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Biomedical subjects

A Neetens

Publications and source records attributed to A Neetens.

At least 19 recordsLinked to original sources
PubMed1998

[Critical (foveal) flicker fusion frequency (CFF) is helpful in differential diagnosis of organic lesions from orthoptic amblyopias].

PURPOSE: To measure critical (foveal) flicker fusion frequencies (CFF) in normal eyes, unilateral maculopathies and neuropathies and in orthoptic amblyopias. METHODS: A newly developed apparatus (4F) with LED's measured subjective foveal CFF by ascending and descending mode in a group of normals and patients. RESULTS: The apparatus (4F) measures temporal resolution. Foveal CFF ist more reduced in neuropathies than in maculopathies. In contrast, CFF in amblyopic eyes is hardly reduced, in most cases equal or better than in the dominant fellow eye. This is independent from the visual acuity of the amblyopic eye. CONCLUSION: CFF testing is useful in the evaluation of unexplained (unilateral) reduction of visual acuity. A dissociation between visual acuity and CFF (within normal range) is present in cases of amblyopia.

Amblyopia↗
PubMed1993

Human retinal pigment epithelial cells from different donors continuously produce a vascular endothelial cell-stimulating factor into serum-free medium.

Mitogenic activities of human retinal pigment epithelial cell-conditioned medium (HRPE-CM) with different effects, such as inhibition, stimulation or no effect, on the proliferation of vascular endothelial cells (EC) in vitro have been reported. In this study, 14 HRPE cell lines were established from normal human eyes. Human umbilical vein endothelial cells (HUVEC) in the early passages were used as target cells to detect the mitogenic activity of HRPE-CM on the growth of vascular EC. Our results confirm that HRPE cells in culture continuously synthesize and secrete HUVEC growth substance(s) into a serum-free medium. The ability of HRPE cell lines to produce this mitogen seem unrelated either to in vivo donor factors or to in vitro cell life span. Using an enzyme-linked immunosorbance assay, we demonstrated that only HRPE cell extract, not HRPE-CM, can be recognized by basic fibroblast growth factor (bFGF)-specific antibody, though identical bioactivities on the growth of HUVEC were found in both preparations. The active component in HRPE-CM was heat- and trypsin-sensitive, and stable at extremes of pH (2.5 to 10.0). In addition, the bioactive molecule could not pass through a M(r) 30,000 cut-off membrane, suggesting that it is a fairly high molecular mass polypeptide. These observations suggest that the EC growth factor in HRPE-CM is distinct from fibroblast growth factors (FGFs).

Cell Division↗
PubMed1992

Foveal flicker-fusion frequencies: a simple, new apparatus (4F).

While spatial resolution may be easily assessed with contrast-sensitivity frequency (CSF) data, determination of foveal flicker-fusion frequency (4F) is a simple method of providing the ophthalmic practitioner with accurate information about temporal resolution. The authors describe a simple apparatus that controls luminance, light intensity, light intervals, stimulus size, homogeneity of background illumination, and binocular gaze, especially when using two wavelengths, allowing an increased number of applications with reliable and comparable results. It may prove to be a useful tool for screening, clinical and subclinical assessment, and for evaluating visual acuity, also during follow-up.

Adolescent↗
PubMed1992

[Optic neuritis in non-Hodgkin's lymphoma].

Optic neuropathy during non-Hodgkin lymphoma is a late central nervous system complication of unfavourable prognosis. It appears especially with involvement of the bone marrow. A normal cerebrospinal fluid, lack of any beneficial effect of the chemo-corticotherapy and absence of papilledema suggest paraneoplastic, or iatrogenic (radio and (or) chemotherapeutic) neuropathy with conclusive histopathological proof only at autopsy. More frequently, cerebrospinal fluid containing malignant cells, papilledema and a beneficial effect of the chemocortico-therapy suggests malignant infiltration of the optic nerve as occurs in our case. Optic neuropathy during non-Hodgkin lymphoma may exceptionally precede the systemic disease by several years. Early oculomotor involvement suggests meningeal malignant infiltration as found in meningeal carcinomatosis.

Evoked Potentials, Visual↗
PubMed1992

Recent pathogenic concepts of primary open angle glaucoma and soft glaucoma (POAG).

Loss of mainly field in POAG is due to Schnabel's cavernous atrophy of the axons at their scleral passage, built up by aligned stacks of glial collagen (IV and I) tissue plates, which contain capillaries. Organisation, size and structural surroundings encircle isolated or grouped axons not evenly distributed. The stereotype pattern of fieldloss linked to a characteristic optic nerve lesion suggests POAG be considered a N.O. disease as raised IOP may be only one of the risk factors. Are cavernous atrophy (loss of field) and the trabecular spaces narrowing (rise of IOP) both the result of the same pathogenic mechanism acting on the collagen fiber (IV and I) of the scleral coat, resp. lamina cribrosa (posterior segment) and trabecular meshwork (anterior segment)? If so, IOP-rise only worsens the condition as will do a hemodynamic energy crisis at the level of the axons. Interactive dominance at any of both levels may explain unexpected discrepancies between IOP and fieldloss. Considering "to treat or not to treat" accurate field loss predictability testing, urgent research topic, are discussed.

Anterior Chamber↗
PubMed1991

Photon correlation spectroscopy of light scattered by eye lenses in in vivo conditions.

The application of photon correlation spectroscopy on mammalian eye lenses in vivo is revisited. It is shown that the use of a short wavelength laser type and a logarithmic correlator improves the signal-to-noise ratio to such an extent that shorter measurement times are possible without impairing the information content of the correlation function. Experimental correlation functions obtained in vivo on a rabbit eye lens, are analyzed with several techniques. The histogram approach is most successful for the determination of the distribution function of relaxation processes in the correlation function and proposes four different populations of components in the lens. This result is comparable to that from in vitro measurements on highly concentrated solutions of alpha-crystallins and of fiber cell cytoplasm, the former proteins being the main scattering components both in vivo and in vitro in the eye lens system. Our results indicate that the application of photon correlation spectroscopy on eye lenses in vivo offers new perspectives to use this technique as a fast, noninvasive tool to study relaxation phenomena in normal and cataractous lenses. The sensitivity of the method allows it to be used as an important analytical technique in the study of prevention and treatment of cataract.

Absorptiometry, Photon↗
PubMed1991

[Macular neuroretinopathy].

The isolated presumably inflammatory involvement mostly acute and unilateral of the photoreceptor layer of the retina, in the macular region, has been described as clinical entity: macular neuroretinopathy. Three cases are presented. Its evolution, ophthalmoscopic appearance (cuneiform tear drop), negative angiofluorography, normal electroophthalmography, differentiates neuroretinopathy from cystoid edema (CME), retinoschisis, acute macular multifocal placoid pigmentepitheliopathy, pigmentepitheliitis, and "Multiple evanescent white dot syndrome" (MEWDS). Visual acuity is mildly decreased but its recovery is poor even after a long period of time. Secondarily the pigmentepithelium may be involved. MEWDS is characterised by a primary fruste involvement of the pigmentepithelial layer simultaneously with a secondary involvement of the choriocapillaris, and possibly photoreceptor layer.

Adult↗
PubMed1988

The use of iodinated density gradient media for the isolation of rod outer segments.

Sucrose, nycodenz, metrizamide and a mixture of equal volumes of sucrose and metrizamide were used as density gradient media for the isolation of retinal rod outer segments. The high osmolarity of sucrose had a strongly negative effect on the nature of the rod outer segments, whereas they were much better preserved using iodinated density gradient media such as nycodenz and metrizamide for their isolation.

Animals↗
PubMed1988

Lid lag in Guillain-Barré-Strohl syndrome.

Apparent sustained lid lag appears to be a peculiar neuro-ophthalmologic finding in Guillain-Barré-Strohl syndrome. We propose that the sign occurs with peripheral facial paralysis and it results after attempted forced lid closure, rather than being of central origin.

Adult↗
PubMed1988

[Inner neuroretinopathy with night blindness and generalized peripheral neuropathy].

The present paper describes a 62-year-old male patient with progressive night blindness and generalized peripheral neuropathy linked to HLA A29 and HLA B12. Multiple yellowish patches, radiating from the optic disk, were observed at the level of the retina, though they were not clearly outlined during angiofluorography. No signs nor symptoms of inflammation were present. There was also a discrepancy between the visual field and the objective ophthalmoscopic findings. The author has coined the term inner neuroretinopathy to define this phenomenon. Differential diagnosis with birdshot and vitiliginous retinopathy is extensively discussed.

Diagnosis, Differential↗
PubMed1988

[Functional monocular hemianopsia].

Certain patients with reduction or loss of central visual function and/or hemianopic changes of the visual field can be classified as well-informed malingerers, individuals who are easily influenced by suggestion, or neurotics suffering from "conversion hysteria." The main symptom is one of a functional sensory change (loss or reduction of visual field). The task falling to the ophthalmologist is to prove the contrary, using certain subjective and objective tests to prove the incompatibility of the results with the physiological facts. The authors discuss the specificity of these tests in this context and present a number of cases with the characteristic temporal or nasal functional hemianopsia comparing them with patients who have hemianopsias due to real anatomic lesions.

Adolescent↗