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Biomedical subjects

D Spinelli

Publications and source records attributed to D Spinelli.

At least 73 records · Page 4Linked to original sources
PubMed1982

Contrast influence on perceived orientation.

When two gratings of slightly different orientation and equal contrast are presented dichoptically the observer perceives a unique fused grating at an orientation intermediate between the two (cyclofusion). We show here that if the contrast of the two gratings is different the perceived orientation of the fused grating depends on the relative contrast of the two monocular images. The results show that the perceived orientation varies linearly with the contrast difference, provided that the contrast values of the gratings presented to each eye are such as to give rise to a fused image. In these conditions, the perceived orientation is the average of the two monocular orientations, weighted with their contrast.

Depth Perception↗
PubMed1982

[Effects of timolol maleate on untreated contralateral eyes (author's transl)].

The efficacity of installations of 0,5 p. cent timolol maleate unilaterally was statistically evaluated in 15 subjects: 5 with open-angle glaucoma, 5 with secondary glaucoma, and 5 normal subjects. A reduction in intraocular pressure was observed in all cases, not only in treated eyes, but also, though to a lesser degree, in untreated eyes. Effects were almost totally lacking on lacrimal secretion, corneal sensitivity, and pupil size in both eyes. The hypothesis is raised of possible unilateral treatment in selected patients with ocular hypertension and/or trabecular glaucoma.

Adult↗
PubMed1981

The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway.

Electroretinogram (ERG) responses to alternating gratings have been recorded in patients with temporary occlusion of the retinal artery, retrobulbar optic neuritis, and other ganglion cell diseases. The ERG responses to alternating gratings were absent in first case and dramatically depressed in the others, whereas the ERG responses to light flashes or to homogeneous flickering light were normal. These findings corroborate recent evidence from studies on the cat, showing that the ERG in response to alternating gratings is correlated with ganglion cell activity.

Animals↗
PubMed1980

Scotopic contrast sensitivity in infants evaluated by evoked potentials.

The contrast sensitivity function of infants 2 1/2 to 6 months old has been obtained at mean luminances of 6 and 0.06 cd/m2 by recording visual evoked potentials in response to simusoidal gratings of various spatial frequencies alternating in phase at 8 Hz. The scotopic contrast sensitivity develops earlier than the photopic contrast sensitivity, reaching values very close to those of the adult between 4 and 5 months of age. This suggests that mechanisms responsible for adaptive changes of receptive field organization from night to day vision are not yet mature at this age.

Adult↗
PubMed1978

Accuracy of evoked potential refractometry using bar gratings.

We recorded cortical potentials evoked by phase-alternating square-wave gratings. Significant effects of varying the refractive power of the eye are obtained only at 5 cycles/degree (cy/deg) and above. The extrapolation to zero amplitude of the evoked response as a function of spatial frequency predicts the psychophysical visual acuity even for the myopic eye. As the sensitivity of meridional refraction using sufficiently fine bar gratings is better than 0.5 D it provides a suitable means for the measurement of astigmatism.

Astigmatism↗
PubMed1978

Binocular vision tested with visual evoked potentials in children and infants.

Evoked potentials (EP's) in response to phase-alternating gratings were recorded from normal and stereoblind or stereodefective subjects (adults and children) under monocular and binocular viewing conditions. The amplitude of the binocular EP was found to exceed the larger monocular EP in normal but not in stereodefective subjects, no matter whether the amplitudes of the two monocular EP's were the same or not. This finding provides an objective method for screening out defects of binocular vision. EP's recorded from a group of infants 2 to 18 months old suggest that a larger amplitude of the binocular EP, as compared with the monocular EP's, is the norm even in the earliest period of life.

Adult↗