed1994

Complications of myopic photorefractive keratectomy with the excimer laser.

BACKGROUND: Although many thousands of myopic eyes have been operated on by excimer laser photorefractive keratectomy (PRK), the safety of this procedure is still a concern. METHODS: The results and complications of PRK have been studied for up to 2 years in a prospective trial including 193 eyes in 146 patients. In addition, specific complications of PRK are described that occurred in patients outside the prospective study. RESULTS: Two eyes (1.2%) lost two lines of best-spectacle-corrected visual acuity 1 year after surgery, but at 2 years one of these eyes had regained baseline visual acuity. At 1 year, 12 eyes (7.1%) had lost more than two lines of visual acuity under glare conditions. Significant complications such as manifest scarring, overcorrection, undercorrection, and continued regression are dependent on attempted refraction. Eccentric ablations with resultant induced astigmatism are rare and the incidence is dependent on the experience of the surgeon. Progressive hyperopia did not occur. CONCLUSION: Except in corrections greater than 6 diopters, complications after PRK are rare. Assuming an appropriate patient selection, PRK may be considered a relatively safe procedure compared with other refractive procedures.

Adult↗

PubMed1993

[Pre- and postoperative corneal topography after combined single suture and running suture in ECCE. An analysis using the video keratoscope].

In a prospective study with 45 patients undergoing extracapsular cataract extraction (ECCE) with implantation of posterior chamber lens, curvature measurements of the cornea by means of computerized videokeratoscope were taken postoperatively. Analysis of the corneal shape on color-coded topographic maps of astigmatism showed an hourglass-shaped formation in all patients with a main axis in the sense of general astigmatism. Within a 3-mm zone (optical zone) the steepest meridian in all eyes was 96.1 +/- 13.3 degrees with an astigmatism of +4.4 +/- 2.1 D (1st postoperative day). Postoperatively we found that 35.6% of the patients examined had irregular astigmatism that could not be corroborated by the readings from the Javal ophthalmometer. An irregular astigmatism, corneal topographic analysis reveals regions peripheral to the center with a peak corneal refractive power of +43.8 +/- 1.4 D. In contrast to the conventional methods (for example, Javal ophthalmometer, autokeratometer), computerized videokeratoscope analysis provides additional and useful information on the corneal topography after intraocular operations.

Aged↗

PubMed1993

Central corneal iron deposit after photorefractive keratectomy.

Iron lines in the corneal epithelium are well-documented clinical signs in various circumstances. After photorefractive keratectomy, a new type of iron deposit can be found: a central round spot that occurred in more than 80% of cases of 1 year after surgery. It can be recognized at the slitlamp 6 months after surgery, and its incidence is related to the amount of attempted refractive change. In otherwise clear corneas, the central iron spot is the only clinical sign of a previously performed photorefractive keratectomy.

Adult↗

PubMed1992

[Computerized videokeratoscopy. Indications for postoperative suture removal].

Twenty-three patients who had a high degree of postoperative astigmatism (3 D) after extracapsular cataract extraction were examined in a prospective study with a computerized videokeratoscope. Sutures were removed within the first 3 months postoperatively, and an examination with the videokeratoscope was performed at the same time. In addition, corneal power was measured with a keratometer for comparison. A comparative map demonstrating the change in corneal shape can be obtained by simple subtraction of the pre- and postoperative keratographs (color-coded topographical maps). Immediately after suture removal the corneal curvature was flattened in the steepest meridian (3 mm and 5 mm zone), resulting in an average net change in cylindrical refraction of -1.3 (+/- 1.7)D. The steepest meridian moved slightly in a counterclockwise direction (-5.79 +/- 29.4 degrees). The topographical analysis of all cases showed that suture removal along the steepest meridian reduced astigmatism by flattening the steepest meridian and steepening the flattest meridian. As the peripheral cornea becomes steeper, the central cornea flattens in a meridian. Morphologically, three different patterns were found. In 52% the reduction in astigmatism was "symmetric", in 21% it was "round", and in 26% it was "irregular". As a result of the study, a topographical model of the cornea will be given, showing the average net change in diopters power at various locations on the surface of the cornea. These results cannot be described by the use of ordinary keratometers.

Astigmatism↗

PubMed1990

[Differential diagnosis of papillary carcinomas of the thyroid, using image analysis and three dimensional reconstruction from serial sections].

Papillae with fibrovascular cores are characteristic of papillary carcinoma of the thyroid. Papillae may be found in diffuse hyperplasia, nodular hyperplasia, Hashimoto's disease and follicular adenoma. Tissues from ten benign hyperplasias and ten papillary carcinomas were reconstructed from serial sections with three dimensional reconstruction programs. Significant qualitative and quantitative differences were found between the hyperplasia and the carcinoma. The principal differences between papillae of papillary carcinoma and hyperplasia were more clearly seen in the three dimensional reconstruction, than by means of morphometric methods. Certain criteria, e.g. the volume of papillae, were useful only with regard to the third dimension. Nevertheless, three dimensional reconstruction of biological tissue is a time consuming procedure which is not yet suitable for routine examination.

Carcinoma, Papillary↗

PubMedDate not supplied

Aspheric photorefractive keratectomy with excimer laser.

BACKGROUND: Increased spherical aberration of the cornea is a common finding after excimer laser keratorefractive keratectomy. The shape of the paracentral cornea is probably related to the incidence of side effects like glare and halos at night depending on ablation zone size and pupil diameter. Aspheric curvature changes of the paracentral cornea at the edge of the ablation may decrease those side effects. MATERIALS AND METHODS: Fifteen patients were treated with photorefractive keratectomy for myopia correction with a Summit excimer laser (Summit Technology, Waltham, Mass), one eye using a standard spherical algorithm and the fellow eye using a new aspherical algorithm. Eyes were followed for 6 to 18 months. RESULTS: None of 15 patients reported halos in the aspherically corrected eye stronger than in the fellow eye, whereas five patients claimed stronger halos in the spherically corrected eye. The effective clear zone size was 3.16 +/- 0.35 mm in the spherical cases compared to 3.43 +/- 0.31 in the aspherical cases, although the same ablation zone diameters of 5 mm were used. This difference is highly statistically significant. Effective spherical aberration based on raytracing analysis of the central 5 mm of the corneal topographic maps was significantly smaller in the corneas with aspheric correction than in those with spheric corrections. CONCLUSION: These results indicate better optical homogeneity in eyes after aspheric photorefractive keratectomy for myopia compared to standard spherical corrections.

Adult↗