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Biomedical subjects

B Lachenmayr

Publications and source records attributed to B Lachenmayr.

10 recordsLinked to original sources
PubMed1990

[Predicting visual acuity in media opacities and uncorrectable refractive errors. Assessing so-called "retinal visual acuity"].

Three different components contribute to the modulation transfer function of the visual system: (1) formation of the optical image (refractive media, pupil); (2) scattering of light in the prereceptoral layers of the retina; (3) neuronal processing in the retina und superior visual centers. In the presence of media opacities or non-correctable refractive errors, the clinical question often arises as to which macular function can be expected under the assumption of normal optical image formation (e.g. prior to cataract extraction, corneal transplantation, or vitrectomy). Simple tests such as light projection, color discrimination, and two-point discrimination cannot provide adequate information about macular function. The same holds true for the global luminance ERG. The X-ray phosphene is obsolete. The Maddox rod (with limitations), transilluminated Amsler grid, and various entoptic phenomena (Purkinje vascular phenomenon, foveal chagrin, Haidinger's brushes, blue field phenomenon) are available as qualitative subjective tests. Maxwellian view systems with pinhole aperture (potential acuity meter PAM) and the interferometers (retinometer, visometer, SITE-IRAS interferometer) provide quantitative subjective methods. The flash VECP is primarily a qualitative objective test that allows semiquantitative acuity prediction under special conditions (unilateral opacities). Psychophysical criteria that are less affected by the quality of the retinal image show promising developments in future subjective tests, e.g. optotypes in positive contrast, optotypes or targets superimposed on a background of optical noise, or hyperacuity. Future objective test developments are pattern VECP or even pattern ERG elicited by interferometric stimulation, speckle VECP and focal ERG.

Cataract↗
PubMed1990

[Measuring temporal transmission properties of the visual system. Diagnostic value in suspected optic nerve neuritis].

The temporal transfer properties of the visual system were examined in 157 patients with suspected acute optic neuritis or papillitis. Foveal modulation sensitivity was measured as a function of temporal frequency (DeLange curve) both for the affected eye and the unaffected fellow eye. Patients with acute optic neuritis typically show a reduction of foveal modulation sensitivity at all temporal frequencies, high temporal frequencies above 10 cps being more markedly affected. The aim of the present study was to determine the sensitivity and specificity of this simple psychophysical procedure for the diagnosis of neuritis or papillitis in a reasonably large population of patients with suspected acute optic neuritis or papillitis. In each case the final diagnosis was confirmed by evaluation of the clinical signs and symptoms, the course of disease and additional diagnostic procedures, e.g. electrophysiology, perimetry, neurological examination including CT, lumbal puncture and examination of cerebrospinal fluid. In 136 cases (86.6%) the result read from the DeLange curve was correctly positive or negative. In 17 cases (10.8%) the DeLange curve indicated a false-positive and in 4 cases (2.6%), a false-negative result.

Flicker Fusion↗
PubMed1989

[Peripheral vision--function and significance].

The human retina may be divided into two parts, representing different functional capabilities: the center, i.e., the fovea, and the much greater periphery. Under photopic conditions the fovea has a very high spatial resolution, a high light-difference sensitivity, and a good perception of slow movements. Opposed to this the periphery shows an especially high temporal resolution and a good perception of fast movements. This enables the visual system to detect dangerous objects appearing in the periphery as soon as possible and to induce a detailed analysis in the fovea after triggering a fixational movement.

Fovea Centralis↗
PubMed1989

Fate of late complications in type I diabetic patients after successful pancreas-kidney transplantation.

The success rate of pancreas transplantation allows us to study in more detail the potential beneficial effects of normoglycemia on secondary complications in diabetes mellitus. We report a prospective follow-up (mean 26 mo) of metabolic control, neuropathy, retinopathy, and peripheral microcirculation in 31 patients with type I (insulin-dependent) diabetes (mean age 33 +/- 1 yr; mean duration of diabetes 21 +/- 1 yr) after combined kidney and segmental pancreas grafting. All patients had normal HbA1 levels. Glucose tolerance (GT), insulin, C-peptide, and glucagon were normal in 22 patients, and impaired oral GT with reduced insulin secretory capacity was seen in 9 patients. During follow-up, there was no deterioration of GT and insulin release. Vascular risk factors, e.g., hypertension, cholesterol, and triglycerides, decreased after grafting. Autonomic neuropathy improved clinically, and R-R variation increased significantly in 3 of 18 patients. Peripheral neuropathy improved clinically in 46% of patients and did not deteriorate in the others. Motor nerve conduction velocity increased greater than 20% in 8, less than 20% in 12, and was unchanged in 8 of 28 recipients. Most of the patients (n = 30) had pretransplant laser treatment of their advanced retinopathy. Posttransplant visual acuity improved at least more than one line in 56%, stabilized in 32%, and deteriorated in 12% of patients. Patients with functioning grafts for greater than 1 yr had no further deterioration of visual acuity. Vitreous hemorrhage frequency and severity dropped markedly from pretransplant (from 69 to 24%) 10 mo after grafting. Retinal morphology remained stable in all eyes except two.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Automated flicker perimetry].

Flicker fusion frequency (FFF), the threshold criterion of flicker perimetry, is a functional parameter of the temporal transfer properties of the visual system. An automated flicker perimeter suitable for clinical routine purposes is presented that allows perimetric examination of the central visual field with high spatial resolution. The intent of the present study was to investigate the outcome of flicker perimetry in comparison to static light-sense perimetry. In the majority of cases of ocular hypertension and suspected glaucoma (n = 31), chronic open-angle glaucoma (n = 36) and acute neuritis/papillitis (n = 10) defects are indicated by flicker perimetry in areas of the visual field with normal light sensitivity according to static light-sense perimetry (Octopus 201, program G 1). In many cases of preproliferative diabetic retinopathy (n = 10), however, flicker perimetry indicates fewer defects than static perimetry (Octopus 201, program 32). The results collected up to now suggest that automated flicker perimetry might represent a specific functional test of the retinal Y-ganglion cells.

Diabetic Retinopathy↗
PubMed1988

[Perimetry yesterday and today].

The historical development of perimetry, from the first technical devices for testing the visual field (arc perimeter) through the manual hemispherical perimeters (Tübingen and Goldmann perimeters) to the latest developments in automated, computer-controlled perimeters, is described with reference to the basic measuring methods and strategies on the one hand and technical realization on the other. The future development of perimetry will be characterized by a refinement of measured value statistics and the testing of perimetric procedures that test more complex physiological functions than sensitivity to differences (e.g., analysis of temporal transmission characteristics in flicker perimetry.

Europe↗