PubMed Health⌕ Search

Biomedical subjects

E Marg

Publications and source records attributed to E Marg.

At least 19 recordsLinked to original sources
PubMed1991

Magnetostimulation of vision: direct noninvasive stimulation of the retina and the visual brain.

The history of magnetophosphenes and their closely related predecessor, electrophosphenes, is described from the mid-18th century to the present time. The current era of magnetic stimulation started in 1985 with the development of a practical capacitor-discharge electromagnetic stimulator by Barker and his colleagues at the University of Sheffield, and their application of it to the brain with Merton and Morton at the National Hospital, London. The safety of magnetostimulation of the brain is discussed as well as the advantages of magnetostimulation over electrostimulation. Principles of magnetostimulation of nerves and magnetic measurement are considered. Effects on motor and sensory systems of the brain are described including magnetic perceptual suppression in the visual cortex and other pioneering work of Amassian, Cracco and Maccabee at SUNY Health, Brooklyn. Magnetophosphenes from retinal and cortical magnetostimulation are distinguished. Now that visual cortical stimulation is possible with the strong magnetic pulses generated by capacitor-discharge instruments, the functional viability of the visual cortex may be tested directly and noninvasively.

Electric Stimulation↗
PubMed1988

Imaging visual function of the human brain.

Imaging of human brain structure and activity with particular reference to visual function is reviewed along with methods of obtaining the data including computed tomographic (CT) scan, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET). The literature is reviewed and the potential for a new understanding of brain visual function is discussed. PET is reviewed from basic physical principles to the most recent visual brain findings with oxygen-15. It is shown that there is a potential for submillimeter localization of visual functions with sequentially different visual stimuli designed for the temporal separation of the responses. Single photon emission computed tomography (SPECT), a less expensive substitute for PET, is also discussed. MRS is covered from basic physical principles to the current state of the art of in vivo biochemical analysis. Future possible clinical applications are discussed. Improved understanding of the functional neural organization of vision and brain will open a window to maps and circuits of human brain function.

Brain↗
PubMed1988

[HIV infection: neuropsychiatric symptoms].

Basing on the actual publications, the most important neurological and psychopathological symptoms of HIV-infection are systematically reported. Opportunistic infections are producing important neurological symptoms. A case of Cryptococcus neoformans-Infection of the brain is described.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Amblyopia and congenital esotropia. Visually evoked potential measurements.

Amblyopia in patients with congenital esotropia was studied using visually evoked cortical potentials. In only four of 31 patients with esotropia and no abducting nystagmus was amblyopia detected before surgery. Postoperatively, 19 of these patients had amblyopia. In contrast, nine of the 11 patients with esotropia and nystagmus exhibited amblyopia before surgery. We conclude that amblyopia occurs infrequently in patients with congenital esotropia and no nystagmus until surgery reduces the angle of deviation and breaks down the cross-fixation reflex.

Amblyopia↗
PubMed1984

Stimulus deprivation amblyopia in children. Sensitivity, plasticity, and elasticity (SPE).

In the SPE model we propose, sensitivity (S) to deprivation results in changes that may be either plastic (P) (permanent) or elastic (E) (temporary). The effects of various levels (hours per day) of monocular occlusion in amblyopic children are measured as the change in visual acuity in each eye. At the patching level extremes (12 or more hours per day, zero hours per day) the effects on visual acuity in the two eyes are reciprocal, but nearly equal (symmetrical). At intermediate levels of occlusion, the asymmetries in effects necessary for successful occlusion can be demonstrated. Additional measurements of SPE parameters in children may allow for the determination of occlusion dose response whereby the risks of occlusion amblyopia and interference with binocularity may be avoided.

Amblyopia↗
PubMed1982

Long-term visual results in bilateral congenital cataracts.

In 24 infants who underwent surgery for bilateral congenital cataracts, 29 eyes (60%) achieved visual acuities of 6/18 (20/60) or better and 13 (27%) had visual acuities of 6/60 (20/200) or worse. The best results occurred in patients who underwent surgery before they were 8 weeks old. Only one patient of the seven operated on after the age of 8 weeks achieved a visual acuity of better than 6/60 (20/200). These favorable visual outcomes were the result of early surgery, short intervals between operations on fellow eyes (48 hours or less), total bilateral occlusion between operations, careful postoperative monitoring with retinoscopy and visual-evoked potentials, and early correction of aphakia.

Age Factors↗
PubMed1982

Prentice-Memorial Lecture: Is the animal model for stimulus deprivation amblyopia in children valid or useful?

The animal models are not, strictly speaking, valid for clinical application to children, primarily because of the large differences in the duration of the critical or sensitive period. However, they do provide a useful conceptual framework to follow, especially while determining the waxing and waning of the amblyopia in each eye by preferential looking or visual evoked potential acuity methods. These methods allow us to detect or determine the degree of amblyopia and guide the treatment or prevention of stimulus deprivation amblyopia in each child by direct measurement. The reciprocal effect of amblyopia found by Thomas, Mohindra and Held in infants by the preferential looking method and confirmed and extended in age by our group with the visual evoked potential acuity method could have been predicted by the animal modelers from the cross-suturing experiments. It appears that more harm than good may be done by patching infants for the treatment of amblyopia without measuring the acuity of each eye to avoid the significant loss of connections to the patched eye and to both eyes (binocular units).

Amblyopia↗
PubMed1982

Eye patching and visual evoked potential acuity in children four months to eight years old.

The monocular visual acuities of six children aged 4 months to 8 years were measured using visual evoked potentials (VEP's) before and during patching therapy. A seventh child had both Snellen and VEP monocular acuities determined before patching. In a cooperative child, it was estimated that VEP acuity was within 0.25 octaves (one line on an eye chart) of Snellen acuity. In the four children less than 3 years of age, patching resulted in a 1.8-octave decrease in acuity of the patched eye and a 2.0-octave improvement in the unpatched eye. After cessation of patching therapy, acuity of the previously patched eye improved 2.0 octaves and that of the abnormal eye declined 1.75 octaves. In the two children older than 4 years, patching resulted in 1.25-octave acuity decrease in the patched eye. Cessation of patching resulted in a 1.25-octave improvement in acuity of the patched eye. No permanent deleterious effects of patching on acuity were observed.

Age Factors↗
PubMed1981

Effect of natural deprivation and unilateral eye patching on visual acuity of infants and children. Evoked potential measurements.

Evoked potential measurements of visual acuity were made on four children aged from 5 months to 8 years. They were deprived of normal visual stimulation by various disorders: unilateral aphakia from a congenital cataract, vitreous hemorrhage, polar cataract, and esotropia. In the two younger children, aged 5 and 15 months, respectively, the visual acuity improved when the eye had good optical imagery and declined with poor or no imagery. Reversal of the imagery to the contralateral eyes again brought large changes in opposite directions. In the two older children, aged 4 and 8 years, respectively, there were marked decreases in acuity in the patched eye, but little or no change in the unpatched eye. It is not know whether these differences are due to age or to the original kind of visual disorder, such as deprivation, occlusion, or strabismus, or are merely individual differences. It is clear, however, that some children exhibit large changes in acuity in response to visual deprivation or patching, or to its removal, in a readily reversible manner. Also, we have demonstrated that visually evoked potential acuities may be obtained from pediatric, clinical patients without regard to age, which may be useful in management of the conditions.

Animals↗
PubMed1981

Good visual function after neonatal surgery for congenital monocular cataracts.

We treated eight neonates who had total, monocular, congenital cataracts with surgery, occlusion, and contact lenses. Visual results in all eight patients were good. In five patients visual acuities improved to 6/9 (20/30) or better in the aphakic eye. In three patients visual acuities improved to 6/24 (20/80) or better. Problems with contact lenses probably accounted for the poorer results in two of these three patients. Binocularity was not demonstrated in any of our patients.

Aphakia, Postcataract↗
PubMed1979

[The clinical picture of essential myoclonus].

Familial essential myoclonus, a rare hereditary disease, is characterized by spontaneous myocloni without any other neurological and psychic symptoms. The report deals with two sisters who suffered from the disease and in whose family the syndrome occurred in two more generations. The outlook for a favourable therapeutic effect is limited. The prognosis is good.

Adolescent↗
PubMed1978

Computer-assisted eye examination. VI. Identification and correction of errors in the Refractor III system for subjective examination.

A computer-assisted subjective eye examination was administered to 80 patients. They were also examined in the conventional manual way. The results of the computer-assisted examination were compared with those obtained by conventional subjective methods to identify errors of hardware, software, and optometric flow charting and other problems. An 87.5% satisfactory prescription level was found for the distance prescription. The 12.5% unsatisfactory results are accounted for by several kinds of error. The percentage of unsatisfactory refractive results was greater for near than for distance measures because of special flow-chart and software problems, which were subsequently corrected. With implementation of the changes initiated as a result of this investigation, satisfactory refractive results approaching 95% can be expected.

Adolescent↗
PubMed1978

[Lymphadenopathy in phenytoin treatment].

The authors report on a 20-year-old patient who developed hydantoin lymphadenopathy during treatment with diphenylhydantoin. The problems associated with clinical and histological delimination from malignant lymphomata are described by reference to the literature. Hydantoin lymphadenopathy is regarded as a drug-induced allergic and toxic process.

Adult↗
PubMed1978

A reconsideration of visual evoked potentials for fast automated ophthalmic refractions.

Visual evoked potentials (VEP's) recorded from the scalp are sensitive to retinal image sharpness and thus to changes in the refractive state of the eye. Initially the responses to checkerboard flash or reversal stimuli were computer-averaged in order to raise the signal above the noise, primarily the electroencephalogram (EEG). Recently analogue Fourier signal analysis has been proposed for using the VEP for rapid clinical refraction. We have confirmed that this method can measure the spherical refractive state to within +/- 0.50D. However, because of large slow-wave fluctuations, measurements of changes within +/- 1.00D are not always clear. Despite its promise the method does not appear to be clinically useful at present.

Diagnosis, Computer-Assisted↗
PubMed1978

Computer-assisted eye examination. VII. Final evaluation of the refractor. III system for subjective examination after reducing software and hardware errors.

Eighty patient-volunteers were refracted by the computer-assisted Refractor III system and the results were compared with those obtained by the usual manual method. For the distance prescription 95% of the results were satisfactory. For the near add all were satisfactory. Relative validity of the system was also measured objectively by repeatability data. System test differences and test-retest manual-examination data were found comparable, indicating that the validity of the system is similar to that of the manual method. Further developments are expected to improve reliability, simplify maintenance, and extend testing so that the system will be an economical and useful instrument in eye clinics.

Adolescent↗