Search PubMed⌕ Search

Biomedical subjects

M Fahle

Publications and source records attributed to M Fahle.

99 records · Page 6Linked to original sources
PubMed1983

Non-fusable stimuli and the role of binocular inhibition in normal and pathologic vision, especially strabismus.

Stimuli on corresponding points of both retinae that cannot be fused may cause binocular rivalry: the stimuli suppress each other alternately. This effect was used to study the influence of image sharpness upon binocular inhibition. Blurring an image means decreasing its contrast and attenuating its high spatial frequencies. Both factors diminish the time that a stimulus is perceived during rivalry. This fact has implications both for normal vision--as objects off the horopter are normally blurred--and for disturbed vision when the image of one or both eyes is (locally) deteriorated. In both cases, the binocular field of view can be combined from the 'good' parts of both eyes. Hence, the field of view may consist, in a piece-meal fashion, of parts stemming from the right or the left eye exclusively and others where both images are superimposed. We present evidence for the hypothesis that there is a common neural mechanism causing both binocular rivalry and functional amblyopia in anisometropia and strabismus. Consequences of the results on rivalry suppression for the pathophysiology and therapy of strabismic amblyopia are discussed.

Adolescent↗
PubMed1982

[The influence of systemic digitalis application on intraocular pressure].

The intraocular pressure (IOP) of ten healthy subjects was measured before and after a 2-week systemic application of beta-methyldigoxin. The drug led to a highly significant decrease of IOP of on the average 2 mm Hg. The decrease was independent of the blood concentration of glycoside - at least within the therapeutic range. There was a positive correlation between IOP before digoxin application and the subsequent IOP decrease. The rate of outflow increased, but not significantly. Implications for the therapy of glaucoma are briefly discussed.

Adult↗
PubMed1982

Binocular rivalry: suppression depends on orientation and spatial frequency.

In binocular rivalry the time during which different stimuli are perceived depends--amongst other things--on their spatial frequency (sf) contents, on contrast and on orientation. Limiting the sf-range of both periodic and aperiodic stimuli in different ways (while keeping the contrast constant) decreased their predominance. This result seems to corroborate the concept of spatial frequency channels in human vision. Decreasing the contrast also decreased predominance. Thus blurred patterns are suppressed by sharply focused ones because of both their lower contrast and their loss of high sf's. This has consequences for the therapy of strabismic amblyopia. Obliquely oriented patterns were almost as dominant as vertical ones and much more than horizontal ones. Instead of a conventional "oblique-effect" we found a "vertical-effect".

Adolescent↗
PubMed1980

A dichoptic edge effect resulting from binocular contour dominance.

If one eye sees a bright field on a dark surround while a homogeneous background is presented to the other eye, then a distinct dark zone appears at the outer borders of the field. If the surround is coloured, then the zone is of corresponding hue. The effect disappears if the edge of the field can be fused with a bar of appropriate contrast. The influence of parameters such as pattern contrast and size were studied quantitatively. A model is proposed relating the effect to receptive-field organisation and the fusion process.

Color↗
PubMedDate not supplied

Visual performance and recovery in recently detoxified alcoholics.

In order to assess the impact of chronic alcohol misuse on basic visual functions, we investigated motion perception, visual short-term memory, and visual divided attention in recently detoxified patients and matched controls by means of visual psychophysical tasks. Subjects were tested twice within the first 3 weeks of detoxification in order to assess the potential recovery of visual performance. Patients demonstrated significant impairments in visual perception of coherent motion for slow, but not faster, speeds, and in speed discrimination as assessed by random dot kinematograms. Visual short-term memory tested with a delayed vernier discrimination task, on the other hand, was not significantly affected in patients. When processing hierarchical letters, a divided attention task, detoxified patients showed neither impairments in overall attentional capacity nor attentional allocation, but slightly enhanced interference of global information on local target processing. The results of the visual divided attention task contradict the predictions of the 'right hemisphere' hypothesis of alcoholism: global target information - mediated by the right hemisphere - was not only accessible to detoxified patients, but seemed to exert an even greater influence on local processing during early detoxification, than in matched controls. Limited recovery within the first 3 weeks was seen only in visual speed discrimination. Recently detoxified patients revealed deficits similar to intoxicated social drinkers in identical tests of visual perception of motion, but not visual short-term memory.

Adult↗
PubMedDate not supplied

Visual acuity after segmental buckling and non-drainage: a 15-year follow-up.

BACKGROUND: The question addressed is: how does the postoperative visual acuity in eyes treated with segmental buckling compare over time with the paired fellow eyes? METHODS: 107 detachments were followed prospectively for 15 years. The eyes were divided into: group I, macula attached (46); group II, macula partially detached (10); group III, macula completely detached (51). Mean preoperative visual acuity was 20/30 in group I, 20/100 in group II, and 20/400 in group III. The operation consisted of segmental buckling without drainage. No eye had cerclage or vitrectomy. RESULTS: The retina remained attached in 99 eyes during the 15-year follow-up. The mean visual acuity of all patients improved six months postoperatively to 20/40 with a maximum of 20/30 at one year. Thereafter there was a linear decrease in all three groups. CONCLUSIONS: Visual acuity improved during the first year, followed by a linear decrease of 0.07 line/year. The paired eyes decreased similarly in relation to age. There was no real difference in the visual acuity of the operated and unoperated eyes (P = 0.079) during the 15 years of follow-up. Mean visual acuity was 20/40 in the operated eyes of 72 patients who were living after 15 years. These data present a challenge to those surgeons who use techniques that include encircling the eye to review and compare their long-term visual results.

Drainage↗