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Biomedical subjects

H W Leibowitz

Publications and source records attributed to H W Leibowitz.

At least 55 records · Page 3Linked to original sources
PubMed1980

Saccadic eye movements and body sway.

Different conditions of moving retinal images show differential influences on postural stability. A surrounding pattern moved during steady fixation increases body sway, but similar image motions generated by voluntary saccades do not. Mechanisms for postural control do not respond to visual feedback during saccades. Analogous principles in saccadic suppression and space constancy are discussed.

Biofeedback, Psychology↗
PubMed1980

Independence of radial localization from refractive error.

Localization of single stimuli presented individually on the circumference of an imaginary circle was determined with and without three diopters of refractive error introduced by spherical lenses. The presence of blur had no effect on localization accuracy.

Humans↗
PubMed1979

Correction of empty-field myopia on the basis of the dark-focus of accommodation.

The influence of negative spherical corrections on the detection of a small increment flash presented in a uniform field or Ganzfeld were determined. The range investigated included each observer's normal correction as well as values based on the focus assumed by each observer in total darkness (dark-focus of accomodation). A correction equivalent to the dark-focus resulted in maximum sensitivity. The results suggest a convenient technique for the determination of optimal correction for empty-field viewing conditions.

Accommodation, Ocular↗
PubMed1978

New evidence for the intermediate position of relaxed accommodation.

Experimental evidence is presented that the focus of the eye tends to return passively to an individually characteristic intermediate resting position or dark-focus whenever (1) the stimulus to accommodation is degraded or (2) when the quality of the image is independent of focus. Based on measurements of the dark-focus with a laser optometer, it is possible to predict the magnitude of night, empty field, and instrument myopia on an individual basis. The role of the intermediate dark-focus as a factor in accommodation also provides an explanation for the paradoxical variation of visual acuity with observation distance. Applications to night myopia and night driving are described, and implications for clinical practice are discussed.

Accommodation, Ocular↗
PubMed1978

The effect of refractive error on size constancy and shape constancy.

The effect of refractive error was determined for both size constancy and shape constancy. Although an error of 1.5 diopters reduces shape constancy, 3.0 diopters of blur had no effect on size constancy. The results are discussed in terms of the multiple mechanisms subserving the perceptual constancies. The importance of cues from the peripheral visual fields for size constancy and the role of foveally mediated texture and stereopsis cues for shape constancy are emphasized.

Adult↗
PubMed1976

Human conjunctivitis. I. Diagnostic evaluation.

One hundred forty-three patients (207 eyes) with conjunctivitis or blepharoconjunctivitis were studied. Attempts were made to establish an etiologic diagnosis by clinical and laboratory methods. The etiologic diagnosis that was made on the basis of the initial clinical examination correlated poorly with the results of standard laboratory tests. Conversely, the standard laboratory evaluation failed to establish a definitive diagnosis in the majority of cases. These findings suggest that the diagnostic dogmatism prevalent in conjunctivitis is unwarranted. Morphologic signs and routine laboratory tests leave us without a verified etiologic diagnosis in a substantial number of cases.¿

Acute Disease↗
PubMed1976

Night myopia: cause and a possible basis for amelioration.

The relationship between night myopia under simulated night driving conditions and the dark focus accomodation was examined. Over a range of luminance and contrast conditions typical of the night driving situation, college-age subjects accommodated to about one-half the difference between a distant simulated road sign and their individual dark focus. Subsequent laboratory and field experiments demonstrated that: (1) a negative correction equal to one-half the value of the dark focus significantly improved night visual performance as compared with their normal or full dark-focus correction, and (2) greater improvements in performance were obtained for subjects who exhibited a relatively near dark focus.

Accidents, Traffic↗
PubMed1976

An experimental study of the efficacy of perceptual-motor training.

The efficacy of 40 h of perceptual-motor training among a group of culturally disadvantaged kindergarten children was investigated. The training procedures produced a significant improvement in perceptual-motor abilities such that each group was raised to a "non-dysfunctioning" level as evaluated by the Rosner-Richman Perceptual Motor Survey. In terms of the design of this study, the effects observed and the differences obtained cannot be attributed either to maturation or to attendance in school per se.

Child Development↗
PubMed1975

Anomalous myopias and the intermediate dark focus of accommodation.

The dark focus of accommodation for an individual observer correlates highly with the magnitude of night, empty field, and instrument myopia. These anomalous myopias are interpreted as resulting from the passive return of accommodation to an individually determined intermediate dark focus when the stimulus for accommodation is degraded or absent, or when the need for accommodation is eliminated.

Accommodation, Ocular↗